Week 10 Quiz

A human skin cell is diploid, with 46 chromosomes in 23 pairs. Which describes a human egg cell made by meiosis?

Select one.

• Haploid, with 23 chromosomes, one from every pair
• Diploid, with 46 chromosomes, the same as the skin cell
• Haploid, with 23 half-chromosomes cut from the 46
• Diploid, with 92 chromosomes ready for fertilization

In a body cell, one chromosome of a pair came from the mother and its partner came from the father; both carry the same genes in the same order. What are these two chromosomes called?

Select one.

• Sister chromatids
• Nonsister chromatids of one chromosome
• Homologous chromosomes
• Daughter chromosomes from mitosis

In meiosis I of the three-pair model cell, what separates and moves to opposite poles?

Select one.

• The sister chromatids of each chromosome
• The homologous chromosomes of each pair, with sisters still joined
• The cytoplasm only, while the chromosomes stay together
• Single chromatids from every chromosome at once

True or false: a cell copies its DNA a second time between meiosis I and meiosis II, so that each of the four final cells gets a fresh copy.

True or false.

• True
• False

When does crossing over happen, and what does it produce?

Select one.

• In anaphase of mitosis; two identical daughter cells
• In meiosis II; new combinations between chromosomes
• In the S phase; a second copy of every chromosome
• In prophase I; new combinations within a chromosome

The three-pair model cell has a long, a medium, and a short pair, with copies B and R in each pair. From independent assortment alone, how many genetically different gametes can it make?

Select one.

• 8
• 6
• 3
• 9

A human has 23 chromosome pairs. From independent assortment alone, how many genetically different gametes can one person make?

Select one.

• 23, one kind per pair
• 46, one kind per chromosome
• 2 × 23 = 46 kinds
• 2²³ = 8,388,608 kinds

Select every statement that is true of meiosis but not of mitosis.

Select every option that applies.

• It produces four haploid cells
• Homologous chromosomes pair up in prophase I
• It produces two cells identical to the parent
• It is the division that repairs a scraped knee
• Its new cells differ genetically from each other

Evolution by natural selection is the unifying framework of biology. Why does the variation made by meiosis and fertilization matter to it?

Select one.

• Meiosis lets each organism choose the traits it will need
• Natural selection can only act on differences that already exist
• Variation makes every offspring identical to its parents
• Natural selection works only on cells copied by mitosis

In this week's lab you model meiosis with paper chromosomes labeled B and R. Which statement treats the paper cell the way a scientist treats a model?

Select one.

• It shows exactly how every real cell divides, so its count is a measurement
• It proves that every human gamete is labeled B or R
• It is a simplification that shows the counting rule, which then scales to real cells
• It replaces the need to know what happens in prophase I