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Module II Mendelian Genetics & Probability Theory

Module II Mendelian Genetics & Probability Theory. SEXUAL REPRODUCTION involves.

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Module II Mendelian Genetics & Probability Theory

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  1. Module II Mendelian Genetics & Probability Theory

  2. SEXUAL REPRODUCTIONinvolves • Manufacture of gametes (gametogenesis) through the process of meiosis (consists of 2 specialized cell divisions in which the chromosome number of the resulting cells is reduced from diploid (2n) to a haploid (n) number) • Gametogenesis occurs in specialized cells in the reproductive organs (gonads) • In animals, testes are male gonads and ovaries are female gonads • The union of male and female gametes (fertilization) produces a zygote • In humans, male gametes are sperms and female gametes are ova

  3. GENETICS • Genetics is the study of heredity and variation in organisms • Genes are the hereditary units transmitted from one generation to the next • Genes reside in the long molecules of deoxyribonucleic acid (DNA) that exists within the cell • DNA, in conjunction with a protein matrix forms nucleoprotein and becomes organized into structures called chromosomes that are found in the nucleus of the cell

  4. ALLELES • Mutation is a change in some part of the DNA • The result of a mutation is a change of character or trait of the individual • Through a mutation, a gene may be changed into two or more alternative forms called alleles • Homologous chromosomes are genetically similar

  5. MENDEL’S LAWS • Law of segregation: If a parent contains 2 alleles of a trait, only 1 is transmitted through a gamete to the offspring • Law of independent assortment: Segregation of one gene pair occurs independently of any other gene pair

  6. MENDELIAN INHERITANCE (Assumes Mendel’s Laws and independence of environmental conditions) • Phenotype – traits possessed by an organism ( may be visible, like color) • Genotype – All alleles of a gene possessed by an individual. Classified as: • Homozygous – union of gametes carrying identical alleles; produce homozygotes • Heterozygous – union of gametes carrying different alleles; produce heterozygotes

  7. DOMINANT & RECESSIVE ALLELES • A Dominant allele of a gene dictates the phenotype of the organism. Indicated by a capital letter, a homozygous dominant individual could have a genotype shown as AA. A heterozygous genotype would be shown as Aa to indicate the presence of a recessive allele form of the gene. • A Recessive allele does not determine phenotype in the presence of a dominant allele. Indicated by a lower case letter. A homozygous recessive individual could have a genotype shown as aa. • A heterozygous individual who possesses a recessive allele is called a carrier

  8. SIX MONOFACTORIAL CROSSES(summarized in table below)

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