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37 terms

genes and genetic diseases

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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