TBL 5 Flashcards
Tay- Sachs disease inheritance pattern
Heterogenous Lysosomal storage disease
insertion
results from a 4 base nucleotide insertions in the encoding gene Hexosaminidase A( HEXA)
enzyme that is faulty if Tay-Sachs
results from a 4 base nucleotide insertions (causes frameshift mutation) in the encoding gene Hexosaminidase A ( HEXA gene)
defective protein
what are the clinical effects of tay sachs
almost solely in brain, predominate site GM2 ganglionside synthesis
clinical presentation of T-sachs
good at birth, presentation of of disease happens at 3-6 months then undergo neurological deterioration until death 2-6 years
example of disease of trinucleotide repeats
Fragile x and Huntingtons disease
trinucleotide repeat mutation characteristics
The genes affected tend to be polymorphic, meaning there is already a variable number of repeat units in the
normal population.
increase repeats with generations
Huntington disease was thought to be a typical ________________(dom or rec)
condition with age-dependent penetrance, but it has some unique
inheritance patterns.
autosomal dominant
Huntington Disease trinucleotide repeat, in which gene, and what protein does it affect?
multiple CAG nucleotides into the HTT gene (4p16.3) encoding
the protein Huntingtin.
anticipation of Huntington
– Disease appears to develop at an earlier and earlier age as it is
transmitted through the generation, known as anticipation.
– This anticipation seems to occur only when the mutant allele is
transmitted by an affected father and not by an affected mother, known
as parental transmission bias
Huntington disease individuals have ____which cause _____aggregates
– CAG repeats cause long tracts of polyglutamine in the mutant protein.
– Mutant proteins aggregate, forming nuclear inclusions, causing
neurodegeneration
Huntington disease individuals, they will have_______CAG repeats.
- An unaffected individual has between 6 and 35 CAG repeats.
- In Huntington disease individuals, they will have >40 CAG repeats.
Fragile X syndrome is a _________-repeat disorder caused
by the insertion of multiple_____nucleotides in the _______gene on X chromosome
trinucleotide-
CGG
familial
mental retardation-1 (FMR1)
The inheritance pattern fragile x is ________.
The inheritance pattern is X-linked with incomplete
penetrance in females (50-60%)
An unaffected individuals for fragile x has between _______ CGG
repeats.
6 and 55
- Individuals with fragile x with the pre-mutation will have between ______
pre-mutation will have between 55 –
200 repeats.
- Affected individuals with fragile x will have _______.
what does this cause
greater than 230
expanded repeat leads to excessive methylation of the
promoter of FMR1, preventing normal promoter function
and leading to gene silencing
_________most common genetic cause of intellectual disability in
males and, overall, the second most common cause after
Down syndrome.
Most common genetic cause of intellectual disability in
males and, overall, the second most common cause after
Down syndrome.
example of incomplete penetrance_____
what does incomplete penetrance mean?
split-hand/food malformation
Only 70% of the people who have the mutation exhibit the
clinical defect.
failure of penetrance skip generations
what will disturb hardy-weinberg equilibrium?
nonrandom mating increases the
proportion of homozygotes
which mutation helps individuals be resistant to to HIV-1?
delta 32 CCR5 Mutation
CCR5 gene encodes protein CCR5, a receptor on the outside of immune cells, and is also a
co-receptor for strains of HIV-1.
–Individuals that are homozygous for the Δ32 allele are resistant to most strains of HIV-1.
Forms of nonrandom mating found in human populations:
Forms of nonrandom mating found in human populations:
–Stratification- a population in which there are a number of
subgroups that have—for a variety of historical, cultural, or
religious reasons—remained relatively genetically separate
during modern times.
–Assortative mating - the choice of a mate because the mate
possesses some particular trait.
–Consanguinity (Inbreeding) - Being descended from the
same ancestor.
genetic drift
random fluctuations in allele frequencies in small populations is
called genetic drift.
possible by chance alone
what is the founder effect
when a person in a small population has a mutation and changes the frequency of alleles
–Indicate mutant allele may have arisen as founder mutation about
400–1000 years ago in the Navajo population.
Genetic bottleneck-
Genetic bottleneck - when a large population undergoes a drastic but
temporary reduction in numbers.
Different types of mutation at the same disease locus are called_______
allelic heterogeneity.
________of molecular evolution states that genetic variation is due to genetic mutations (creating new
alleles) and genetic drift.
Neutral theory
