Mutations

Question 1

Name all the point mutations

Substitutions

Deletion or addition/insertion

Answer 1

Substitutions  the replacement of one base in a DNA sequence by another base

i) Silent Mutation
has no effect on the operation of the cell
 usually occur in the noncoding regions of DNA (introns)
 may also result due to the redundant nature of the genetic code

ii) Missense Mutation
occurs when a change in the base sequence of DNA alters a codon,
leading to a different amino acid being placed in the protein sequence
 this may alter the folding pattern of the protein and thus the
protein may not function properly

iii) Nonsense Mutation
occurs when a change in the DNA sequence causes a stop codon to replace a codon specifying an amino acid, only part of the protein is created, often lethal to the cell

 missense and nonsense mutations arise from the substitution of one base pair for another, this affects one amino acid in the sequence

2. Deletion or Addition/Insertion
    the elimination or addition/insertion of a base pair or group of base pairs from a DNA sequence
   i) Frame Shift Mutation
   changes the entire amino acid sequence following the mutation
    frameshift mutations may be the result of deletions or insertions
    a deletion occurs when one or more nucleotides are removed
   from the DNA sequence, this shifts all codons and alters them

Question 2

B. Chromosomal Mutations

Answer 2

Inactivation of gene if translocation is within a coding segment
i) Translocation
 the transfer of a fragment of DNA from one site in the genome
(chromosome) to another location
 usually occurs between two nonhomologous chromosomes
 segments of chromosomes break off and exchange places
 some fragments of DNA, called transposable elements
consistently move from one location to another in the genome

ii) Inversion
the reversal of a segment of DNA within a chromosome
 no gain or loss of genetic material but may disrupt transcription

Question 3

what are the causes of genetic mutation

Answer 3

x rays
UV light
chemicals - ethidium bromide (DNA gels), asbestos

errors of DNA replication and DNA polymerase 1 fails proof reading

Question 4

effects of translocation

Answer 4

protein with altered function

Question 5

affects of deletion/insertion

Answer 5

defective protein