High School Biology Unlocked: Your Key to Understanding and Mastering Complex Biology Concepts (High School Subject Review) by Princeton Review

Author:Princeton Review
Language: eng
Format: azw3
ISBN: 9781101921517
Publisher: Random House Children's Books
Published: 2016-11-29T05:00:00+00:00

Trapped Together: A Story of Genetic Linkage

Independent assortment and crossing over help make gametes with as much genetic variation as possible, but sometimes certain alleles get stuck together. Genes on the same chromosome are called linked genes because their DNA is linked. Even though crossing over can occur, it does not easily occur when the genes are very close together.

If the alleles don’t get swapped through crossing over, they remain trapped together on a chromosome. This means that they will end up in the same gamete. They are linked and where one goes, the other goes. If certain alleles appear together more often than randomness should allow, they might be linked.

Unfortunately, since most physical traits in humans are determined by more than one gene, it is difficult to point out an example of linkage in humans, but in fruit flies the eye color and body color genes are on the same chromosome. When offspring are studied, fruit flies with a particular body color often have the same color eyes.

Note: Genetic linkage is different from sex-linkage. Sex-linkage means that a gene is on either the X or the Y chromosome so it is more commonly linked to one of the sexes.

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