Genetics-Exam 1 (ch 1-4)

What is genetics?

study of genes and what they do; branch of biology that deals with heredity and variation

root of the natural diversity that we observe among members of the same species as well as among different species

Genetic variation

Gene

"Unit of heredity", usually described according to the way it affects the traits or characteristics of an organism

How many genes are there?

Around 30,000-35,000

How much of the genome is coded for?

less than 5 %

What is the largest cellular molecule in humans?

DNA

Categories of larger cellular molecules:

Nucleic acids (DNA, RNA), Proteins, Carbohydrates and lipids

Proteome

All the proteins that a cell makes at a given time

Constitutive Gene

Unregulated; different cell types; transcribed continually; different types

Housekeeping Gene

Ongoing business; histones; continually made; can control (turn on/off) housekeeping depending on growth cycle

Inducible

Gene that can be turned on or off; produces proteins on a continual basis

Genetic Code

DNA sequences within most genes contain the information to direct the order of amino acids within polypeptides

Which codon is the least conserved?

Last

Does every gene code for a protein?

NO! tRNA, rRNA, mRNA

When studying a genetic cross, the second generation following the initial cross is identified by which of the following?

a. P generation

b. F1 generation

c. F2 generation

d. F3 generation

e. P3 generation

F2 generation

A true bredding line of green pod pea plants is crossed with a true-breeding line of yellow pod plants. All of their offspring have green pods. From this information, it can be stated that the green color is_____.

a. recessive

b. dominant

c. subservient

d. blended

e. non of the answers are correct

dominant

When Mendel crossed two plants that were heterozygous for a single trait, what was the phenotypic ratio of their offspring?

a. 1 : 2 : 1

b. 9 : 3 : 3 : 1

c. 3 : 1

d. 7 : 4

e. varied depending on the trait

3:1

An individual who has two identical alleles for a trait is said to be _____.

a. homozygous

b. heterozygous

c. isozygous

d. a variant

homozygous

The genetic composition of an individual is called its _____.

a. phenotype

b. genotype

c. hybrid

d. dominance

e. non of the answers are correct

genotype

The likelihood that the observation variation from the expected is due to random chance is called the _____.

a. P value

b. Goodness of fit

c. degree of freedom

d. X value

e. none of the answers are correct

P value

A karyotype is a(n) _____.

a. organelle of eukaryotic cells

b. stage of prophase I in meiosis

c. division of the cytoplasmic material following mitosis

d. photographic representation of the chromosomes of a cell

e. non of the answers are correct

photographic representation of the chromosomes of a cell

During sexual reproduction, each parent contributes one set of chromosomes. Similar chromosomes from each parent are called ____.

a. karyotypes

b. sister chromatids

c. homologues

d. sex chromosomes

homologues

Which of the following would contain genetic material that is 100% identical?

a. homologous chromosomes

b. sister chromatids

c. X and Y chromosomes

d. all of the answers are identical

sister chromatids

The location of a gene on a chromosome is called its ____.

a. karyotype

b. allele

c. locus

d. homologue

Locus

During this phase of the cell cycle the sister chromatids are formed.

a. G1 phase

b. G2 phase

c. S phase

d. prophase

e. Cytokineses

S phase

What is a merozygote?

a. a zygote with a maternal effect

b. prokaryotic cell that is haploid after binary fission

c. prokaryotic cell with wild and variant types of plasmids

d. prokaryotic cell without plasmids

Prokaryotic cell without plasmids

The chromosomes start to condense

Prophase

The sister chromatids separate and head towards opposite poles of the cell.

Anaphase

The centrosomes move to opposite poles of the cell.

Prometaphase

The chromosomes line-up in the center of the cell.

Metaphase

The nuclear membrane starts to disassociate.

sister chromatids condense & become visible under a LM

mitotic spindle apparatus is formed

Prophase

The nuclear membrane reforms around the chromosomes

telophase

The microtubules of the spindle fiber attach to the kinetochore.

nuclear membrane fragments into vesicles

kinetochore fibers capture or beginning to make contact with kinetochores at the centromeres

Prometaphase

The separated sister chromatids are now considered independent chromosomes.

Anaphase

Correct sequence of cell division

Prophase, prometaphase, metaphase, anaphase, telophase

In humans, which sex is considered to be the heterogametic sex?

