Genetics test 1 study guide

The condition that exists when an organism gains or loses one or more chromosomes but not a complete haploid set is known as ________.

polyploidy

euploidy

aneuploidy

triploidy

trisomy

aneuploidy

________ is viewed as a major cause of aneuploidy.

Colchicine treatment

Segmental deletions

Heat treatment

Nondisjunction

X-ray mutations

Nondisjunction

What explanation is generally given for lethality of monosomic individuals?

Monosomy may unmask recessive lethals that are tolerated in heterozygotes carrying the wild-type allele.

The gametes of monosomic individuals cannot undergo meiosis, and this is lethal.

Cells count the number of chromosomes they have and will undergo apoptosis when the chromosome number is incorrect.

Monosomic chromosomes cannot undergo mitosis correctly.

The loss of a single chromosome is not generally lethal, unless the individual is inbred.

Monosomy may unmask recessive lethals that are tolerated in heterozygotes carrying the wild-type allele.

What is the leading cause of Down syndrome?

In older females, chromosome 21 is duplicated leading to abnormal egg formation.

In older parents, there is egg/sperm incompatibility leading to duplication of chromosome 21.

Aberrant implantation in the uterus leads to developmental problems in the fetus.

The nondisjunctional event that produces Down syndrome occurs more frequently during oogenesis in women older than age 35.

In men over 25, sperm formation is impaired and produces monosomic children.

The nondisjunctional event that produces Down syndrome occurs more frequently during oogenesis in women older than age 35.

Although fertility is reduced in both sexes, females have higher fertility rates than males. Assume that children are born to a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome?

-One-third of the offspring would be expected to have Down syndrome.

-Two-thirds of the offspring would be expected to have Down syndrome.

-All the children would be expected to have Down syndrome.

-None of the offspring would be expected to have Down syndrome.

-One-half of the offspring would be expected to have Down syndrome.

One-half of the offspring would be expected to have Down syndrome.

While there is reduced fertility in both sexes, females have higher fertility than males. Given the fact that conceptuses with 48 chromosomes (four #21 chromosomes) are not likely to survive early development, what percentage of surviving offspring would be expected to have Down syndrome if both parents have Down syndrome?

One-third of the surviving offspring would be expected to have Down syndrome.

All the children would be expected to have Down syndrome.

None of the surviving offspring would be expected to have Down syndrome.

Two-thirds of the surviving offspring would be expected to have Down syndrome.

One-half of the surviving offspring would be expected to have Down syndrome.

Two-thirds of the surviving offspring would be expected to have Down syndrome.

A son is born with Kleinfelter's syndrome and hemophilia. His father was normal and his mother was a carrier for the recessive X-linked blood clotting disorder. What occurred in meiosis to produce this genetic outcome?

nondisjunction in meiosis I of the father

nondisjunction in meiosis II of the father

nondisjunction in either meiosis I or meiosis II of the mother

nondisjunction in meiosis I of the mother

nondisjunction in meiosis II of the mother

nondisjunction in meiosis II of the mother

Given that a human normally contains 46 chromosomes, give the chromosome number for each of the following conditions:

Triploid

Trisomy 13

69, 47

69, 45

138, 47

138, 45

96, 47

69, 47

Assume that an organism has a diploid chromosome number of 14. There would be ________ chromosomes in a tetraploid.

14

28

42

56

104

28

Assume that a species has a diploid chromosome number of 24. The term applied to an individual with 36 chromosomes would be ________.

triploid

monoploid

allopolyploid

aneuploidy

tetraploid

triploid

An allotetraploid was formed through hybridization between two parental species, one with haploid number n1 = 3, and the other with n2 = 2. How many chromosomes would you see in the somatic cells of the hybrid?

1

5

6

10

12

10

The horse is 2n = 64, and the donkey is 2n = 62. If crossed, they produce the hybrid mule. There are _______chromosomes in a mule somatic cell. This cell is _________.

