Alleles segregate during gamete formation, but do they do it independently?
Alleles segregate during gamete formation, but do they do it independently?
Two-factor Cross, F1
RRYY x rryyRound/yellow peas wrinkled/green
What will offspring look like?
Gives hybrid plants needed for next cross
Two-Factor Cross, F2
RrYy x RrYy
Independent Assortment
•Genes for different traits can segregate independently during the formation of gametes.
•Leads to genetic variation in plants, animals, and other organisms.
Not all genes show simple patterns of dominant and
recessive
•Incomplete dominance•Codominance•Multiple alleles•Polygenic traits•Sex-linked
Incomplete Dominance
• One allele NOT dominant over another
• Four o’clock plants
RR x WW
RW
Codominance• Both alleles contribute to the
phenotype
• Chicken: black feathers codom with white
• Heterozygous = erminette (speckled)
• Humans: protein controlling cholesterol levels
• Blood type
Multiple Alleles
• Many genes have more than 2 alleles
• Coat color in rabbits
• Human gene for blood type
Polygenic Traits• Traits controlled by two or more genes
• At least three genes involved in reddish-brown pigment in eyes of fruit flies
• Different combinations of alleles produce different eye colors
• Polygenic traits often show a wide range of phenotypes
• Skin color in humans partly because more than four different genes probably control this trait
Sex-linked Genes