10 Meiosis and Sexual Life Cycles

Which of the following transmits genes from both parents to child, or from one generation of a family to another? DNA gametes somatic cells mitosis nucleotides Answer: B © 2016 Pearson Education, Inc.

Which of the following transmits genes from both parents to child, or from one generation of a family to another? DNA gametes somatic cells mitosis nucleotides © 2016 Pearson Education, Inc. 3

In animals, fertilization is to zygote as meiosis is to which of the following? mitosis diploid chromosome replication gamete Answer: E. Discuss why. © 2016 Pearson Education, Inc. 4

In animals, fertilization is to zygote as meiosis is to which of the following? mitosis diploid chromosome replication gamete © 2016 Pearson Education, Inc. 5

Privet shrubs and humans each have a diploid number of 46 chromosomes per cell. Why are the two species so dissimilar? Privet chromosomes undergo only mitosis. Privet chromosomes are shaped differently. Human chromosomes have genes grouped together differently. The two species have appreciably different genes. Privets do not have sex chromosomes. Answer: D © 2016 Pearson Education, Inc. 6

Privet shrubs and humans each have a diploid number of 46 chromosomes per cell. Why are the two species so dissimilar? Privet chromosomes undergo only mitosis. Privet chromosomes are shaped differently. Human chromosomes have genes grouped together differently. The two species have appreciably different genes. Privets do not have sex chromosomes. © 2016 Pearson Education, Inc. 7

Why is it more practical to prepare karyotypes by viewing somatic diploid cells rather than haploid gametes? Answer: Cells can be made to divide and mitosis can be halted at metaphase; both sets of chromosomes need to be examined. © 2016 Pearson Education, Inc. 8

Diploid cells may undergo either mitosis or meiosis. Can haploid cells Diploid cells may undergo either mitosis or meiosis. Can haploid cells? Why or why not? Answer: Haploid cells cannot undergo meiosis because the chromosomes cannot pair. © 2016 Pearson Education, Inc. 9

At what stage is the independent assortment of chromosomes determined? prophase I pairing of homologs anaphase II separation of homologs metaphase I alignment of paired homologs telophase I Answer: C © 2016 Pearson Education, Inc. 10

At what stage is the independent assortment of chromosomes determined? prophase I pairing of homologs anaphase II separation of homologs metaphase I alignment of paired homologs telophase I © 2016 Pearson Education, Inc. 11

What allows sister chromatids to separate in which phase of meiosis? release of cohesin along sister chromatid arms in anaphase I crossing over of chromatids in prophase I release of cohesin at centromeres in anaphase I release of cohesin at centromeres in anaphase II crossing over of homologs in prophase I Answer: D © 2016 Pearson Education, Inc. 12

What allows sister chromatids to separate in which phase of meiosis? release of cohesin along sister chromatid arms in anaphase I crossing over of chromatids in prophase I release of cohesin at centromeres in anaphase I release of cohesin at centromeres in anaphase II crossing over of homologs in prophase I © 2016 Pearson Education, Inc. 13

What are three ways in which gametes from one individual diploid cell can be different from one another? Answer: mutation, crossing over, independent assortment © 2016 Pearson Education, Inc. 14

Prophase I of meiosis is generally the longest phase of meiosis Prophase I of meiosis is generally the longest phase of meiosis. Why might this be? Answer: Chromosomes must pair and cross over, besides the cell going through mitosis-like morphological changes such as spindle formation and chromosome condensation. © 2016 Pearson Education, Inc. 15

In this cell, what phase is represented? mitotic metaphase meiosis I anaphase meiosis I metaphase meiosis II anaphase meiosis II metaphase Answer: C. See Figure 10.8. © 2016 Pearson Education, Inc. 16

In this cell, what phase is represented? mitotic metaphase meiosis I anaphase meiosis I metaphase meiosis II anaphase meiosis II metaphase © 2016 Pearson Education, Inc. 17

What is the main advantage of sexual reproduction over asexual reproduction? It is more efficient at producing offspring. Two parents can invest resources in offspring. It allows for more competition. It increases genetic variation among offspring. Answer: D © 2016 Pearson Education, Inc.

What is the main advantage of sexual reproduction over asexual reproduction? It is more efficient at producing offspring. Two parents can invest resources in offspring. It allows for more competition. It increases genetic variation among offspring. © 2016 Pearson Education, Inc.