Male

The process by which a geneticist can determine if a trait is on an autosome or sex chromosome is to conduct a(n):

a. reciprocal cross

b. karyotype

c. self-fertilization

d. X-linked cross

a. reciprocal cross

Genes, such as Mic2, that are found on both the X and Y chromosome are examples of _____.

a. pseudoatuosomal inheritance

b. sex-linkage

c. hemizygous inheritance

d. X-O sex determination

Pseudoautosomal inheritance

A heterozygote possesses a phenotype that is intermediate between the homozygous dominant and homozygous recessive phenotypes. This is most likely an example of _____.

a. codominance

b. incomplete dominance

c. incomplete penetrance

d. sex-influenced inheritance

Incomplete dominance

In human blood groups, the fact that an individual can have an AB blood type is an example of _____.

a. incomplete dominance

b. incomplete penetrance

c. sex-influenced trait

d. temperature-sensitive conditional allele

e. codominance

Codominance

An individual with type A blood and an individual with type B blood mate and have an offspring. What blood type is NOT possible in their offspring?

a. type O blood

b. type A blood

c. type B blood

d. type AB blood

e. all blood types are possible

all blood types are possible

For a certain trait a heterozygous individual has a selective advantage than a homozygous dominant of homozygous recessive individual. This is called _______.

a. codominance

b. incomplete dominance

c. overdominance

d. incomplete penetrance

e. multiple allele systems

Overdominance

If a geneticist describes a trait as being 70% penetrant, what would they mean?

a. the expression of the trait varies by individual

b. it is lethal in 30% of the individuals who have the trait

c. only 70% of the individuals who carry the trait express the trait

d. the trait is present in 70% of the population

Only 70% of the individuals who carry the trait express the trait

If an allele is dominant in one sex, and recessive in another, it is an example of _____.

a. sex-limited inheritance

b. sex-influenced inheritance

c. incomplete dominance

d. simple Mendelian inheritance

e. incomplete dominance

Sex-influenced inheritance

Epistasis is _______.

a. another term for overdominance

b. when one gene can mask the expression of a second gene

c. a trait that is only expressed in one sex of the species

d. when two dominant alleles can be expressed the same individual

e. none of the answers are correct

When one gene can mask the expression of a second gene.

A woman who is heterozygous for X-linked baldness marries a man who is nonbald. Which of the following would be true of their offspring?

a. all would be bald

b. all of the females would be nonbald, all males would be bald

c. all of the females would be nonbald and 1/2 of the females would be bald

d. 1/2 of females would be bald and 1/2 of the females would be bald

e. all would be nonbald

All of the females would be nonbald, 1/2 of the males would be bald

Which of the following statistical tests is used to determine if two genes are linked or assorting independently?

a. sum rule

b. binomial expansion

c. product rule

d. chi-square test

chi-square test

Crossing over is more likely to occur between genes that are ____ on a chromosome.

a. close together

b. far apart

far apart.

A testcross is always performed between the individual with the dominant phenotype and an individual who is _____.

a. heterozygous for the genes

b. homozygous dominant for the genes

c. homozygous recessive for the genes

d. lacking the genes

e. none of the answers are correct

homozygous recessive for the genes.

While mapping two genes in Drosophilia you observe 30 recombinants among 200 total offspring. What is the distance between these genes?

a. 30 map units

b. 6.67 map units

c. 200 map units

d. 15 map units

15 map units

The Mic2 gene is only found on the Y chromosome, which makes it _____.

a. hemizygous

b. holandric

c. angiogenic

d. androgenic

Holandric

Opposite of a mutant allele

a. multiple allele

b. dominant

c. recessive

d. wild type

Wild type

In the Lysis solution used to extract DNA in lab were chelators of what?

a. nucleases

b. membrane

c. DNA

d. cofactors of nucleases

e. all of the answers are correct

Cofactors of nucleases

Which of the following is primarily responsible for the maternal effect?

a. sperm cells

b. oocytes

c. nurse cells

d. placenta

Nurse cells

The coat color of calico cats is a result of _____.

a. maternal inheritance

b. x-inactivation

c. imprinting

d. extranuclear inheritance

b. x-inactivation

How many Barr bodies would an individual with a XXY genotype possess?

a. o

b. 1

c. 2

d. none of the answers are correct

b. 1

Expression of ______ would inhibit X-inactivation

a. Xic

b. Xist

c. TsiX

d. all of the answers are correct

e. none of the answers are correct

c. TsiX

Inheritance patterns that obey two laws: the law of segregation and the law of independent assortment

Mendelian Inheritance

More than one wild-type allele occurring in a natural population

Genetic polymorphism

Codes for a protein without which the organism cannot survive (~1/3 of all genes)

