1. Mendel Law Exceptions and Sex Linkage
Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes.

2. Essential Knowledge
3A4: The inheritance pattern of many traits cannot be explained by simple Mendelian genetics.

3. Cross white roses (WW) with red roses (RR) Pink roses (RW)!
Incomplete Dominance
Cross white roses (WW) with red roses (RR) Pink roses (RW)!
Heterozygous offspring are in b/t the 2 homozygous phenotypes. BLENDING!

4. Codominance A condition in which both alleles show up in phenotype.
Neither allele is recessive.

5. Codominance

6. Codominance: Piebald Black-Pastel Ball Python

7. Traits that are controlled by 2 or more genes.
Polygenic Traits
Traits that are controlled by 2 or more genes.
Ex: skin/eye color in humans controlled by > 4 genes  Creates wide range of trait

8. Multiple Alleles Some genes have more than 2 alleles.
Ex: Blood type: 4 phenotypes: A, B, AB, O
Alleles: i, iA, or iB
But, still only get 2 copies of allele, from mom and dad!

9. (a) The three alleles for the ABO blood groups
Fig
Allele
Carbohydrate IA A IB B i
none
(a) The three alleles for the ABO blood groups
and their associated carbohydrates
Red blood cell
appearance
Phenotype
(blood group)
Genotype
IAIA or IA i A
IBIB or IB i B
Figure Multiple alleles for the ABO blood groups
IAIB AB ii O
(b) Blood group genotypes and phenotypes

10. Gene Linkage Genes for traits can be inherited together  linked.
Each chromosome is actually a group of linked genes.

11. Can you tell which traits are linked?

12. Determination of Sex Girls: XX (homologous sex chroms) X
Boys: XY (non-homol. sex chroms)
Only ends of Y have regions homologous to X X Y

14. Found on sex chroms, mainly X (contains more DNA).
Sex Linked Genes
Found on sex chroms, mainly X (contains more DNA).
Easy to spot b/c many males will have trait  XY..if trait is on X, no competition on Y (less DNA)

16. Fruit Fly Genetics! Good for genetic studies (Drosophila melanogaster:
 breed at a high rate
 A generation can be bred every 2 weeks
 Only have 4 pairs of chromosomes
Morgan, an embryologist did many studies with these to locate genes on chromosomes

17. Wild type = normal phenotype
Traits alternative to wild type: mutant phenotypes

18. Some Traits are Sex Limited and Expression Depends on Sex of Individual

19. Some Traits Result from Nonnuclear Inheritance
Ex: Chloroplasts and mitochondria are randomly assorted to gametes and daughter cells

20. In Animals…
Mitochondrial DNA is passed on by egg, not sperm  inherit mitochondria traits from mom.

21. Let’s do a Problem!

22. Sex Linked Fruit Fly Sample Probs and Lab