2n = 126; aneuploid

2n = 126; euploid

2n = 63; aneuploid

2n = 63; euploid

either 2n = 64 or 2n = 62, depending on whether the mother was the horse or the donkey; euploid

2n = 63; aneuploid

How do deletions and translocations in chromosomes often occur?

-chromosomes will fuse telomere to telomere

-chromosomes will break and the sticky ends will rejoin

-during meiosis I, sister chromatid exchange leads to abnormalities

-when cells undergo meiosis II, chromosomes naturally break when sister chromatids are being pulled apart

-colchicine treatment causes chromosomal rearrangements

chromosomes will break and the sticky ends will rejoin

What error of meiosis leads to both a duplication and a deletion?

replication errors

X-ray chromosomal breakage

unequal crossing over

D loop formation

replication cross formation

unequal crossing over

Which of the following is not a potential outcome of a gene duplication?

they may result in gene redundancy

they may result in providing the raw material for evolution

they may produce phenotypic variation

they may lead to the development of gene families

they may lead to translocation cross formation during synapsis

they may lead to translocation cross formation during synapsis

A ________ inversion is one whose breakpoints do not flank the centromere.

paracentric

pericentric

acentric

dicentric

segmental

paracentric

What type of chromosomal configuration does the following diagram illustrate?

(two outside going around and two inside making a loop-centromeres on outside)

inversion (paricentric) heterozygote

reciprocal translocation heterozygote

inversion (paracentric) heterozygote

simple translocation heterozygote

inversion (paracentric) homozygote

inversion (paracentric) heterozygote

Inversion heterokaryotypes are often characterized as having reduced crossing over and reduced fertility. Assume that you were examining a strain of organisms you knew to be inversion heterokaryotypes and saw a relatively high number of double chromatid bridges extending between anaphase I nuclei, as indicated in the following drawing. What is the product of this type of inversion loop? (two outside going around and two inside making a loop-centromeres on outside-cross between strand 1 and 4 and 2 and 3)

two acentric fragments and two dicentric chromosomes

one acentric fragment, one dicentric chromosome, and two wild-type chromosomes

four wild-type chromosomes

two chromosomes with deletions and two with duplications

two chromosomes with deletions and two acentric fragments

two acentric fragments and two dicentric chromosomes

The following structure is observed during prophase 1. It could be due to which of the following conditions?

CD

AB__EF

AB--EF

pericentric inversion

duplication

deletion

insertion

deletion

insertion

A pure line of plants of genotype a/a;b/b;c/c;d/d;e/e (all recessive to wild type) was crossed to a wild type. One F1 individual expressed the recessive alleles c, d, and e. This individual most likely arose from:

gene mutation in wild-type parent

reversion in the quadruple mutant

deletion in the quadruple mutant

deletion in the wild type

reversion in the wild type

deletion in the wild type

An indication of a reciprocal translocation is

-two genes on different chromosomes show recombination frequency of 50%

-two genes on different chromosomes show recombination frequency of 0%

-two genes on different chromosomes show linkage

-Recombination frequency of linked genes drops to zero

-Recombination frequency of linked genes decreases

two genes on different chromosomes show linkage

The two loci P and Bz are normally 36 m.u. apart on the same arm of a certain plant chromosome. A paracentric inversion spans about one- fourth of this region, but does not include either of the loci. What approximate recombinant frequency between P and Bz would you predict in plants that are heterozygous for the paracentric inversion?

0%

25%

27%

30%

36%

41%

27%

The two loci P and Bz are normally 36 m.u. apart on the same arm of a certain plant chromosome. A paracentric inversion spans about one- fourth of this region, but does not include either of the loci. What approximate recombinant frequency between P and Bz would you predict in plants that are homozygous for the paracentric inversion?

0%

25%

27%

30%

36%

41%

41%

In a mammal how many inactivated X chromosomes (Barr bodies) would be present in cells of individuals who were XXX?

0

1

2

4

5

2

Klinefelter and Turner syndromes have how many chromosomes, respectively?

