mutations

Question 1

what is a silent mutation

Answer 1

A point mutation where the codon codes for an amino acid that does not significantly affect the protein created (e.g AAG changed to AAA still codes for the AA lys)

Question 2

what are the three types of substitution mutations and explain what they are

Answer 2

silent: does not affect the protein (wobble hypothesis)
missense: A genetic alteration in which a single base pair substitution alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position (e.g CAT -> CGT makes it go from HIS AA to ARG AA)
Nonsense Mutation: A genetic alteration that causes the premature termination of a protein. protein then becomes useless (e.g AUG -> AUG (stop))

Question 3

sickle sell anemia

Answer 3

• missense mutation example
• GAG to GTG
• valine instead of glutamate
• Polymerization of hemoglobin & warps RBCs (They become long)

Question 4

Frameshift mutations

Answer 4

• • or – 1 bp changes reading frame
• results in nonsense mutation
• ## Two frameshift mutations can cancel each other out.

Question 5

insertion and deletion (frameshift)

Answer 5

insertion: Adding a nucleotide to the sequence.
AUG GGA UUC AAC…
(+) C after AUG:
AUG CGG AUU CAA C…

Deletion: Deleting a nucleotide in the sequence

AUG GGA UUC AAC…
(-) 1st G after AUG:
AUG GAU UCA AC…

Question 6

inversion mutation

Answer 6

occur when a section of DNA breaks away from a chromosome during the reproductive process and then reattaches to the chromosome in reversed order

Result of small scale
mutations:
Positive ☺
No effect
negative

Question 7

CHROMOSONAL MUTATION (large scale)
Nondisjunction

Answer 7

Uneven splitting of chromosomes during
meiosis

Question 8

CHROMOSONAL MUTATION (large scale)
Translocation

Answer 8

the movement DNA sections between
different chromosomes

Question 9

CHROMOSONAL MUTATION (large scale) Inversion:

Answer 9

One segment reverses its order on the
chromosome.

Question 10

CHROMOSONAL MUTATION (large scale) Transposons:

Answer 10

genes that randomly change position on
chromosomes

Question 11

CHROMOSONAL MUTATION (large scale)
Fusion:

Answer 11

two chromosomes join

Question 12

causes of mutations

Answer 12

Spontaneous Mutations: caused by
errors in DNA replication.
Induced Mutations
Chemical Mutagens
Viruses

Question 13

Chemical Mutagens:

Answer 13

Molecules that enter the cell 🡪 nucleus ☹

Can be base analogs – similar structure to DNA
bases, but do not pair properly, thus cause
substitutions

Can bond to bases and change their shape

Can insert themselves in the helix causing
frameshift mutations (nitrates, benzene
compounds)

Most are carcinogenic – cancer causing

Question 14

Induced Mutations:

Answer 14

Cause by external mutagens, substances and
energies
* Physical Mutagens:
High energy radiation: X-rays and gamma rays
UV radiation: makes covalent bonds between
adjacent T bases (Thymine Dimer) 🡪 warps DNA

Question 15

Viruses

Answer 15

Insert their DNA in the host
cell, thus can interrupt host
cell genes

E.g. HPV (Cervical Cancer),
herpes virus (Liver cancer)