Lecture 1 - genetics/genomics

gene

functional units of DNA

locus

exact location of a gene on a chromosome

allele

homologous copies of a gene

inherit 2 alleles for each gene; 1 from mom, 1 from dad

46 chromosomes, 23 pairs; 22 autosomal pairs, 1 sex pair

genotype

genetic makeup

phenotype

physical, observable characteristics

karyotype

complete set of chromosome

homozygote

individual with identical alleles ex. AA or aa

heterozygote

individual with different alleles ex. Aa

dominant

traits that require only 1 copy of a factor for it to be expressed

recessive

traits that require 2 copies of a factor for it to be expressed

mutation/variant

change from reference DNA sequence

autosomal dominant

vertical pattern

multiple generations affected bc only takes one copy to express phenotype

examples of autosomal dominant diseases

huntington’s disease, neurofibromatosis, marfan syndrome, osteogenesis imperfecta

autosomal recessive

horizontal pattern

inheritance from carrier parents

parents may not display abnormal phenotype

examples of autosomal recessive diseases

cystic fibrosis, sickle cell anemia, thalassemia

codominance

both alleles expressed in phenotype

x-linked inheritance

mostly vertical pattern, but may skip a generation

most are recessive

males are more severely affected because they only need one mutant allele to display phenotype

males = hemizygous; cannot be heterozygous or homozygous

no male to male transmission

x-linked dominant

less common

if father is affected, all daughters will be affected

if ONLY father is affected (mother unaffected), son will not be affected

ex. hypophosphatemic rickets, rett syndrome

x-linked recessive

more common

ex. colorblindness, hemophilia A, duchenne muscular dystrophy, becker’s muscular dystrophy, G6PD deficiency

mitochondrial

can only come from the mother

if affected mother, will pass down to ALL offspring

males do not transmit mutation

ex. leber’s hereditary optic neuropathy, leigh syndrome

transcription

DNA → mRNA

translation

mRNA → proteins

germinal variant

genetic change that occurs during egg or sperm formation

before fertilization

inherited from parents

ex. radiation, chemical mutagen

somatic variant

genetic change that occurs after conception

during embryogenesis or adulthood

not inherited from parents

usually environmental

non-disjunction

chromosomes don’t separate properly during meiosis

results in loss or gain of chromosome

monosomy - 1 instead of 2

polysomy - 3 or more instead of 2

trisomy - 3 instead of 2 (most common)

trisomy 13

patau syndrome

trisomy 18

edward’s syndrome

trisomy 21

down syndrome

XXY

kleinfelter syndrome

XYY

polysomy Y

XXX

trisomy X

X0

turner syndrome

translocation/inversion

rearrangement of chromosome arms of non-homologous chromosomes

deletion

loss of chromosomal material (partial)