Gene R and gene T are genetically linked. Answer the following questions concerning a dihybrid organism with the genotype Rt/rT:


Can you make a general statement about how the occurrence of two crossover events between a given pair of linked genes affects the estimate of recombination frequency?

Verified step by step guidance

1. Understand the concept of genetic linkage: Genetic linkage occurs when genes are located close to each other on the same chromosome, and they tend to be inherited together. Recombination frequency measures how often crossing over occurs between two linked genes during meiosis.
2. Recall the impact of crossover events: A single crossover event between two linked genes can result in recombinant gametes. However, when two crossover events occur between the same pair of genes, they can cancel each other out, leading to gametes that appear non-recombinant.
3. Consider the recombination frequency for closely linked genes: For genes with a small recombination frequency (closely linked), the likelihood of two crossover events occurring between them is very low. Therefore, the recombination frequency estimate is less affected by double crossovers.
4. Analyze the recombination frequency for genes farther apart: For genes with a higher recombination frequency (farther apart), the probability of double crossover events increases. These double crossovers can lead to an underestimation of the true recombination frequency because they produce gametes that appear non-recombinant.
5. Conclude the general statement: Double crossover events reduce the accuracy of recombination frequency estimates, especially for gene pairs with higher recombination frequencies. This is because double crossovers can mask the occurrence of recombination events, leading to an underestimation of the true frequency.

Key Concepts

Genetic Linkage

Genetic linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together during meiosis. This occurs because linked genes are less likely to be separated by recombination events. Understanding linkage is crucial for predicting inheritance patterns and calculating recombination frequencies, which indicate how often crossover events occur between genes.

Recombination Frequency

Recombination frequency is a measure of the likelihood that two genes will be separated during meiosis due to crossing over. It is calculated as the number of recombinant offspring divided by the total number of offspring. A lower recombination frequency suggests that genes are closely linked, while a higher frequency indicates they are further apart, allowing for more crossover events.

Crossover Events

Crossover events occur during meiosis when homologous chromosomes exchange segments of genetic material. The number of crossover events between two linked genes can significantly influence the recombination frequency. In cases with two crossover events, the likelihood of producing recombinant gametes increases, which can lead to a more accurate estimate of the genetic distance between the genes involved.