Chapter 10 -3

NWRC

Bio 30

Gene Linkage and Polyploidy• except for identical twins,

no two people look exactly alike. While genes determine most of our physical characteristics, the exact combination of genes we inherit, and thus our physical traits, is in part due to a process our chromosomes undergo, known as genetic recombination.

Genetic recombination

• Genetic recombination happens during meiosis, a special type of cell division that occurs during formation of sperm and egg cells and gives them the correct number of chromosomes.

Genetic recombination

• Inside the cells that produce sperm and eggs, chromosomes become paired. While they are pressed together, the chromosomes may break, and each may swap a portion of its genetic material for the matching portion from its mate. This form of recombination is called crossing-over. .

Gene Linkage

• refers to the association of two or more phenotypic characters in inheritance because the genes controlling these characters are located in the same chromosome. Genes carried by the same chromosome are members of the same linkage group; the number of linkage groups corresponds, therefore, to the basic number of chromosomes in the organism in question.

Gene Linkage

• Genes that are linked generally travel together during gamete formation and are an exception to Mendel’s Law of Independent assortment.

Polyploidy

• Condition in which a cell or organism has more than two complete sets of chromosomes. Humans have two sets, 2 x 23 (46) chromosomes, while wheat, for example, has 6 sets, 6 x 7 (42) chromosomes.

Assessment

• 1

When genes are exchanged on the chromosome genetic variation occurs

• 2.

• 3.Possibly to create bigger flowers, larger yields, bigger fruits etc.

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