Mendelian Genetics

Mendelian Genetics - homologous chromosomes separate at...

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Mendelian Genetics Through these meticulous experiments, Mendel came up with a 5-part hypothesis to explain the inheritance of single traits 1. Each trait is determined by pairs of genes; each organism has two alleles for each gene, one on each homologous chromosome Ex: white-flowered plants have different alleles than purple- flowered plants When two different alleles are present in an organism (heterozygous), a dominant allele may mask a recessive allele, even though the recessive allele is still present Ex: In edible peas the purple-flower trait is dominant to the white-flower trait (purple allele + white allele = purple flower) The pairs of alleles on homologous chromosomes separate, or segregate, from each other during meiosis , which is known as Mendel’s law of segregation (i.e. only one allele from the parent is passed on in a sperm or egg) Chance determines which allele is included in a given gamete—because
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Unformatted text preview: homologous chromosomes separate at random during meiosis Organisms have two copies of alleles for a given gene; some are homozygous for that gene (same alleles); some organisms are heterozygous for that gene (two different alleles) Punnett square: %perecent chance fr offspring Sex chromoshomes,sex-linked genes 5 realms of non mendelian genetics Abo blood groups Carriers, gentic disorders Nondisjunction The incorrect separation of chromosomes or in meiotic cell division is known as nondisjunction Nondisjunction causes gametes to have too many and too few chromosomes The frequency of nondisjunction increases with age Most embryos that arise from fusion of gametes with abnormal chromosome numbers spontaneously abort, but some survive to birth Nondisjunction in chromosomes 13, 18, 21, and sex chromosomes may survive to birth...
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This note was uploaded on 11/19/2011 for the course BIO 1320 taught by Professor Farr during the Fall '08 term at Texas State.

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