46, 45

47, 45

45, 47

46, 46

47, 46

47, 45

A color-blind woman with Turner syndrome (XO) has a father who is color blind. Given that the gene for the color-blind condition is recessive and X-linked, provide a likely explanation for the origin of the color-blind and cytogenetic conditions in the woman.

nondisjunction in the father at meiosis I

nondisjunction in the father in meiosis I or II

nondisjunction in the mother in meiosis I or II

nondisjunction in the mother in meiosis I and in the father in meiosis II

no abnormalities had to occur to produce this daughter

nondisjunction in the mother in meiosis I or II

For an individual with the XXY chromosomal composition, the expected number of Barr bodies in interphase cells is ________.

variable

one

two

three

zero

one

A woman is found to be karyotypically XXX. The presence of an extra X chromosome could not result from:

non-disjunction in a maternal meiocyte at meiosis I

non-disjunction in a maternal meiocyte at meiosis II

non-disjunction in a paternal meiocyte at meiosis I

non-disjunction in a paternal meiocyte at meiosis II

non-disjunction in a paternal meiocyte at meiosis I

Nondisjunction in the first meiotic division in a male human could result at fertilization in _____.

YY condition

Turner syndrome

Klinefelter syndrome

X syndrome

either B or C

either B or C

How many Barr bodies would one expect to see in cells of Turner syndrome females and Klinefelter syndrome males?

one and zero

one and one

zero and two

zero and zero

zero and one

zero and one

Which of the following karyotypes would lead to male characteristics in humans?

XO

XXY

XYY

XO and XYY

XXY and XYY

XXY and XYY

A man observed his stained epithelial cells and saw a Barr body. If a karyotype was performed on his cells, what would you expect to see?

46, X Y

46 X X

47 X X Y

47 X Y Y

Either c or d

47 X X Y

The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female?

4:1 male to female

2:1 male to female

3:1 male to female

1:2 male to female

1:1 male to female

2:1 male to female

Yellow jackets are wasps that possess an unusual genetic system known as haplodiploidy. Females are diploid and arise from the sexual union of a female and male. In contrast, males are haploid and are produced asexually by females. Males transmit their single allele to their female offspring, but do not contribute to male production. Assume that eye color and wing length in yellow jackets are controlled by two independent loci, with black eyes dominant over yellow eyes at one locus and long wings dominant over short wings at another. If you cross a female that is heterozygous at both loci with a yellow-eyed long-winged male then, what genotypes and phenotypes would you find in the male and female offspring of this cross? What would the frequencies of these genotypes and phenotypes be?

Male offspring: Because of independent assortment, males represent the gametes of the female. So, the male offspring would have genotype frequencies of 25% BL (black long), 25% Bl (black short), 25% bL (yellow long), and 25% bl (yellow short). The phenotype frequencies would be the same as the genotype frequencies.

Female offspring: The male parent necessarily contributes the only alleles he has (bL). The female parent may produce four types of gametes with equal frequency, BL, Bl, bL, or bl. Consequently, the genotype frequencies of the females will be 25% BbLL (black long), 25% BbLl (black long), 25% bbLL (yellow long), and 25% bbLL (yellow long). The phenotype frequencies are thus 50% black long and 50% yellow long.

In humans, the genetic basis for determining the sex "male" is accomplished by the presence of _______.

portion of the Y chromosome

one X chromosome

balance between the number of X chromosomes and the number of haploid

sets of autosomes

high levels of estrogen

multiple alleles scattered throughout the autosomes

portion of the Y chromosome

A small part of the human Y chromosome contains the gene that is responsible for determining maleness. What is the name of this gene?

medulla

SRY

Xist

Dax

NRY

SRY

Which statement best describes human sex determination?

Females are heterogametic.

Individuals with a Y chromosome are male.

Individuals with two X chromosomes are female.

Individuals with at least twice as many X chromosomes as Y chromosomes are female.

Individuals with one X chromosome are male.

Individuals with a Y chromosome are male.

Under what condition might a human female have the XY sex chromosome complement?

She has an XX chromosome and a Y chromosome.

This is not possible.

