Early lethal alleles - ANSWER cause embryonic death so that a particular class of
progeny isn't observed among the offspring
Autosomal dominant lethal alleles - ANSWER homozygous dominant individuals
are never seen- lethal
Compound heterozygote - ANSWER An individual w 2 different mutant alleles for
the same gene; Ex: cystic fibrosis
Incomplete dominance - ANSWER 1 allele is not fully dominant over the other;
heterozygote has an intermediate phenotype; Ex: Familial Hypercholesterolemia
Codominance - ANSWER Neither allele is dominant over the other; expression of
both alleles is observed as a distinct phenotype in the heterozygous individual; Ex:
AB blood type
Epistasis - ANSWER A gene that affects the expression of another gene. A gene
that masks another gene. 2 different genes, not necessarily near each other.
Penetrance and Expressivity - ANSWER The same alleles in 1 person can result in
different degrees of a phenotype in another person. Penetrance: all or none
expression of a genotype. Expressivitiy: severity or extent of a phenotype. A
genotype that produces a phenotype in everyone who inherits it is 100% penetrant
Pleiotropy - ANSWER Many different phenotypes result from a single genotype
Genetic heterogeneity - ANSWER mutations in different genes that produce the
, same phenotype; the different genes can be on the same or different chromosomes
Phenocopies - ANSWER environmentally caused trait that appears to be inherited
mtDNA - ANSWER a closed, circular mini-chromosome; mitochondria contains a
small amount of these that is different from the DNA in the nucleus. Smaller than a
chromosome, contains only 37 genes. Each cell has many mitochondria, each
mitochondria has mtDNA; no crossing over; fewer types of DNA repair- mutations
can happen more often; inherited only from mother; high exposure to O2 free
radicals- can increase likelihood of developing mutations; no histones (DNA
associated proteins); genes aren't interrupted (no introns/exons); tight, compact
Mitochondrial Disorders - ANSWER inherited from maternal line only. Result
from mutations in mtDNA genes. S/S fatigue, weak muscles. Muscle, eyes.
Mutations in mt tRNA or rRNA genes are most devastating bc the affects all mt
protein production. Mt disorders can be prevented in next gene by injecting healthy
mt into oocytes
Heteroplasmy - ANSWER a conditions in which some mt chromosomes have a
mutation and others don't. Mt are distributed randomly during cell division. Over
time, all chromosomes within 1 mitochondrion tend to be all wild-type or all
mutant.
Heteroplasmic - ANSWER this woman can produce oocytes that are mostly wild
type or mutant so she can pass a mt disease to offspring even though she doesn't
have it herself; can result in variable expressivity in offspring who inherit it
Homoplasmy - ANSWER lethal condition in which embryos don't develop
3-Parent Babies - ANSWER Approach used so woman who know they're carrying
mt disease don't pass it down. Can do w pronuclear transfer. Start w mother's
unfertilized egg (heteroplasmic); then unfertilized donor egg (healthy); nucleaus of
moms egg is transferred into donor egg; fathers sperm fertilizes donors egg and
then transferred into uterus to make healthy kid
mtDNA use - ANSWER in forensic analysis and DNA identification; to study
human origins
Linkage - ANSWER Genes located near each other on same chromosome don't
segregate independently. They're inherited together. This is called linkage.
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