Genetics

Test Cross - Cob Marked-R Alleles 1:1 (Purple - Yellow)

This cob is the product of a test cross involving pollen of a plant of unknown genotype, but having purple fruits, (RR or Rr) and a plant that was homozygous recesive (rr). A test cross is a method that allows us to determine what the unknown gynotype is (RR or Rr). Count 100 fruit.

How many are purple and how many are yellow?

Based on these results can you determine the unknown genotype?

Is it actually necessary to count a large sample of fruits? Explain

DihybridCross - Cob Marked-R and Su Alleles 9:3:3:1

This cob is the result of crossing two F1 plants which were heterozygous for the two alleles indicated. One parent is homozygous dominant purple smooth (RRSuSu) and the other is homozygous recessive yellow wrinkled (rrsusu).

Count 100 kernels on the cob above and use the calculator below to determine your .

 CHI-SQUARE CALCULATOR
 Enter the observed number and the expected ratio below.

Observed # Ratio


CATEGORY 1 
CATEGORY 2 
CATEGORY 3 
CATEGORY 4 

Observed
Expected
chi-square


Use the calculated value and the table below to see if the cob above is a 9:3:3:1 cob.  (Note that your degrees of freedom is now 3)
 
 
 

First published Sept 95: Modified June 2020
Copyright © Michael Shaw 2019 (Images and Text)

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