Help with a VERY HARD genetics question PLEASE?

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Discussion Overview

The discussion revolves around a genetics problem involving Manx cats, specifically focusing on allele frequencies in a population of these cats. Participants are addressing questions related to the frequency of the Manx allele in different generations and the underlying processes affecting these frequencies.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes a calculation for the frequency of the Manx allele in the first generation zygotes, suggesting a frequency of 0.25 based on a cross of heterozygotes and homozygotes.
  • Another participant challenges the initial assumptions about the founders, indicating that the population consists solely of Manx cats (heterozygotes), which may alter the calculations for part (a).
  • For part (b), a participant attempts to calculate the frequency of the Manx allele in breeding age individuals, arriving at a value of 0.375.
  • In response to part (c), one participant suggests that genetic drift may be the process under study, though they express uncertainty about the correctness of their answers.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the calculations or the assumptions regarding the population of Manx cats. There are competing views on how to approach the problem, particularly concerning the founders' genotypes.

Contextual Notes

Participants note the importance of the founders' genotypes in calculating allele frequencies, indicating that the initial assumptions may significantly impact the results. There is also uncertainty regarding the correctness of the proposed answers.

Who May Find This Useful

This discussion may be useful for students studying genetics, particularly those interested in allele frequency calculations and the implications of population genetics concepts.

paradoxium
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I'm a first-year college student and I'm havnig a lot of trouble with a particular question. Here goes:

Manx cats are tailess and when crossed with one another produceo n averaeg one long-tailed cat for every 2 Manx. The allele is lethal in homozygous condition due to problems arisiging in development of the lower vertebrae.

Suppose an island were populated with Manx cats.

(a) What would the ferquency of Manx allele be in first generation zygotes produced by the founders? Indciate as completely as possible your argument for this and the next question?

(b) What would the frequency of the Manx allele be in breeding age individuals of thsi generation?

(c) What process is under study in this change in allele frequencies (one sentence or phrase only)?
 
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What are your own answers so far?
 
For (a), my friends and I came up with:

Aa X aa --> 2 tailess (Aa) + 2 long-tailed (aa)
Manx allele = A (dominant)

Frequency = 2A/(6a + 2A) = 2/8 = 1/4 = 0.25

For (b):

The number of individuals can be calculated by:

2Aa = 2 X 0.25 (1-0.25) = 0.375

For (c):

Genetic drift??

I'm not sure if any of the our answers are right. Any help will be much appreciated. THANKS!
 
I'll offer some help with part (a) and see how things go from there. You're right that Manx cats are heterozygotes, and in this example appears to be a dominant trait. However, take careful note of the founders for part (a). The problem states that the island is populated with Manx cats, not a mix of Manx and cats with tails. So your founders are all heterozygotes, not a cross of heterozygotes and homozygotes. See how that affects your calculations.
 

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