Three genes affecting flower characters in a species of primrose (Primula sp.) a
ID: 168291 • Letter: T
Question
Three genes affecting flower characters in a species of primrose (Primula sp.) are shown in the table below. In order to determine the relationship between the genes, a true-breeding long style, red stigma and red flower primrose was crossed with a true breeding short style, green stigma, magenta flower primrose. The F1 primrose was then subjected to a testcross. a. Write the genotypes of the Parent truebreeders. b. Write the genotypes of the F1 testcross parents. Draw the chromosomes so that you can follow which alleles are potentially on which chromosome. c. Draw a Punnet square for the F1 test cross. Write the expected phenotypic ratios. d. The progeny of that cross are tabulated below. Fill in the table for each progeny type as P (for parental), SCO (for single crossover) and DCO (for double crossover). Then write the gene order. e. Write the gene order and determine the distance between them.Explanation / Answer
The 2 groups of cross genes with style, stigma, ovary and flower in the parents are considered for the female flower only and similar genes can be assumed for the male flower with antheridia and pollen grains.
a)genotype of true parent primrose fllower breeders--
LLSSFF(short style, green stigma, magenta flower)(dominant) x llssff(long style,red stigma,red flower)(recessive)
F1 generation progeny---
b)F1 test cross--LlSsFf,LlSsFf,llSsff,llSsFf,LlssFf,LlssFf,LlSsff,LlSsff.
c)LlSsFf(heterozygous dominant) x llssff (recessive parent)
phenotypic ratio--6:2=3:1.
d)gene order is --LFS and lfs on the chromosome for parental recombination as the lowest gene recombination frequency combination are LSf and lsF, DCO-LCF and lcf, SCO in the L-F region--LFs and lfS, SCO in the F--S region--lFS and Lfs, null cross over LfS and lFs.
d)gene order---L---(11.68cM)--F---(33.96cM)--S on the chromosome.
e)distance between the L and F=(16+18+5+4) x 100/368 =11.68cM,
distance between F and S=(63+5+53+4) x 100/368=33.96cM.
male x female LSF LSF lsf LlSsFf LlSsFf lsf LlSsFf LlSsFfRelated Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.