nucleic acids

Question 1

DNA gyrase

Answer 1

moves in advance of helicase and relives strains in the DNA molecule that are created when teh double helix is uncoiled to prevent the strands from forming tight supercois

Question 2

Helicase

Answer 2

uncoild the DNA double helix and splits in into two template strands.

Question 3

Single stranded binding proteins

Answer 3

keep the strands apart long enough to allow the template strand to be copied

Question 4

DNA polymerase lll

Answer 4

adds nucleotides in a 5’ to 3’ direction. on teh leading strand it moves in the same direction as the replication fork, close to helicase. starts next to the primer.

Question 5

DNA primase

Answer 5

adds a short length of RNA attached by base pairing to a template strand of DNA polymerase to bind and begin replication

Question 6

Okazaki fragments

Answer 6

short lengths of DNA formed between RNA primers on teh lagging starnd due to teh movement of DNA polymerase III from 5’ to 3’

Question 7

DNA polymerase l

Answer 7

removes the RNA primer and replaces it with DNA. a nick is left in the sugar-phosphate backbone where to nucleotides are still unconnected

Question 8

DNA ligase

Answer 8

seals up the nick left by DNA polymerase l by making a sugar phosphate bond

Question 9

coding sequences

Answer 9

transcribed and translated when a cell requires a protein they code for

Question 10

non-coding sequences

Answer 10

regulates gene expression, some are sites where a protein can bind that aither promote or supress teh transcription

Question 11

introns

Answer 11

non-coding. removed from mRNA before translation

Question 12

exons

Answer 12

coding. spliced together to form mature mRNA

Question 13

tandem repeats

Answer 13

regions where adjacent sections of DNA have the same base sequence within genomes of humans and otehr species.

Question 14

structure of nucleotides

Answer 14

8 histone proteins with DNA srapped twice around teh core and DNA linker countinuing towards teh next nucleosome

Question 15

gene expression

Answer 15

the production of mRNA by transcription of a gene and then the production of polypeptides by translation of the mRNA

Question 16

promoter

Answer 16

a base sequence close to the start of a gene (non-coding)

Question 17

RNA polymerase

Answer 17

binds to the promoter in prokaryotes and then starts transcribing

Question 18

repressor proteins

Answer 18

bind to the promoter ans prevents transcription

Question 19

transcription factors

Answer 19

bind to the proteins, allowing RNA polymerase to bind and then initiate transcription

Question 20

methylation

Answer 20

addition of a methyl group - inhibits transcription

Question 20

methylation

Answer 20

addition of a methyl group - inhibits transcription

Question 21

small sub-unit of ribosome

Answer 21

a binding site for mRNA

Question 22

large sub-unit of ribosome

Answer 22

three binding sites for tRNA; A site for tRNA bringing in an aminoacid, P site for tRNA carrying a growing polypeptide, and E site for tRNA exiting the ribosome

Question 23

stages of translation

Answer 23

small subunit bind to mRNA with a strat codon. tRNA with a comeplementary anticodon binds. teh large subunit bind to teh small subunit. mRNA is positioned to that teh initiator tRNA is in the P site. a tRNA with a complementray anticodon to the adjacent bind to A site. a peptide bodn form between aminoacids held by tRNA in the P and A sites.

Question 24

stages of elongation

Answer 24

the ribosome moves three bases on along teh mRNA towards the 3’ end, causing the tRNA in the P site to the E site and the tRNA carring the polypeptide from teh A to the P site. A become vacant. tRNA in the E site detaches and moves away, E site is also vacant. tRNA with complementary anticodon binds to A site . the growing polypeptide is linked with the aminoacid on the tRNA in the A site by teh formation of peptide bonds

Question 25

termination of translation

Answer 25

ribosome moves along the mRNA until it reaches a stop codon. polypeptide is released from the tRNA in the P site. tRNA detaches from P site, mRNA detaches from the small subunit, and large and small subunits seperate

Question 26

primary structure

Answer 26

polypeptide chain

Question 27

secondary structure

Answer 27

hydrogen bonds develop between amino acids in the polypeptide chain, forming either beta-pleated sheets or an alpha helix.

Question 28

tertiary structure

Answer 28

formed when polypeptide chains fold up after translation

Question 29

quaternary structure

Answer 29

fomed by linking two or more polypeptides to form a single protein

Question 30

crick and watson

Answer 30

DNA structure

Question 31

meselson and stahl

Answer 31

semi conservative DNA replication

Question 32

polymerase chain reaction (PCR)|

Answer 32

used for copying DNA artificially. taq DNA polymerase is usedto copy the original molecule multiple times,