Chapter 13

• Living organisms are distinguished by their ability to reproduce their own kind.
• Offspring resemble their parents more than they do less closely related individuals of the same species.
• The transmission of traits from one generation to the next is called heredity or inheritance.
• However, offspring differ somewhat from parents and siblings, demonstrating variation.
• Farmers have bred plants and animals for desired traits for thousands of years, but the mechanisms of heredity and variation eluded biologists until the development of genetics in the 20th century.
• Genetics is the scientific study of heredity and variation.

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in Figure 13.4.

A certain female's number 12 chromosomes both have the blue gene and number 19 chromosomes both have the long gene. As cells in her ovaries undergo meiosis, her resulting eggs (ova) may have which of the following?

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A) either two number 12 chromosomes with blue genes or two with orange genes
B) either two number 19 chromosomes with long genes or two with short genes
C) either one blue or one orange gene in addition to either one long or one short gene
D) one chromosome 12 with one blue gene and one chromosome 19 with one long gene