1. C-Notes: Patterns of Inheritance (Variations on Mendel’s Law)
Stnd: 3a
C-Notes: Patterns of Inheritance (Variations on Mendel’s Law)
01/29/14
Objective:
SWBAT: identify the many factors that affects the phenotypes by the interactions of alleles in a gene.

2. How is Sex Determination (gender) in humans determined?
Last pair of chromosomes (# 23; x and y)
The Male determines sex of the offspring
How is Sex Determination (gender) in humans determined?

3. INHERITANCE PATTERNS XX XY SEX DETERMINATION **Male determines sex**
50% chance male 50% chance female X Y XX XY X X

4. What are Sex Chromosomes?
The chromosomes carries the genes that determine whether an individual is female or male.
Mendel’s peas did not have sex chromosomes.
Mendel worked with peas that had female and male parts on the same plant.
What are Sex Chromosomes?

5. How are Male and Female chromosomes expressed?
During Meiosis, the “sex chromosome” pair separate.
Female chromosome is symbolized with an X and the Male chromosome with a Y.
A female produces egg cells with two X chromosomes in her body cells.
Ex: genotype is XX.
A male produces sperm cells with an X and a Y chromosome in his body cells.
Ex: His genotype is XY
What is the probability for having a girl or boy child?
(using a Punnett square)
How are Male and Female chromosomes expressed?

6. What is Incomplete Dominance?
Neither allele is completely dominant nor completely recessive.
The heterozygous phenotypes is intermediate between the two homozygous phenotypes.
The phenotypes shows a blend of the 2 traits
just like “mixing paints”.
Ex: Parent flowers Red and White makes pink offspring
EX: Straight and curly hair makes Wavy hair
What is Incomplete Dominance?

7. List the genotypes. 4RW List the phenotypes. 4 Pink W W R W R W R pink
Example: Cross a homozygous red carnation flower (RR) with a homozygous white flower (WW).
List the genotypes.
4RW
List the phenotypes.
4 Pink
W W R W R W R
pink
pink R W R W
pink
pink

8. List the genotypes. 2RW, 2WW List the phenotypes. 2 Pink, 2White R W R
Example: Cross one heterozygous pink (RW) 4 o’clock flower with a White flower (WW).
List the genotypes.
2RW, 2WW
List the phenotypes.
2 Pink, 2White
R W R W W W W
pink
white R W W W
pink
white

9. Incomplete dominance

10. Example 2-Incomplete Dominance

11. An organism that has both alleles equally expressed in a heterozygote (displays both phenotypes at the same time).
Ex: ABO Blood type
Ex: For example, a cross between a black cat (BB) and a tan cat (TT) results in a tabby cat (black and tan mixed together).
What is Codominance?

12. Codominance red white roan
Defined: When both alleles are dominant and equally expressed
The colors do NOT blend together, but are equally seen
Ex: Cattle Coat
Red cow x White cow =
Roan Cow
Ex: Human Blood types
Type A x Type B = Type AB
red
white
roan

13. Blood types are another example of codominance.
The ABO blood types result from codominant alleles
This blood group consists of 3 different alleles
Dominant A allele
Dominant B allele
Recessive O allele
A and B are equally
dominant
Many genes have more than two alleles.

14. B B A A B A B A B A B List the genotypes. 4AB List the phenotypes.
Ex: Cross Jason who is homozygous for type A blood with Maria who is homozygous for type B blood.
List the genotypes.
4AB
List the phenotypes.
4 type AB blood
B B A A B A B A B A B

15. B o A o A B A o B o o o List the genotypes. 1AB, 1Ao, 1Bo, 1oo
Ex: Cross Mike who is heterozygous for type A blood with Lisa who is heterozygous for type B blood.
List the genotypes.
1AB, 1Ao, 1Bo, 1oo
List the phenotypes.
1 type AB blood
1 type A blood
1 type B blood
1 type o blood
Probability of Heterozygous individual?
75%
B o A o A B A o B o o o

16. In humans, hair, eye and skin color are polygenic traits.
Some traits which have many possible phenotypes that are determined by more than one gene
The interactions of theses genes allows for the large numbers of phenotypes.
Ex: Feather color in parakeets is determined by two genes.
One gene controls yellow color and the other controls blue color.
In humans, hair, eye and skin color are
polygenic traits.
The range in skin colors of humans is determined by no less than four genes!
What is Polygenic Traits?

17. Many genes may interact to produce one trait.
Polygenic traits are produced by two or more genes.
Order of dominance: brown > green > blue.

18. What factors interacts (affects) with genotypes?
Environmental
Genes provide a tendency toward a phenotype that the environment can alter.
Phenotype is a combination of genotype and environment
EX: The sex in sea turtles is determined by both genes and the temperature of the environment
During the development of the embryo, higher temperature favors the production of males.
2. Nutrition
EX: In humans, height is an example of a phenotype determined by genes and by the environment.
But if a person does not get the proper nutrients, he or she may not reach his or her potential height.
What factors interacts (affects) with genotypes?