11-3 Exploring Mendelian Genetics & 11-5 Linkage/Gene Maps Interactive Notes pgs. 270-274 pgs. 279-280

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

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

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)

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

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.

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

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

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

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

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

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

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

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