BIOL 3000 Genetics Exam 1

The functions of mitotic cell division in the life cycles of an organism may include

asexual reproduction, growth, replacement of older cells, repair of injured tissues

X-linked dominant

1. Both males and females are usually affected; often more females than males are affected 2. Does not skip generations. Affected sons must have an affected mother; affected daughters must have either an affected mother or an affected father 3. Affected fathers will pass the trait on to all their daughters 4. Affected mothers (if heterozygous) will pass the trait on to half of their sons and half of their daughters

Y-linked

1. Only makes are affected 2. Passed from father to all sons 3. Does not skip generations

Autosomal dominant trait

1. Usually appears in both sexes with equal frequency 2. Both sexes transmit the trait to their offspring 3. Does not skip generations 4. Affected offspring must have an affected parent unless they possess a new mutation 5. When one parent is affected (heterozygous) and the other parent is unaffected, approximately half of the offspring will be affected 6. Unaffected parents do not transmit the trait

Autosomal recessive

1. Usually appears in both sexes with equal frequency 2. Tends to skip generations 3. Affected offspring are usually born to unaffected parents 4. When both parents are heterozygous, approximately one-fourth of the offspring will be affected 5. Appears more frequently among the children of consanguine marriages

X-linked recessive

1. Usually more males than females are affected 2. Affected sons are usually born to unaffected mothers; thus, the trait skips generations 3. Approximately half of a carrier (heterozygous) mother's sons are affected 4. Never passed from father to son 5. All daughters of affected fathers are carriers

If a couple is planning on having three children, what is the probability that all three children are going to be the same sex (3 boys or 3 girls)?

1/4

What is the probability that two lizards that are heterozygous for stripes on their tails (Ss) will produce an offspring that is homozygous for no stripes (ss)?

1/4

If there are 20 chromatids in a cell at prophase, how many centromeres are there?

10

If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?

16

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. Those cells would have ________ picograms at the end of the S phase and _________ picograms at the end of G2.

16:16

In a human cell at prophase I, there are ______ tetrads

23

Given the parents AABBCc and AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?

3/4

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

8

What is the difference between a monohybrid cross and a dihybrid cross?

A monohybrid cross involves organisms that are heterozygous for a single character, whereas a dihybrid cross involves organisms that are heterozygous for two characters

Which of the following represents the possible genotype(s) resulting from a cross between an individual homozygous for black hair (BB) and a heterozygous (Bb) individual?

BB and Bb

Which of the following events does not occur during meiosis I? A. DNA exchange B. pairing of homologous chromosomes C. separation of sister chromatids D. separation of homologous chromosomes E. crossing over between homologous chromosomes

C

Which of the following is false regarding the bacterial chromosome? A. It consists of a single, circular DNA molecule B. DNA replication begins at the origin of replication C. Its centromeres uncouple during metaphase of mitosis D. It is highly folded within the cell E. It has genes that control binary fission

C. Its centromeres uncouple during metaphase of mitosis

The kinetochore serves which of the following functions? A. Kinetochores anchor spindles fibers to centrioles B. Kinetochores are the site of DNA synthesis C. Kinetochores regulate the length of the cell cycle D. Kinetochores attach to microtubules during mitosis E. Kinetochores are involved in cytokinesis

D

A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei containing how many chromosomes?

D. 46

Which of the following statements is not true? A. Mitosis produces new nuclei with exactly the same chromosomal endowment as the parent nucleus B. Mitosis may occur within cytokinesis C. Mitosis and cytokinesis are required for asexual reproduction D. All cells come from a preexisting cell E. The mitotic spindles in prokaryotic cells are composed of microtubules

E.

Cells that are in a dividing state are in which phase?

G0

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Traits are inherited in discrete units, and are not the results of "blending"

Tallness (T) is dominant to dwarfness (t), while red (R) flower color is incompletely dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?

TtRr - tall and pink

Which of the following is the term for a human cell that contains 22 pairs of autosomes and two X chromosomes?

a female somatic cell

The physical location of a particular gene on a chromosome is called

a locus

During prophase I, each chiasma represents

a site of crossing over

What is a genetic cross between an individual showing a dominant phenotype (but of unknown genotype) and a homozygous recessive individual called?

a testcross

A maternal homologue and a paternal homologue associate to form

a tetrad

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?

about 8 million

Separation of paired alleles takes place during

anaphase I of meiosis

During which of the following stages of meiosis do the sister centromere separate?

anaphase II

Which of the following organisms does not reproduce cells by mitosis and cytokinesis?

bacterium

Why is color blindness more common in males than in females?

because females would have to receive two copies of the recessive color blindness gene to actually express the trait, because a male only needs to receive the recessive gene from his mother to be color-blind, because color blindness is an X-linked trait

In humans, brown eyes are dominant and blue eyes are recessive. If two brown-eyed individuals have a child with blue eyes, that means

both parents are heterozygous for eye color

How does the sexual life cycle increase the genetic variation in a species?

by allowing independent assortment of chromosomes, by allowing random fertilization, by allowing crossing over

A brown-eyed couple already has a child with brown eyes. What is the probability that their next child will have blue eyes?

can't predict

The centromere is a region in which

chromatids are attached to one another

If meiosis did not occur in sexually reproducing organisms then

chromosome number would double in each generation

The sources of genetic variation during meiosis are

crossing over and the random assortment of maternal and paternal chromosomes

The zygote contains the __________ complement of chromosomes

diploid

A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates

dominance

Which of the following events does not occur in prophase II?

formation of chiasmata

Of the following, the best conclusion concerning the difference between the S phase for beta and gamma is that

gamma contains more DNA than beta

After telophase I of meiosis, the chromosomal makeup of each daughter cell is

haploid, and the chromosomes are composed of two chromatids

A cell in G1

has half the amount of DNA present in a prophase nucleus

Which of the following must be true for a female to inherit hemophilia (X-linked recessive)?

her father has the disease

When pink flowered plants were crossed they produced offspring with red, pink, and white flowers in a ratio of 1:2:1. This is an example of

incomplete dominance

What are the possible phenotypes if the mother has Type A blood and the father has type AB blood?

insufficient information is available

DNA may be replicated during

interphase

Human genetics can be effectively studied using

medical records of diseases within families

The correct number of chromosomes is maintained during sexual reproduction by

meiosis, which reduces the chromosome number by half, followed by fertilization

The somatic cells derived from a single-celled zygote divide by which process?

mitosis

Pea plants were particularly well suited for use in Mendel's breeding experiments for all of the following reasons except that

peas have an unusually long generation time

A particular gene that controls seed coat color in peas also determines the susceptibility of these peas to a particular disease. This situation is referred to as

pleiotropy

Homologous chromosomes come together or pair during

prophase I

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ration of 1 red: 2 roan: 1 white?

roan, roan

__________ contain identical DNA sequences and are held together by ___________.

sister chromatids; centromeres

During prophase I of meiosis, homologous chromosomes lie side by side. This phenomenon is known as:

tetrad formation

How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?

the daughter cells have the same number of chromosomes and the same amount of DNA

A plant with purple flowers is allowed to self-pollinate. Generation after generation, it produced purple flowers. This is an example of

true-breeding

Using standard conventions for naming alleles, which of the following pairs is correct?

tt - homozygous

The genotype for a pea plant that is homozygous recessive for both height and pea color would be

ttyy

Breeding a yellow dog with a brown dog produced puppies with both yellow and brown hairs. This is an example of

variegation

Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with

two nuclei