EXAM TWO

dominant

Gain-of-function mutations are associated with being ________

1:2:1, 1:2:1

Assume that a cross is made between two organisms that are both heterozygous for a gene that shows incomplete dominance. What phenotypic and genotypic ratios are expected in the offspring?

9

Assume that a dihybrid cross for two different traits (AaBb × AaBb) is made in which the gene loci are autosomal, independently assorting, and incompletely dominant. How many different phenotypes are expected in the offspring?

1:2:1:2:4:2:1:2:1

Assume that a dihybrid cross for two different traits (AaBb × AaBb) is made in which the gene loci are autosomal, independently assorting, and both incompletely dominant. What phenotypic ratio would you expect from such a cross?

properties of sister chromatids and homologous chromosomes.

In codominance, both phenotypes are expressed in heterozygotes. In incomplete dominance, the heterozygote shows a phenotype that is intermediate between the two homozygotes.

What is the difference between incomplete dominance and codominance?

B

An individual test his blood type by placing drops of blood in anti-A sera and anti-B sera with the results as follows: What is the blood type of this individual?

This can be the father of the daughter but not the son.

Based on the following pedigree, with blood types provided (and ignoring the Bombay phenotype), what conclusions about paternity can be drawn?

multiple alleles

The presence of more than two alternative forms of a given gene would be called ________

A homozygote for a recessive lethal allele will not survive.

Which of the following statements is always true when mutations occur in genes whose products are essential to an organism's survival?

1/8

A couple each with blood type AB and normal pigmentation have a child with AB blood type and albinism. What is the probability that their next child will have the same phenotype as the first child?

9:3:4, 9:7

Typical ratios resulting from epistatic interactions in dihybrid crosses would be ________.

1/2

In the mouse, gene B can produce black pigment from a colorless precursor molecule. A mouse having at least one B allele can produce black pigment, whereas the homozygous recessive mouse (bb) cannot and is albino. The agouti locus (A) can convert the black pigment to brown in the presence of at least one dominant A allele, whereas the homozygous recessive (aa) cannot convert the black pigment to brown. What would be the probability of an albino mouse offspring if the parents were genotypes AaBb and AAbb?

12 (white): 3 (yellow): 1 (green)

Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Assume that two fully heterozygous plants are crossed. Give the phenotype ratio of the offspring.

Rrpp x RrPp

Comb shape in chickens represents one of the classic examples of gene interaction. Two gene pairs interact to influence the shape of the comb. The genes for rose comb (R) and pea comb (P) together produce walnut comb. The fully homozygous recessive condition (rrpp) produces the single comb. Assume that a rose-comb chicken is crossed with a walnut-comb chicken and the following offspring are produced: 17 walnut, 16 rose, 7 pea, 6 single. What are the probable genotypes of the parents?

complementation

Individuals from two separate true-breeding strains of white deer mice are crossed yielding all grey offspring. White is recessive to gray color based on crossing mice from each strain with a grey mouse. Which of the following would best explain this result?

whether two mutations that produce the same phenotype reside in the same or different genes

Complementation analysis is used to determine __________.

pleiotropy

The phenomenon of a gene which has multiple phenotypic effects on an individual is referred to as ________.

hemizygous

Because of the mechanism of sex determination, males of many species can be neither homozygous nor heterozygous. Such males are said to be ________.

In a diploid organism, one member of the sex chromosome pair may be inactivated without consequence; the lack of sex chromosomes (one or both) is not lethal to the organism; Sex chromosomes carry genes responsible for the development of male or female gonads.

How do sex chromosomes contrast with autosomes?

sex determination

____ genes signal developmental pathways whereby the sexes are generated

sexual differentiation

____ is the complex set of responses by cells, tissues, and organs to those genetic signals.

a portion of the Y chromosome

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

47, XXY

Klinefelter syndrome in humans, which leads to underdeveloped testes and sterility, is caused by which chromosomal condition?

SRY

Which of the following elements is responsible for determining male sex in humans?

PARS

Which of the following elements allows for homologous pairing in meiosis?

improper segregation of sex chromosomes during meiosis

Klinefelter syndrome (47, XXY) and Turner syndrome (45, X) are due to __________.

The presence of two X chromosomes determines whether the gonadal ridges develop into ovaries or testes.

Which of the following statements regarding sexual differentiation in humans is FALSE?

They are generally taller than average.

Which of the following statements about XYY males is true?

They are homologous regions of the X and Y chromosomes.

What are pseudoautosomal regions (PARs) on the sex chromosomes?

Nondisjunction results in ova that carry either two X chromosomes or none. The former results in Klinefelter syndrome when fertilized by a Y-containing sperm, and the latter results in Turner syndrome when fertilized by an X-containing sperm.

