Mendelian Genetics

1
Mendelian Genetics

• Unit VI
• Start December 4
• Finish December 20

2
Gregor Mendel

• Discovered the key to understanding genetics
• Experimented with peas (Pisum sativum)
• Developed the rules of genetics for peas
• Rules are sets of patterns that predict heredity
• Patterns formed basis of Genetics
• More information

3
Mendels Experiment

• Step 1 P Generation (Parent)
• Several generations of peas allowed to
  self-pollinate
• Resulted in pure breeding
• Pure Breeding All offspring would display only
  one form of a trait
• Step 2 F1 Generation (First Filial)
• Cross pollination of contrasting varieties of the
  P Generation
• Step 3 F2 Generation (Second Filial)
• Allowed F1 Generation to self-pollinate
• Results F1 Generation
• Showed only 1 trait which was named dominant
• The trait that was not displayed is called
  recessive
• F2 Generation
• Showed the dominant and recessive in a ratio of
  31
• 311 True dominant, 2 untrue dominant, 1
  Recessive(121)

4
Picture
5
Theory of Inheritance

• 1. Parent to offspring
• Parents do not transmit information directly to
  their offspring (DNA)
• 2. Genes
• For each trait, an individual has two factors
  (genes)
• One factor from mother and one factor from father
• If the factors are the same, the individual is
  homozygous
• If the factors are different the individual is
  heterozygous
• 3. Allele
• Each copy of a factor is called an allele.
• The physical appearance, or phenotype, is
  determined by the alleles that code for traits.
• The set of alleles is called a genotypes.
• 4. Allele Receiving
• An individual receives 1 allele from one parent
  and the other allele from the other parent.
• Each allele can be passed down.
• 5. Allele Presence
• The presence of an allele does not guarantee that
  a trait will be expressed (displayed).
• In heterozygous individuals, only the dominant
  alleles is expressed.
• The members of each pair of alleles separate when
  gametes are formed.

6
Law of Segregation

• Video

7
Law of Independent Assortment

• Pairs of alleles separate independently of one
  another during gamete formation.
• Only applies to genes far apart or on different
  chromosomes.

More Information