| A | B |
|---|
| chromosome map | a diagram of allele positions on a chromosome |
| deletion | a mutation in which a segment of DNA breaks off a chromosome |
| frame shift mutation | a mutation that results in the misreading of the code during translation because of a change in a reading frame |
| germ-cell mutation | a change in the DNA of a sex cell |
| inversion | a mutation that occurs when a chromosome piece breaks off and reattaches in reverse orientation |
| sex linkage | the presence of a gene on a sex chromosome |
| linkage group | the group of genes, located on the same chromosome, that are usually inherited together |
| map unit | a unit in chromosome mapping equal to a 1 percent occurence of crossing-over |
| nondisjunction | the failure of homologous chromosomes to separate during meiosis or the failure of sister chromatids to separate during mitosis |
| point mutation | the change of a single nitrogen-containing base within a codon |
| sickle cell anemia | the genetic disorder that causes by a point mutation that substitutes adenine for thymine in a single DNA codon |
| somatic mutation | a mutation that occurs in a body cell |
| substitution | a point mutation in which one nucleotide in a codon is replaced with a different nucleotide |
| translocation | a mutation in which a broken piece of chromosome attaches to a nonhomologouse chromosome |
| X-linked gene | a gene found on the X chromosome |
| Y-linked gene | a gene found on the Y chromosome |
| aminocentesis | a procedure used in fetal diagnosis in which fetal cells are removed from the amniotic fluid |
| carrier | individuals who have one copy of a recessive autosomal allele |
| chorionic villi sampling | a procedure involving the analysis of the chorionic villi to diagnose fetal genotypes |
| colorblindness | a recessive X-linked disorder in which an individual cannot distinguish between certain colors |
| Down syndrome | a disorder caused by an extra twenty-first chromosome and characterized by a number of physical and mental abnormalities |
| Duchenne muscular dystrophy | a form of muscular dystrophy that weakens and progressively destroys muscle tissue |
| genetic counseling | the process of informing a couple about their genetic makeup, which has the potential to affect their offspring |
| genetic disorder | a disease that has a genetic basis |
| genetic marker | a short section of DNA that indicates the presence of an allele that codes for a trait |
| genetic screening | an examination of a person's genetic makeup |
| hemophilia | a trait in which the blood lacks a protein that is essential for clotting |
| Huntington's disease | a human genetic disorder caused by a dominant allele resulting in involuntary movements, mental deterioration, and eventual death |
| monosomy | a condition in a diploid cell in which one chromosome of one pair is missing as a result of nondisjunction during meiosis |
| multiple-allele trait | traits that are controlled by three or more alleles of the same gene that code for a single trait |
| polygenic trait | a trait that is controlled by two or more genes |
| pedigree | a diagram of genetic history of an individual |
| phenylketonuria | a genetic disorder in which the body cannot metabolize phenylalanine |
| sex-influenced trait | a trait that is influenced by the presence of male or female sex hormones |
| single-allele trait | a trait controlled by a single allele |
| trisomy | a chromosomal anomaly in which an individual has an extra chromosome in any of the chromosome pairs |
| trisomy-21 | a human congenital disorder caused by trisomy of chromosome 21 due to the failure of the sister chromatids to separate during mitosis or the failure of homologous chromosomes to separate during meiosis |