The X chromosome has a mutation such that it is able to overpower the Y chromosome.

This female would have one complete X chromosome and a Y chromosome that lacks SRY.

The Y chromosome has an active Xist gene on it.

This female would have one complete X chromosome and a Y chromosome that lacks SRY.

Which of the following statements below is false?

Normally in humans, all the sons of a male showing an X-linked phenotype will inherit the trait.

Normally in humans, all the sons of a female homozygous for an X-linked recessive gene will inherit that trait.

Normally in humans, a male that is carrying an X-linked dominant trait will pass it to all his daughters.

At meiosis I, the X and Y chromosomes line up as if they were homologs.

Normally in humans, females are carriers of X-linked recessive traits if they are heterozygous.

Normally in humans, all the sons of a male showing an X-linked phenotype will inherit the trait.

Assume that a man who carries an X-linked gene has children. Assuming normal meiosis and random combination of gametes, the man would pass this gene to ________.

half of his daughters

all of his daughters

all of his sons

half of his sons

all of his children

all of his daughters

A young boy is diagnosed with hemophilia, a recessive, X-linked condition. If neither parent has hemophilia, what are their genotypes?

XAXa, XAY

XAXA, XaY

XaXa, XAYA

Mother could be either XAXA or XAXa, but father is XaY

cannot predict from the information given

XAXa, XAY

One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: In this problem, you must include the probability of having a daughter in your computation of the final probability.)

1/16

1/8

1/4

1/2

3/4

1/4

Which of the following statements is false?

An individual with Klinefelter syndrome generally has one Barr body.

An individual with Turner Syndrome has no Barr bodies.

typical XX human female has one Barr body.

Dosage compensation is accomplished in humans by inactivation of the Y chromosome.

In a cell with X chromosomes lacking the XIC, there is still X inactivation.

Dosage compensation is accomplished in humans by inactivation of the Y chromosome.

Dosage compensation in mammals typically involves the random inactivation of one of the two X chromosomes relatively early in development. Such X chromosome inactivation often leads to phenotypic mosaicism. Assume that black fur in cats is due to the X-linked recessive gene b, whereas its dominant allele B produces yellow fur. A Bb heterozygote is a mosaic called "tortoise shell" or "calico." A mating between a black male and a calico female occurred. Give the phenotypes of the offspring.

all black regardless of sex

all calico regardless of sex

calico females and yellow males

calico females, yellow females, black males, and yellow males

calico females, black females, yellow males, and black males

calico females, black females, yellow males, and black males

A cross is made between a female calico cat and a male cat having the gene for black fur on his X chromosome. What fraction of the offspring would one expect to be calico?

1/2

1/4

none

3/4

2/3

1/4

In a mammal how many inactivated X chromosomes (Barr bodies) would be present in cells of individuals who were XXX?

0

1

2

4

5

2

Nondisjunction in the first meiotic division in a male human could result at fertilization in _____.

YY condition

Turner syndrome

Klinefelter syndrome

X syndrome

either B or C

either B or C

The amino acid tryptophan is abbreviated "trp." An E. coli trp− auxotroph can grow on _____.

minimal medium

minimal medium without tryptophan (trp)

Minimal medium plus tryptophan (trp)

complete medium

Both c and d are correct

Both c and d are correct

A bacterial strain is able to grow on rich medium (which contains all the amino acids, vitamins, and a variety of carbon sources) but not on minimal medium or on minimal medium supplemented with leucine. What could be the genotype(s) of this bacterial strain with respect to the arg and leu loci?

arg+ leu-

arg- leu+

arg+ leu- or arg- leu+

arg- leu- or arg+ leu-

arg- leu- or arg- leu+

Analyze the following growth of a bacterial colony.

Medium Growth

Complete with glucose Yes

Complete with lactose (no glucose) Yes

Minimal No

Minimal media plus biotin, threonine, leucine, methionine, and lactose Yes

Minimal media plus biotin, leucine, and glucose No

Minimal media plus threonine, leucine, and lactose No

Minimal media plus leucine, methionine, and glucose Yes

What is the genotype of the bacterium?

bio+, thr+, lac−

leu+, met-, lac+

leu+, met+, lac−

bio+, thr+, leu+, met+

bio+, leu+, lac−

leu+, met-, lac+

Which of the following is true about the interrupted mating technique?

