End-of-topic test: Meiosis

Unit 5 · Topic 5.1 end-of-topic test

Suggested time: about 54 minutes. Answer everything, then press Submit the test to see the feedback and scoring guides.

Answer every question. For each multiple-choice question, pick one option. When you have answered every question, press Submit the test; the feedback then gives the reasoning for each. For the free-response questions, write one short sentence for each step of your reasoning, each on its own line, and make every link clear (so, because, therefore). That is what the exam’s ‘paragraph form’ means for you: linked sentences, not bullet points. Show any calculation, then open the scoring guide and mark your own work against it. In every drawing, a chromosome from the mother is dark and one from the father is light.

Question 1

Six chromosomes from one midge cell, numbered 1 to 6.

A midge’s body cells hold six chromosomes. The six from one cell are drawn below and numbered 1 to 6. In every drawing here the mother’s chromosomes are dark and the father’s are light.

Which two chromosomes are a homologous pair?

A. Chromosomes 1 and 2 B. Chromosomes 1 and 4 C. Chromosomes 1 and 6 D. Chromosomes 3 and 6

Question 2

One guinea pig’s homologous pair with the fur-color position boxed: black on the maternal homolog, cream on the paternal.

In guinea pigs, a gene sets fur color. One guinea pig’s homologous pair is drawn below: at the fur-color position, the homolog from the mother carries the black version of the gene and the homolog from the father carries the cream version.

What are the black version and the cream version?

A. Two different genes, one for black fur and one for cream fur B. Two sister chromatids of one chromosome C. Two alleles of the fur-color gene D. Two complete chromosome sets

Question 3

A chimpanzee’s body cells each hold 48 chromosomes.

Which of the following cells is haploid?

A. A cell with 24 chromosomes, one of every pair B. A cell holding both members of 12 pairs and neither member of the other 12 C. A cell with 48 chromosomes, two of every length D. A cell with 96 chromosomes, four of every length

Question 4

An axolotl’s body cells hold 28 chromosomes. An egg and a sperm fuse.

Which statement about the zygote is correct?

A. It holds 14 chromosomes, one set from each parent B. It holds 56 chromosomes, both parents’ full sets C. It is the egg before the sperm enters it D. It holds 28 chromosomes and divides by mitosis to build the body

Question 5

An iguana’s body cells hold 36 chromosomes and its gametes hold 18.

Why must the chromosome count be halved before fertilization?

A. Because a gamete is too small to hold a full set of chromosomes B. Because mitosis after fertilization would halve the count back down anyway C. Because the zygote keeps only one of the two parents’ sets D. Because fertilization adds the two sets together, so two full sets would give 72

Question 6

One of the two cells from a badger’s meiosis I begins meiosis II. A student says that the cell’s homologous pairs come together again before meiosis II can part them.

Which of the following statements about the student’s claim is correct?

A. The student is right: the pairs come together before each of the two divisions B. The student is wrong: the cell is haploid, so it holds no homologous pairs to bring together C. The student is right: meiosis II is a repeat of meiosis I D. The student is wrong: the cell still holds every pair, and the pairs do not need to come together again

Question 7

A shrew cell, frozen part way through a division.

A cell from a shrew is drawn below, frozen part way through a division.

Which stage is the cell in?

A. Anaphase I B. Anaphase II C. Anaphase of mitosis D. Metaphase I

Question 8

A plant’s body cells each hold 20 chromosomes. One cell goes through meiosis. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

What is the chromosome count per cell after meiosis I, and after meiosis II?

A. 20 after meiosis I, and 10 after meiosis II B. 10 after meiosis I, and 5 after meiosis II C. 10 after meiosis I, and 10 after meiosis II D. 20 after meiosis I, and 20 after meiosis II

Question 9

A sedge cell, part way through a division.

A cell from a species of sedge whose body cells hold six chromosomes is drawn below. Its chromosomes are condensed, and there is no nuclear envelope.

Which feature of the drawing belongs to prophase I alone, so that it rules out prophase of mitosis?

A. The chromosomes have condensed B. The nuclear envelope has broken down C. Spindle fibers reach in from the two poles D. The homologs lie paired along their length

Question 10

Two mite cells, numbered 1 and 2, each frozen part way through a division.

A mite’s body cells hold four chromosomes. Two of its cells are drawn below, numbered 1 and 2, each frozen part way through a division. All the chromosomes are drawn. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

Which drawing shows anaphase I?

