MUTATION 1

Question 1

what is a mutation

Answer 1

a random unpredictable change in DNA molecule

Question 2

what type of mutation can occur in DNA

Answer 2

1. Substitution
2. Deletion
3. Insertion
4. Duplication
5. Inversion

Question 3

explain substitution mutation

Answer 3

• type of mutation where one base is replaced by another
• usually has no effect becuase the DNA code is degenerate,each amino acid can be coded by more than one codon

Question 4

explain deletion mutation

Answer 4

• removal of one or more bases
• Has an effect becuase the bases are read as triplets,if one pair is removed then the whoile sequence is read differently
• This is called a frame shift.

Question 5

explain insertion mutation

Answer 5

• one or more bases are added into the DNA
• This has an effect becuase bases are read as triplets,if one pair is added the whole sequence is read differently therefore causes a frameshift

Question 6

explain inversion mutation

Answer 6

when the sequence of bases is reversed

Question 7

expalin why a mutation my be harmful

Answer 7

• mutations can produce a different amino acid sequence (primary structure) in the protein the DNA is coding for.
• This results in the secondary and tertiary structure of the protein being different.
• As a result the protein function is disrupted.

Question 8

how is sickel cell anamia caused.

Answer 8

• Sicke cell anamia is caused by a substitution mutation
• in the gene that codes for one of the polypeptide chain in haemoglobin
• The effect of this is that the shape of haemoglobin is changed,therefore it cannot carry oxygen.

Question 9

what is a frameshift mutation

Answer 9

• caused mainly be insertion and deletion mutation
• The adding and removing of bases causes the whole sequence to be read differently
• This is called a frameshift.

Question 10

what is a silent mutation

Answer 10

• a mutation that has no effect on protein function
• the mutation chages the base in a triplet but the amino acid that the triplet codes for doesnt change
• This happens because the genetic code is degenerate,so there is more than one triplet code for an amino acid
• usually point mutations are silent

Question 11

what type of mutation causes cystic fibrosis

Answer 11

deletion of triplet base pairs

This causes the whole sequence to be read differently (this is called a framehift)

Question 12

Explain how a tumor can be caused

Answer 12

• Growth promoting genes are called protooncogenes
• Some of these genes can be turned into oncogenes by point mutation
• This alters the ability of prootoncogenes to be switched off
• They remain permenatly switched on
• Oncogenes promote unregulated cell division which lead to tumor.

Question 13

what type of mutation causes Huntingtion disease

Answer 13

• Duplication mutation where the triplet code is repeated
• If the duplication expands over a threshold value the protien is sufficiently altered to cause Huntington disease
• Symptoms inlude dementia and loss of motor control