Time of contact is not applicable to this protocol.

Donor will pass only beneficial genes to the recipient.

Genes will be passed from the centromere.

Genes are transferred from the donor to recipient in a linear fashion based upon time of contact.

Genes are transferred from the donor to recipient in a linear fashion based upon time of contact.

The interrupted mating technique was used with a series of Hfr strains and the following results were obtained.

1) LQRYX

2) QLPZ

3) BTZP

4) LPZTB

5) PLQRY

What is the order of the genes?

BTPZLQRYX

XYRPZTBQL

PTZXBYRQL

XYRQLPZTB

RLQZTBXYP

XYRQLPZTB

In an Hfr × F− mating, if the order of transfer of loci is leu - azi - ton - lac, one can conclude that _____.

leu is adjacent to lac

leu is adjacent to the point of origin

the next transferred locus will be gal

there are five time units between azi and ton

all of the above are true

leu is adjacent to the point of origin

Describing bacterial conjugation, which of the following matings is most likely to result in a change from F- to F+?

donor F− recipient F+

donor F− recipient Hfr

donor Hfr recipient F-

donor Hfr recipient F+

donor F+ recipient F−

donor F+ recipient F−

Describe the state of the F factor in an Hfr, F+, and F- cell.

An Hfr strain has the fertility factor F integrated into the chromosome. An F+ strain has the fertility factor free in the cytoplasm. An F- strain lacks the fertility factor.

If two loci cotransform frequently, _____.

they are both on the same plasmid

they are both carried by the same phage D N A molecule

they are closely linked

they are on the same chromosome but more than 50 map units apart E. they are unlinked

they are closely linked

What is meant by the term cotransformation?

Several pieces of DNA can form heteroduplexes in a cell.

A cell can pick up more than one F factor.

More than one phage infects a bacterial cell.

An F− cell can become F+ several times in a life cycle.

Cotransformation occurs when several linked genes are transformed simultaneously

Cotransformation occurs when several linked genes are transformed simultaneously

If two bacterial genes are very closely linked (less than one map unit apart), then their frequency of co-transduction will be:

less than 1%.

more than 1%, but no more than 25%.

between 25% and 50%.

between 50% and 75%. E. very high, almost 100%.

very high, almost 100%.

very high, almost 100%.

An a+ b+ c+ d+ e+ donor strain is used to transform an a- b- c- d- e- strain. The recipient culture is plated on various media with the results shown in the following table. (Note that a- indicates a requirement for A as a nutrient, and so forth.)

One of these genes is very far away from the others. Which one?

Compounds added to minimal medium

Presence (+) or absence (-) of colonies

CDE -

BDE -

BCE +

BCD +

ADE -

ACE -

ACD-

ABE-

ABD +

ABC -

A

B

C

D

E

B

An a+ b+ c+ d+ e+ donor strain is used to transform an a- b- c- d- e- strain. The recipient culture is plated on various media with the results shown in the following table. (Note that a- indicates a requirement for A as a nutrient, and so forth.)

Which of the following statements is true about the gene order?

Compounds added to minimal medium

Presence (+) or absence (-) of colonies

CDE -

BDE -

BCE +

BCD +

ADE -

ACE -

ACD-

ABE-

ABD +

ABC -

C is between E and D

A is between B and D

B is between A and D

E is between C and A

D is between E and A

E is between C and A

A generalized transducing phage is used to transduce an v- w- x- y- z- recipient strain of E. coli with an v+ w+ x+ y+ z+ donor. The recipient culture is plated on various media with the results as shown in the table below (Note that v- indicates a requirement for V as a nutrient, and so forth.)

Which of the genes is closest to gene y?

