Genetics Intermediate Traits

Traits Most traits are controlled by more than 1 gene Most traits have multiple alleles

Incomplete dominance For some traits, neither allele is dominant Blending occurs Ex. Snapdragons Cross a red flower with a white flower and get pink flowered offspring

Problem A true breeding red snapdragon is crossbred with a true breeding white snapdragon. Red and white colors are considered to be incompletely dominant. What will the phenotypic ratio of their offspring be?

Codominance Both alleles are expressed in the same organism Ex. Chicken feathers Black feathered rooster + a white feathered hen = offspring with some white feathers and some black feathers

Problem In a certain type of rabbit, black fur is codominant with brown fur resulting in an agouti color. If a true breeding black fur rabbit and an agouti rabbit are bred, what will the phenotypic ratio of the offspring be?

Multple Alleles Each organism has only 2 possible alleles for a trait Multiple alleles for the trait may exist in the entire population Ex. Human Blood types A, B, AB, O

Blood Types A and B are CODOMINANT A and B are DOMINANT over O Written as IA, IB, and I IA IA produce A blood type IA i produce A blood type IB IB produce B blood type IB i produce B blood type ii proudces O blood type What type of parents can produce offspring with any blood type?

Problem A man with type O blood marries a woman with type A blood. They have a son with type O blood. Several years later they get a divorce and the wife is suing the husband for child support. Is it possible that he should have to pay?

Problem A man with type O blood marries a woman with type A blood. They have a son with type B blood. Several years later they get a divorce and the wife is suing the husband for child support. Is it possible that he should have to pay?

Polygenetic Traits Some traits are controlled by more than one gene Ex. In humans Height Eye color Skin color

Intermediate Patterns of Inheritance Pattern of Inheritance Description Example Incomplete Dominance One allele is not completely dominant over another Snapdragons: Red flowered plant and white flowered plant crossed make pink flowered plants Codominance Both alleles contribute to the phenotype Chicken variety: black feathered chicken X with a white feathered chicken = white and black feathered chicken Multiple alleles A gene has more than 2 alleles possible Human blood type: IA and IB (codominant) and i Polygenetic Traits Traits are controlled by more than 1 gene Human skin color: wide range of colors due to several different genes

Chromosomes 2 types Autosomes are any type of chromosome other than a sex chromosome Sex chromosomes are X and Y Females XX – always donate an X Males XY – determines gender of offspring

Sex – Linked Traits Determined by alleles located on the sex chromosomes (X and Y chromosomes) Males have 1 X chromosome meaning they are more likely to show a sex linked recessive trait Ex. Albinism, hemophilia, blindness, muscular dystrophy are sex linked

Karyotypes Visual display of all the chromosomes in an organism Indicate chromosomal abnormalities Broken, missing, or extra Down’s syndrome

Down’s syndrome Results from an extra 21st chromosome

Turner’s syndrome Only 1 X chromosome and no Y Always Female Usually develop normally but may result in shorter stature

Triple X Goes undiagnosed most of the time Estimated 1 out of 10 girls are XXX

XYY syndrome Extra Y chromosome Only in Males

Klinefelter syndrome Males Tendency to develop female-like characteristics