1 autosomes all except sex chromosomes 2 sex

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1) Autosomes - all except sex chromosomes 2) Sex chromosomes Cell Division Mitosis Meiosis 7b. MITOSIS Somatic cells divide during growth and repair “Mitosis” is the “simple cell division” of somatic cells 7.C MEIOSIS Sex cells Reduction of chromosomes critical “Meiosis” produces egg or sperm cells Each with only 23 (half) chromosomes Recombination During meiosis
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The Evolutionary Significance of Meiosis Increases genetic variation quickly Contributes to role of natural selection 8. New Frontiers Since discovery of DNA structure Field of genetics has revolutionized biological science Some examples below Polymerase Chain Reaction (PCR) Now use small samples Make copies of a DNA segment DNA “Fingerprinting” Recombinant DNA Technology Transfers genes from cells from one species into another species Cloning Making a genetically identical organism (for example by inserting a nucleus into an egg)
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Human Genome Project International effort to sequence the entire human genome “Genome”: entire genetic makeup of an individual or species Human Genes Years away from knowing the functions of all of the DNA segments Chap 4: HEREDITY AND EVOLUTION 2. Genetic Principles Discovered by Mendel Gregor Mendel Experimenting with garden pea traits Involved observation and experimentation Discovered fundamental principles of how traits inherited A. Segregation Different expression of same trait controlled by discrete “units” B. Dominance and Recessiveness Mendel recognized that traits not expressed are still present Recessive - trait seemed lost (masked)
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Dominant - expressed trait Related terms Gene - segment of DNA Locus - location of gene on chromosome Alleles - variation or alternate forms of genes at same locus Homozygous - two copies of same allele Heterozygous - two different alleles at locus Genotype - actual genetic makeup Phenotype - observed characteristic Punnet Square Represents different ways alleles combined C. Independent Assortment No relationship between two traits 3. Mendelian Inheritance in Humans Mendelian traits or “discrete traits” Controlled by alleles at one genetic locus Examples include ABO blood system
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ABO blood group systems Governed by three alleles A, B, and O in population Individual has two 4. Polygenic Inheritance “Polygenic ” or continuous traits Influenced by alleles at two or more loci Each contributing to phenotype Polygenic examples Polygenic traits - more readily observable variation in humans Continuous - like height of population uninterrupted from shortest to tallest 5. Genetic and Environmental Factors Genotype sets limits Many polygenic traits obviously influenced by environment For example adult stature affected by nutrition 6. Mitochondrial Inheritance Much recent attention
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