1. Mendel’s Laws of Heredity
Why we look the way we look...

2. Mendel used peas... They reproduce sexually
They have two distinct, male and female, sex cells called gametes
Their traits are easy to isolate

3. Mendel crossed them
Fertilization - the uniting of male and female gametes
Cross - combining gametes from parents with different traits

4. What Did Mendel Find?
He discovered different laws and rules that explain factors affecting heredity.

5. 1. Rule of Dominance
The trait that is observed in the offspring is the dominant trait (uppercase)
The trait that is masked in the offspring is the recessive trait (lowercase)

6. 2. Law of Segregation Genes appear in pairs on homologous chromosomes
are SEPARATED when gametes are formed
and recombine during fertilization

7. 3. Law of Independent Assortment
Genes for different traits are inherited independently of each other
because homologous chromosomes move randomly to gametes
Explains why siblings look different

8. Genetics Continued Dihybrid crosses Exceptions to Mendelian Genetics
Incomplete vs. Complete Dominance
Codominance
Sex-Linked Genetics
Blood Types (Multiple Alleles)

9. Monohybrid Vs Dihybrid
Monohybrid Cross - crossing parents who differ in only one trait (AA with aa)
Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee)

10. S= yellow s= green Y= round y= wrinkled How many round yellow?
How many round green?
How many wrinkled yellow?
How many wrinkled green?

11. Show a dihybrid cross between two complete heterozygotes
S= yellow
s= green
Y= round
y= wrinkled
Show a dihybrid cross between two complete heterozygotes
How many round yellow?
How many round green?
How many wrinkled yellow?
How many wrinkled green?

12. S= yellow s= green Y= round y= wrinkled How many round yellow?
How many round green?
How many wrinkled yellow?
How many wrinkled green?

13. Dihybrid Cross - 2 traits

14. What’s on our agenda? Monday: Welcome back! Brief Genetics Review
Learn Blood Types & Blood type punnetts
Tuesday: Learn Pedigrees
Wednesday: Receive Genetics Test Study Guide
Material= Mendel’s laws, Punnetts, Dihybrids, Ratios, Codomiance, Incomplete Dominance, Sex-linked Inheritance, Blood types, Pedigrees
Thurs: Take Genetics Unit Test
Friday: Receive FULL YEAR study guide in preparation for MCAS (June 1 & 2). Due 5/31 (D & E, due 5/27 F Block
Left to cover: Ecology, Evolution

15. Non-Mendelian Genetics:
Exceptions to Complete Dominance

16. Incomplete Dominance - Blend
Heterozygous genotype= blend of two phenotypes
RR= Red
RW= pink
WW= white
(For many genes, such as the two mentioned above, the dominant allele codes for the presence of some characteristic (like, “B” codes for “make brown pigment” in someone’s eyes), and the recessive allele codes for something along the lines of, “I don’t know how to make that,” (like “b” codes for the absence of brown pigment in someone’s eyes, so by “default,” the eyes turn out blue). If someone is a heterozygote (Bb), that person has one set of instructions for “make brown” and one set of instructions for, “I don’t know how to make brown,” with the result that the person ends up with brown eyes. There are, however, some genes where both alleles code for “something.” One classic example is that in many flowering plants such as roses, snapdragons, and hibiscus, there is a gene for flower color with two alleles: red and white. However, in that case, white is not merely the absence of red, but that allele actually codes for, “make white pigment.” Thus the flowers on a plant that is heterozygous have two sets of instructions: “make red,” and “make white,” with the result that the flowers turn out mid-way in between; they’re pink.)

17. Codominance – Both show
Both alleles of the trait show in the heterozygote

18. Codominance: Both traits show in heterozygotes
Try these: what are the phenotype ratios?
4:51
TRY ANOTHER!Calico Cat Colors
B: Black
Y: Yellow
NOTES: Horse Fur Color
R= Brown
W= White

19. Sex-Linked

20. Sex-Linked
4:51

21. Sex-linked Punnett C= color-blindness XX= Female XY= Male
Is mom colorblind?
Is dad colorblind?
What is the chance that they have:
a colorblind girl?
a female carrier?
an unaffected male?
an affected male?
C= color blindness

22. Polygenic: controlled by many genes
Polygenic inheritance is a fancy term for those genetic traits that are controlled by more than 1 gene
Height, Skin Color
Because there are MANY genes that influence polygenic inheritance, you see a spectrum of phenotypes
DIDN”T DO WITH D

25. Blood Types: Multiple Alleles
What is multiple allele inheritance?
Non-Mendelian Inheritance Pattern
involves more than just 2 alleles
that means there is more than two phenotypes
0:45

26. Blood Types: Multiple Alleles
Example: Blood Type (Red Blood Cells)
There are markers on the surface of RBCs
Our immune system has antibodies: ATTACK foreign invaders (germs, viruses)
YOU DO NOT WANT ANTIBODY for your BLOOD TYPE
What would be the result? Your immune system attacks your body!!

27. Multiple Alleles - Blood Type
Specific protein surface on RED BLOOD SURFACE antibodies for every shape in immune system except your own blood: DO NOT WANT TO ATTACK OUR OWN CELLS
Universal Donor (can give to everyone): 0 Blood…. why?
Universal Recipient (can accept from anyone): AB Blood…..why?