Classical Genetics

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Classical Genetics

• The Legacy of Gregor Mendel
• Or
• The Monk with the Missing Peas

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The Big Question

• Why do children look like their parents?

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Thats GENETICS!

• The scientific study of heredity
• Heredity the passing down of traits from
  parents to offspring via genes and chromosomes

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Who started genetics?Gregor Mendel of course!!!

• Gregor Mendel
• Austrian monk in 1860s
• Studied different traits of the garden pea
• Discovered the basic laws of genetics
• Father of Genetics

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More Mendel!!!

• 1st person to succeed in predicting how traits
  are passed from one generation to next

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Why is Mendel SO important?

• Studied one trait at a time
• Analyzed his data mathematically
• Looked at multiple traits
• Used multiple trials

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Why peas?

• Quick growing
• Lots of different traits

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So what did Mendel find out?

• Genes and Alleles
• GENE section of DNA that determines a trait
  (Mendel called them factors)
• ALLELE particular form of a trait (represented
  by letters)
• EX plant size
• T is the tall allele
• t is the short allele

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Combinations of Alleles

• We get one allele from each parent
• Three possible combinations
• TT homozygous dominant
• Tt heterozygous
• tt homozygous recessive

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Dominant/Recessive

• One allele is dominant over the other (capable of
  masking the recessive allele)

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New Vocabulary

• Genotype - combination of alleles that an
  individual has. (TT, tt, Tt)
• Phenotype - physical appearance of a trait (Tall,
  Tall, Short)

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So how do we write this?

• Remember T Tall and t short
• So if a plant is..
• Genotype Phenotype
• Homozygous Dominant
• Heterozygous
• Homozygous Recessive

Tall
TT
Tall
Tt
tt
Short
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Punnett Square
Mothers Genes

• A way to show which genes can combine when an egg
  and sperm join
• Letters are used in place of genes
• Large letter dominant gene (T)
• Small letter recessive gene (t)

Fathers Genes
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Punnett Square

• Large letter goes first in heterozygous organisms
  (Ff)
• Lets do a cross between a pure dominant male
  (sperm) for free earlobes (FF) and a female
  (egg) who is heterozygous for free earlobes (Ff)

F f


F F
FF
Ff
FF
Ff
F is dominant over f
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What are the expected results?
F f
FF Free Earlobes Ff Free Earlobes
FF Free Earlobes Ff Free Earlobes
F F