Monohybrid Single-gene crosses. TT x tt

Law of Segregation Each allele inherited separately. The alleles for each gene segregate from each other, so that each gamete carries only one allele for each gene. Ex: A Tt (tall) plant can pass on either its dominant T allele, or its recessive t allele to each sex cell (gamete) Tt

Dihybrid Two gene cross Shows two different genes getting passed from one generation to another.

Mendel wondered if the segregation of one pair of alleles affects another pair For example, does the gene that determines the gene that determines the shape of the seed affect the gene for seed color?

Dihybrid practice Lets cross two pea plants that are heterozygous for height and pod color. Parents: TtGg x TtGg First, lets determine the possible gametes these parents can create: TtGg TtGg

Now use these 4 gametes in a dihybrid punnett square to see what offspring they would create Since each parent now makes 4 possible gametes, there are going to be more boxes in our punnett square.

Try one on your own: In guinnea pigs, short hair is dominant to long hair. Also in guinnea pigs, black eyes are dominant to red eyes. A male guinnea pig that is heterozygous for both traits is crossed with a female that is long haired and red eyed. What are the expected phenotypes of their offspring and in what proportion?

Independent assortment Genes for different traits can segregate independently during the formation of gametes.

END OF MENDELIAN GENETICS