Pt2- medelinan genetics- june 18

• 2 possible alleles exist for a trait

• No dominance exists

• Heterozygous individuals express both alleles simultaneously----> results in a 3^rd phenotype

• Seen in some flower colors, in coats of some animals, in some feather coloration of birds and also in the coloration of bird beaks

• In humans, seen in handedness

incomplete dominance

the key consist of what instead of capital and lower case letters

same capital with different subscript

inherited in humans through incomplete dominance

handedness

H^R=

H^L=

=right handed

=left handed

• More than 2 possible alleles exist for a trait

• This yields multiple possible phenotypes

• Example:  Human Blood typing (ABO)

multiple alles

3 possible alleles of multiple alleles

I^A=”A”

I^B= “B”

i = “O”

I^A and I^B bloodtypes are what alleles

codominant

I^A I^A  (homozygous) or I^Ai (heterozygous)=

blood type A

I^B I^B  (homozygous) or I^Bi (heterozygous)=

blood type B

ii (homozygous recessive)

blood type O

I^A I^B (heterozygous)

blood type AB

what does it mean that blood type I^A and I^B are codominant?

they are each dominant over the O allele (i), but are equally expressed when paired together

proteins produced by red blood cells

• recognize similar blood types

Antigens

protein molecules produced by white blood cells

• reject or are against foreign blood types

Antibodies

Blood type A produces what antigens and antibodies

A antigens and anit-B anitbodies

blood type B produces what antigens and anitbodies

B antigens and anti-A antibodies

Blood type O produces what antibodies and antigens

no antigens and anti-A and anti-B antibodies

blood type AB produces what antigens and what antibodies

A and B antigens and no antibodies

universal donor

• can donate blood to any other blood type

• can only receive from others of the same blood type

blood type O

universal recipient (acceptor)

• can receive blood from any other blood type

• can only donate to others with AB

blood type AB

can donate blood to A or AB but can only receive from A or O

blood type A

can donate blood to B or AB, but can only receive from B or O

blood type B

the interaction between two gene pairs

• with some traits, one gene pair can alter or affect the expression of a second gene pair

epistasis

multiple gene pairs influence the expression of one trait

• eye color, hair color

polygenic inheritance