UNIT 16 - Pedigrees and Karyotypes

pedigree chart

a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next

complete dominance

a relationship in which one allele is completely dominant over another

autosomal recessive

two copies of an abnormal gene must be present in order for the disease or trait to develop

autosomal dominant

inheritance pattern of a dominant allele on an autosome

karyotype

the number and visual appearance of the chromosomes in the cell nuclei of an organism or species

nondisjunction

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei

trisomy

a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities

trisomy 21

condition in which an individual has three number 21 chromosomes, resulting in Down syndrome

Turner's Syndrome

a genetic defect in which affected women have only one X chromosome, causing developmental abnormalities and infertility

Klinefelter Syndrome

a chromosomal trisomy in which males have an extra X chromosome resulting in an XXY condition; affected individuals typically have reduced fertility