How does nondisjunction in human female gametes give rise to Klinefelter and Turner syndrome offspring following fertilization by a normal male gamete?

It would be detrimental to sex-determining mechanisms due to crossing over.

It is believed that any male-determining genes contained on the Upper Y chromosome in humans are not located in the limited region that synapses with the X chromosome during meiosis. What might be the outcome if such genes were located in this region?

2:1 male to female

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?

There would be a reduced number of males

If a population of humans carries an X-linked lethal recessive allele that causes spontaneous abortions in the first trimester, how would you expect this to affect the sex ratio of that population?

one

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

Klinefelter's and normal female

Which of the following has one Barr body?

Xist

Which of the following elements represents a large untranslated transcript involved in inactivation?

The formation of Barr bodies ensures that males and females have equal doses of genes on the X chromosome.

Which of the following statements about Barr bodies is true?

two

A human with the karyotype 49, XXXYY forms _______ Barr bodies.

In females, one of the X chromosomes is condensed and largely inactive so that each sex has one active X chromosome.

How do mammals, including humans, solve the "dosage problem" caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?

It is a darkly stained region near the nuclear envelope of interphase cells. It is an inactivated X chromosome.There will be one less Barr body than the number of X chromosomes.It is seen in nuclei of mammals with two or more X chromosomes

What is a Barr body, and where is it found in a cell?

Inactivation of an X chromosome occurs at random early in embryonic development. Inactivated X chromosomes are in some way "marked" such that all clonally related cells have the same X chromosome inactivated.

Define the Lyon hypothesis.

intersex

A fruit fly with a chromosome formulation of 2X:3A would be which of the following?

metamale

A fruit fly with an X:A ratio of .33 would which sexual morphology?

aneuploidy

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

euploidy

The condition that exists where complete haploid sets of chromosomes are present is known as ________.

nondisjunction

Which of the following is viewed as a major cause of aneuploidy?

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

Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. Although fertility is reduced in both sexes, females have higher fertility rates than males. Van Dyke et al. (1995; Down Syndrome Research and Practice 3[2]:65-69) summarize data involving children born of Down syndrome individuals. 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?

trisomic

If a species has a haploid number of 10, what term would we use to describe an individual with 11 chromosomes?

amniocentesis, chorionic villus sampling, and noninvasive prenatal genetic diagnosis

Which of the following is a method for harvesting fetal cells for karyotyping?

Patau syndrome

Which genetic disease is caused by a trisomy for chromosome 13?

tetraploid

If a species has diploid number of 10, but gave rise to progeny with 20 chromosomes, what term would we use to describe the progeny?

triploid

If two sperm fertilize a single ovum the resulting zygote would be considered a ________.

autopolyploidy

A diploid gamete that is fertilized by a haploid gamete from the same species would be an example of ________.

amphidiploidy

What term is used when two known diploid species fertilize to create a tetraploid offspring?

trisomy

a gain of one chromosome in addition to an otherwise diploid genome.

aneuploidy

a general condition when an organism gains or loses one or more chromosomes but not a complete set.

amphidiploid

an autotetraploid derived from two known original species.

euploidy

a general condition where complete haploid sets of chromosomes are present.

allopolyploidy

is the case of polyploidy when the chromosomes originate from the hybridization of two different species, usually closely related.

autotetraploid

a polyploid that has two extra sets of chromosomes, identical to the normal haploid complement of the same species, in addition to its diploid genome.

autopolyploidy

the addition of one or more extra sets of chromosomes, identical to the normal haploid complement of the same species.

a translocation between chromosome 21 and a member of the D chromosome group

Although the most frequent forms of Down syndrome are caused by a random error, nondisjunction of chromosome 21, Down syndrome occasionally runs in families. The cause of this form of familial Down syndrome is ________.

The baby received a 14/21, DG translocation from one of the parents.

During prenatal screening a couple is told that their baby is 46XX. At birth; however, the baby is diagnosed as Down's syndrome. Whats is possible explanation for this?

Autosomal Recessive

Typically skips generations. Affected individuals (aa) frequently have unaffected carrier parents (Aa). The trait appears equally in both sexes. Example: Albinism.

Autosomal Dominant

Almost always appears in every single generation. Affected individuals must have at least one affected parent. Unaffected individuals (aa) cannot pass on the trait. Example: Huntington disease

X-Linked Recessive

Many more males than females affected; no male-to-male transmission (fathers cannot pass X to sons).

X-linked Dominant

Appears in every generation, affected father must pass the trait to all of his daughters. An affected male cannot pass an X-linked dominant trait to his sons