Codominance and Sex-linked traits

CODOMINANCE 2 alleles are dominant and both are expressed Most common examples are blood type and flower color.

Blood Type 3 possible alleles: A, B, O 4 possible PHENOTYPES: AABBO Both alleles A and B are dominant. When both A and B alleles are present, they are both expressed. Type O is recessive.

There are multiple genotypes: Phenotype A = Genotype AA, Ao Phenotype B = Genotype BB. Bo Phenotype AB = Genotype AB Phenotype O = Genotype oo Blood Type

Punnett Squares are worked the same way as before: Cross AA with Bo What are the possible Genotypes? Phenotypes? AA AB Ao B o

Sex-linked traits Sex is determined by the X and Y chromosomes. XX is female XY is male

Genotype uses Xs and Ys. Female = XX Male = XY Sex-linked traits

Cross a male and a female. What are the frequencies of: female offspring? Male offspring? Sex-linked traits XX X Y XX XY

Some genes are only found on the X or the Y chromosome. These traits are SEX-LINKED. Common examples include Hemophilia and colr-blindness. Sex-linked traits

The alleles you are looking at are written as superscripts on the X and Y chromosomes. X B X B X B Y Sex-linked traits

Example: The gene for colorblindess is only found on the X chromosome B= normal vision; b= colorblind Female with normal vision: X B X b or X B X B Female with colorblindness: X b X b Male with normal vision: X B Y Male with colorblindness: X b Y Sex-linked traits

Punnett squares work the same way, use X and Y in the genotypes. Sex-linked traits Cross a heterozygous normal vision female with a normal vision male. Genotypes? Phenotypes? XBXB XbXb XBXB Y XBXBXBXB XBXbXBXb XBYXBY XbYXbY