Patterns of Single Gene Inheritance Flashcards
Compound heterozygous
both alleles are mutant, but mutant in different locations on gene
Hemizygous
Abnormal gene is located on x chromosome
allelic heterogeneity
different mutations occurring on same gene
Phenotypic heterogeniety
Different mutations in same gene producing different phenotypes
Locus heterogeneity
Mutations at different loci that produce same phenotype
Long QT syndrome
phenotype caused my mutations in more than one gene-all have same
locus heterogeniety
4 factors that confound pedigree interpretation
early lethality in disorder
small family size
variable age of onset, decreased penetrance or variable expressivity
non-mendelian inheritance
Auto rec features
must have 2 mutant alleles and no wild type
-can have different try of mutation in each allele-compound heterozygote
Reduce/eliminate function of gene product
Affect function of enzymes usually
Rare
Carrier frequency
Prevalence of disease in given population
4 factors that affect risk of inheritance of auto rec disorder
Carrier frequency
Consantuinity-close or closer than second cousins
-increase chance that both parents are carriers of the same mutant allele
Inbreeding
Genetic isolates
Key features of AR pedgree
parents are unaffected carriers
males=females
usually recurrence of risk to unborn is 1/4
phenotype found in siblings
oblligate heterozygote
person who you are sure is a carrier
Auto dom inheritance features (AD)
Every affected individual has affected parent (if completely penetrant)
Male to male transmission
Males and females equally infected
1/2 of offspring have risk
Normal siblings have all normal offspring
Incomplete dominance
Individual is homozygous for AD mutation is more severely affected then individual who is heterozygous
X linked inheritance
No male to male transmission
X link inactivation results in very different clinical presentations for females
-unbalanced inactivation can result in carrier woman with phenotype
Many more affected males than females
Heterozygous females are usually unaffected
Gene is transmitted from affected male to all daughters
Hidden passage through series of carrier females
x linked dominane
trait NEVER passed from father to son
Many more females than males
Reduced penetrance
all or none
Probability that mutant gene will have any phenotype at all
Variable expressiity
sevirty varies with same exact genotype
Sex limited traits
Genes can be carried by opposite sex but an not display because anatomical/physiological difference
Hemochromatosis
Most common single gene inherited disease in US
Sex influenced pheotype
hemochromatosis
more common in male or female because reason (menstruation lowers iron levels)
Mosaicism
Presence of at least two cell lines that differ genetically from single zygote
Pure somatic vs pure germline mosaicism
Present in soem tissues in the embryo but not germ cells
Depends on whether the mutation occurred before or after the separation of gremlin cells from somatic cells
Parents are normal, not carrier, and more than one child affected with AD or XLR disorder
New mutations
Very low probability per gamete
Affected child will share allies for all other genes with parents
Can result in genetic lethal
Very rare in AR-need to mutate both alleles
Genomic imprinting
Sex of transmitting parents plays role in expression of phenotype
100 human genes that only one copy can be active
Parent of origen
Specific pattern is present in all somatic cells, but reversed in germ cells
Prader willi syndrome
vs
angleman
Loss of fathers chromosome part
Loss of mothers chromosome part
TNR disorder principlas
Molecular characteristics and consequences of expansion differ
Tendency for repeat expansion depends on transmitting parent
premutaitons
Genetic anticipation
premutation phenotype
can be mildly to affected or even normal
genetic anticipation
More TNRs more early and more severe disease is
Male limited precocious puberty
Mutation in lut hormone gene
Always on
ONLY IN BOYS
Heteromales-secondary sex char early
Parents pass methylation to kids
NO WHAT THE FUCK- REVERSED IN GAMETES
