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Mendel and Heredity

Mendel and Heredity. Chapter 8. Heredity – the passing of characteristics from parents to offspring. Genetics – branch of biology that focuses on heredity. Who was Gregor Mendel?. An Austrian Monk Parents were peasants, so he learned about agriculture very early on

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Mendel and Heredity

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  1. Mendel and Heredity Chapter 8

  2. Heredity – the passing of characteristics from parents to offspring Genetics – branch of biology that focuses on heredity Who was Gregor Mendel? • An Austrian Monk • Parents were peasants, so he learned about agriculture very early on • he experimented breeding of different varieties of garden peas

  3. Mendel’s Peas

  4. Studied 7 Different Traits (characteristics) • trait = single form of a character ex. Purple flower • character = inherited characteristic ex. Flower color

  5. Mendel = Father of Genetics Experimented by crossing plants and counting each kind of offspring was produced and analyzed all the data Parent generation – 1st individuals crossed F1 generation – produced from P generation F2 generation – F1 self-pollinates

  6. Cross Pollinate Cross-pollinating purple flowers with white produced only purple flowers in the first filial generation.

  7. Producing an F2 Generation Allowing the F1 generation to self-pollinate, he found that in the secondfilial generation there was about a 3:1 ratio of purple flowers to white. He did hundreds and thousands of crosses

  8. What does this mean? • Before this experiment, people thought offspring had a blend of parents traits • experiment proved this to be false • Offspring show one or the other not a blend • Organisms have 2 factors for each character • some factors (traits) are recessive while others are dominant • gene – segment of DNA on a chromosome that controls a particular hereditary trait • allele -Two or more alternative forms of a gene (each parent gives one allele for a given trait)

  9. Dominant and Recessive Genes • Dominant genes – genes that keep other genes from showing their traits • Recessive genes – the genes that do not show their traits when dominant genes are present

  10. Genes on the Choromsome Human LCN6 gene location on chromosome 9q34 A, Ideogram of chromosome 9. Filled triangle near the long arm telomere indicates the location of the lipocalin-rich region containing LCN6. B, Arrangement of lipocalin genes from 126 to 136 megabases from the telomere of the short arm (not to scale). Arrows indicate direction of transcription of each gene. LCN5 and LCN8 indicate uncharacterized genes similar to mouse Lcn5 and 8. Positions were taken from MapView at the The National Center for Biotechnology Information (NCBI) website Human Genome Build 34, Version 1. C, Intron-exon structure of LCN6 gene. Black boxes indicate translated regions and white boxes indicate untranslated regions of exons. Hamil et al. Reproductive Biology and Endocrinology 2003 1:112 doi:10.1186/1477-7827-1-112 http://www.rbej.com/content/1/1/112/figure/F1?highres=y

  11. Law of Segregation The two alleles separate when the gametes are formed, and only one allele is present in each gamete.

  12. Letters Represent Alleles • Geneticists use letters be used to represent alleles. • A capital letter = Dominant trait • A lowercase letter = a recessive trait • The same letter is used to indicate both alleles Examples: Flower color: P= purple, p= white Seed color: Y= yellow, y = green Seed shape: R = wrinkled, r = round

  13. Human Traits: tongue rolling ability Rolling = Dominant Not Rolling = Recessive

  14. Trait: Dimples or No Dimples Dimples = Dominant No Dimples = Recessive

  15. Trait: Curved Thumb or Straight Thumb Straight = Dominant Curved = Recessive

  16. Homozygous • If two alleles of a particular gene present in an individual are the same, the individual is said to be homozygous for that characteristic • AA = homozygous dominant • aa = homozygous recessive

  17. Heterozygous • If the alleles of a particular gene present in an individual are different, the individual is heterozygous for that characteristics • Aa = heterozygous

  18. Phenotype • The physical appearance of a characteristic • If the letter A represents the color of a chicken’s feathers and A = brown and a = white, the possible phenotypes for chicken feather are either brown or white

  19. Genotype • The set of alleles (or genes) that an individual has for a characteristic • Chickens could have the genotype AA, Aa, or aa (homozygous dominant, heterozygous, or homozygous recessive) for feather color

  20. Probability • The likelihood that a specific event will occur (usually expressed as a decimal, percentage or a fraction)

  21. Punnett Square • A diagram that biologists use to aid them in predicting the probable distribution of inherited traits in offspring http://celebritygeckos.com/Portals/28/Genetics/Genetics/basicpunnetsquare.JPG

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