Chapter 10 Definitions
autosome: any chromosome other than the sex chromosome
base deletion: a mutation in which a nucleotide is lost from the DNA sequence
base insertion: a mutation in which a nucleotide base is added to the DNA sequence
carrier: an individual who is heterozygous for a recessive trait
chromosome mapping: a method of determining the relative position of genes on a chromosome using information on crossover frequency
crossing over: exchange of parts between two homologous chromosomes
deletion: a mutation in which a chromosomal piece breaks off and is lost
frame-shift mutation: a mutation in which a base deletion or insertion cause the gene's message to be translated incorrectly
incomplete linkage: the breaking apart of genes in the same linkage group through crossing over of chromosomal material
inversion: a mutation in which a segment of DNA in a chromosome flips upside down, but remains in place
linkage group: genes that occur together on the same chromosome
monosomy: the condition of missing a chromosome
mutagen: any agent that increases the rate of mutation
mutation: a change in the genetic material that results from an error in the replication of DNA
nondisjunction: the failure of homologous chromosomes to segregate during meiosis
point mutation: a mutation in which one base replaces another in the DNA chain
polyploid: a condition of having extra sets of chromosomes
red-green color blindness: the inability to distinguish red from green
sex chromosome: one pair of chromosomes related to the sex of an individual
sex-linked gene: a gene located on or linked to the sex chromosome
sex-linked trait: a characteristic determined by genes on the X chromosome
translocation: a mutation in which a chromosomal piece becomes attached to another chromosome
trisomy: the condition of having an extra chromosome
Chapter 11 Definitions
genetic marker: a known DNA sequence that lies close to a disease causing gene, indicating the presence of this gene
hemoglobin: a protein in red blood cells responsible for oxygen transport.
hemophilia: a sex-linked disorder in humans in which blood cannot clot
Huntington disease: a fatal genetic disorder caused by a dominant gene, the symptoms of the disease being loss of muscle co-ordination and mental deterioration
karyotype: a photograph of a cells chromosomes, arranged in order from largest to smallest
Klinefelter syndrome: a condition in males that includes abnormal sexual development resulting from the presence of an extra X chromosome
melanin: a dark pigment
multiple allele: three or more different alleles for a giver trait
pedigree: a diagram showing how a trait is inherited in the family
phenylketonuria (PKU): a genetic disease in which the absence of an enzyme causes a build-up of the amino acid phenylalanine causing severe retardation
polygenic inheritance: a condition in which characteristics are governed by more than one gene
sex-influenced trait: characteristic that is dominant in one sex and recessive in the other
sex-limited gene: a gene that is expressed only in the individuals of a certain sex
sickle-cell disease: a hereditary disease in which hemoglobin is abnormal and red blood cells are sickle shaped
sickle cell trait: the condition of being heterozygous for sickle-cell disease
syndrome: a group of symptoms with a single underlying cause
Turner syndrome: a condition in females that includes abnormal sexual development, resulting from the absence of the X chromosome
ultrasound: a technique using sound waves to locate and view a fetus in the uterus