9.1 Chromosomes and Recombination
| Walter Sutton published two papers on the chromosome theory of heredity. |
| He believed that particular genes were located on particular chromosomes. |
| Morgan found that some traits did not assort independently. |
| Linked genes - genes on the same chromosome. |
| Genetic recombination - shuffling of genes into new combinations by crossing over. |
| Gene mapping - locating genes on chromosomes. |
| Recombination occurs more frequently when genes are far apart on the chromosome. |
9.2 Genes on Chromosomes
| Males have 2 sex chromosomes - X and Y. |
| Mutation - spontaneous change in a gene or chromosome. |
9.3 Chromosomes and Sex Determination
| Karotyping - grouping by type and size of chromosomes from a cell. |
| Most genes have no matching allele on the other chromosome such as X and Y chromosomes called nonhomologous. |
| Autosomes - all chromosome pairs except sex chromosomes. |
| In segregation, half the male's sperm wil carry the X or Y chromosome. |
| If a Y-carrying sperm fertilizes an egg, the zygote will be male due to receiving an X and Y chromosome. |
| Sex of alligator embryos is determined by temperature the eggs develop. |
| Sex-limited traits - autosomal traits that are expressed in only one sex.. |
| Beard growth in males and milk production in females are examples of sex-limited traits. |
| Sex-influenced traits - expressed in both sexes, but they are expressed differently. |
9.4 Chromosome Mutations
| Deletion - one or more genes maybe lost entirely from chromosome during division. |
| Inversion - fragment of chromosome may break free, turning around and reattaching itself in reverse order. |
| Nondisjunction - failure of chromatids to separate during cell division. |
| Monosomy - zygote receives only one chromosome instead of two. |
| Polyploidy - nondisjunction occurs in all the pairs of chromosomes at once. |