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Mendelian Genetics

Mendelian Genetics. Unit 5. Define heredity and genetics. Heredity – the passing of characteristics (traits) from parents to offspring Genetics – the study of heredity. Gregor Mendel. The Father of Genetics Austrian Monk

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Mendelian Genetics

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  1. Mendelian Genetics Unit 5

  2. Define heredity and genetics • Heredity – the passing of characteristics (traits) from parents to offspring • Genetics – the study of heredity

  3. Gregor Mendel • The Father of Genetics • Austrian Monk • Studied pea plants and how traits were passed from one generation to the next

  4. Trait – specific characteristic that varies from one individual to another (seed color, plant height) • P generation – parents • F1 generation – offspring of P • Hybrid – offspring of cross between parents with different traits

  5. Mendel’s conclusions • Biological inheritance is determined by factors (genes) that are passed from one generation to the next • Alleles – different forms of a gene (short or tall plant) • Principle of dominance – some alleles are dominant and some are recessive • Dominant forms of a trait are expressed and mask the recessive form • Dominant alleles = capital letters, recessive alleles = lower case letters Tall Short Tall Tall Tall Tall Tall Short

  6. Mendel’s conclusions cont’d… 1. inheritance is determined by GENES 2. There are different forms of a gene= alleles Ex. Gene- coat color • one allele codes for a black coat the other allele codes for a white coat

  7. Mendel’s Conclusions cont’d… 3. Principle of dominance • Some alleles are dominant and others are recessive • Recessive traits can be hidden whenever a dominant allele is present • Ex. Tall plant (T) x short plant (t) = tall offspring (T) What allele was dominant?

  8. Mendel’s conclusions 4. The Law of Segregation: Alleles separate during meiosis. Remember: alleles are different forms of a gene & a gene is on a chromosome. Remember: Each gamete(egg & sperm) carries a single copy of each gene

  9. Mendel’s conclusions • The Law of Independent Assortment: • If genes are on different chromosomes then they are inherited separately(independently). • Opposite thought: • Genes on same chromosome are inherited together= Gene Linkage • Crossing-over can sometimes separate these genes.

  10. Phenotypes & Genotypes 1. Phenotype: appearance of an organism Example: short, tall, green, yellow 2.Genotype: gene combination of an organism Example: tt, TT, Tt, gg, GG

  11. Traits can be DOMINANT or recessive • DOMINANT TRAITS: EXHIBITED TRAIT(ONE YOU SEE) • WRITTEN WITH AT LEAST 1 CAPITAL Example: Tt or TT • Recessive traits: inhibited trait,(one you do not see) • Written with lowercase letters Example: tt

  12. Heterozygous vs. Homozygous • Heterozygous: the 2 alleles are different • Also called hybrids Example: Tt -heterozygous • Homozygous: the 2 alleles are the same • Example: TT means homozygous dominant, and tt means homozygous recessive • Also called Pure bred

  13. Monohybrid Crosses Tt X Tt Cross Go to Section:

  14. Monohybrid Crosses cont’d… Tt X Tt Cross Go to Section:

  15. Probability: the chance or percentage of chance of a trait being exhibited

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