1. If two traits, dwarfism and stem color, were on the same pair of chromosomes
ID: 60331 • Letter: 1
Question
1. If two traits, dwarfism and stem color, were on the same pair of chromosomes would you expect an F2 generation of 9:3:3:1 for a di hybrid cross? Use Mendel’s laws and your understanding of meiosis to explain your answer.
2. A budding plant breeder discovers a rare mutant of Brassica that is almost entirely white. The plastids in the leaves have a mutant that results in white plastids. If the breeder uses the pollen from this mutant to pollinate a plant with normal green leaves what kind of leaves would you expect to see in the offspring? Explain.
Explanation / Answer
Individual inherit one allele of each gene from both the parent, ( from egg and sperm). If the genotype of egg is DC (dwarfism and colour) and the genotype sperm is dc, then the offspring has genotype DCdc
In F2 generation, DCdc X DCdc, D-dwarf, C-green colour, d- Tall, c-brown colour
The phenotypic ratio of each gene is 9:3:3:1 for a di hybrid cross
9/16: phenotypic Dwarf green
3/16: phenotypic Dwarf brown
3/16: phenotypic Tall green
1/16: phenotypic Tall brown
2. Mutant white allele is homozygous ll
Normal green leaves is LL
Gametes from mutant white leaves of white allele ll x Gametes from normal green leaves of allele LL
L L
l Ll Ll
l Ll Ll
The cross between dominant allele, normal green leaves and mutant recessive allele, white plastids resulted with all dominant offspring.
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