Compounds added to minimal media

Presence (+) or absence (-) of colonies

XYZ -

WYZ -

WXZ +

WXY +

VYZ -

VXZ -

VXY -

VWZ -

VWY +

VWX -

v

w

x

y

z

v

Linkage affects expected ratios because it violates which of Mendel's postulates?

That there are two alleles for a gene in diploid organisms

Segregation of alleles at meiosis

Alleles have dominant-recessive relationship

That homologs independently assort in meiosis

Linkage does not affect ratios

That homologs independently assort in meiosis

Three genes on the Drosophila X chromosome are examined pairwise. It is determined that they have the following recombination rates:

(1) yellow, white 0.5%(2) white, miniature 34.5%(3) yellow, miniature 35.4%

Which two genes are physically closest together?

Yellow and white

White and miniature

Yellow and miniature

All three are about equally spaced

One cannot tell from this information

Yellow and white

Two genes that are 60 map units apart are expected to show _____

25% recombination

30% recombination

40% recombination

50% recombination

60% recombination

50% recombination

The genes A B C occur in that order in fruit flies. A is 10 map units from B, and B is 20 map units from C. If you test crossed triply heterozygous A B C/abc how much recombination would you expect between genes A and B?

10%

20%

30%

50%

0.2%

10%

A plant of genotype CCdd is crossed to ccDD and the F1 is testcrossed to ccdd. If the genes are unlinked, what percentage of ccdd recombinants will result?

0

.25

.5

.75

1.0

0

.25

A plant of genotype CCdd is crossed to ccDD and the F1 is testcrossed to ccdd. If the genes are separated by 20 m.u., what proportion of ccdd recombinants will result?

0

.1

.2

.25

.375

.5

.75

1.0

0

The genes A B C occur in that order in fruit flies. A is 10 map units from B, and B is 20 map units from C. How far is A from C?

0.2 map units

10 map units

20 map units

30 map units

40 map units

30 map units

Assume that a cross is made between AaBb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: AaBb, Aabb, aaBb, aabb. These results are consistent with the following circumstance:

independent assortment.

alternation of generations.

complete linkage.

incomplete dominance.

hemizygosity.

independent assortment.

The genes A B C occur in that order in fruit flies. A is 10 map units from B, and B is 20 map units from C. What is the expected frequency of double crossovers?

0.02%

2%

10%

20%

30%

2%

You have read that in guinea pigs, black fur is dominant to white fur. You are surprised then when your two white guinea pigs have all black F1. When you cross the F1, you observe 9:7 black:white. How do you best explain this?

Incomplete dominance

Codominance

Lethal alleles

Sex-limited expression

Two genes are responsible for the trait

Two genes are responsible for the trait

Multiple mutations that are found to be present in a single gene are said to belong to the same ________ group.

phenotypic

allelic

transfer

complementation

expression

complementation

You are trying to study heart development and you using a fish as a model organism. You identify three homozygous mutant lines that have embryos with slow-beating hearts. You name the genes slowheart1, slowheart2, and slowheart3. You perform complementation tests of the the lines and the results are shown.

Cross 1: slowheart1 X slowheart2 results in embryos with slow-beating hearts.

Cross 2: slowheart1 X slowheart3 results in embryos with wild-type heartbeat rate.

Cross 3: slowheart2 X slowheart3 results in embryos with wild-type heartbeat rate.

Which mutant lines are likely to have mutations in the same gene?

slowheart1 and slowheart3 are likely mutations in the same gene

slowheart1 and slowheart2 are likely mutations in the same gene

slowheart2 and slowheart3 are likely mutations in the same gene

All three have mutations in different genes

All three have mutations in the same gene

slowheart1 and slowheart2 are likely mutations in the same gene

Duchenne muscular dystrophy is caused by a recessive X-linked allele. A man with this disorder _____ .

could have inherited it from either parent

must have inherited it from his mother

must have inherited it from both parents

can pass it along to all of his children

can pass it along to only his sons

must have inherited it from his mother

A human female who is heterozygous for the recessive X-linked trait color-blindness marries a male who is not color-blind. What proportion of the couple's male offspring will be color-blind?

