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L20 The sexual cycle, meiosis and the value of sex

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• Explain what the sexual cycle is. • Identify the structures of meiosis. • Summarise the order of events in meiosis. • Compare and contrast the events that occur in meiosis and mitosis. • Illustrate how meiosis leads to gametic and zygotic diversity
Mer Scott
Quiz by Mer Scott, updated more than 1 year ago
Mer Scott
Created by Mer Scott almost 7 years ago
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Resource summary

Question 1

Question
Choose the incorrect statement about the sexual cycle.
Answer
  • Adult eukaryotic cells are diploid.
  • Cells in the ovaries and testes are the only cells which undergo meiosis.
  • Gametic cells are diploid.
  • The ovum or sperm is haploid.
  • When an adult gametic cell undergoes mitosis, it is still diploid.

Question 2

Question
Choose the correct statements.
Answer
  • Two gametes which are haploid fuse to make a diploid zygote.
  • Meiosis halves the number of of chromosomes going into gametes.
  • Mitosis creates two haploid daughter cells.
  • Meiosis creates four diploid daughter cells.

Question 3

Question
Meiosis I separates sister chromatids.
Answer
  • True
  • False

Question 4

Question
Choose the incorrect statement about Meiosis I.
Answer
  • Crossing over occurs between homologous pairs during metaphase.
  • Four sister chromatids form a tetrad in prophase.
  • Crossing over occurs at a chiasmata, the joining of a locus on each chromatid.
  • In anaphase I, sister chromatids remain attached when the spindles shorten.

Question 5

Question
Meiosis I produces two diploid cells.
Answer
  • True
  • False

Question 6

Question
Choose the statements about Meiosis II that are false.
Answer
  • Two haploid cells with doubled chromosomes enter prophase II.
  • Crossing over occurs between sister chromosomes during prophase II.
  • In anaphase II, sister chromatids are pulled apart.
  • At the end of telophase II, two haploid cells are present.

Question 7

Question
There are no chiasmata formed in mitosis.
Answer
  • True
  • False

Question 8

Question
If the sperm of a mouse has 3 picograms of DNA, the amount of DNA in the nucleus of a somatic cell about to divide by mitosis would be:
Answer
  • 3pg
  • 6pg
  • 12pg
  • 24pg

Question 9

Question
The structures that move to the spindle poles at anaphase of meiosis I usually differ from those that move to the poles at anaphase II with respect to:
Answer
  • chromatid number
  • gene copy number
  • the ratio of maternal to paternal genes
  • all of the above

Question 10

Question
In males, diploid [blank_start]primary[blank_end] spermatocytes undergo meiosis [blank_start]I[blank_end] to produce two [blank_start]haploid[blank_end] secondary spermatocytes. These undergo meiosis [blank_start]II[blank_end] to form haploid spermatids, or, sperm. Tens of [blank_start]millions[blank_end] of these can be produced per day. In females, 500,000 [blank_start]diploid primary[blank_end] oocytes are present in a six month old fetus. These begin meiosis I but are suspended in [blank_start]prophase I[blank_end] until ovulation. After ovulation, meiosis I [blank_start]finished[blank_end] and produces two haploid cells, one becomes a [blank_start]secondary[blank_end] oocyte and the other becomes the first polar body. The first polar body is suspended in [blank_start]metaphase II[blank_end] until fertilisation, upon which it completes meiosis II and makes two [blank_start]haploid polar bodies[blank_end]. The secondary oocyte undergoes meiosis II to produce the fourth polar body, and the [blank_start]ovum[blank_end], which are both haploid. [blank_start]Less[blank_end] than 500 ovum will be produced in the female lifespan.
Answer
  • primary
  • I
  • haploid
  • II
  • millions
  • thousands
  • diploid primary
  • prophase I
  • finishes
  • secondary
  • metaphase II
  • haploid polar bodies
  • ovum
  • Less

Question 11

Question
How can you calculate the possible number of gamete combinations using the haploid number n?
Answer
  • 2n
  • 2n^2
  • n^2
  • 2^n

Question 12

Question
Because of sexual reproduction, and because human's haploid number is 23 chromosomes, there are approximately 8 million gametic combinations.
Answer
  • True
  • False

Question 13

Question
Drosophila males do not undergo crossing over at meiosis. If Drosophila has a diploid number of 8, how many genetically distinct types of gametes can be produced by a male Drosophila?
Answer
  • 4
  • 8
  • 16
  • 32

Question 14

Question
Presence of the sexual cycle in a species has the potential to:
Answer
  • decrease competition among offspring
  • allow the species to respond better to parasites
  • increase evolutionary flexibility
  • all of the above
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