You are studying three linked genes in snapdragons. The flower color locus is in

Question

You are studying three linked genes in snapdragons. The flower color locus is in the center. There are 11.3 cM between the flower color locus and the plant height locus. There are 10.7 cM between the flower color locus and the leaf type locus. The coefficient of coincidence is 0.8. Pure-breeding tall, red-flowered plants with fuzzy leaves were crossed to pure-breeding dwarf, blue-flowered plants with smooth leaves. The F1 were testcrossed. Calculate the proportion of the testcross progeny that are expected to be dwarf with blue flowers. Round properly to 4 decimal digits.

Explanation / Answer

It is a triple cross whi ch is tangled & Tough to solve

So you first need to draw a chart the names & distances between them

First, the offspring need to be arranged
into reciprocal pairs of no crossovers,

Because there is a higher probability of
having no crossovers, the two
genotypes with the highest number of
offspring are NCO (no crossover) .
There are two sets of SCO, and the two
with the lowest offspring will be DCO.

Next you need to determine which order
of alleles on the chromosome will result in
the DCO.

Now how to calculate the distance

Distance influences the probability of
crossover.
• The larger the distance, the more likely
crossover will occur.
• The shorter the distance, crossover will occur
less frequently.
• To determine the distance, add the number of
times crossover occurred between the two loci.
SCO+DCO/ Total Offspring * 100=
number of map units between genes.

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