27.2 Human Traits

27.2 Human Traits

•Survey•Complete Dominance•Incomplete Dominance•X-Linked Traits

Types of Traits

• Physical traits: hair, eyes, skin, features, height, weight, shape

• Psychological traits: personality, shyness, personal skills, social skills

• Chemical: blood type, predisposition to genetic disorders, diabetes, ect.

Complete Dominance

• In a heterozygous genotype, Bb, the dominant allele always appears in the phenotype

Complete Dominance

• For example, for one of the gerbil fur color genes, that wild type agouti/brown allele (B) is completely dominant to the black (b) allele of the same gene. Bb gerbils are brown.

• And you can't tell by looking at a brown gerbil whether it is BB or Bb, no matter how closely or carefully you look.

Incomplete Dominance

• Neither allele is dominant, they are both partially expressed

• Blended

Sickle-Cell Anemia

• fatal anemia marked by sickle-shaped red blood cells,

• Causes pain in the joints, fever, leg ulcers, and jaundice.

• Incomplete Dominance

• RR’

Sickle-Cell Genes

Alleles

• R = round red blood cell

• R’ = sickle red blood cell

Geneotypes

• RR = all round blood cells

• R’R’ = all sickle blood cells

• RR’ = half round and half sickle blood cells

Codominance

• Both alleles of a gene pair in a heterozygote are fully expressed,

• Neither one being dominant or recessive to the other.

Codominance

• Human Blood Types

Inheritance Patterns

• AB is codominant• A and B are equal• AO and BO is

complete dominance• O is recessive

X-linked Traits

• Genes found on the X chromosome, but not the Y

• Girls: XrXr or XXr

• Boys :XrY

• Carrier: mother can carry the allele, but not get the disorder

• Carrier: X Xr

X-Linked Disorders

1. Color blindness

2. Hemophilia

3. Duchene Muscular Dystrophy

Color Blindness

• Red and green look like gray

• C = ability to see colors

• c = color blind to red and green

• Males are more likely to be colorblind

• They only need one recessive gene

• XcY males or XcXc females

What numbers do you see ?