1. 11-3 Exploring Mendelian Genetics & 11-5 Linkage/Gene Maps
Interactive Notes pgs
pgs

2. Mendel’s next step…
Mendel discovered alleles separate during gamete formation, but do traits affect each other?

3. The 2 Factor Cross: F1 rryy RRYY Crossed true-breeding plants
Round yellow peas (RRYY) x wrinkled green peas (rryy)
All of the F1 offspring were hybrids (RrYy)
rryy ry RY
RrYy
RRYY

4. The 2 Factor Cross: F2 Mendel crossed the F1 hybrids
Many new combinations of alleles occurred that were not in either parent
Alleles for seed shape (R/r) segregated independently of those for seed color (Y/y)
This means that genes for different traits do not influence each other (Independent Assortment)

5. Dihybrid Cross R = round shape r = wrinkled shape Y = yellow seed
y = green seed

6. Mendel’s 4 Principles of Genetics
1) Inheritance of characteristics is determined by units called genes that are passed from parent to offspring.
2) When 2 or more alleles for a gene exist, some may be dominant and others recessive.
3) In sexually reproducing organisms, each adult has a copy of the gene from each parent. These genes segregate in gamete formation.
4) Alleles for different genes usually segregate independently of each other.

7. Beyond Dominant & Recessive Alleles
Exceptions to Mendel’s principles:
Some alleles are neither dominant nor recessive

8. Incomplete Dominance
Heterozygous phenotype is a mix of the 2 homozygous phenotypes
EX: red & white  pink

9. Codominance Heterozygous phenotype shows both characteristics
Ex: Blood type- alleles A & B are codominant

10. Multiple Alleles Genes that have more than 2 alleles
Ex: coat color in rabbits (1 gene4 different alleles)

11. Polygenic Traits
Controlled by 2 or more genes
Ex: human height

12. Genetics & the Environment
Characteristics are determined by the interaction between genes and the environment

13. What happens to genes on the same chromosome?
Thomas Hunt Morgan did research on fruit flies (Drosophila) to study gene linkage
He discovered:
Some genes are always inherited together
It is chromosomes that separate during gamete formation, NOT GENES

14. Gene Maps
Gene maps show where a particular gene is located on a chromosome
If genes are closer together recombination is less likely
If genes are far apart, recombination is more likely