Intro Flashcards
Genes that determine cell identity and positioning during embryonic development
Homeobox (Hox) genes
Number of genes humans have
20,000
Silent substitutions
redundancy of genetic code
Missense mutation
Produce change in single AA
Nonsense mutation
Produce one of the stop codons in mRNA (causes termination)
Frameshift
Result from addition or deletion of number of bases not a multiple of 3
First demonstration that mutation in structural gene could cause AA sub in corresponding protein
Sickle cell (GAG to GTG)
Incidence of newborns with single gene or chromosomal disorder
1:60
Incidence of people under age 25 with genetic disorder
1:20
Types of nontraditional inheritance
Microdeletion, imprinting, trinucleotide repeats
Anticipation
severity increases and younger age of diagnosis as passed from generation to next
Segregation
alleles are paired and each gamete normally receives one member of the pair
Independent assortment
Gene pairs tend to segregate independently of each other
Exception to independent assortment
Linkage
Gene locus
specific location on chromosome
Allele
alternative forms of a gene at given locus
Allelic heterogeneity
different mutant alleles at the same locus produce an abnormal phenotype (ex: CF)
Locus heterogeneity
Mutations at two or more loci cause similar phenotype (ex: retinitis pigmentosa, adult polycystic kidney disease, AD breast cancer)
Adult polycystic kidney disease (APKD)
AD, progressive accumulation of renal cysts (also liver cysts, hypertension, cerebral aneurysms), caused by mutations in genes of PKD1 or PKD2
Pleiotropy
single mutant allele can have widespread effects in different tissues or organ systems (ex: marfan syndrome with cardio, musculoskeletal, and ocular)
Penetrance
proportion of individuals with mutant genotypes that express a mutant phenotype (range 0-1). Complete is 100%
Expressivity
Variability in degree of phenotypic expression seen in different individuals with mutant genotype
True dominant
Heterozygous expression is same as homozygous (ex: HD)
Sex-limited/sex-influenced
expression is affected by sex of individual (ex: male pattern baldness)