COMPLEX PATTERNS OF INHERITANCE 7 2 pg 1

COMPLEX PATTERNS OF INHERITANCE 7. 2 pg. 1

NON-MENDELIAN INHERITANCE

INCOMPLETE DOMINANCE Heterozygous phenotype is a mixture of the two homozygous phenotype; neither is dominant.

INCOMPLETE DOMINANCE Example: four-o’clock plant RR=red flowers Rr= _______ flowers rr= white flowers

INCOMPLETE DOMINANCE

INCOMPLETE DOMINANCE EXAMPLE A red flower (RR) and pink flower (RW) are crossed. What are the resulting offspring phenotypes and percentages?

GENETIC COUNSELING – ANALYZING INHERITANCE OF GENETIC TRAITS - PEDIGREES So far, we have only looked at pedigrees that have completely filled in shapes for organisms that exhibit a trait, and empty shapes for organisms that do not exhibit a trait. Red White Pedigrees can also show more detailed information. A half filled shape shows a heterozygote. If the pedigree to the left represents snapdragons, what are the phenotypes of the offspring in the generation II?

CO-DOMINANCE Phenotypes of both homozygotes are expressed equally. WW=white feathers BB=black feathers BW=black AND white feathers x

CO-DOMINANCE EXAMPLE A black chicken (BB) and a black-andwhite chicken (BW) mate. What are the resulting percentages of each possible phenotype?

POLYGENIC TRAITS Polygenic inheritance is expressed when multiple genes each make a small contribution to the overall phenotype. • Allows for more than 2 or 3 variations in expressed phenotypes • For example, skin color ranges from very fair to very dark skin shades. • At least 378 genes are involved in determining skin color

POLYGENIC TRAITS • Environment can contribute to the polygenic phenotype (known as multifactorial inheritance). • Punnett squares are complicated for polygenic inheritance.