2. You are studying two genes that are linked: The Twitch and Freckle genes. There are two alleles of each gene: Tis dominant to t, where T results in twitching behavior & t is no twitching F is dominant to f, where F results in freckles & f is no freckles You have been told the T and F loci are 36 map units apart. 36 m.u. a. We have a heterozygous individual (Tf/tF); their replicated chromosomes pictured at right. The heterozygote mates with a homozygous recessive individual. What is the probability they will have a child that is twitchy and freckled? b. Hypothetically speaking, if the individuals from part a had 25 children, what do you expect their phenotypes to be, and in what proportions? How does this differ from what you would expect if there was no linkage between these loci?

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**Genetic Linkage and Probability Study**

**Exercise 2: Gene Linkage in Twitch and Freckle Traits**

You are studying two genes that are linked: The Twitch and Freckle genes. There are two alleles of each gene:

- **T** is dominant to **t**, where T results in twitching behavior and t results in no twitching.
- **F** is dominant to **f**, where F results in freckles and f results in no freckles.

The T and F loci are 36 map units apart.

**a. Probability of Twitchy and Freckled Offspring**

We have a heterozygous individual (Tf/tF); their replicated chromosomes are pictured on the right. The heterozygote mates with a homozygous recessive individual (tf/tf). What is the probability they will have a child that is twitchy and freckled?

**b. Hypothetical Offspring Phenotypes**

If the individuals from part a had 25 children, what do you expect their phenotypes to be, and in what proportions? How does this differ from what you would expect if there was no linkage between these loci?

**Diagram Explanation**

- The diagram on the right illustrates a pair of homologous chromosomes.
- The map distance between the **T (Twitch gene)** and **F (Freckle gene)** loci is marked as 36 map units.
- The upper line represents a chromosome with alleles T and f, and the lower line represents another chromosome with alleles t and F.
- This linkage map shows the physical proximity of the two gene loci on the chromosome, indicating the likelihood of recombination.

**Considerations for Analysis:**

- Understand the concept of genetic linkage and how it affects inheritance patterns.
- Use recombination frequency (36%) for calculating expected offspring phenotypes.
- Compare linked versus unlinked inheritance scenarios to highlight the impact of genetic linkage.
Transcribed Image Text:**Genetic Linkage and Probability Study** **Exercise 2: Gene Linkage in Twitch and Freckle Traits** You are studying two genes that are linked: The Twitch and Freckle genes. There are two alleles of each gene: - **T** is dominant to **t**, where T results in twitching behavior and t results in no twitching. - **F** is dominant to **f**, where F results in freckles and f results in no freckles. The T and F loci are 36 map units apart. **a. Probability of Twitchy and Freckled Offspring** We have a heterozygous individual (Tf/tF); their replicated chromosomes are pictured on the right. The heterozygote mates with a homozygous recessive individual (tf/tf). What is the probability they will have a child that is twitchy and freckled? **b. Hypothetical Offspring Phenotypes** If the individuals from part a had 25 children, what do you expect their phenotypes to be, and in what proportions? How does this differ from what you would expect if there was no linkage between these loci? **Diagram Explanation** - The diagram on the right illustrates a pair of homologous chromosomes. - The map distance between the **T (Twitch gene)** and **F (Freckle gene)** loci is marked as 36 map units. - The upper line represents a chromosome with alleles T and f, and the lower line represents another chromosome with alleles t and F. - This linkage map shows the physical proximity of the two gene loci on the chromosome, indicating the likelihood of recombination. **Considerations for Analysis:** - Understand the concept of genetic linkage and how it affects inheritance patterns. - Use recombination frequency (36%) for calculating expected offspring phenotypes. - Compare linked versus unlinked inheritance scenarios to highlight the impact of genetic linkage.
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