Question

The distance between linked genes is directly proportional to A. the frequency of crossing over. B. the frequency of nonsense codons. C. the length of polypeptide chains. D. the ratio of AT:GC.

Short answer

A. the frequency of crossing over.

Step-by-step solution

- Understand the Concept of Linked Genes

Linked genes are genes that are located close to each other on the same chromosome. Because they are physically close, these genes tend to be inherited together during the process of meiosis.

- Define Crossing Over

Crossing over is a process that occurs during meiosis where homologous chromosomes exchange segments of their genetic material. This results in new combinations of alleles and contributes to genetic diversity.

- Analyze the Relationship

The frequency of crossing over between two genes is higher when the genes are farther apart on the chromosome. Conversely, the frequency of crossing over is lower when the genes are closer together.

- Identify the Correct Option

Since the frequency of crossing over correlates with the distance between genes, the distance between linked genes is directly proportional to the frequency of crossing over.

Key concepts

crossing over

Crossing over occurs during the process of meiosis, specifically in prophase I. This is when homologous chromosomes pair up and exchange segments of their genetic material. The result of this exchange is new combinations of alleles on each chromosome, which leads to increased genetic diversity in offspring.

Crossing over is crucial because it ensures that the genetic material is shuffled, allowing for variation in the genetic makeup. This is important for natural selection and evolution as it increases the chances of beneficial traits being passed on.

The frequency of crossing over is not random. It is influenced by the physical distance between the genes on the chromosome:

• Genes that are further apart have a higher chance of crossing over.
• Genes that are closer together have a lower chance of crossing over.

genetic linkage

Genetic linkage refers to the tendency of genes located close to each other on the same chromosome to be inherited together. Unlike independent assortment, which applies to genes on different chromosomes or far apart on the same chromosome, linked genes do not segregate independently.

These linked genes are passed on as a group during meiosis unless crossing over occurs between them. The closer the genes, the less likely they are to be separated by crossing over.

The measure of the distance between two linked genes is often expressed in map units (centiMorgans, cM). One map unit is equivalent to a 1% recombination frequency. This unit helps geneticists determine the relative position of genes on a chromosome. Understanding genetic linkage and map units is crucial in fields like genetic mapping and breeding programs.

meiosis

Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four haploid cells. This process is essential for sexual reproduction as it ensures that offspring have the same chromosome number as their parents.

Meiosis occurs in two stages: Meiosis I and Meiosis II. Each has its own sub-stages:

• Prophase
• Metaphase
• Anaphase
• Telophase

During Meiosis I, homologous chromosomes pair up and exchange segments through crossing over. This step is critical for genetic diversity. By the end of Meiosis II, the result is four genetically unique haploid cells.

Understanding meiosis is essential for comprehending how traits are passed from one generation to the next, and it plays a key role in areas like genetics and evolutionary biology.