Two-Factor Crosses II Flashcards
What are linked genes?
Genes on the same chromosome
What are unlinked genes?
Genes on different chromosomes
What experiment was first done by Bateson and Punnett in 1905?
Sweet pea flowers and their flower color and pollen length
What colors were observed in sweet peas?
Purple (P, dominant)
Red (p, recessive)
What pollen lengths were observed in sweet peas?
Long (L, dom)
Round (l, rec)
What was the EXPECTED ratio for the F2
of sweet peas?
9:3:3:1
What was the ACTUAL ratio for the F2 of sweet peas?
3:1, because heterozygous alleles cannot be inherited from linked genes
What were the expected phenotypes for the F1 offspring?
Purple and Long
Red and Round
What were the unexpected phenotypes for the F1 offspring?
Purple and Round
Red and Long
What occurred when Bateson and Punnett repeated their experiments?
The same frequency of recombinant offspring was observed.
Other gene pairs would show different frequencies of recombinant offspring.
What does the frequency of recombinant offspring depend on?
The distance between the two genes on a chromosome
Where does crossing over along the chromosome?
Crossing over occurs randomly anywhere along the length of a chromosome
What are “parental and nonrecombinant” offspring?
The “expected”
What are “nonparental or recombinant” offspring?
