MORE GENETICS VOCABULARY & EXAMPLES

Multiple Alleles

Incomplete Dominance

Co dominance

Sex-linked

Multiple AllelesA. Human Blood Groups

1. ABO Blood Groups

a. Type A: A antigen, IA IA or IA i

b. Type B: B antigen, IB IB or IB i

c. Type AB: both A&B antigens, IA IB

d. Type O: no antigens, ii

How common are the blood types?

O+ A+ B+ AB+ O- A- B- AB-

37.4% 35.7% 8.5% 3.4% 6.6% 6.3% 1.5% 0.6%

Incomplete Dominance

Heterozygous has a “blended” look

Neither allele covers or hides the other

Mix

Alleles are mixed.

For example, red cows crossed with white will create roan (orange) cows.

INCOMPLETE DOMINANCE

Co Dominance

Both alleles are expressed

Can look checkered or spotted

Appaloosa horses, speckled chickens, Sickle Cell Anemia

Codominance-Coco the spotted chicken

Sex Linked Traits Found on X

chromosome More than 100 sex-

linked genetic disorders

The Y chromosome is much smaller than the X chromosome and appears to have only a few genes.

Hemophilia Muscular

Dystrophy Color Blindness

Color Blind

Mother XCX-

XC YXC XCXC

Daughter

(Normal Vision)

XCYSon(Normal Vision)

X- X- XC

Daughter

(Carrier)

X-YSon(colorblind)

Father XCY

Polygenic Traits

POLYGENIC TRAIT (POLY=MANY)

EYE COLOR & SKIN COLOR ARE TRAITS CONTROLLED BY MANY GENES.

PEDIGREE

CHART THAT SHOWS HOW A TRAIT IS INHERITED WITHIN A FAMILY

CONT.

WHEN A PERSON HAS THE RECESSIVE GENE THAT CAUSES A DISEASE BUT IS NOT AFFECTED BY IT, THEY ARE CALLED A

CARRIER (Tt)