Genetics Flashcards
gamete cells are ___loid and somatic cells are ___loid
haploid
diploid
totipotent cells…
can differentiate to become any human cell
DNA found in the…
nucleolus
pyrimidines
thymine
cytosine
purines
adenine
guanine
3 base pairs
codon
autosomes
first 22 of 23 pairs in males & females
sex chromosomes
remaining 23rd pair of chromosomes - XX (homologous) in females, XY (nonhomologous) in males
mutation
any inherited alteration of genetic material
silent mutation
has no effect, codon still codes for same amino acid
missence
mutation that causes replacement with an incorrect amino acid - changes protein itself
nonsense
premature stop - protein is unfinished
frameshift
mutation that involves deletion or insertion of a base pair - 2 or 4 in a codon rather than 3
________ mutations have the worst outcomes for the organism
frameshift
mutagen
any agent known to increase the frequency of mutations
from __ to __ weeks, the fetus is not susceptible to teratogens
0-2
period in which fetus is most susceptible to teratogens
2-8 weeks, embryonic stage
locus
position of a gene along a chromosome
allele
different form of a particular gene at a given locus
we have one from each parent
polymorphism
locus that has 2+ alleles that occur with appreciable frequency
homozygous
loci on a pair of chromosomes have identical genes
heterozygous
loci on a pair of chromosomes have different genes
genotype
composition of genes at a given locus
phenotype
outward appearance of genetics
penetrance
percentage of individuals with a certain genotype who also express the expected phenotype
Autosomal dominance causes __% penetrance
100%
incomplete penetrance
individual who has a gene for a disease but does not express it
expressivity
extent of variation in phenotype associated with a certain genotype
examples of diseases with varying expressivity
hemophilia A
neurofibramatosis
how we depict a family affected by a genetic disease
pedigree
consanguinity & effects
incest
increases risk for genetic defects
recurrence risk
probability that an individual will develop a genetic disease
3 types of genetic disorders
single-gene
chromosomal
multifactorial
if you have a gene, you will have disorder
autosomal dominant inheritance
difference between sexes r/t autosomal dominant
no difference
generational skipping c autosomal dominant?
no
most common parent configuration for people c autosomal dominant disorders
normal parent + affected heterozygous parent
requires both parents to transmit gene
autosomal recessive inheritance
Heterozygous carriers can pass disease, but do not express it
autosomal recessive
difference between sexes r/t autosomal recessive
no difference
generational skipping c autosomal recessive?
yes
recurrence risk for autosomal recessive
25%
why are sex linked disorders seen more in men?
Y does not contain all of same DNA as X - no “backup allele” if something is wrong on X chromosome
Affected father does not transmit disease to _____, but will always transmit it to _____
son
daughter
sons of female carriers have __% risk of being affected
50
duchenne muscular dystrophy is an x-linked (dominant/recessive) disorder affecting mainly (males/females)
recessive
males
any abnormalities to chromosomes
chromosomal aberrations
euploid
has a multiple of 23 chromosomes
polyploidy
euploid cells with >46 chromosomes
triploidy
69 pairs
tetraploidy
92 pairs
aneuploidy
somatic cell not containing a multiple of 23 pairs of chromosomes
trisomy
contains 3 copies of 1 chromosome
trisomy 21
down syndrome
monosomy
contains only 1 copy of any chromosome
lethal aneuploidy
monosomy
usual cause of aneuploidy
nondisjunction
nondisjunction
failure of homologous chromosomes or sister chromatids to separate during mitosis or meiosis
partial trisomy
an extra portion of a chromosome is present in each cell
down syndrome risk increases c maternal age >35 because
rate of nondisjuction increases
down syndrome characteristics
Mentally challenged, low nasal bridge, epicanthal folds, protruding tongue, low-set ears, poor muscle tone
chromosomal mosaic
Somebody who has part of a genetic defect on part of the cells in their body
Sex chromosome aneuploidy
variation of XX or XY
XXX
trisomy x
symptoms of trisomy x
sterility, menstrual irregularity, and/or intellectual disability
X
turner syndrome
symptoms of turner syndrome
underdeveloped ovaries, sterility, short stature, webbing of neck, edema, underdeveloped breasts, wide nipples
XXY, XXXY
Klinefelter syndrome
symptoms of Klinefelter syndrome
male appearance, may develop female-like breasts, small genitals, sterility, sparse body hair, long limbs
Deletion of short arm of chromosome 5
Cri-du-chat syndrome
Cri-du-chat characteristics
microcephaly, round face, low-set ears
Severe cognitive delays & developmental deficits
fragile site along long arm of X chromosome
fragile X syndrome
fragile x characteristics
Intellectual disability, broad foreahead, elongated face, large ears, crossed eyes, highly arched palette, etc
Higher incidence in males
disorders most difficult to predict
multifactorial
ex. of a multifactorial disorder affecting males more than females
pyloric stenosis
epigenetics
Study of biological mechanisms that switch genes on and off
3 epigenetic mechanisms
DNA methylation
histone modification
RNA-based mechanisms
DNA methylation - what is it, what does it do
attachment of methyl group to cytosine
Silences genes
Aberrant methylation can lead to misregulation of oncogenes & tumor-suppressor genes`
“spools” of DNA
histones
histone de/acetylation
addition or removal of acetyl group
RNA-based mechanisms involve _____ RNA and _____RNA
noncoding
micro