Essential gene

Not absolutely required for survival, although they are likely to be beneficial to the organism

Nonessential genes

An allele that has the potential to cause the death of an organism. Prevent cell division and thereby cause an organism to die at a very early stage. (Huntington disease)

Lethal allele

Will kill organism only if or when certain environment conditions arise (ex: temperature-sensitive lethal alleles)

Conditional lethal alleles

Within a population this allele will kill some individuals, but not all (not well understood)

Semilethal alleles

Condition in which the phenotype is intermediate between the corresponding homozygous individuals. Two alleles produce intermediate results; heterozygotes have same intermediate phenotype. 50% of the normal protein is not sufficient to produce the same phenotype as a homozyogte

Incomplete dominance

Phenomenon in which an allele that is expected to cause a particular phenotype does not. Described at the population level (polydactyly)

Incomplete penetrance

Term used to describe the outcome of traits is the degree to which the trait is expressed

Expressivity

Refers to the effects of environmental variation on a phenotype

Norm of reaction

Structures within living cells that contain the genetic material

Chromosome

In eukaryotic cells, complex between DNA and proteins (histones)

chromatin

In prokaryotic cells, single type of circular chromosome in a region of the cytoplasm

nucleoid

Nearly identical members of paired chromosomes

Homologues

Increases cell size, RNA, and proteins

G1

Chromosomes doubled (sister chromatids)

S phase

Further cell growth and protein synthesis

G2 phase

Object of mitosis

to evenly distribute replicated chromosomes into two daughter cells with each nuclei having a complementary chromosomes

Gametes of equal size, structure and motility

Isogamous

Gametes different in size, structure, and motility

Heterogamous

Larger non-motile egg; smaller motile sperm

Oogamous

Chromosomes begin to condense and become visible with a light microscope

chromosomes begin to search nucleus for their homologue

often takes on a horse shoe shape; ends associated with proteins on nuclear lamina

Leptotena

Homologous chromosomes recognize and align themselves along their entire lengths (synapsis)

two pairs of aligned or associated sister chromatids are referred to as bivalents or tetrads

Zygotena

In most eukaryotic species, a synaptonemal complex (binding of lateral elements via transverse filaments) is formed between homologous chromsomes

during synapsis, crossing over occurs; recombinant DNA

Pachytena

Synaptonemal complex disappears

becomes easier to the 4 homologous chromatids also known as "tetrads"

chiasmata become visible

bivalent pulls apart slightly, and microscopically it becomes easier to see that it is composed of four chromatids

in females, meosis is arrest at this stage when female embryos are 5 months and will not resume process until puberty

Diplotena

Chromosomes shorten and thicken

Nuclear membrane fragments

Spindle fibers begin to form

Synaptonemal complex completely disappears

Nucleolus disappears

Diakinesis

X-O system

Male XO

Female XX

Many insects

ZW system

Male ZZ

Female ZW

birds and some fish

Term used to describe the single copy of an X-linked gene in males. Ex: colorblindness

Hemizygous

Sex-linked gene located on the Y chromosome (few compared to X-linked)

secondary male characteristics

Holandric genes

Short region of homology between the X and Y chromosomes some sex-linked genes have the same inheritance pattern as autosomes (males can transmit such genes to both male and female offspring)

Pseudoautosomal inheritance

when an offspring receives a combination of alleles that differs from those in the parental generation

genetic recombination

Probablity that one of two or more mutually exclusive (can't occur at the same time) events will occur is equal to the sum of the individual probabilities of the events

Add probabilities; "either/or"

Sum rule

Probability that two or more independent events (occurrence of one does not affect the probability of the other) will occur is equal to the product of their individual probabilities

Multiply probabilities; "and"

Product rule

Used to predict the probability of an unordered combination of events or unspecified order

____ out of 20

Binomial Expansion Equation

Deviation between the observed and expected outcomes

Random sampling error

What is the link between phenotype and genotype?

Proteins. determines function

Nearly identical members of paired chromosomes

homologues

Each tetrad interacts with spindle fibers to facilitate movement to the metaphasal plate

alignement on plate is random with regard to homologues

Metaphase 1

Each half of the tetrad has been pulled toward opposite poles in a process called "disjunction."

one tetrad has now become 2 dyads

Anaphase 1

Sister chromatids reach respective poles and decondense

Nuclear membrane reforms to produce two separate nuclei

Telophase 1

Term used to describe the single copy of an X-linked gene in males

hemizygous