Genetics Flashcards
Chromosomal abberations
= abnormalities either aneuploidy (wrong #) or deletions, inversions, etc
Aneuploidy
normal: 22 pairs of autosomal chromosomes + sex chromosomes
- identify in karyotypes
- can’t see point mutations or frameshifts
Down’s
Trisomy 21
Turner’s
XO / 45X
Kleinfelter’s
XXY
One X chromosome silenced in females
Barr bodies
Trisomy 13 and 18
developmental impairments
Karyotype bands
- dye stains
- if you can stain dye, dye permeates DNA = euchromatin
alleles
- form of gene
- 2; one on each chrom (one from mom, one from dad)
Crossing over
- prophase 1
- b/w homologous chromosomes of non-sister chromatids
- increase variation
- help pair homologous chromosomes
Meiosis
- gametogenesis
- ploidy reduced at Anaphase 1 (homologous chromosomes separate
- sis chromatids separated at anaphase 2
(2 x 2n) -> 2(2 x 1n) ->4 (1n)
Mendel’s law of segregation (1st) =
-alleles separate during anaphase 1
2nd- law of indep assortment- non-linked genes = recomb freq of 50%, otherwise linked closer to 0 (mom vs dad)
spermatogonium
-stem cell: self-renewal OR commit to meiosis
spermatogonium = one mom, one dad
primary spermatocyte = it has been replicated
a mutation in a primary spermatocyte (during or after DNA repl) would result in either a 1:3 or 3:1 mutation
test cross
a dominant of unknown genotype with recessive to figure out unknown genotype
monohybrid cross
both parents are heterozygous
Recessive pedigree
-generational skipping
codominance example
blood type ABO
Sex linked
-on MCAT, X linked
males more affected b/c HEMIZYGOUS- only have one X
-males cannot be carriers
-males are more likely to be colorblind; rhodopsin coded for on X chromosome
X linked carrier mom, normal dad;
a) affected daughters?
b) affected sons?
- all daughters normal- 1/2 carriers, 1/2 fully fine
- 1/2 males affected; x from mom
X linked affected dad, normal mom;
a) affected daughters?
b) affected sons?
a) all carrier daughters
b) none
X linked affected dad, carrier mom;
a) affected daughters?
b) affected sons?
a) 1/2 carriers, 1/2 affected
b) 1/2 affected, 1/2 normal
Huntington’s
-dominant, 100% penetrant
CF
-recessive, 100% penetrant
expressivity
-how bad will it be?
-given the phenotype, how much will you express it?
spectrum of severity / impairment
