Molecular Genetics

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The behavior of genetic markers during the propagation of organisms follows a few simple rules.

• As first noted by Gregor Mendel, genetic characters are discrete entities.
• Their visible manifestations (such as plant height, seed shape, etc.) may be masked in some organisms, but the characters are nevertheless present. Masked characters are said to be recessive and masking characters, dominant.
• The presence of masked characters is revealed in subsequent generations. Mendel said that they segregate in subsequent generations
• Most eukaryotes have two sets of genes (are diploid).
• Mendel's studies with pairs of characters led him to propose that genetic characters segregate independently.
• Some genes are present only as one set (sex-linked).
• Subsequent work revealed that some pairs of genetic characters are linked.
• Pairs of linked characters can exchange partners, a process called recombination.
• Recombination between two genetic characters lowers the apparent degree of linkage between them. Thus, pairs of linked genetic characters vary in the strength of linkage.
• Studies of the degree of linkage of many pairs revealed a consistent linear relationship. The linear relationship allows the construction of linear maps.

This is page 1111 of Molecular Genetics by Ulrich Melcher, ©1997, 1998, 2000