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Chapter 12
Human Genetics
| Term | Definition |
|---|---|
| sex chromosomes | genes that determine the sex of an individual |
| autosomes | chromosomes that do not determine the sex of a person |
| sex-linked trait | a trait that is coded by an allele on a sex chromosome |
| linked genes | a pair of genes that tend to be inherited together |
| chromosome map | a diagram that shows the linear order of genes on a chromosome |
| map unit | a frequency of crossing over one percent |
| Germ-cell mutations | mutations in the gametes |
| somatic-cell mutations | mutations in the body cells |
| lethal mutations | cause death (usually before birth) |
| deletion | the loss of a piece of chromosome due to breakage |
| inversion | a chromosomal segment breaks off and flips around |
| translocation | a piece of one chromosome breaks off and goes onto another |
| nondisjunction | a chromosome does not separate during meiosis |
| point mutation | substitution, addition, or removal of a single nucleotide |
| substitution | one nucleotide replaces another |
| frameshift mutation | an incorrect grouping of the remaining codons |
| insertion mutations | one or more nucleotides are added to a gene |
| pedigree | a diagram that shows how a trait is passed along through generations |
| genetic disorders | diseases or disabling conditions that have a genetic basis |
| carriers | people who have recessive genes but not the disease |
| polygenic | characters that are influenced by several genes |
| complex characters | characters influenced by elements and genes |
| multiple alleles | genes with 3 or more alleles |
| codominance | both alleles are dominant |
| incomplete dominance | a trait that is intermediate between the parents |
| sex-influenced traits | autosomal traits |
| huntington's disease | an autosomal dominant condition characterized by forgetfulness and irritability |
| amniocentesis | removing fluid from pregnant women to see genes/sex of baby |
| chorionic villi sampling | doctor takes sample of chorionic villi cells to find genetic diseases |
| genetic counseling | informing a person about their genetic makeup |
| gene therapy | placing healthy genes into genes that are defective |