• Document: Chapter 13: Meiosis and Sexual Life Cycles
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Name__________________________Period___________ Chapter 13: Meiosis and Sexual Life Cycles Concept 13.1 Offspring acquire genes from parents by inheriting chromosomes 1. Let’s begin with a review of several terms that you may already know. Define: gene: A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses) locus: A specific place along the length of a chromosome where a given gene is located gamete: A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote. male gamete: Sperm female gamete: Eggs asexual reproduction: The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical to the parent. sexual reproduction: A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes 2. How many chromosomes are in human cells? What is a chromosome? There are 46 chromosomes in human somatic cells. A chromosome is a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins. 3. Which type of reproduction will result in genetically identical offspring? Asexual reproduction Concept 13.2 Fertilization and meiosis alternate in sexual life cycles 4. What is a somatic cell? Give examples of two human somatic cell types. A somatic cell is any cell in a multicellular organism except a sperm or egg or their precursors. Examples may vary but could include bone cells, skin cells, blood cells, etc. Copyright © 2011 Pearson Education, Inc. -1- 5. How does a somatic cell compare to a gamete in terms of chromosome number? Unlike somatic cells, gametes contain a single set of chromosomes. Such cells are called haploid cells, and each has a haploid number of chromosomes (n). For humans, the haploid number is 23. Description # in Human Cells Sex chromosome A chromosome responsible for determining the sex of an 1 individual Autosome A chromosome that is not directly involved in determining 22 sex; not a sex chromosome 7. What is a karyotype? How is it prepared? When images of the chromosomes are arranged in pairs, starting with the longest chromosomes, the resulting ordered display is called a karyotype. Karyotypes are prepared from isolated somatic cells, which are treated with a drug to stimulate mitosis and then grown in culture for several days. Cells arrested in metaphase, when chromosomes are most highly condensed, are stained and then viewed with a microscope equipped with a digital camera. A photograph of the chromosomes is displayed on a computer monitor, and the images of the chromosomes are arranged into pairs according to their appearance. 8. What are three things that can be determined from a karyotype? (Study the Research Method, Figure 13.3, in your text carefully for this information.) Size of the chromosome, position of the centromere, and pattern of the stained bands 9. Explain what is meant by homologous chromosomes. A pair of chromosomes of the same length, centromere position, and staining pattern 10. Cells that have only one of each homologous pair are said to be haploid, a condition that is represented by n. Cells that have two of each homologous pair are said to be diploid or 2n. For each of the following, is the cell haploid or diploid? liver cell diploid gamete haploid egg cell haploid zygote diploid skin cell diploid sperm haploid somatic cell diploid sex cell haploid 11. The muscle cells of a dog have 78 chromosomes. Fill in the correct chromosome number in a bone cell 78, sperm 39, haploid cell 39, somatic cell 78, and zygote 78. Copyright © 2011 Pearson Education, Inc. -2- 12. In the cell at right, the chromosomes are shaded in two colors to represent the parent of origin. On this sketch, label the following: See page 251 of your text for the labeled figure. a. sister chromatids b. homologous chromosomes c. centromere d. replicated chromosome e. maternal chromosomes 13. How many chromoso

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