Genetics Since Mendel

1
Genetics Since Mendel

• Chapter 5, Section 2
• PART I

2
Incomplete Dominance

• Produces a phenotype (what is looks like) that is
  a mix between the 2 homozygous parents
• However, it doesnt mix like paint colors can
  mix. . . There are lots of spots
• some of these spots look like one parent, while
  some of these spots look like the other parent,
  so overall the new offspring looks like a mix of
  the parents

3
Incomplete Dominance

• The letters used in Punnett squares are different
  for incomplete dominance
• Because neither allele is dominant over the
  other, there is not capital or lower case letter.
  . . both letters are capital except one of the
  letters has an apostrophe added to it ()
• We call this prime

4
Incomplete Dominance

• Example
• Cross a plant of red (FF) four oclock flowers
  with a plant of white (FF) four oclock flowers
• The results are pink (FF) flowers

5
Incomplete Dominance

• Cross a plant with pink four oclock flowers with
  another plant with pink four oclock flowers
• The outcome is a combination of all three
  phenotypes

6
Multiple Alleles

• Multiple alleles exist when a trait has more than
  two possible alleles
• Example- Blood Types
• 3 alleles A, B, and O
• A and B are dominant to O, but equal to each
  other
• What are the 6 genotypes of blood? (Try to list
  these on your own. You may use your book to help
  you.)

7
Polygenic Inheritance

• When a group of gene pairs acts together to
  produce a trait
• Skin, hair, and eye color are examples of traits
  controlled by polygenic inheritance
• Egg production in chickens and grain color in
  wheat are also controlled by polygenic inheritance

8
Polygenic Inheritance

• Environment can affect how some genes are
  expressed or if they are expressed at all
• The decisions you make may influence how genes
  get expressed. . . Certain behaviors may increase
  your risk of developing cancer
• If a person with a high risk of getting skin
  cancer limits their exposure and takes care of
  their skin, they may never develop cancer