CHAPTER 5: Linkage, Recombination, & Gene Mapping

A set of flashcards covering key concepts from Chapter 5 on Linkage, Recombination, and Gene Mapping, including definitions, processes, calculations, and implications.

What are syntenic genes?

Genes located on the SAME chromosome.

Define genetic linkage.

When genes are inherited together MORE often than expected by chance (more than 50% of the time).

What is the expected offspring ratio for two unlinked genes in a testcross?

1:1:1:1 ratio.

What is crossing-over?

The exchange of genetic material between homologous chromosomes during Meiosis I.

What is recombination frequency (RF)?

The percentage of recombinant offspring produced in a genetic cross.

What does 1% recombination frequency represent in terms of gene mapping?

1 map unit (m.u.) or 1 centiMorgan (cM).

What is the maximum recombination frequency?

Recombination frequency can NEVER exceed 50%.

How do you identify parental and recombinant gametes in a testcross?

Parental gametes have the same allele combinations as the parents, while recombinant gametes have new combinations.

What is the significance of chiasmata during meiosis?

They are physical points where crossing-over occurs, essential for chromosome pairing and separation.

What is the purpose of the Chi-Square test in genetics?

To determine if deviations from expected ratios are due to linkage or random chance.

What does the null hypothesis (H₀) imply in linkage studies?

The assumption that the genes are NOT linked and assort independently.

Why can't genetic distances measured through RF always correlate to physical distances?

Double crossovers can mask recombination events, and regions can have variable recombination rates.

What is interference in relation to double crossovers in genetics?

The phenomenon where the occurrence of one crossover event reduces the probability of another occurring nearby.

What is the conclusion if p-value ≤ 0.05 during a Chi-Square test?

Reject the null hypothesis, indicating that the genes are likely linked.

What are twin spots in Drosophila?

Adjacent patches of tissue with different genotypes, evidence of mitotic recombination.

What is the important medical implication of mitotic recombination?

It can lead to cancer development when it causes loss of function in tumor suppressor genes.

How do you calculate degrees of freedom in a Chi-Square test?

df = N - 1, where N is the number of phenotypic classes.

What is the importance of using three-point crosses in gene mapping?

They are more efficient and accurate for determining gene order than two-point crosses.