Molecular basis of inheritance

Question 1

What are processed genes?

Answer 1

• Intronless copies of other genes
• Reverse transcription and reintegration
• Occassionally remains functional

Question 2

What is repetitive DNA?

Answer 2

• Satellite DNA

- Interspersed repeats scattered around the genome

Question 3

What is satellite DNA?

Answer 3

• Large blocks at centromeres and heterochromatic chromosomal regions
• Tandemly repeated sequences
• Size of blocks may be polymorphic

Question 4

What is Alphoid DNA

Answer 4

• Type of satellite DNA at centromeres
• 171 base pairs
• Sequence shows chromosome-specific sequence variation
• Required for assembly of the centromere

Question 5

What are interspersed repeats?

Answer 5

• Scattered around the genome

- Individual copies present at many locations

Question 6

What types of mutations are there?

Answer 6

• Large deletions/insertions (effects variable, DMD)
• Gross rearrangements (Haem A)
• Point mutations
• Trinucleotide repeat expansions

Question 7

What are conservative & non-conservative point mutations?

Answer 7

C= change in amino acid but not protein
N= change in amino acid and protein

Question 8

What does a frameshift mutation do?

Answer 8

• Alters protein sequence beyond mutation

- May truncate protein

Question 9

What does a nonsense mutation do?

Answer 9

• Truncated protein produced

- May exploit this for mutation detection

Question 10

What are the types of trinucleotide repeat expansions and diseases they cause?

Answer 10

-Polyglutamine repeats (CAG)
Neurodegenerative disorders, Huntington’s, Spinocerebellar ataxias
-Large non-coding repeat expansions
Fragile X, Myotonic dystrophy
-Mutational instability
Occasional=Huntington’s, Frequent=Fragile X

Question 11

How is Fragile X Syndrome caused?

Answer 11

• CGG repeats normal 5-50 mutation >200

- Repeat expansion determines inheritance pattern