8B. Dihybrid Crosses Flashcards
1
Q
Dihybrid crosses are
A
predicted genetic outcomes for two genes that are either linked or assort independently
2
Q
Dihybrid cross (unlinked) instructions
A
- Assign letters to each allele
- Write parent line
- Write the gametes (FOIL)
- Draw 4 × 4 grid, write all possible allele combinations
- Complete the cross
- Find the phenotypic ratio
3
Q
What is the phenotype ratio for unlinked genes with heterozygous parents
A
9:3:3:1
4
Q
Linked genes are
A
genes which are on the same chromosomes and are inherited together
5
Q
Do linked genes go through independent assortment
A
No
6
Q
The chances of crossing over occurring are calculated by
A
Map units
7
Q
One map unit is
A
one per cent chance of crossing over and offspring containing a recombinant chromosome.
8
Q
To determine if two genes are linked
A
a test cross can be performed.
9
Q
Dihybrid cross (linked) instructions
A
- Assign letters to each allele
- Draw a 1 × 4 grid, write father’s alleles and mother’s alleles.
- Write the gametes (use ab/ab form for each parent)
- Do two crosses
- Find genotype and phenotype ratios
- Determine gametes of heterozygous parent by checking the test crosses.
10
Q
Homozygous parents only produce
A
ab/ab
11
Q
Heterozygous parents can produce
A
AB/ab or Ab/aB
