bio 111 chapter 11 hw2

Consider a cell that has three pairs of chromosomes. What fraction of the gametes produced from this cell will contain only maternal chromosomes?

1/8

How many bivalents are formed in a cell with 20 chromosomes at the beginning of meiosis I?

10

Consider a cell that has four pairs of chromosomes. What is the number of possible chromosome orientations in that cell?

16

If a germ-line cell from an owl contains 8 picograms of DNA during G1 of interphase, how many picograms of DNA would be present in each cell during prophase I of meiosis? (Enter the number only, not the units.)

16

Nondisjunction is the failure of homologous chromosomes to separate during meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. As a result, both homologous chromosomes or both sister chromatids migrate to the same pole of the cell. This produces daughter cells with an imbalance of chromosomes. If 18 pairs of sister chromatids segregate normally during meiosis II in cats (n=19) but we have nondisjunction of 1 pair, then at the end of meiosis II we will have

2 cells with 19 chromosomes, 1 with 20, and 1 with 18

If sister chromatids failed to separate during meiosis II, what would the resulting gametes look like?

2 gametes will be normal, 1 gamete will have 2 of the effected chromosomes, and 1 gamete will have 0 of the effected chromosomes

A cell biologist examines a diploid cell from a particular species of butterfly during prometaphase of mitosis and determines that 10 centromeres are present. Based on this finding, how many chromatids should be present in a single cell from this species in metaphase I of meiosis?

20

Consider a cell that has a diploid chromosome number of 10 (2N=10). How many possible gametes can this cell produce?

32

A geneticist examines a somatic cell from a fly during metaphase of mitosis and determines that 16 chromatids are present. If a germ-line cell from this species divides by meiosis, then at the end of meiosis I (including the first cytokinesis) each cell will contain

4 chromosomes with 8 DNA molecules

If a germ-line cell from a salamander contains 10 picograms of DNA during G1 of interphase, how many picograms of DNA would be present in each gamete produced by this species? (Enter the number only, not the units.)

5

Random orientation of chromosomes during meiosis increases the amount of variation in the next generation. What other process during meiosis leads to an increase in variation in the next generation?

Crossing over between homologous chromosomes

What event in meiosis I leads to the cell becoming haploid rather than the separation of sister chromatids?

Formation of bivalents lead to spindle fibers from opposite poles attaching to homologous chromosomes.

During anaphase I of meiosis, ____I____ move towards opposite cell poles, whereas during anaphase II of meiosis, ____II____ are separated.

I = homologous chromosomes ; II = sister chromatids

Meiosis II separates sister chromatids. What might make sister chromatids differ from each other?

If sister chromatids were recombined during crossing ove

How is the formation of the spindle during mitosis and meiosis I different?

In mitosis spindle fibers from both centrosomes attach to each chromosome's centromere, in meiosis I the spindle fibers from only one centrosome attach to a chromosome's centromere

Why are two phases of meiosis necessary?

In order to both reduce the chromosome number and separate sister chromatids

A cell biologist examines a leaf cell from an alfalfa plant during metaphase of mitosis and determines that 32 chromatids are present. The role of fertilization in this species is to (Check all that apply)

Produce a new cell that has a combination of chromosomes from 2 different parents Increase the number of chromosomes per cell from 8 to 16 Combine the chromosomes from 2 haploid cells into a single diploid cell

How can you compare the complement of DNA in an interphase (G1) diploid cell and a cell that has just completed meiosis I?

They have the same amount of DNA, but the meiotic cell has half as many chromosomes.

Sister chromatids move to opposite poles of the cell during (Check all that apply.)

anaphase II of meiosis anaphase of mitosis

Which of the following events occur during prophase I?

breakdown of nuclear envelope, condensation of chromosomes, and movement of centrosomes

Which of the following is unique to meiosis?

crossing-over

In 95% of cases of Down's syndrome, there is one extra chromosome (number 21) in every cell. This aneuploid condition is most likely the result of

failure of 1 homologous pair to segregate during meiosis.

At the end of meiosis II, there are

four haploid cells, with each chromosome consisting of a single chromatid.

A cell in G2 before meiosis begins, compared with one of the four cells produced at the end of meiosis II, has

four times as much DNA and twice as many chromosomes

In animals, cells that will eventually undergo meiosis to produce the gametes are set aside early in the course of development. These cells are called

germ-line cells.

Daughter cells produced in meiosis have

half the number of chromosomes as daughter cells produced in mitosis

Which cells never divide by meiosis? (Check all that apply.) haploid cells

haploid cells somatic cells zygotes

At the end of meiosis I, each daughter cell is

haploid, and each chromosome consists of two chromatids.

The four daughter cells produced in meiosis

have one of each pair of chromosomes found in the parent cel

Synapsis is the side-by-side alignment of

homologous chromosomes.

The function of sexual reproduction is to increase variation within populations. Meiosis is the molecular mechanism that leads to sexual reproduction. As such, some of the features that make it unique lead to genetic diversity. Which of these unique features are responsible for increasing genetic diversity?

homologous recombination and reduction division

The number of chromosomes per cell is reduced from two sets to one set during

meiosis I.

During which stage of meiosis would you find a cell with a diploid chromosome number and chromosomes that are all attached to spindle fibers?

metaphase I

Random orientation of homologous chromosomes occurs in ________ of meiosis.

metaphase I

A crossover in meiosis is an exchange of genetic material between

non-sister chromatids of homologous chromosomes

The spindle apparatus is fully formed by the end of

prometaphase II.

Which of the following events occur during anaphase I?

separation of homologous chromosomes

Separation of ________ occurs in anaphase II of meiosis.

sister chromatids

Crossing over is possible due to what event that occurs in meiosis I but not mitosis?

synapsis

Which of the following features are unique to meiosis?

synapsis, homologous recombination, and reduction division

During which stage of meiosis would you find haploid cells with 1/4 as much DNA as its mother cell?

telophase II

Chromosome duplication occurs prior to both mitosis and meiosis.

true

The number of cells produced in meiosis is

twice the number of cells produced in mitosis