dna mutations 2b (dynamic mutations)

Question 1

what is a dynamic mutation?

an example?

Answer 1

unstable dna- can increase in length with each generation. when array expands above critical number you get pathology.
trinucleotide repeats.

Question 2

how does expansion of a mutation occur?

Answer 2

slippage during dna replication

Question 3

Fragile X is caused by a mutation in which gene?

what are the symptoms of fragile x?

Answer 3

FMR1

retardation and ADD

Question 4

What does the product of the FMR1 gene do?

Answer 4

it binds mrnas to assist with their transport and translation. especially in neuronal cells

Question 5

which trinucleotide repeat is fragile x caused by?

what does the expanded repeat do?

Answer 5

CGG

methylates the genes promoter

Question 6

In which area of the gene is the repeat which is responsible for fragile x?

Answer 6

non coding region. 5’ untranslated region

Question 7

What type of inheritance does fragile X follow? And what are some strange things about its inheritance?

Answer 7

x linked recessive
normal transmitting male
affected female
anticipation

Question 8

what is anticipation?

Answer 8

disease increases with severity with subsequent generations

Question 9

what is the premutation range?

what is the pre mutation range for fragile x?

Answer 9

this is the number of repeats at which the phenotype isnt displayed but the repeats are unstable and they are prone to mutate.
55-200

Question 10

Friedreich’s Ataxia is caused by a mutation in which gene?

What does the disease cause biochemically?

Answer 10

FRDA

Reduces frataxin in the mitochondria, which reduces energy production and the accumulation of free ions increases.

Question 11

the trinucleotide repeat of Friedreich’s ataxia?

where in the gene is the mutation that causes FA?

Answer 11

GAA

within intron of the non coding region.

Question 12

what type of inheritance pattern does Friedreich’s ataxia follow?
what are the symptoms?

Answer 12

autosomal recessive

loss of speech, coordination and balance

Question 13

What disease is caused by a triplet expansion in the DMPK gene?
what is the repeat?

Answer 13

Myotonic dystrophy

CTG

Question 14

Is myotonic dystrophy caused by mutation in coding or non coding region?
Where in the gene is the triplet expansion that causes it?

Answer 14

non coding

The last exon 3’ UTR region.

Question 15

symptoms of myotonic dystrophy?

what unusual inheritance pattern does it follow?

Answer 15

progressive muscle wasting

anticipation

Question 16

myotonic dystrophy is a dominant rna disorder.
what gene product is made by someone with the disease?
how does it cause a phenotype?

Answer 16

repetitive non coding rna sequence.
it is trapped in nuclear foci and co-localises with muscleblind proteins which are needed for processing mrna transcripts. causes missplicing.

Question 17

Which trinucleotide repeat expansion is responsible for Huntington’s disease?
which amino acid does this repeat code for?

Answer 17

CAG

glutamine

Question 18

what type of tract disorder is Huntington’s disease described as?
symptoms?
how is phenotype produced?

Answer 18

polyglutamine tract disorder
neurodegenerative
aggregation of glutamine tracts which cannot be disposed of and are toxic to neurones

Question 19

in what area of the gene is the mutation responsible for huntingtons disease?
which chrom?

Answer 19

coding region. exon 1.

4p

Question 20

what causes Huntington’s disease to become earlier onset?

Answer 20

more trinucleotide repeats