1. INHERITANCE
Chapter 5

2. Review What is the process that makes somatic cells?
What is the process that makes gametes?
How many chromosomes in a somatic cell?
How many in a gamete?

3. Review What is the process that makes somatic cells? mitosis
What is the process that makes gametes? meiosis
How many chromosomes in a somatic cell? 46
How many in a gamete? 23

4. MENDELIAN GENETICS Genetics was unknown in Darwin’s time
Gregor Mendel bred pea plants and discovered the laws of inheritance
He was successful partly because the traits he observed were simple traits, controlled by only one gene
These are now called Mendelian traits
Examples: black fur or white fur
Right-handed or left-handed

6. MENDELIAL GENETICS Mendel’s laws of inheritance:
1. Principle of Segregation: chromosomes inherited from mom and dad stay separated
2. Principle of Independent Assortment: you have an equal chance of inheriting each gene from each parent

7. MENDELIAL GENETICS
A gene is a segment of a chromosome’s DNA that codes for specific functions or traits
Genotype is the 2 alleles at a given locus. They are represented by letters. (ex. Aa or AA)
If an individual inherits two alleles that code for the same form of a trait they are homozygous. If they have different forms they are heterozygous.

8. MENDELIAL GENETICS
If an allele is always expressed when present, it is dominant. If it is masked, it is recessive. The only time recessive traits are expressed is if they are both recessive, or homozygous recessive.
Homozygous dominant: 2 dominant forms (AA)
Homozygous recessive: 2 recessive forms (aa)
Heterozygous: one of each (Aa)
Dominant does not mean better, healthier, or more common

9. MENDELIAL GENETICS The physical expression of a trait is the phenotype
So, the genotype is the actual genes and the phenotype is the observable form of the genes
Genotype: BB, phenotype: B blood type
If a specific trait is coded for by a gene on a chromosome pair numbered 1-22 it is an autosomal trait
If it is on the 23rd pair it is a sex-linked trait
Important for Extra Credit Assignment

10. AUTOSOMAL TRAITS
We will deal with discrete traits: there are clear categories
Continuous traits are not measurable and have an unlimited number of possibilities (we won’t use these)

11. TRANSMISSION OF TRAITS: ONE AT A TIME
Let’s look at albinism
Recessive autosomal gene
AA and Aa would result in normal melanin and no albinism
aa is the only form that would result in albinism
To predict probability of a trait in offspring:
List genotype of mother and father
Figure out what alleles for this trait will be carried by gametes of mother and father
Set up a Punnett Square
Fill it in
List the possible genotypes and phenotypes and the probability of each
List the ratio of phenotypes and genotypes

12. TRANSMISSION OF TRAITS: ONE AT A TIME
Let’s do the example on page 86-87

13. ASSIGNMENT
Lab 5 Handout
Genetics Practice WS

14. BLOOD TYPING
Each different blood type is coded for by genes at different loci on our chromosomes
Blood type is determined by the kind of antigen on the red blood cell
Each person has antibodies against foreign blood antigens. You can test for blood type by adding antigens and seeing the reaction
If antibodies attack antigens, the result is the clumping of blood, or agglutination

16. BLOOD TYPING The ABO blood group is a unique trait
Alleles called A, B, or O determine the type of antigen on the cell
Genotypes are: AA, AO, AB, BO, BB, or OO
A and B alleles are both dominant over O
A and B are codominant
So, OO is the only way to get type O blood
AB is the codominant form
Chart on page 93 summarizes this

17. BLOOD TYPING
Blood types for the ABO blood group must match if blood from a donor is used for a recipient
Type O blood does not provoke agglutination with A, B, or AB so it is the universal donor
Type AB has neither anti-A nor anti-B antibodies so it is the universal recipient

18. RH BLOOD GROUP
Blood type associated with the Rh blood group are Rh+ and Rh-
Homozygous dominant form is Rh+
Homozygous recessive form is Rh-
A person with Rh+ has antigens on the surface of red blood cells that provoke production of antibodies for Rh-
Rh incompatibility can occur between a mother and her fetus, which can result in anemia

19. ASSIGNMENT
Blood Type Lab
Put answers on Handout

20. SEX-LINKED TRAITS Sex-linked traits can be on X or Y chromosome
Most are X-linked
An example is red/green colorblindness. Most are males because this trait is transmitted by a recessive gene on the X chromosome
A female has a better chance of getting a dominant X that will mask the gene, but males only have 1 X, so the trait will show
Males are hemizygous

21. EXAMPLE, PAGE 97
A man with normal vision and a woman who is a carrier for colorblindness are having a child
1. list genotypes of each parent
2. set up Punnett Square
3. fill it in
4. list possible genotypes and phenotypes

22. PEDIGREES
Search for patterns of transmission of traits from one generation to the next
We do this by constructing a pedigree
There are 5 modes of inheritance. We focus on 3:
1. autosomal recessive: 2 unaffected parents and affected child. Child’s trait is “hidden”
2. autosomal dominant: 2 affected parents have unaffected offspring
3. X-linked: males get it more often

24. Work on Self-tests
5.1
#1, #2(a & b), #4, #7
5.2
All