Some genes are said to be “linked”. Explain this term and the implications it has as to the inheritance of certain traits. Provide 2 (human) examples of linked genes?
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When two genes are said to be "linked," it means that they are located close to each other on the same chromosome. During the formation of gametes (egg or sperm cells), these genes tend to be inherited together as a single unit, rather than segregating independently. This is because genetic recombination, which is the shuffling and exchange of genetic material that occurs during meiosis, is less likely to occur between closely located genes.
The implications of linked genes in inheritance are that they may not segregate independently during the process of genetic recombination. As a result, the expected genetic ratios predicted by Mendelian genetics may be altered.
Here are two examples of linked genes in humans:
1. Eye color and hair color: Genes for eye color and hair color are often located close together on the same chromosome. Generally, individuals with brown eyes tend to also have dark hair, while individuals with blue eyes generally have lighter hair. This is because the genes responsible for eye color and hair color are linked and inherited together.
2. Hemophilia and color blindness: The genes for hemophilia (a blood clotting disorder) and color blindness are also linked. Both of these conditions are more commonly found in males because these genes are located on the X chromosome. Since males have only one X chromosome, they are more likely to inherit linked genes from their mother, who carries these genes on her X chromosome.
To determine whether two genes are linked and estimate the distance between them, scientists use a technique called genetic mapping. This involves analyzing the patterns of inheritance in large populations and observing how linked genes are transmitted from one generation to the next.