End-of-topic test: Meiosis

Unit 5 · Topic 5.1 end-of-topic test

Answer every question. For each multiple-choice question, pick one option and press Check; the feedback tells you what a wrong choice assumed. For the two free-response questions, write your answer in full sentences and show any calculation, then open the scoring guide and mark your own work against it. In every drawing, a chromosome from the mother is teal and one from the father is dark.

Question 1

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

A beetle’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 teal and the father’s are dark.

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 mouse’s homologous pair with the fur-color position boxed: black on the maternal homolog, brown on the paternal.

In mice, one gene sets fur color. One mouse’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 brown version.

What are the black version and the brown version?

A. Two different genes at two positions B. Two sister chromatids of one chromosome C. Two alleles of the one fur-color gene D. Two complete chromosome sets

Question 3

A goat’s body cells each hold 60 chromosomes. A goat’s egg holds 30 chromosomes.

Which statement describes the egg?

A. Haploid: one complete chromosome set B. Diploid, because 30 chromosomes are still two sets C. Neither, because any 30 of the 60 could be present D. Haploid, but not a complete set

Question 4

In a newt, an egg and a sperm fuse, and a swimming larva later grows by many cell divisions.

Which cell is the zygote?

A. The egg before the sperm reaches it B. The sperm after it enters the egg C. Each cell of the larva’s tail D. The single cell made when the egg and sperm fuse

Question 5

A lizard’s body cells each hold 36 chromosomes. Suppose its gametes carried 36 chromosomes each, like its body cells, and still fused at fertilization.

What would happen to the chromosome count of its offspring?

A. It would stay at 36, because fertilization halves the count B. It would be 18, because each gamete gives half C. It would be 72 in the offspring and then return to 36 D. It would be 72 in the offspring, and double again each generation

Question 6

A cell in the testis of a rabbit goes through meiosis.

Which statement describes meiosis?

A. One DNA copying, then two divisions: four haploid cells B. One DNA copying, then one division: two diploid cells C. Two DNA copyings, then two divisions: four diploid cells D. No DNA copying, then two divisions: two haploid cells

Question 7

Two moth cells, numbered 1 and 2, with chromosomes moving toward the poles.

Two cells from a moth are drawn below, numbered 1 and 2, each frozen while its chromosomes move toward the poles.

Which drawing shows meiosis I, and what shows it?

A. Drawing 1, because whole chromosomes of two chromatids are moving apart B. Drawing 2, because the chromosomes are moving toward the poles C. Drawing 1, because the sister chromatids are moving apart D. Drawing 2, because whole chromosomes are moving apart

Question 8

A plant’s body cells each hold 20 chromosomes. One cell goes through meiosis.

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 lily cell with six condensed chromosomes lying in three pairs, spindle fibers reaching in, no nuclear envelope.

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

Which stage is the cell in, and what in the drawing shows it?

A. Prophase of mitosis, because the chromosomes have condensed B. Metaphase I, because the pairs have formed C. Prophase II, because the envelope has broken down D. Prophase I, because the homologs lie paired along their length

Question 10

Two grasshopper cells, numbered 1 and 2, with chromosomes across the middle and fibers attached.

Two cells from a grasshopper are drawn below, numbered 1 and 2. In both, the chromosomes sit across the middle of the cell with fibers attached.

Which drawing shows metaphase I, and what tells you?

A. Drawing 1, because every chromosome sits on the equator B. Drawing 2, because homologous pairs sit at the equator side by side C. Drawing 1, because the chromosomes are still X-shaped D. Both, because fibers from both poles reach every chromosome

Question 11

In a cell from an onion 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 plant whose body cells hold 10 chromosomes has just finished meiosis I and cytokinesis.

How many chromosomes does each of the two cells hold, and how many chromatids does each of those chromosomes have?

A. 10, each a single chromatid B. 5, each still two sister chromatids C. 10, each still two sister chromatids D. 5, each a single chromatid

Question 13

A snail cell with three X-shaped chromosomes in one row across the middle, fibers from both poles.

A cell from a snail whose body cells hold six chromosomes is drawn below, part way through meiosis.

Which stage is the cell in?

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

Question 14

A cicada cell with a furrow across its middle and a dashed envelope on each side around two X-shaped chromosomes.

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

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 toad’s ovary holds 8 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

One of the two cells that a rabbit’s meiosis I produced now goes through meiosis II.

Which statement describes the chromosome number of the two cells this division produces?

