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Genetics Gregor Mendel Known as the father of genetics. Worked with garden peas.

Genetics Gregor Mendel Known as the father of genetics. Worked with garden peas. Led to knowledge of inheritance. Heredity – transmission of traits from parents to the offspring. Gene – the basic unit of inheritance. Made of DNA. In sexual reproduction: One gene from the male parent.

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Genetics Gregor Mendel Known as the father of genetics. Worked with garden peas.

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  1. Genetics • Gregor Mendel • Known as the father of genetics. • Worked with garden peas. • Led to knowledge of inheritance. • Heredity – transmission of traits from parents to the offspring. • Gene – the basic unit of inheritance. • Made of DNA. • In sexual reproduction: • One gene from the male parent. • One gene from the female parent. • Why you have two copies of same chromosome.

  2. Alleles – alternate forms of a gene. • Ex: seed color (yellow, green seed) • Dominant and Recessive alleles • Dominant alleles – an allele that masks the presence of another allele. • Always use capital letters. • Recessive alleles – an allele that is being masked by the dominant allele. • Always use lower-case letters. • Homozygous – when both alleles are the same (homo = same). • Homozygous Dominant (AA) or homozygous recessive (aa) • Heterozygous – when both alleles are NOT the same (Hetero = different) • Heterozygous dominant (Aa)

  3. Genotype – genetic makeup of an organism. • Ex: AA, Aa, aa • Geno = genes, genetics • Phenotype – physical appearance of an organism. • Ex: tall, yellow, wrinkled • Pheno = physical • Mendel’s work • Three Principles: • Principle of dominance – an allele masks another allele. • Principle of Segregation – two alleles for a characteristics separate during gamete formation.

  4. Principle of Independent Assortment – alleles for different characteristics (genes) are distributed to gametes independently. • Punnett Squares – used to describe the ratio of expected outcomes of a genetic cross. • Monohybrid cross – (mono meaning one) 1 trait is crossed. • Have two alleles for each gene. • Ex: T = tall, dom t = short TT x tt (parents)

  5. More ex: TT x Tt Tt x Tt • Testcross – an individual with unknown genotype is crossed with a homozygous recessive individual. • Ex: rabbit color B = black, dom b = brown BB x bb Bb x bb • If any brown rabbits then the parents were heterozygous, if not then they were homozygous.

  6. Incomplete dominance – when one allele does not completely mask another. • The organism shows a blend of the two. • Ex: Japanese 4 o’clocks R = red W = white RR x WW RW = pink • Codominance – when both alleles contribute to the phenotype of the organism (no blending). • Ex: cattle color R = red r = white RR x Rr Rr = roan • Polygenic traits – traits controlled by two or more genes. (poly = many)

  7. Sex-linked traits – trait occurs only on a sex chromosome. • Ex: colorblindness XX = female B = normal, dom XY = male b = colorblindness XBXB = normal female XBXb = normal female, carrier XbXb = colorblind female XBY = normal male XbY = colorblind male XBXb x XBY

  8. Blood types: • A blood = IAIA or IAi • B blood = IBIB or IBi • AB blood = IAIB • O blood = ii • Dihybrid Crosses – two genes are crossed at the same time. • Ex: seed color and texture P = purple kernel, dom P = yellow kernel, rec S = smooth, dom S = wrinkled PpSs x PpSs (remember Foil – for all possible combinations of gametes)

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