Genetics Ch. 2

In which stage of the cell cycle is G0 located?

G1

If a typical somatic cell has 64 chromosomes, how many chromosomes are expected in each gamete of that organism?

32

In a healthy male, how many sperm cells would be expected to be formed from (a) 400 primary spermatocytes? (b) 400 secondary spermatocytes?

(a) 1600; (b) 800

List in order of occurrence the phases of (a) mitosis and (b) prophase I of meiosis

(a) prophase, prometaphase, metaphase, anaphase, telophase (b) leptonema, zygonema, pachynema, diplonema, diakinesis

In a healthy female, how many secondary oocytes would be expected to form from 100 primary oocytes? How many first polar bodies would be expected from 100 primary oocytes?

100; 100

The ant, Myrmecia pilosula, is found in Australia and is named bulldog because of its aggressive behavior. It is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words, 2n = 2. (Males are haploid and have just one chromosome.) Which of the following figures would most likely represent a correct configuration of chromosomes in a metaphase I cell of a female?

2 full chromosomes not centered

The house fly, Musca domestica, has a haploid chromosome number of 6. How many chromatids should be present in a diploid, somatic, metaphase cell?

24

Myrmecia pilosula actually consists of several virtually identical, closely related species, with females having chromosome numbers of 18, 20, 32, 48, 60, 62, and 64. Assume one crossed a female of species (A) with 32 chromosomes and a male of species (B) with 9 chromosomes (males are haploid, and each gamete contains the n complement). How many chromosomes would one expect in the body (somatic) cells of the female offspring?

25

In an organism with 52 chromosomes, how many bivalents would be expected to form during meiosis?

26

How many haploid sets of chromosomes are present in a diploid individual cell with a chromosome number of 46? 32?

2;2

How many haploid sets of chromosomes are present in an individual cell that is tetraploid (4n)?

4

There is about as much nuclear DNA in a primary spermatocyte as in ________ (how many) spermatids?

4

For the purposes of this question, assume that a G1 somatic cell nucleus in a female Myrmecia pilosula contains 2 picograms of DNA. How much DNA would be expected in a metaphase I cell of a female?

4 picograms

You may have heard through various media of an animal alleged to be the hybrid of a rabbit and a cat. Given that the cat (Felis domesticus) has a diploid chromosome number of 38 and a rabbit (Oryctolagus cuniculus) has a diploid chromosome number of 44, what would be the expected chromosome number in the somatic tissues of this alleged hybrid?

41

The horse (Equus caballus) has 32 pairs of chromosomes, whereas the donkey (Equus asinus) has 31 pairs of chromosomes. How many chromosomes would be expected in the somatic tissue of a mule?

63

Regarding the mitotic cell cycle, what is meant by a checkpoint?

A checkpoint is the portion of a cell cycle that is sensitive to a variety of conditions that impact the eventual health of the cell or individual. Such checkpoints often restrict passage to the next event in the cell cycle.

Assume that the somatic cells of a male contain one pair of homologous chromosomes (e.g., AaAb), and an additional chromosome without a homolog (e.g., W). What chromosomal combinations would be expected in the meiotic products (spermatids) of a single primary spermatocyte? (There may be more than one answer.)

AaW, AaW, Ab, Ab or Aa, Aa, AbW, AbW

During interphase of the cell cycle, ________.

DNA content essentially doubles

During meiosis, chromosome number reduction takes place in anaphase II. (T/V)

False

When cells withdraw from the continuous cell cycle and enter a "quiescent" phase, they are said to be in what stage?

G0

Trisomy 21 or Down syndrome occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome #21. Such individuals therefore have 47 chromosomes. Assume that a mating occurs between a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome? Justify your answer.

One-half of the offspring would be expected to have Down syndrome because of 2 × 1 segregation of chromosome #21 at anaphase I.

A chromosome may contain one or two chromatids in different phases of the mitotic or meiotic cell cycle. (T/V)

TRUE

An organism with a diploid chromosome number of 46 will produce 223 combinations of chromosomes at the end of meiosis.

TRUE

If a typical G1 nucleus contains 2C (two complements) of DNA, a gamete that is haploid (n) contains 1C of DNA. (T/V)

TRUE

A bivalent at pachytene contains four chromatids. (T/V)

True

An organism with a haploid number of 10 will produce 1024 combinations of chromosomes at the end of meiosis. (T/V)

True

If a typical G1 nucleus is 2n and contains 2C (two complements) of DNA, a prophase I cell is 2n and contains 4C of DNA. (T/V)

True

S phase is the part of interphase when DNA duplication takes place. (T/V)

True

The centromere of a chromosome separates during anaphase. (T/V)

True

The meiotic cell cycle involves two cell divisions but only one DNA replication. (T/V)

True

What is meant by the term chiasma?

areas where chromatids intertwine during meiosis

Name two cellular organelles, each having genetic material, that are involved in either photosynthesis or respiration.

chloroplasts and mitochondria

Two terms, reductional and equational, generally refer to which stages of meiosis (I or II)?

meiosis I and meiosis II, respectively

After which meiotic stage (meiosis I or II) would one expect monads to be formed?

meiosis II

List four terms used to describe the normal morphologies, with respect to arm ratio, of eukaryotic chromosomes.

metacentric, submetacentric, acrocentric, telocentric

List, in order of appearance, all the cell types expected to be formed during oogenesis

oogonium, primary oocyte, secondary oocyte and first polar body, ootid and second polar body

Name two evolutionarily significant benefits of meiosis that are not present in mitosis.

reshuffling of homologous chromosomes and crossing over

The nucleolus organizer (NOR) is responsible for production of what type of cell structure?

ribosome

Homologous chromosomes are those that can be matched by virtue of their similar structure and function within a nucleus. Which chromosomes making up a genome do not follow the same characteristics of homology?

sex-determining chromosomes

What is the outcome of synapsis, a significant event in meiosis?

side-by-side alignment of homologous chromosomes

List, in order of appearance, all the cell types expected to be formed during (a) spermatogenesis

spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid, spermatozoa