Friday, October 30th Complex Heredity Dear class- Your job is to go through these powerpoints to learn about the last topic before our first Unit test. This topic is a lot simpler than dihybrid crosses, so I know you can do it! You will hand in the complex heredity packet at the end of class. Failure to complete the assignment will result in a mandatory tutoring for Thursday 11/5. You must show work to receive credit. Have a Happy Halloween!! -Dr. Hyde HW: Genetics Vocabulary Crossword

Today’s Topic: Complex Heredity Find your notes to fill in the blanks and work on the problems

Objective Today we will be able to predict the traits of offspring for genes that are controlled by complete dominance, incomplete dominance, and co-dominance.

Complete Dominance  So far, we have learned about complete dominance.  In complete dominance, the dominant allele completely covers up the recessive allele.  Take for example Mendel’s pea plants

Blood Types  Blood type is inherited from your parents  Your blood type is one of the following:  Blood Type A  Blood Type B  Blood Type O  Or Blood Type AB How is it possible to have a blood type that has 2 dominant letters (AB) ? This is due to co-dominance.

1. Codominance: both alleles are completely dominant and contribute to the phenotype  When heterozygous, both phenotypes are represented separately WW (white) RR (Red) RW (Red and White)

Blood Types There are three alleles that control blood type: A (dominant) B (dominant) O (recessive) GenotypePhenotype AA, AO BB, BO AB Blood Type A Blood Type B Blood Type AB 2 alleles are dominant  

Practice question A woman with blood type A (AO) and a man with blood type AB (AB) have a baby. What are the possible blood types of their child?

Practice question A woman with blood type A (AO) and a man with blood type AB (AB) have a baby. What are the possible blood types of their child? AAAB AO BO AB A O

Practice question Answers: Type A, B and AB blood AAAB AO BO AB A O

A man with blood type A (AA) and a woman with blood type O have a child. What are the possible blood types of their children? You Try!

Answer: Type A blood You Try!

Example 2  Suppose we have a black and a white chicken.  Based on our knowledge of complete dominance, we would expect a chicken with the heterozygous genotype to express a black phenotype

How is this possible?  But as it turns out, if you cross a white a black chicken, you may end up with a chicken that looks like this:

How is this possible?  This is another example of codominance.

Codominance Practice In some chickens, the gene for feather color is controlled by codominance. The allele for black is B, the allele for white is W. Both are dominant. The heterozygous phenotype (BW) is knows as erminette (black and white spotted). If you cross two erminette chickens, how many will be white?

Codominance Practice In some chickens, the gene for feather color is controlled by codominance. The allele for black is B, the allele for white is W. Both are dominant. The heterozygous phenotype (BW) is knows as erminette (black and white spotted). If you cross two erminette chickens, how many will be white? BB BW WW B W B W

Codominance Practice Answer= 1/4= 25 BB BW WW B W B W

If black chickens (BB) are codominant to white chickens (WW), what are the possible offspring of a mating between a black chicken (BB) and a black and white chicken (BW)? You Try!

Answer: 50% Black, 50% Black and White You Try!

 Now we’ve learned about complete dominance and co-dominance.  There is one more type of complex heredity we will study….

2. Incomplete Dominance: neither allele is dominant or recessive  Heterozygous genotypes show an in- between or blended version of the trait  When heterozygous, a third phenotype appears  Example: Snapdragons

What it looks like…. In a certain species of fish, blue scales (BB) are incompletely dominant to yellow scales (YY). If you cross a blue fish with a green fish (BY), how many offspring will be yellow?

What it looks like…. In a certain species of fish, blue scales (BB) are incompletely dominant to yellow scales (YY). If you cross a blue fish with a green fish (BY), how many offspring will be yellow? BB BY B B B Y

What it looks like…. 0% are yellow BB BY B B B Y

If red flowers (RR) are incompletely dominant to white flowers (WW), show the offspring of a cross between two pink flowers (RW) You Try!

What it looks like…. ¼ Red, 2/4 Pink, ¼ White RRRW WW R W R W

Remember, if the question is related to co-dominance or incomplete dominance, it must say it in the question! If it does not, assume it is complete dominance (also known as Mendelian Inheritance)

Independent Practice  Your task is to complete the page titled “Complex Heredity Practice”  If you finish early, check your answers with the substitute, and hand it in.  You must hand in your paper by the end of class to receive credit.