12 **Sexual Reproduction and Genetic Variation**Genetic variation describes the genetic differences in DNA segments of organisms within a population. Genetic variation is important because it enables some individuals to have traits that are favorable in a changing environment. Sexual reproduction is a method that introduces genetic variation.A human being is a diploid organism whose somatic cells contain 46 chromosomes found in 23 homologous pairs. Sexual reproduction requires that sex cells, or gametes, reduce their number of chromosomes in order for fertilization to occur. In humans, meiosis is the process that forms the gametes required for reproduction. The diagram shows the process of meiosis.**Diagram Explanation:**The diagram on the left illustrates the phases of meiosis, including:- **Interphase**: DNA is replicated.- **Prophase I**: Chromosomes condense and crossing over occurs.- **Metaphase I**: Chromosome pairs align in the center.- **Anaphase I**: Homologous chromosomes are pulled apart.- **Telophase I and Cytokinesis**: Cells split into two.- **Prophase II, Metaphase II, Anaphase II, Telophase II**: Chromatids are separated leading to four genetically different gametes.**Crossing Over***Definition*: The exchange of genetic material between non-sister chromatids of homologous chromosomes.As the chromosome pairs line up during prophase I, some material from the chromatids switch to the exact same position on the other chromatids. This exchange can happen multiple times on the same pair of chromosomes. The diagram shows crossing over and the resulting gametes.**Crossing Over Diagram**:- **Homologous Pair**: Two chromosomes align.- **Crossing Over**: Segments of genetic material are exchanged.- **Gametes**: Resulting in chromosomes with new combinations of genes.**Question**Which BEST describes how crossing over increases genetic diversity?- A. Crossing over increases genetic diversity because it prevents genetic mutations from occurring within the genes.- B. Crossing over increases genetic diversity because it ensures that offspring receive the dominant alleles for traits.- C. Crossing over increases genetic diversity because it results in new combinations of genes on each chromosome. *(Correct Answer)*- D. Crossing over increases genetic diversity because it creates an uneven amount of genetic material on the chromatids. ### Meiosis Process and Genetic Variation**Diagram of Meiosis:**The diagram illustrates the stages of meiosis, which is the process of cell division that reduces the chromosome number by half, resulting in the production of four gamete cells. This process is crucial for sexual reproduction and introduces genetic variation. The stages shown are:- **Prophase I**- **Metaphase I**- **Anaphase I**- **Telophase I**- **Cytokinesis**- **Prophase II**- **Metaphase II**- **Anaphase II**- **Telophase II**- **Cytokinesis**Each stage is depicted with cells dividing, showing the movement and separation of chromosomes.**Table: Introduction of Genetic Variation**1. **Crossing Over:** - Description: The exchange of genetic material between non-sister chromatids of homologous chromosomes. 2. **Law of Segregation:** - Description: Alleles that are normally paired are separated, and each gamete receives only one randomly selected copy of a gene.3. **Law of Independent Assortment:** - Description: The alleles of different genes do not influence one another and get sorted into gametes independently of one another.4. **Random Fertilization:** - Description: Fertilization is a random event where any male gamete can fuse with any female gamete to form a new individual.5. **Mutation:** - Description: Gametes receive too few or too many chromosomes.These components collectively contribute to the genetic diversity observed in sexually reproducing organisms.

Crossing over is a key cellular event that occurs during the meiosis I of cell division. During this…

Sexual Reproduction and Genetic Variation Genetic variation describes the genetic differences in DNA segments of organisms within a population. Genetic variation is important because it enables some individuals to have traits that are favorable in a changing environment. Sexual reproduction is a method that introduces genetic variation. A human being is a diploid organism whose somatic cells contain 46 chromosomes found in 23 homologous pairs. Sexual reproduction requires that sex cells, or gametes, reduce their number of chromosomes in order for fertilization to occur. In humans, meiosis is the process that forms the gametes required for reproduction. The diagram shows the process of meiosis. Cytokinesis Interphase G' Telophase 11 Anaphase II Interphase Prophase Metaphase Metaphase Prophase Crossing over chromatids of homologous chromosomes. Telophase Anaphase I 7 Genetic variation can be introduced during the process of meiosis in different ways as shown in the table. The exchange of genetic material between non-sister As the chromosome pairs line up during prophase I, some material from the chromatids switch to the exact same position on the other chromosomes. This exchange can happen multiple times on the same pair of chromosomes. The diagram shows crossing over and the resulting gametes. CA 0₂ M-1111 Homologous Pair Crossing over Which BEST describes how crossing over increases genetic diversity? C D O O A Crossing over increases genetic diversity because it prevents genetic mutations from occurring within the genes. B B D. Gametes Crossing over increases genetic diversity because it ensures that offspring receive the dominant alleles for traits. Crossing over increases genetic diversity because it results in new combinations of genes on each chromosome. Crossing over increases genetic diversity because it creates an uneven amount of genetic material on the chromatids.

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...