Chapter 4 - Section 4.4 - Study Guide - Assess Your Learning Outcomes - Page 137: 2

**1. Organization of the Karyotype:** - A karyotype is a visual representation of an individual's complete set of chromosomes, arranged in a specific order. It's typically created by staining and photographing an individual's chromosomes during metaphase of cell division and then arranging them by size, banding patterns, and other characteristics. - In humans, karyotypes are usually organized into 23 pairs of chromosomes, with one chromosome from each pair coming from the mother (maternal) and the other from the father (paternal). These pairs are numbered from 1 to 22, with the last pair being the sex chromosomes (X and Y), determining an individual's sex. **2. Number of Homologous Pairs of Human Chromosomes:** - There are 22 pairs of homologous (similar in size and genetic content) chromosomes in humans, known as autosomes. - The 23rd pair consists of the sex chromosomes (X and Y), which determine an individual's sex. In females, this pair is XX, while in males, it is XY. **3. Why Chromosomes Occur in Homologous Pairs:** - Chromosomes occur in homologous pairs to allow for genetic diversity and to facilitate the process of sexual reproduction. Each member of a homologous pair carries similar genes but may have variations (alleles) that can lead to different traits. This diversity is essential for the adaptation and evolution of a species. **4. Differences Between Haploid and Diploid Cells:** - **Haploid Cells:** Haploid cells have half the number of chromosomes as diploid cells. In humans, haploid cells contain 23 chromosomes. Haploid cells are typically involved in sexual reproduction. In males, sperm cells are haploid, while in females, egg cells are haploid. When a haploid sperm fertilizes a haploid egg, a diploid zygote is formed, which then develops into a new individual. - **Diploid Cells:** Diploid cells have a full set of chromosomes, meaning they have two copies (homologous pairs) of each chromosome. In humans, diploid cells have 46 chromosomes (23 pairs). Most somatic (body) cells in humans are diploid, including skin cells, muscle cells, and most other cell types. Diploid cells contain genetic information from both parents, which contributes to an individual's genetic diversity. **5. Differences Between Germ Cells and Somatic Cells:** - **Germ Cells:** Germ cells are specialized cells that give rise to gametes (sperm and egg cells) through a process called meiosis. Germ cells are haploid, meaning they have half the number of chromosomes as somatic cells (23 in humans). They are essential for sexual reproduction, as they combine during fertilization to form a diploid zygote. - **Somatic Cells:** Somatic cells are all the non-reproductive cells in an organism. They make up the tissues and organs of the body. Somatic cells are typically diploid, containing the full complement of chromosomes (46 in humans). They undergo mitosis, a process of cell division, to produce new somatic cells for growth, repair, and maintenance of the body. In summary, the organization of the karyotype in humans includes 22 pairs of homologous autosomes and one pair of sex chromosomes. Chromosomes occur in homologous pairs to ensure genetic diversity. Haploid cells have half the chromosome number of diploid cells, and germ cells give rise to gametes for reproduction, while somatic cells make up the body tissues and organs.

**1. Organization of the Karyotype:** - A karyotype is a visual representation of an individual's complete set of chromosomes, arranged in a specific order. It's typically created by staining and photographing an individual's chromosomes during metaphase of cell division and then arranging them by size, banding patterns, and other characteristics. - In humans, karyotypes are usually organized into 23 pairs of chromosomes, with one chromosome from each pair coming from the mother (maternal) and the other from the father (paternal). These pairs are numbered from 1 to 22, with the last pair being the sex chromosomes (X and Y), determining an individual's sex. **2. Number of Homologous Pairs of Human Chromosomes:** - There are 22 pairs of homologous (similar in size and genetic content) chromosomes in humans, known as autosomes. - The 23rd pair consists of the sex chromosomes (X and Y), which determine an individual's sex. In females, this pair is XX, while in males, it is XY. **3. Why Chromosomes Occur in Homologous Pairs:** - Chromosomes occur in homologous pairs to allow for genetic diversity and to facilitate the process of sexual reproduction. Each member of a homologous pair carries similar genes but may have variations (alleles) that can lead to different traits. This diversity is essential for the adaptation and evolution of a species. **4. Differences Between Haploid and Diploid Cells:** - **Haploid Cells:** Haploid cells have half the number of chromosomes as diploid cells. In humans, haploid cells contain 23 chromosomes. Haploid cells are typically involved in sexual reproduction. In males, sperm cells are haploid, while in females, egg cells are haploid. When a haploid sperm fertilizes a haploid egg, a diploid zygote is formed, which then develops into a new individual. - **Diploid Cells:** Diploid cells have a full set of chromosomes, meaning they have two copies (homologous pairs) of each chromosome. In humans, diploid cells have 46 chromosomes (23 pairs). Most somatic (body) cells in humans are diploid, including skin cells, muscle cells, and most other cell types. Diploid cells contain genetic information from both parents, which contributes to an individual's genetic diversity. **5. Differences Between Germ Cells and Somatic Cells:** - **Germ Cells:** Germ cells are specialized cells that give rise to gametes (sperm and egg cells) through a process called meiosis. Germ cells are haploid, meaning they have half the number of chromosomes as somatic cells (23 in humans). They are essential for sexual reproduction, as they combine during fertilization to form a diploid zygote. - **Somatic Cells:** Somatic cells are all the non-reproductive cells in an organism. They make up the tissues and organs of the body. Somatic cells are typically diploid, containing the full complement of chromosomes (46 in humans). They undergo mitosis, a process of cell division, to produce new somatic cells for growth, repair, and maintenance of the body. In summary, the organization of the karyotype in humans includes 22 pairs of homologous autosomes and one pair of sex chromosomes. Chromosomes occur in homologous pairs to ensure genetic diversity. Haploid cells have half the chromosome number of diploid cells, and germ cells give rise to gametes for reproduction, while somatic cells make up the body tissues and organs.