1. 11-2 Genetic Crosses

2. 1. Genotype and Phenotype
A. Genotype: the genetic make-up of an organism. The alleles that the organism inherits from the parents.
1.. Example – BB, Bb, bb, TT, Tt, tt
B. Phenotype: the physical appearance of an organism as a result of its genotype.

3. C. Homozygous: when both alleles of a pair are alike.
1. example – BB or bb
D. Heterozygous: when both alleles of a pair are different.
1. example – Bb
E. Probability: the likelihood that a specific event will occur.

4. Probability Punnett Squares - are used to see the probability of
different traits inherited
by the offspring

5. 2. Different Punnett Square crosses
A. Homozygous Dom – Homozygous Dom =
100% Homozygous Dominate
B. Homozygous Dom.- Homozygous Rec. = 100 % Heterozygous Dominate.
C. Heterozygous – Homozygous Dom. =
50 % - 50%
D. Heterozygous – Heterozygous =
25% Homo. Dom. , 50% Hetero. Dom., 25% homozygous rec.

6. A. Involves only one pair of contrasting traits.
2. Monohybrid crosses
A. Involves only one pair of contrasting traits.

8. is crossed with a homozygous recessive individual.
E. Testcrosses: an individual with unknown genotype
is crossed with a homozygous
recessive
individual.

9. F. Incomplete Dominance- Occurs when two or more alleles influence the phenotype, resulting in neither factors takes on the dominant role and they compromise in a third trait.

10. Incomplete dominance

11. Complete dominance

12. H. Codominance: occurs when both alleles for a gene are expressed in a heterozygous offspring.
1. No trait is dominant and there is no blending of traits. Both traits are shown equally.

13. Co-dominance – Blood types

14. Chapter 11
Section 11:3
Dihybrids

15. 3. Dihybrid Crosses A. Involves two pairs of contrasting traits

18. Constructing a Di-Hybrid cross
1. Dominant – Dominant
2. Dominant – Recessive
3. Recessive – Dominant
4. Recessive – Recessive