0

.25

.5

.75

1.0

0

A human female who is heterozygous for the recessive X-linked trait color-blindness marries a male who is not color-blind. What proportion of the couple's offspring will be heterozygous carriers?

0

.25

.5

.75

1.0

0

Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what percentage of their offspring would be expected to have straight hair?

25%

50%

75%

100%

It is impossible to predict the outcome.

50%

In a plant species, if the B allele (blue flowers) and the b allele (white flowers) are incompletely dominant (B b is light blue), what offspring ratio is expected in a cross between a blue-flowered plant and a white-flowered plant?

1/4 blue:1/2 light blue:1/4 white

1/2 blue:1/2 white

all light blue

3/4 blue:1/4 white

1/3 blue:1/3 light blue:1/3 white

all light blue

If a mother has type A blood and her son has type O blood, what are the possible blood types of her son's father?

type O only

types A or O

types B or O

types A, B, or O

any blood type

types A, B, or O

A cross between two short-tailed mice results in offspring in the ratio of 2/3 short-tailed and 1/3 long-tailed. The best explanation for this result is that _____.

two alleles are codominant

there is a recessive lethal allele

there are at least three alleles

there is simple dominance between two alleles

there is a dominant lethal allele

there is a recessive lethal allele

Multiple mutations that are found to be present in a single gene are said to belong to the same ________ group.

phenotypic

allelic

transfer

complementation

expression

complementation

Your mentor asks you to determine if the mutants belong to the same complementation group. What is true about flies that belong to the same complementation

group?

They all have the same mutation in the same wing- development gene.

All flies in a complementation group have identical DNA sequences for this gene.

They all have some mutation in the same wing-development gene.

Each strain may have a different mutation, but the same gene is mutated in all strains in a complementation group.

They all have some mutation in some wing-development gene.

Each strain may have a different mutation in a different gene, but all strains within a complementation group have the same phenotype.

They all have some mutation in the same wing-development gene.

Each strain may have a different mutation, but the same gene is mutated in all strains in a complementation group.

Assume that a cross is made between AaBb and aabb

plants and that the offspring occur in the following numbers: 106

AaBb, 48 Aabb, 52 aaBb, 94 aabb

These results are consistent with the following circumstance:

sex-linked inheritance with 30% crossing over.

100% recombination.

independent assortment.

linkage with 50% crossing over.

linkage with approximately 33 map units between the two gene loci.

linkage with approximately 33 map units between the two gene loci.

The cross

GE/ge ×ge/ge produces the following progeny:GE/ge 404;ge/ge 396; gE/ge 97;Ge/ge 103.

From these data, one can conclude that there are ________ map units between the G and E loci.

10

25

5

20

15

20

In

Drosophila, assume that the gene for scute bristles(s)

is located at map position 0.0 and that the gene for ruby eyes (r) is at position 15.0. Both genes are located on the X chromosome and are recessive to their wild-type alleles. A cross is made between scute-bristled females and ruby-eyed males. Phenotypically wild-type F1 females were then mated to homozygous double mutant males, and 1000 offspring were produced. Give the frequency of scute

expected.

425

Assume that two genes are 80 map units apart on chromosome II of Drosophila and that a cross is made between a doubly heterozygous female and a homozygous recessive male. What percent recombination would be expected in the offspring of this type of

cross?

50

Which of the following statements about conjugation is true? DNA is transferred from an F+ cell to an F- cell. The F factor is an element that is found in the chromosome of an F+ cell. Only competent cells can undergo conjugation.One strand of DNA from an F+ cell integrates into the chromosome of an

F- cell, and the other strand is degraded.

DNA is transferred from an

F+ cell to an F− cell.

How is a merozygote formed?

The F factor is excised from the chromosome of an Hfr strain, causing it to revert to F−.

The F factor and several adjacent genes are excised from the chromosome of an Hfr cell and transferred to an F− strain.

The F factor is inserted into the chromosome of an F+ cell, causing it to revert to F−.

