Question

Calculate the changes in allelic frequencies from one generation to the next in an open pollinating crop, depending on whether selection against the recessive allele (a) is done before or after flowering. For simplicity, assume you are dealing with F2 with 1 aa : 2 Aa : 1AA; that you start with four individuals, you can recognize only the recessive homozygotes (aa), mating is random and each plant produces the same number of gametes and progeny. What will be frequency of a in F3, with selection (aa removal) before flowering and after flowering? Note: in F2 the frequency of a is 50%. In absence of selection it will remain the same in F3. But you are applying selection against a, in two different ways. A hint: Punnett’s square will help a great deal.

          Calculate the changes in allelic frequencies from one generation to the next in an open pollinating crop, depending on whether selection against the recessive allele (a) is done before or after flowering.

For simplicity, assume you are dealing with F2 with 1 aa : 2 Aa : 1AA; that you start with four individuals, you can recognize only the recessive homozygotes (aa), mating is random and each plant produces the same number of gametes and progeny.

What will be frequency of a in F3, with selection (aa removal) before flowering and after flowering?

Note: in F2 the frequency of a is 50%. In absence of selection it will remain the same in F3. But you are applying selection against a, in two different ways.

A hint: Punnett’s square will help a great deal.

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Calculate the changes in allelic frequencies from one generation to the next in an open pollinating crop, depending on whether selection against the recessive allele (a) is done before or after flowering.

For simplicity, assume you are dealing with F2 with 1 aa : 2 Aa : 1AA; that you start with four individuals, you can recognize only the recessive homozygotes (aa), mating is random and each plant produces the same number of gametes and progeny.

What will be frequency of a in F3, with selection (aa removal) before flowering and after flowering?

Note: in F2 the frequency of a is 50%. In absence of selection it will remain the same in F3. But you are applying selection against a, in two different ways.

A hint: Punnett’s square will help a great deal.

Added by James W.

Biology for AP Courses

Julianne Zedalis, John Eggebrecht

Instant Answer

Solved by Expert Supreeta N

05/12/2023

Step 1

In F2, we have 1 aa, 2 Aa, and 1 AA individuals. The total number of alleles is 2(1+2+1) = 8, and the frequency of a is 50% (4 out of 8 alleles). Show more…

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Calculate the changes in allelic frequencies from one generation to the next in an open pollinating crop, depending on whether selection against the recessive allele (a) is done before or after flowering. For simplicity, assume you are dealing with F2 with 1 aa : 2 Aa : 1AA; that you start with four individuals, you can recognize only the recessive homozygotes (aa), mating is random and each plant produces the same number of gametes and progeny. What will be frequency of a in F3, with selection (aa removal) before flowering and after flowering? Note: in F2 the frequency of a is 50%. In absence of selection it will remain the same in F3. But you are applying selection against a, in two different ways. A hint: Punnett’s square will help a great deal.

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00:01 Hello students, in the given f2 generation the frequency of recessive allele that is small a is 0 .5.

00:24 Since we start with the four individuals the numbers of homozygous recessive that is small letter a small letter a and the numbers of heterozygous capital a small a and homozygous dominant capital a capital a individuals will be each one.

00:53 If we select against the recessive allele that is small letter a small letter a before flowering we remove small a small a individuals from the population.

01:10 So it will be removed.

01:15 The remaining individuals will be all either capital a small a or capital a capital a.

01:23 If we assume random mating the expected frequencies of the three genotypes in f3 generation that can be calculated using bannett square that is capital a small a into capital a small a.

01:54 So that is 25 percentage will get capital a capital a 50 percentage with capital a small a and 25 percentage with small a small a.

02:09 So small a is removed before flowering so it doesn't appear in the f3.

02:18 So now capital a capital a into capital a small a we get 50 percentage capital a capital a and 50 percentage will be capital a small a.

02:32 Again capital a capital a into capital a capital a here 100 percentage will be capital a capital a only.

02:44 So the frequency of the recessive allele small letter a frequency in the f3 generation is simply the frequency of small a small a genotype which is zero.

03:03 In this case since we removed all small a small a individuals before flowering therefore the frequency of the recessive allele in the f3 generation with selection before flowering is said to be zero...

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