Genetic Code and DNA

Question 1

Central Dogma

Answer 1

information flows from DNA to RNA to protein

Question 2

Genetic Code

Answer 2

DNA/RNA contain a genetic code
DNA: A, T, G, C
RNA: A, U, G, C
the code is combined in 3 letter sequences which each code for a specific amino acid

Question 3

Why are there 64 codes for only 20 amino acids?

Answer 3

helps with error – if there is an error in the code, it might not matter and will still code for the same amino acid due to the redundancy
nearly all are specified by just the two base pairs and some have room for error in the 3rd
3rd base of codon is known as the “wobble” position

Question 4

What is the start codon?

Answer 4

AUG

codes for methionine

Question 5

What are the stop codons?

Answer 5

UAA, UAG, UGA

Question 6

What kind of replication does DNA undergo?

Answer 6

Semi-conservative: each strand serves are a copy. The resulting replicated DNA has one of the original and one newly synthesized

Question 7

Helicase

Answer 7

unwinds DNA helix and separates the two strands

Question 8

Single-stranded DNA-binding proteins

Answer 8

keep the separated strands from immediately reannealing

Question 9

Primase

Answer 9

synthesizes a short RNA primer with a free 3’ OH group - used as the starting point of synthesis of a new strand

Question 10

DNA Polymerase

Answer 10

reads template in the 3’ to 5’ direction and synthesizes in the 5’ to 3’ direction
new strand is anitparallel to the original strand

Question 11

DNA Gyrase aka DNA topoisomerase II

Answer 11

alleviates supercoiling

Question 12

Ligase

Answer 12

links together Okazaki fragments

Question 13

What DNA polymerases should you be aware of for prokaryotes?

Answer 13

DNA polymerase I - assists with Okazaki fragments, removing RNA primer through excision repair
DNA polymerase II - involved with repair
DNA polymerase III - involved with main process of DNA synthesis

Question 14

What DNA polymerases should you be aware of for eukaryotes?

Answer 14

DNA polymerase α - initiates synthesis in replication in both leading and lagging stands
DNA polymerase δ - takes over after it has been initiated. also adds DNA nucleotides when the RNA primer is removed
DNA polymerase ε - assists in extension of leading strand, also assists in DNA repair
DNA polymerase β - assists in DNA repair
DNA polymerase γ - replicates mitochondrial DNA
Reverse Transcriptase - type of polymerases that operates with an RNA template in retroviruses
Telomerase - extends telomeres - shortening of these over time thought to contribute to aging. They are found in stem cells and cancer cells