module 2: nucleotides and nucleic acids

Question 1

what is a nucleotide

Answer 1

used to make nucleic acids
a pentose sugar, a nitrogenous base, a phosphate group
e.g. ATP and ADP

Question 2

what sugar is in DNA

Answer 2

deoxyribose

Question 3

what are the 4 DNA bases

Answer 3

purine- adenine, guanine
pyrimidine- cytosine, thymie

Question 4

what is the difference between purine and pyrimidine bases

Answer 4

purine- 2 carbon nitrogen rings
pyrimidine- one carbon nitrogen ring so smaller

Question 5

what sugar is in RNA

Answer 5

ribose

Question 6

what bases are in RNA

Answer 6

adenine, guanine, cytosine, uracil

Question 7

what bond joins nucleotides

Answer 7

phosphodiester

Question 8

what do 2 polynucleotide strands form

Answer 8

double helix
held together by hydrogen bonds
run anti parallel

Question 9

how do the bases pair

Answer 9

a to t with 2 hydrogen bonds
g to c with 3 hydrogen bonds

Question 10

what is used to purify DNA

Answer 10

solution of detergent, salt and distilled water
cells that have been broken up

Question 11

how does DNA self-replicate

Answer 11

-DNA helicase breaks H bonds between strands causing them to unzip and unwind
-each strand template strands that free floating nucleotides join to by complementary base pairs
-nucleotides joined by DNA polymerase to form sugar-phosphate backbone
-hydrogen bonds from between bases and form double helix
-this is semiconservative replication

Question 12

what is a gene

Answer 12

sequence of DNA that codes for a polypeptide

Question 13

what do base sequences code for

Answer 13

amino acids

Question 14

why is DNA made into mRNA

Answer 14

it is too large to leave the nucleus

Question 15

3 factors of the genetic code

Answer 15

non over-lapping
degenerate
universal

Question 16

what is the genetic code

Answer 16

sequence of base triplets in DNA or mRNA that codes for amino acids

Question 17

describe transcription

Answer 17

1- RNA polymerase unzips and unwinds DNA breaking hydrogen bonds
2- free floating RNA nucleotides line up along template strand and joined by phosphodiester bonds by RNA polymerase creating mRNA
3- orinal 2 strands re-form with hydrogen bonds
4- RNA polymerase reaches stop codon
5- mRNA moves out of nucleus through pore and attaches to ribosome in cytoplasm

Question 18

describe translation

Answer 18

1- mRNA attaches to ribosome and tRNA carry amino acids to ribosome
2- tRNA molecule has complementary anti-codon to start codon on mRNA to binds
3- second tRNA binds to next codon on mRNA
4-rRNA in ribosome catalyses peptide bond between the two amino acids attached to tRNA, first tRNA moves leaving amino acid behind
5- 3rd tRNA brings amino acid that binds to others and second tRNA moves away
6- process continues until polypeptide chain formed and stop codon reached