Chapter 12 bio

Chapter 12 bio - Chapter 12: Meiosis Key concepts: 1....

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Chapter 12: Meiosis Key concepts: 1. Meiosis is a type of nuclear division resulting in cells that have half as many chromosomes as the parent cell. In animals it leads to the formation of eggs and sperm. 2. Each cell made by meiosis receives a different combination of chromosomes, each cell produced by meiosis receives a different complement of genes. The offspring are genetically different and distinct from their parents 3. The leading hypothesis to explain meiosis is that genetically varied offspring are more likely to thrive in thrive in environments where parasites and disesase are common 4. if mistakes occur during meiosis, the resulting egg and sperm may contain the wrong number of chromosomes. A sperm and an egg unite to form a new individual fertilization Sex cells are called gametes . Formed by meiosis o Is the nuclear division that leads to a halving of chromosome number. Distinct types of chromosomes: autosomes are non-sex chromosomes while chromosomes associated with the sex of the individual are considered to be sex chromosomes. Homologous chromosomes are the two chromosomes of each type. Also known as homologs . They have the same size and shape. o Homologous chromosomes carry the same genes. Genes are a section of dna that influences some hereditary trait of an individual. Traits are certain characteristics. o Allele- different versions of the same gene o Homologous chromosomes carry the same genes, but each homolog may contain different alleles. Karyotypes show the number and the types of chromosomes present. Diploid- “double form”. Organisms with this have two alleles of each gene. One on each of the homologous pairs of chromosomes. Haploid- “single form.” Organisms with this do not have homologous chromosomes. They have one allele of each gene. In simpler organisms. ‘n’ stands for the number of distinct chromosomes in a given cell, known as the haploid number . Humans have a haploid number of 23. Human autosomal cells are 2 n, making them diploid. Ploidy- the combination of the number of sets and n. Diploid cells have 2 n because only 2 chromosomes of each type are present. o Maternal chromosomes come from the mother, paternal chromosomes come from the father. N = how many types of chromosomes, ploidy = the number of each type Polyploidy species have 3 or more of each type of chromosome in each cell. Term Definition Example or Comment Chromosome Structure of DNA and proteins; carries the cell’s hereditary info Eukaryotes have linear, threadlike chromosomes while bacteria and Achaea have one circular plasmid. Sex chromosome
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This note was uploaded on 03/21/2012 for the course BIOSC 150 taught by Professor Dr.newman during the Fall '11 term at Pittsburgh.

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Chapter 12 bio - Chapter 12: Meiosis Key concepts: 1....

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