If one wished to observe chiasmata forming during meiosis, what stage of meiosis would have the best cells to use? prophase I anaphase I prophase II anaphase II Answer: A © 2016 Pearson Education, Inc.

If one wished to observe chiasmata forming during meiosis, what stage of meiosis would have the best cells to use? prophase I anaphase I prophase II anaphase II © 2016 Pearson Education, Inc.

Through independent assortment alone, humans (2n = 46) can create 8,388,608 combinations of chromosomes. When also considering recombination, which expression is the best estimate of the number of chromosomal combinations? >>8,388,608 8,388,608 × 8,388,608 23 × 8,388,608 2 × 8,388,608 Answer: A. The point of the question is to recognize the VAST increase in possibilities afforded by recombination. A few simple calculations on the board can show exponents in the range of 1050 and higher. © 2016 Pearson Education, Inc.

Through independent assortment alone, humans (2n = 46) can create 8,388,608 combinations of chromosomes. When also considering recombination, which expression is the best estimate of the number of chromosomal combinations? >>8,388,608 8,388,608 × 8,388,608 23 × 8,388,608 2 × 8,388,608 © 2016 Pearson Education, Inc.

Consider an organism of karyotype 2n = 4 Consider an organism of karyotype 2n = 4. Which diagram properly depicts metaphase I? a b c d a b c Answer: C. This is a good visual exercise to uncover incomplete understandings of meiosis. d © 2016 Pearson Education, Inc.

Consider an organism of karyotype 2n = 4 Consider an organism of karyotype 2n = 4. Which diagram properly depicts metaphase I? a b c d a b c d © 2016 Pearson Education, Inc.

Consider an organism of karyotype 2n = 4 Consider an organism of karyotype 2n = 4. Which diagram properly depicts metaphase II? a b c d a b c d Answer: B. This is a good visual exercise to uncover incomplete understandings of meiosis. © 2016 Pearson Education, Inc.

Consider an organism of karyotype 2n = 4 Consider an organism of karyotype 2n = 4. Which diagram properly depicts metaphase II? a b c d a b c d © 2016 Pearson Education, Inc.

A haploid set of unreplicated chromosomes (n = 4) of the fruit fly Drosophila melanogaster has a mass of 0.14 pg. What is the mass of DNA in single Drosophila cell in prophase I? 0.14 pg 0.28 pg 0.42 pg 0.56 pg Answer: D. This is a quantitative question that also helps with understanding the relationships between karyotypes, replication, sister chromatids, homologs, and meiosis. © 2016 Pearson Education, Inc.

A haploid set of unreplicated chromosomes (n = 4) of the fruit fly Drosophila melanogaster has a mass of 0.14 pg. What is the mass of DNA in single Drosophila cell in prophase I? 0.14 pg 0.28 pg 0.42 pg 0.56 pg © 2016 Pearson Education, Inc.

A haploid set of unreplicated chromosomes (n = 4) of the fruit fly Drosophila melanogaster has a mass of 0.14 pg. What is the mass of DNA in single Drosophila cell in prophase II? 0.14 pg 0.28 pg 0.42 pg 0.56 pg Answer: B. This is a quantitative question that also helps with understanding the relationships between karyotypes, replication, sister chromatids, homologs, and meiosis. © 2016 Pearson Education, Inc.

A haploid set of unreplicated chromosomes (n = 4) of the fruit fly Drosophila melanogaster has a mass of 0.14 pg. What is the mass of DNA in single Drosophila cell in prophase II? 0.14 pg 0.28 pg 0.42 pg 0.56 pg © 2016 Pearson Education, Inc.

A haploid set of unreplicated chromosomes (n = 4) of the fruit fly Drosophila melanogaster has a mass of 0.14 pg. What is the mass of DNA in single Drosophila cell at the end of telophase II? 0.14 pg 0.28 pg 0.42 pg 0.56 pg Answer: A. This is a quantitative question that also helps with understanding the relationships between karyotypes, replication, sister chromatids, homologs, and meiosis. © 2016 Pearson Education, Inc.

A haploid set of unreplicated chromosomes (n = 4) of the fruit fly Drosophila melanogaster has a mass of 0.14 pg. What is the mass of DNA in single Drosophila cell at the end of telophase II? 0.14 pg 0.28 pg 0.42 pg 0.56 pg © 2016 Pearson Education, Inc.