A. It halves, because a division always halves the count B. It doubles, because each chromatid becomes a chromosome C. It halves, because the sister chromatids are copies D. It stays the same, because each cell receives one chromatid of every chromosome

Question 17

A cell in the anther of a tulip, whose body cells hold 24 chromosomes, completes meiosis.

What does each of the four cells hold?

A. 24 single-chromatid chromosomes B. 12 chromosomes, each still two sister chromatids C. 12 single-chromatid chromosomes, one of every pair D. 6 single-chromatid chromosomes, half of a set

Question 18

A fish’s body cells each hold 16 chromosomes. One cell copies its DNA.

How many chromatids does the cell hold after S phase?

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 divides by meiosis.

In which feature do the two divisions differ?

A. Whether the DNA was copied once in S phase before the division B. Whether a spindle moves the chromosomes C. Whether the stages are named prophase, metaphase, anaphase and telophase D. Whether homologous pairs come together before the chromosomes part

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 · 4 points

Two cells from one lily plant, whose body cells hold 24 chromosomes, are drawn below at metaphase, labeled cell 1 and cell 2. Cell 1 came from a root tip and cell 2 from an anther. Only a few of the chromosomes are drawn, as X shapes.

Cell 1: X-shaped chromosomes in one column across the middle, fibers from both poles. Cell 2: X-shaped chromosomes standing in pairs across the middle, each pair two chromosomes wide.

(a) Identify the division each cell is in, and describe the feature of the drawing that shows it. (1 point)

A full-credit answer: Cell 1 is in mitosis: its chromosomes stand in a single row at the equator, one deep. Cell 2 is in meiosis I: its chromosomes stand in homologous pairs at the equator, two wide.

Check the box for each point your answer earns

cell 1 mitosis (a single row of chromosomes) and cell 2 meiosis I (homologous pairs at the equator).

Common slip: Reading the X shapes as the sign of one division. Both cells have copied chromosomes; pairs against single chromosomes at the equator is what differs.

(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 the number of cells each division finally produces and the chromosome number of each. (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

two cells of 24 from cell 1 and four cells of 12 from cell 2.

Common slip: Halving the count for both, or giving cell 2 two cells. Meiosis halves the count and divides twice.

(d) Explain why the cells cell 1 produces are genetically identical to cell 1, and why the cells cell 2 produces differ from cell 2. (1 point)

A full-credit answer: Every chromosome of cell 1 was copied once in S phase into two identical sister chromatids, and anaphase sends one chromatid of every pair to each pole, so each daughter cell receives one complete copy of the genome. Cell 2’s four cells each hold only one member of each homologous pair, and the two members of a pair may carry different alleles, so the four cells differ from one another and from cell 2.

Check the box for each point your answer earns

mitosis gives identical copies because the sister chromatids are identical and one of each goes to each cell; meiosis gives one member of each pair, and the members may carry different alleles.

Common slip: Saying meiosis’s cells differ because they are haploid. Halving the count is not the reason; it is that each cell gets one member of each pair and the members differ in their alleles.

Free-response score: 0 of 4

Free response 2 · Conceptual Analysis · 4 points

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

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

(a) Calculate the DNA per cell after S phase. (1 point)

Write down the values in the question:

DNA before copying = 4 pg

Write down the equation:

DNA after S phase = 2 \times DNA before copying

Substitute the values into the equation:

DNA after S phase = 2 \times 4 pg = 8 pg

A full-credit answer: 8 pg.

(b) Describe the state of each chromosome in the cell after S phase. (1 point)

A full-credit answer: Every chromosome has been copied into two identical sister chromatids joined at one centromere, so the cell still holds 12 chromosomes, each two chromatids.

Check the box for each point your answer earns

every chromosome is two sister chromatids joined at a centromere (copied), still 12 chromosomes.

Common slip: Saying the cell has 24 chromosomes. Copying doubles the chromatids, not the chromosomes; count 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.

(d) Predict the DNA per cell after meiosis II if the cell had copied its DNA again between the two divisions, and explain what the measured 2 pg shows. (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, and meiosis II would have left 4 pg in each of the four cells. The measured 2 pg is half of 4 pg, so the cells entered meiosis II with the DNA they left meiosis I with: no copying happened between the divisions.

Check the box for each point your answer earns

4 pg if copied, and the measured 2 pg shows no DNA copying between meiosis I and meiosis II.

Common slip: Predicting 8 pg. 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

Multiple choice checked: 0 of 19 correct.

Next: Shuffled pairs