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You have three genes on the same chromosome - A, B and C. Each gene has two alleles in a dominant/recessive relationship. For these genes the homozygous recessive has the mutant phenotype for that trait, the dominant phenotype = wild type for that trait.
Note: phenotypes can be represented by single letters. For example phenotype A = genotypes Aa or AA; phenotype a = genotype aa. Assume that phenotype ab = mutant phenotype for traits a and b, and wild type phenotype for trait C.
You cross an individual heterozygote for all three genes, with an individual who is homozygote recessive for all three. Out of 10,000 offspring you get the following phenotypes and amounts:
Use this information to answer the following questions.
For each phenotype determine if the number of offspring you are observing is greater or less than you'd expect if all three genes are sorting independently (expectation = independent assortment).
Use the information at the top of this page to choose the correct answer.
For phenotype a there are ( less/more) offspring observed than expected.
For phenotype b there are ( less/more) offspring observed
than expected.
For phenotype c there are ( less/more) offspring observed
than expected.
For phenotype ab there are ( less/more) offspring observed
than expected.
For phenotype ac there are (less/more) offspring observed
than expected.
For phenotype bc there are ( less/more) offspring observed
than expected.
For phenotype abc there are ( less/more) offspring observed
than expected.
For wild type there are ( less/more) offspring observed
than expected.
Question 11
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Based on the information given and your answer to the previous questions, what was the genotype of the heterozygous parent, in the correct order?
Select one:
a. BAc/baC
b. ACB/acb
c. ABc/abC
d. AcB/aCb
e. ABC/abc
Clear my choice
Question 12
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Given the information at the top of the page, determine the recombination frequency for A-C. Show your work here!
Note: You will choose the correct answer in the question below (multiple choice). This is for you to show your work.
You can show your work by typing out the math (fractions, % or decimals; can use any format you like) or explaining how you found the answer in words, or a combination of both. Basically any description/showing of your work even if your answer is wrong = 2 marks.
Question 13
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Given the information at the top of the page, what is the recombination frequency for A-C? Frequency is given as a number from 0 to 1.
Select one:
a. 0.03
b. 0.1
c. 0.02
d. 0.05
e. 0.015
10).
Trihybrid testcross ratio would be 1:1:1:1:1:1:1:1. It means that each phenotype would be an equal number, i.e., 10000/8 = 1250.
phenotype a – 98= observed 1250
phenotype b – 150= observed 1250
phenotype c – 4751= observed 1250
phenotype ab – 4749= observed 1250
phenotype ac – 147= observed 1250
phenotype bc – 99= observed 1250
phenotype abc – 3= observed 1250
wild type – 3= observed 1250
For phenotype a there are (less) offspring observed than expected.
For phenotype b there are (less) offspring observed than
expected.
For phenotype c there are (more) offspring observed than
expected.
For phenotype ab there are (more) offspring observed than
expected.
For phenotype ac there are (less) offspring observed than
expected.
For phenotype bc there are (less) offspring observed than
expected.
For phenotype abc there are (less) offspring observed than
expected.
For wild type there are (less) offspring observed than
expected.
11). d. AcB/aCb
Explanation:
phenotype a – 98= aBC
phenotype b – 150=AbC
phenotype c – 4751=ABc
phenotype ab – 4749=abC
phenotype ac – 147=aBc
phenotype bc – 99=Abc
phenotype abc – 3=abc
wild type – 3=ABC
Hint: Always non- recombinant genotypes are large numbered than the recombinant genotypes.
Hence, the parental (non-recombinant) genotypes is ABc/abC
1).
If single cross over occurs between a&b
Normal order = AB/ab
After crossing over = Ab/aB
Ab Progeny= 99+150 = 249
aB progeny = 98+147 = 245
Total progeny = 10000
Total progeny = 494
Recombination frequency between a&b = (Number of recombinants / Total progeny )
= (494/10000) = 0.05%
2).
If single cross over occurs between b&c
Normal order = Bc/bC
After crossing over = BC/bc
BC Progeny= 99+3 = 102
bc progeny = 98+3 = 101
Total progeny = 203
Recombination frequency between b&c = (Number of recombinants / Total progeny )
= (203/10000) = .03%
3).
If single cross over occurs between a&c
Normal order = Ac/aC
After crossing over = AC/ac
AC Progeny= 3+150 = 153
ac progeny = 3+147 = 150
Total progeny = 303
Recombination frequency between a&c = (Number of recombinants / Total progeny )
= (303/10000)= 0.03%
Recombination frequency (%)= distance between the genes (map units)
The order of genes = a-----0.03--------c----0.03m.u.------- b
Therefore, the genotype of heterozygous parent = AcB / aCb
12). a). 0.03