exam q

Question 1

Not all mutations result in a change to the amino acid sequence of the encoded polypeptide.

Answer 1

code degenerate;

Question 2

Why must the primers be complementary to the DNA sequence being amplified?

Answer 2

• to make sure they bind specifically to the region that needs to be replicated
  -this provides.a starting point for dna polymerase
  -so dna nucleotides can be bonded together.

Question 3

Explain how the length and sequence of primers can affect the efficiency of PCR.

Answer 3

-if they’re too short- might not bind specifically to ltarget dna
- too long- not bind efficienty

sequence- specificity to DNA
- may produce non specific binding.

Question 4

What is the principle behind gel electrophoresis?

Answer 4

-smaller dna fragments move furthest , allowing separation of dna fragment s

• negative dna move towards positive terminal.

Question 5

why are h2 bonds broken in pcr

Answer 5

to make dna single stranded so that dna polymerase can work

Question 6

What are the advantages of using PCR in genetic research and forensics?

Answer 6

-speed- produces many copies of dna in a few hrs

forensics- analyse dna from crime scenes

specificity- target specific genes or sequences .

Question 7

which comes first pcr or gel electrophoresis

Answer 7

pcr - there needs to be enough dna to be analysed

Question 8

what does ligase join

Answer 8

-forms phospjodiester bonds
-so foreign dna and plasmid dna together