A. Drawing 1 only B. Drawing 2 only C. Both drawings D. Neither drawing

Question 11

In a cell from a leek flower at anaphase I, the spindle fibers shorten and chromosomes move toward the two poles.

Which partners are being pulled apart?

A. The two members of each homologous pair B. The two sister chromatids of each chromosome C. The two members of each pair and the two chromatids of each member, all at once D. Nothing within a pair: each whole pair is pulled to one pole or the other

Question 12

A cell from a bean plant whose body cells hold 22 chromosomes has just finished meiosis I and cytokinesis. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

How many chromatids does each of the two cells hold?

A. 11 B. 22 C. 44 D. 88

Question 13

An animal cell, part way through a division.

A cell from an animal whose body cells hold six chromosomes is drawn below, part way through meiosis. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

Which stage is the cell in?

A. Metaphase I B. Prophase II C. Metaphase II D. Anaphase II

Question 14

A cicada cell, part way through a division.

A cell from a cicada is drawn below, part way through a division.

Which stage is the cell in?

A. Anaphase I B. Telophase I C. Telophase II D. Telophase of mitosis

Question 15

A cell in a quail’s ovary holds 8 picograms (pg) of DNA before it copies its DNA. It then goes through meiosis.

How much DNA does each cell hold after meiosis I?

A. 16 pg B. 8 pg C. 4 pg D. 2 pg

Question 16

Three drawings from a hedgehog’s cells, numbered 1 to 3.

Three drawings of chromosomes from a hedgehog’s cells are numbered 1 to 3 below. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

Which of the drawings show a homologous pair?

A. Drawing 1 only B. Drawing 2 only C. Drawings 2 and 3 D. Drawings 1, 2 and 3

Question 17

Each of the four cells at the end of meiosis in a tulip holds 12 single-chromatid chromosomes. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

How many chromosomes does a tulip body cell hold, and how many homologous pairs?

A. 12 chromosomes, 6 pairs B. 48 chromosomes, 24 pairs C. 24 chromosomes, 12 pairs D. 12 chromosomes, 12 pairs

Question 18

A fish’s body cells each hold 16 chromosomes. One cell copies its DNA. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

How many chromatids does the cell hold after it copies its DNA?

A. 32 B. 16 C. 8 D. 64

Question 19

A cell in a wheat plant’s root divides by mitosis, and a cell in its anther, the part of the flower that makes pollen, divides by meiosis.

Which feature do the two divisions share?

A. Homologous pairs come together before the chromosomes part B. Four cells are produced C. The chromosome number halves D. The DNA is copied once before the division begins

How to tackle the free-response questions. Read the verb first: describe asks what you see or know; explain asks why or how, so name the mechanism; predict asks what will happen and why; justify asks for the evidence that supports a claim. Each point is earned by one idea, stated in a sentence that names the thing and the mechanism. Extra words earn nothing; a wrong extra can lose the point. If there is a figure or table, use what it shows. When you finish, check the box for each point your answer earns and compare your sentences with the full-credit answer.

Free response 1 · Scientific Investigation · 6 points

Two cells from one tomato plant, whose body cells hold 24 chromosomes, are drawn below at metaphase, labeled cell 1 and cell 2. Both cells hold all 24 chromosomes, but only a few of them are drawn, as X shapes. To count chromosomes, count centromeres. A joined pair of sister chromatids is one chromosome, and a separated chromatid is one chromosome.

Cell 1, left, and cell 2, right, each at metaphase.

(a) Determine whether each cell is in mitosis, meiosis I or meiosis II, using the drawings and the chromosome count. (2 points)

A full-credit answer: Cell 1’s chromosomes stand in a single row at the equator, one deep.
A single row is what mitosis and meiosis II both show.
Cell 1 holds all 24 chromosomes, and a cell in meiosis II holds only 12, so cell 1 is in mitosis.
Cell 2’s chromosomes stand in homologous pairs at the equator, two wide.
Pairs at the equator is what only meiosis I shows, so cell 2 is in meiosis I.

Check the box for each point your answer earns

cell 1 in mitosis, with the ground: a single row at the equator AND the full count of 24 chromosomes (a cell in meiosis II holds 12). cell 2 in meiosis I, with the ground: homologous pairs at the equator, two wide.

Do not award: the number of chromosomes drawn as the feature for either cell; only a few are drawn.

Do not award: a single row alone for cell 1; metaphase II also shows a single row.

Common slip: Naming mitosis for cell 1 from the single row alone. Metaphase II also shows a single row; the full count of 24, where a cell in meiosis II holds 12, is what settles mitosis.

