Chapter 9 - notes9 PDF

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Chapter 9: Sexual Reproduction & Meiosis Characteristics of the average cell: -Average human cell has 23 pairs of chromosomes (1 from each parent = 46 total per cell) -Karyotype = size-ordered chart of all the chromosomes in one cell -Diploid = cells w 2 sets of chromosomes (1 set from each parent) -Autosomes – 22 of our 23 chromosomes -Each chromosome from 1 parent has matching chromosome from other parent = homologous chromosomes (same basic structure) -Homologous chromosomes match even though from different parts -Homologous chromosomes not necessarily identical -Have the same gene in the same order -DON’T necessarily have the same alleles = different versions of genes -Ex: everyone has 2 genes for blood type, but we have some combination of the different possible alleles that code for blood type (A, B, or O) -Person’s homologous chromosomes might be identical: 1 “O” allele from each parent – might also be different: A allele from 1 parent & B allele from the other -Ex: cats have 2 genes for fur length, has possible alleles coding for short/long fur -Sex chromosomes = last pair of chromosomes, determine whether a person will develop: -Ovaries – X & X or Testes – X & Y -Haploid cells = only have 1 set of chromosomes (half) -Gametes = sperm or egg cells, made in ovaries or testes through type of cell division called meiosis Purpose of making haploid cells:

Meiosis = unique type of cell division -Make haploid gametes for sexual reproduction

-2 divisions with 1 parent cell producing 4 daughter cells/gametes -Gametes NOT genetically identical to each other...