TBL 5

Question 1

Tay- Sachs disease inheritance pattern

Answer 1

Heterogenous Lysosomal storage disease

insertion

results from a 4 base nucleotide insertions in the encoding gene Hexosaminidase A( HEXA)

Question 2

enzyme that is faulty if Tay-Sachs

Answer 2

results from a 4 base nucleotide insertions (causes frameshift mutation) in the encoding gene Hexosaminidase A ( HEXA gene)

defective protein

Question 3

what are the clinical effects of tay sachs

Answer 3

almost solely in brain, predominate site GM2 ganglionside synthesis

Question 4

clinical presentation of T-sachs

Answer 4

good at birth, presentation of of disease happens at 3-6 months then undergo neurological deterioration until death 2-6 years

Question 5

example of disease of trinucleotide repeats

Answer 5

Fragile x and Huntingtons disease

Question 6

trinucleotide repeat mutation characteristics

Answer 6

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

Question 7

Huntington disease was thought to be a typical ________________(dom or rec)
condition with age-dependent penetrance, but it has some unique
inheritance patterns.

Answer 7

autosomal dominant

Question 7

Huntington Disease trinucleotide repeat, in which gene, and what protein does it affect?

Answer 7

multiple CAG nucleotides into the HTT gene (4p16.3) encoding
the protein Huntingtin.

Question 8

anticipation of Huntington

Answer 8

– 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

Question 9

Huntington disease individuals have ____which cause _____aggregates

Answer 9

– CAG repeats cause long tracts of polyglutamine in the mutant protein.
– Mutant proteins aggregate, forming nuclear inclusions, causing
neurodegeneration

Question 10

Huntington disease individuals, they will have_______CAG repeats.

Answer 10

• An unaffected individual has between 6 and 35 CAG repeats.
• In Huntington disease individuals, they will have >40 CAG repeats.

Question 11

Fragile X syndrome is a _________-repeat disorder caused
by the insertion of multiple_____nucleotides in the _______gene on X chromosome

Answer 11

trinucleotide-

CGG

familial
mental retardation-1 (FMR1)

Question 12

The inheritance pattern fragile x is ________.

Answer 12

The inheritance pattern is X-linked with incomplete
penetrance in females (50-60%)

Question 13

An unaffected individuals for fragile x has between _______ CGG
repeats.

Answer 13

6 and 55

Question 14

• Individuals with fragile x with the pre-mutation will have between ______

Answer 14

pre-mutation will have between 55 –
200 repeats.

Question 15

• Affected individuals with fragile x will have _______.

what does this cause

Answer 15

greater than 230

expanded repeat leads to excessive methylation of the
promoter of FMR1, preventing normal promoter function
and leading to gene silencing

Question 16

_________most common genetic cause of intellectual disability in
males and, overall, the second most common cause after
Down syndrome.

Answer 16

Most common genetic cause of intellectual disability in
males and, overall, the second most common cause after
Down syndrome.

Question 17

example of incomplete penetrance_____

what does incomplete penetrance mean?

Answer 17

split-hand/food malformation

Only 70% of the people who have the mutation exhibit the
clinical defect.

failure of penetrance skip generations

Question 18

what will disturb hardy-weinberg equilibrium?

Answer 18

nonrandom mating increases the
proportion of homozygotes

Question 18

which mutation helps individuals be resistant to to HIV-1?

Answer 18

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.

Question 19

Forms of nonrandom mating found in human populations:

Answer 19

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.

Question 20

genetic drift

Answer 20

random fluctuations in allele frequencies in small populations is
called genetic drift.

possible by chance alone

Question 21

what is the founder effect

Answer 21

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.

Question 22

Genetic bottleneck-

Answer 22

Genetic bottleneck - when a large population undergoes a drastic but
temporary reduction in numbers.

Question 23

Different types of mutation at the same disease locus are called_______

Answer 23

allelic heterogeneity.

Question 24

________of molecular evolution states that genetic variation is due to genetic mutations (creating new
alleles) and genetic drift.

Answer 24

Neutral theory