mutations and repair

Question 1

what does it mean by genetic code is universal?

Answer 1

all living things use the same 4 bases and codons code for the same amino acid regardless of which organism it is in

Question 2

what does it mean by genetic code is redundant?

Answer 2

more than one codon can code for the same amino acid AGA and AGG both code for Arg

AND

some tRNAs recognize more than one codon

Question 3

what does it mean by genetic code is non ambiguous?

Answer 3

each codon only specifies one amino acid so a codon can’t code for more than one amino acid

Question 4

what is the wobble hypothesis

Answer 4

base pairing rules are flexible in the wobble position which is the third base of the mRNA codon and its corresponding tRNA anticodon

Question 5

what is inosine? what can it do?

Answer 5

a modified form of adenine found in tRNA that can form hydrogen bonds with U, C, or A on the mRNA

Question 6

how does inosine work in the wobble position?

Answer 6

the anticodon CGI can bond with GCA, GCU, or GCC which all result in the addition of the amino acid alanine (Ala)

Question 7

what is a mutation?

Answer 7

a change in the genetic material of an organism

Question 8

what is a genetic disorder or hereditary disease

Answer 8

a harmful mutation in gametes that are passed onto the next generation

Question 9

Describe a spontaneous cause of mutation

Answer 9

errors in the genetic machinery during DNA replication due to enzymes

Question 10

describe an induced cause of mutation

Answer 10

a mutation arising from exposure to mutagenic agents

Question 11

what are transposable elements?

Answer 11

erros during recombination (crossing over)
transposons????

Question 12

mutagen

Answer 12

a substance that can cause a mutation

Question 13

what is the cause of pyrimidine dimers?

Answer 13

UV light

Question 14

what is a pyrimidine dimer?

Answer 14

a type of fused base - DNA damage

Question 15

what is the effect of a pyrimidine dimers

Answer 15

XP

Question 16

describe XP

Answer 16

Xeroderma Pigmentosum (dry skin, change in pigmentation)

• an autosomal recessive genetic disorder that leads to the inability to repair damage caused by UV light which leads to early skin cancer
• mutation in a enzyme in the nucleotide excision repair mechanism
• individuals may need to avoid sunlight

Question 17

what does intercalating mean?

Answer 17

distorting DNA helix between adjacent base pairs which can cause DNAP to ‘stutter’ and copy the mutagen as an extra base pair which many interfere with replication

Question 18

how can a intercalating agent be used in biotechnology?

Answer 18

commonly used for staining and visualizing DNA in biotechnology because it inserts itself into the DNA helix and glows in UV light

Question 19

what is a point mutation?

Answer 19

one nucleotide or base pair is altered

Question 20

what are the types of point mutations:

Answer 20

• substitution: transition, transversion
• frameshift: insertion, deletion

Question 21

what is a substitution mutation?

Answer 21

a small change in a DNA base pair where on nucleotide is replaced with another

Question 22

what is a transition substituion mutation?

Answer 22

a purine to purine

OR

a pyrimidine to pyrimidine

Question 23

what is a transversion substitution mutation

Answer 23

purine to pyrimidine

OR

pyrimidine to purine

Question 24

what is a reading fram

Answer 24

triplet grouping codons of a genetic message

Question 25

what is a frameshift mutation

Answer 25

number of nucelotides added/lost is not a multiple of 3 thus altering the reading frame

Question 26

what is missense mutation

Answer 26

a mutation that does for a different amino acid it may or may not change protein function

Question 27

what is a nonsense mutation? how does it effect protein function?

Answer 27

it codes for a stop codon which results in a truncated polypeptide, it is usually digested by the cell but in the embryoinc stage can be lethal

Question 28

what is a silent mutation

Answer 28

a mutation that still codes for the same amino acid resulting in no change of protein function

Question 29

describe exonuclease repair

Answer 29

mechanisms in place to proofread errors as DNA is being replicated

binds to the ends of nucleotide chain (5’ or 3’)

Question 30

describe endonuclease repair

Answer 30

cell also continuously monitors and repairs DNA outside of replication

binds to the middle of a nucleotide chain

Question 31

nuclease

Answer 31

an enzyme that can break phosphodiester bonds in DNA thus excising our the nucleotide

Question 32

describe exonuclease proofreading and the enzymes involved

Answer 32

DNAP recognizes mismatches during replication
- hydrolizes the phosphodiester bonds releasing te last nucleotide that was just added
- replaces with the correct nucleotide

Question 33

what mechanism of repair does endonuclease proofreading use?

Answer 33

nucleotide excision repair

Question 34

what enzymes are involved in NER and describe what they do

Answer 34

• endonuclease: recognizes and binds to the error then breaks the phosphodiester bonds on the error, and the error is removed
• polymerase: replaes the gap with the correct nucleotides
• ligase: seals the ‘nick’