Biology Chapter 13 Objectives

Biology Chapter 13 Objectives - Chapter 13 Meiosis and...

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Chapter 13 Meiosis and Sexual Life Cycles The Basis of Heredity 1. Traits are transmitted from parents to offspring through heredity. Heredity units that have coded information are called genes. These are inherited, and constitute our genome. 2. Asexual reproduction occurs only when organisms produce offspring that are exact copies of themselves. A single individual is the sole parents and passes copies of all its genes to its offspring. Sexual reproduction involves two parents producing an offspring that has unique combinations of genes inherited from the two parents. The Role of Meiosis in Sexual Life Cycles 3. a. In humans, a somatic cell, any cell other than a gamete, has 46 chromosomes. Gametes are reproductive cells that are the vehicles that transmit genes from one generation to the next. b. The X and Y chromosomes determine an individual’s sex and are called sex chromosomes. Other chromosomes are called autosomes. 4. A diploid cell is any cell with two chromosome sets. It has a diploid number of chromosomes, and is abbreviated 2 n . In humans, the diploid number if 46, the number of chromosomes in somatic cells. Haploid cells, contain a single chromosome set, and are gametes. Each has a haploid number of chromosomes, n . In humans, the haploid number is 23, the number of chromosomes found in a gamete. 5. Fertilization and meiosis must alternate in all sexual life cycles in order to offset the other’s effects on the chromosome number and perpetuate a species’’ chromosome count. 6. In the first type of life cycle which occurs in humans and most other animals, gametes are the only haploid cells. Meiosis occurs during the production of gametes. The diploid divides by mitosis, producing a multicellular organism that is diploid. The second type of life cycle is exhibited by plants and some species of algae. This life cycle includes both diploid and haploid multicellular stages. The
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Biology Chapter 13 Objectives - Chapter 13 Meiosis and...

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