Genetics Mendel Heredity Heredity is the passing of traits from parents to offspring. Heredity.
Mendel and Heredity
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Transcript of Mendel and Heredity
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Mendel and Heredity
Chapter 8
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Heredity – the passing of characteristics from parents to offspring
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
Genetics – branch of biology that focuses on heredity
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Mendel’s Peas
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Studied 7 Different Traits (characteristics)
• trait = single form of a characterex. Purple flower
• character = inherited characteristicex. Flower color
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Mendel = Father of GeneticsExperimented by crossing plants and counting each kind of offspring was produced and analyzed all the data
Parent generation – 1st individuals crossedF1 generation – produced from P generationF2 generation – F1 self-pollinates
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Cross Pollinate
Cross-pollinating purple flowers with white produced only purple flowers in the first filial generation.
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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
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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 blendOrganisms 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)
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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
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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:10.1186/1477-7827-1-112http://www.rbej.com/content/1/1/112/figure/F1?highres=y
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Law of Segregation
The two alleles separate when the gametes are formed, and only one allele is present in each gamete.
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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
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Human Traits: tongue rolling ability
Not Rolling = RecessiveRolling = Dominant
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Trait: Dimples or No Dimples
Dimples = Dominant No Dimples = Recessive
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Curved = RecessiveStraight = Dominant
Trait: Curved Thumb or Straight Thumb
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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 dominantaa = homozygous recessive
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Heterozygous
If the alleles of a particular gene present in an individual are different, the individual is heterozygous for that characteristics
Aa = heterozygous
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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
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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
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Probability
The likelihood that a specific event will occur (usually expressed as a decimal, percentage or a fraction)
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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