genes and genetic diseases

37 terms by mjeglum 

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gene

a segment of DNA that codes for specific gene products

allele

a different form of a particular gene

genotype

the genetic makeup of an organism

phenotype

a visible observation, or tested

gamete

sex cells (sperm and egg)

karyotype

during metaphase, the chromosomes make an ordered display according to their position and size

homozygous

when both alleles of a particular gene on a pair of homologous chromosomes are identical

heterozygous

when two alleles of a certain gene on a pair of homologous chromosomes are not identical

dominant trait

an allele that is observable

recessive trait

an allele that is hidden

penetrance

the percentage of individuals with a specific genotype who also express the expected phenotype

mutagen

agents known to increase the frequency of mutations

expressivity

the extent of variation in phenotype associated with a particular genotype

base-pair substitution

mutation in which one base pair is replaced by another. Sometimes change the amino acid sequence

silent substitution

a mutation in which a base pair is replaced by another, but does not change the amino acid sequence

frame-shift substitution

a mutation that involves the insertion or deletion of one or more base pairs to the DNA molecule. Greatly alters the amino acid sequence

spontaneous mutation

mutation that occurs in absence of exposure to known mutagens

germline mutation

a mechanism by which a child can inherit a genetic disease even though the parents do not express the disease. The mechanism is believed to involve a mutation during the embryonic development of the parent germ cell

mutational hotspots

certain areas of chromosomes that have a particularly high mutation rate

euploid

cells that have a multiple of the normal number of chromosomes

haploid

have only one member of each chromosome pair

diploid

have both member of each chromosome pair. Normal is 23 pairs

polyploidy

when a euploid cell has more than the diploid number of chromosomes

aneuploid

a somatic cell that does not contain a multiple of 23 chromosomes

trisomy

has three copies of one chromosome

monosomy

has only one copy of a given chromosome in a diploid cell

nondisjunction

an error in which homologous chromosomes or sister chromatids fail to separate normally during meiosis or mitosis

deletion

caused by broken chromosomes and loss of DNA

duplication

are a form of chromosomal abberation. Have less serious complications than deletions

inversion

the occurrence of two breaks in a chromosome followed by the reinsertion of the missing fragment at its original site, but in an inverted order

translocation

the interchanging of genetic material between nonhomologous chromosomes

fragile sites

an area where it is more prone to develop breaks and gaps when cultured in a folate-deficient medium

sex-linked

a trait normally found on the sex chromosomes

x-linked

a trait normally found on the x chromosome

carrier

an individual that has a diseased gene but is phenotypically normal

disjunction

the normal separation and migration of chromosomes during cell division

autosomal

abnormal gene

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