The F factor is inserted into the chromosome of an F− cell, causing it to become an Hfr strain.

The F factor and several adjacent genes are excised from the chromosome of an Hfr cell and transferred to an F− strain.

In a bacterial cross in which the donor (Hfr) is a+b+ and the recipient strain (F−) is ab, it is expected that recombinant bacteria ________.

will be a mixture of a+b+, ab, a+b, and ab+

will all be a+b+

will be a mixture of a+b+, a+b, and ab+

will be a mixture of a+b+ and ab

will all remain ab

will be a mixture of a+b+, a+b, and ab+

What is meant by the term cotransformation?

Several pieces of DNA can form heteroduplexes in a cell.

A cell can pick up more than one F factor.

Cotransformation occurs when several linked genes are transformed simultaneously.

More than one phage infects a bacterial cell.

An F cell can become F+ several times in a life cycle.

Cotransformation occurs when several linked genes are transformed simultaneously

Bacteriophages engage in two interactive cycles with bacteria. What are these

cycles?

auxotrophic and prototrophic

negative and positive

insertion and replication

heteroduplex and homoduplex

lytic and lysogenic

lytic and lysogenic

Antibiotic-resistant bacteria are becoming an increasing problem. Some bacteria that were once killed by common antibiotics have acquired the ability to survive in the presence of those antibiotics. How can bacteria acquire antibiotic resistance?

Bacteria can acquire antibiotic-resistance genes by becoming infected with a virus that contains an antibiotic-resistance gene.

Bacteria can gain an antibiotic-resistance gene by conjugating with another species of bacteria.

Bacteria can pick up an antibiotic-resistance gene from the environment through transformation.

Bacteria can acquire random mutations that allow them to grow in the presence of antibiotics.

All

In humans, the genetic basis for determining the sex "male" is accomplished by the presence of

________.

sets of autosomes

a balance between the number of X chromosomes and the number of haploid

high levels of estrogen

one X chromosome

a portion of the Y chromosome

a portion of the Y chromosome

Dosage compensation in mammals typically involves the random inactivation of one of the two X chromosomes relatively early in development. Such X chromosome inactivation often leads to phenotypic mosaicism. Assume that black fur in cats is due to the X-linked recessive gene b, whereas its dominant allele B produces yellow fur. A Bb heterozygote is a mosaic called "tortoise shell" or "calico." A mating between a black male and a calico female occurred. Give the phenotypes of the

offspring.

calico females, black females, yellow makes, and black males

calico females and yellow males

all calico regardless of sex

calico females, yellow females, black males, and yellow males

all black regardless of sex

calico females, black females, yellow makes, and black males

Data produced by C. Bridges in the early part of this century indicate that sex in

Drosophila

is determined by

________.

a balance between the number of X chromosomes and the number of haploid sets of autosomes

the SRY gene

the ratio of X to Y chromosomes

the number of X chromosomes

the number of Y chromosomes

a balance between the number of X chromosomes and the number of haploid sets of autosomes

Which of the following statements about allopolyploid individuals is true?

They may be sterile and unable to produce offspring.

They can be formed when two sperm simultaneously fertilize an ovum within the same species.

They are generated from exposure to colchicine.

They result from a mating between individuals of the same species.

They may be sterile and unable to produce offspring.

Which of the following arrangements would yield the greatest reduction in gamete viability?

An inversion homozygote for a small inversion

An inversion homozygote for a large inversion

An inversion heterozygote for a large inversion

An inversion heterozygote for a small inversion

An inversion heterozygote for a large inversion

This woman is phenotypically normal. But some translocations result in an abnormal phenotype. Under what circumstances might you expect a phenotypic effect of such a rearrangement?

Select the

three

correct

answers.

A-if translocated chromosomal material contains mostly dominant alleles

B-if translocation breakpoints occur within the genes

C-if translocation results in the loss of some genetic material

D-if translocated chromosomal material is essential in sexual differentiation

E-if functioning of the translocated genes depends on their neighboring genes

B, C, E