(b) Calculate the number of chromatids in cell 1 at the stage drawn. (1 point)

Write down the values in the question:

2 n = 24

Write down the equation:

chromatids at metaphase = 2 \times 2 n

Substitute the values into the equation:

chromatids = 2 \times 24 = 48

A full-credit answer: 48 chromatids.

(c) Predict, for each cell, how many cells there will be, and the chromosome number of each, when the cell has finished every division it will go through. (1 point)

A full-credit answer: Cell 1 produces two cells with 24 chromosomes each.
Cell 2 produces four cells with 12 chromosomes each.

Check the box for each point your answer earns

cell 1 two cells of 24 chromosomes AND cell 2 four cells of 12 chromosomes, the counts when all division is over.

Do not award: two cells of 12 for cell 2; that is the end of meiosis I, and meiosis II still follows.

Common slip: Stopping cell 2 at the end of meiosis I (two cells of 12), or halving cell 1’s count. Meiosis divides twice; mitosis keeps the count.

(d) Explain, for each cell, whether the daughter cells match it genetically, and why. (2 points)

A full-credit answer: Every chromosome of cell 1 was copied in S phase into two identical sister chromatids.
At anaphase the spindle sends one chromatid of every chromosome to each pole.
So each daughter cell receives the same 24 chromosomes as cell 1: the daughter cells match it.
Each of cell 2’s four cells holds one member of each pair.
The two members of a pair may carry different alleles.
So cell 2’s cells do not match cell 2.

Check the box for each point your answer earns

cell 1’s daughter cells match it, because the sister chromatids are identical copies and each daughter cell receives one of every chromosome. cell 2’s cells do not match it, because each receives only one member of each pair (it is haploid), and the two members may carry different alleles. Accept the haploid ground on its own.

Common slip: Saying only that cell 2’s cells have fewer chromosomes, without saying what is missing. What is missing is the other member of each pair, and the two members may carry different alleles.

Free-response score: 0 of 6

Free response 2 · Conceptual Analysis · 4 points

The DNA in one cell of a plant, whose body cells hold 12 chromosomes, was measured before the cell copied its DNA, and again in one cell at the end of meiosis. The table below gives the two measurements in picograms (pg).

DNA per cell, in picograms, before copying and after meiosis II.

(a) Calculate the DNA per cell after the cell copies its DNA. (1 point)

Write down the values in the question:

DNA before copying = 4 pg

Write down the equation:

DNA after copying = 2 \times DNA before copying

Substitute the values into the equation:

DNA after copying = 2 \times 4 pg = 8 pg

A full-credit answer: 8 pg.

(b) Explain why the chromosome count stays at 12 after the cell copies its DNA. (1 point)

A full-credit answer: The copying makes two identical sister chromatids of every chromosome.
The two sister chromatids stay joined at one centromere.
Chromosomes are counted by centromere.
So the cell still holds 12 chromosomes, each now two chromatids.

Check the box for each point your answer earns

the reason — each chromosome is now two sister chromatids joined at one centromere, and chromosomes are counted by centromere, so the count stays 12.

Common slip: Saying the cell has 24 chromosomes after the copying. Copying doubles the chromatids, not the centromeres.

(c) Calculate the number of chromatids in one cell after meiosis I. (1 point)

Write down the values in the question:

2 n = 12

n = 6

Write down the equation:

chromatids after meiosis I = 2 \times n

Substitute the values into the equation:

chromatids after meiosis I = 2 \times 6 = 12

A full-credit answer: 12 chromatids: 6 chromosomes, each still two chromatids.

Do not award: 12 with no working.

(d) Evaluate the claim that the plant cell copied its DNA again between meiosis I and meiosis II, using the measured 2 pg. (1 point)

A full-credit answer: After meiosis I each cell holds 4 pg, half of the 8 pg.
If the DNA had been copied again, each cell would have gone from 4 pg to 8 pg.
Meiosis II would then have halved that 8 pg, leaving 4 pg in each of the four cells.
The measured value is 2 pg, half of 4 pg.
So the claim is not supported: no copying happened between the two divisions.

Check the box for each point your answer earns

the judgement (the claim is not supported) AND the ground (a second copying would leave 4 pg per cell after meiosis II; the measured 2 pg is half of that).

Common slip: Predicting 8 pg for a second copying. A second copying would double 4 pg to 8 pg, but meiosis II then halves it again to 4 pg.

Free-response score: 0 of 4

Feedback and scoring guides appear after you submit.

Multiple choice checked: 0 of 19 correct.

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