09/30/2015 Genes and Inheritance

09/30/2015 Genes and Inheritance - short or tall ● traits...

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Genes and Inheritance 09/30/2015 Natural Selection variation within a population inheritance of genes Darwin could not explain where variation came from. Sexual Reproduction gametes: egg & sperm DNA codes for genes, DNA in nucleus of cells Humans have 46 chromosomes Allele (alternative form of a gene) one inherited from mom, one from dad Crossing over: genetic material exchanged between homologous pair Gregor Mendel (1822-1884) discover how traits are inherited by experimenting with pea plants work published in 1866 and rediscovered in 1900 picked pea plants with contrasting features smooth or wrinkled yellow or green short or tall
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Unformatted text preview: short or tall ● traits don’t blend when inherited ● traits stay intact, sometimes they disappear in one generation, then reappear Mendel’s principle of segregation: Genes occur in pairs (alleles). During gamete production, the members of each gene pair separate, so that each gamete contains one member of each pair. Alleles ● same alleles on homologous chromosomes: homozygous ● diFerent alleles on homologous chromosomes: heterozygous ● Dominant: always expressed as phenotype ● Recessive: only expressed in the homozygous state Sex-linked Traits ● red-green, color blindness ● on X chromosome...
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