Facts on File Encyclopedia of Health and Medicine

rather than affect structures of the body. Though
mitochondrial mutations may be single-GENE, they
often have widespread effects across types of cells
in which energy needs are high, such as NERVE
cells and MUSCLEcells.
See also AUTOSOME; CHROMOSOME; FAMILY MEDICAL
PEDIGREE; GENOTYPE; MITOCHONDRIAL DISORDERS; MITO-
CHONDRIAL DNA (MTDNA); MUTATION; SEX CHROMO-
SOME.

karyotype A pictorial presentation of an individ-
ual’s chromosomes, taken from microphotographs
(photographs taken through a microscope) and
arranged in a numeric sequence that aligns the

chromosomes from largest to smallest. This stan-

dardized presentation allows the geneticist to ana-

lyze an individual’s chromosomal profile. A

geneticist can structure a karyotype from any

SOMATIC CELL(nonsex cell) in the body. The most

common application of karyotyping is GENETIC

SCREENINGof a fetus. A geneticist constructs a kary-

otype to evaluate whether an individual has a

GENETIC DISORDER. A karyotype requires DNAfrom a

representative cell in the body, from which the

geneticist extracts and prepares the DNA for

examination under the microscope.

See also CHROMOSOME; GENETIC COUNSELING;

GENETIC DISORDERS;GENETIC TESTING.

karyotype 133

INHERITANCE PATTERNS: AUTOSOMAL TRAITS AND MUTATIONS

Autosomal Recessive Autosomal Dominant
Both parents carriers One parent carrier, Both parents affected One parent affected,
one parent noncarrier one parent unaffected
Each child: Each child: Each child: Each child:
25% condition 50% noncarrier 25% unaffected 50% unaffected
25% noncarrier 50% carrier 25% more severely affected 50% affected
50% carrier than parents
50% affected
Percentages refer to the probability of occurrence.

INHERITANCE PATTERNS: X-LINKED TRAITS AND MUTATIONS

X-Linked Recessive X-Linked Dominant
Mother CARRIER, Mother noncarrier, Mother affected, Mother noncarrier,
father noncarrier father affected father noncarrier father affected
Each daughter: Each daughter: Each daughter or son: Each daughter:
25% noncarrier 100% carrier 50% affected 100% affected
25% carrier Each son: 50% nonaffected Each son:
Each son: 100% noncarrier 100% nonaffected
25% noncarrier
25% affected
Percentages refer to the probability of occurrence.