answers2e_ch09 - Mastering Concepts 9.1 1 How do asexual...

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Mastering Concepts 9.1 1. How do asexual and sexual reproduction differ? Asexual reproduction requires only one parent and produces offspring that are identical, except for mutations. Sexual reproduction requires two parents and produces genetically variable offspring. 2. How can asexually reproducing organisms acquire new genetic information? Mutations can create new gene variants, and some asexually reproducing organisms can acquire new genetic information by exchanging DNA. For example, conjugation can increase genetic diversity in bacteria and Paramecium . 3. Why does sexual reproduction persist even though it requires more energy than asexual reproduction? Sexual reproduction produces the variation needed for a population to survive a changing environment. The mutations giving rise to variation in asexual populations does give variation, but not quickly enough or in great enough degrees to be successful in a rapidly changing environment. 9.2 1. What are autosomes and sex chromosomes? Autosomes are chromosomes that are the same regardless of sex, whereas the sex chromosomes determine male and female. 2. What is a karyotype? A karyotype is a chart that places the homologous chromosomes in size order, matching shape and banding patterns, after halting the cell in metaphase and staining the resulting chromosomes for better visibility. 3. How are the members of a homologous pair similar and different? A homologous pair of chromosomes is composed of two chromosomes that are similar in size, centromere location, and banding pattern. They carry the same sequence of genes (but not necessarily the same alleles) for the same traits. Each member of a homologous pair comes from a different parent. 9.3
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1. What is the difference between somatic and germ cells? Germ cells can undergo meiosis and produce haploid gametes; somatic cells are body cells that reproduce by mitosis. 2. How do haploid and diploid nuclei differ? A diploid cell (2n) has two full sets of chromosomes, with one set coming from each parent. A haploid cell (n) has only one set of chromosomes. 3. What are the roles of meiosis, gamete formation, and fertilization in a sexual life cycle? In meiosis, a diploid cell divides twice to produce four haploid nuclei, reducing the chromosome number by half. Meiosis also creates new allele combinations in the haploid nuclei. Gamete formation packages the haploid chromosomes into reproductive cells. Fertilization merges haploid gametes from two parents, producing a new diploid cell with half its chromosomes coming from each parent. 4. What is a zygote? A zygote is a fertilized egg cell that is the start of a new diploid organism. 9.4 1. What happens during interphase of meiosis? In interphase the cell grows and synthesizes all molecules necessary for cell division; DNA replicates and each chromosome is transformed into a pair of connected sister chromatids; chromatin begins to condense, and spindle proteins are produced.
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