NUCLEOTIDES

Question 1

what 3 parts make up nucleotides

Answer 1

nitrogenous bases
pentose sugar
phosphate group

Question 2

what is the pentose sugar in DNA called

Answer 2

deoxyribose

Question 3

what is the pentose sugar in RNA called

Answer 3

ribose

Question 4

diff between deoxyribose and ribose

Answer 4

ribose has one more O

Question 5

what are the 4 bases in DNA

Answer 5

A T C G

Question 6

A base

Answer 6

Adenine

Question 7

T base

Answer 7

Thymine

Question 8

C base

Answer 8

cytosine

Question 9

G base

Answer 9

guanine

Question 10

RNA bases

Answer 10

A U C G

Question 11

U base

Answer 11

Uracil

Question 12

What does U in RNA differ to in DNA

Answer 12

RNA = Uracil
DNA = Thymine

Question 13

DNA complimentary bases

Answer 13

A - T

C - G

Question 14

RNA complimentary bases

Answer 14

A - U

C - G

Question 15

pyrimadines

Answer 15

thymine
cytosine

Question 16

purines

Answer 16

adenine
guanine

Question 17

difference in pyrimadines and purines

Answer 17

pyrimadines are made from one ring
purines are made from two rings

Question 18

polynucleotides

Answer 18

many nucleotides bonded together by phosphodiester bonds between nuceotides

Question 19

what reaction joins nucleotides together

Answer 19

condensation (+H2O)

Question 20

what reaction breaks bonds between nucleotides

Answer 20

hydrolysis

Question 21

DNA structure

Answer 21

• double helix structure
• 2 polynucleotide strands (nucleotides are held together by phosphodiester bonds)
• sugar-phosphate back bone on outside
• complimentary bases bonded in center (held together by hydrogen bonds)
• polynucleotides ae antiparallel (one runs from 5’ to 3’ but the other runs 3’ to 5’)

Question 22

DNA and RNA differences

Answer 22

DNA found in chromosomes in nucleus but RNA found in cell cytoplasm
DNA nucleotide chain is longer than RNA
DNA is double strand but RNA is one strand
DNA has T base but RNA has U base
DNA has deoxyribose sugar but RNA has ribose sugar

Question 23

DNA transcription

Answer 23

in nucleus:
DNA molecule unwinds using gyrase enzyme
H bonds between complementary base pairs break using DNA helicase enzyme to form replication fork
mRNA copy is made from the free template strand
the original DNA is bonded back together using DNA polymerase enzyme
mRNA leaves nucleus through nuclear pores

Question 24

DNA translation

Answer 24

in cytoplasm:
mRNA attaches to ribosome (w rRNA)
tRNA from cytoplasm has complimentary amino acid anticodon to mRNA
ribosome moves along mRNA length, reading code
when two amino acids are agacent to each other a peptide bond forms
completed chain disassociates from ribosome

Question 25

gyrase enzyme

Answer 25

unwinds double helix

Question 26

DNA helicase enzyme

Answer 26

unzips two strands by breaking h bonds between bases

Question 27

DNA ligase enzyme

Answer 27

seals sugar phosphate backbone in lagging strand

Question 28

DNA polymerase enzyme

Answer 28

forms phosphodiester bonds

Question 29

DNA replication

Answer 29

helicase unzips strands by breaking bases H bonds DNA polymerase synthesises new strand DNA replication completes each new DNA molecule contains one old strand and one new strand

Question 30

semi conservative replication

Answer 30

dna is made up of one old strand and one new strand (copy)

Question 31

evidence for semi-conservative replication

Answer 31

messelson stahl experiment using n-14 and n-15 to see density of dna of e.coli centrifuge results show one copy strand and one old strand of DNA

Question 32

how many h bonds do a-t form

Answer 32

2

Question 33

how many h bonds do c-g form

Answer 33

3

Question 34

what was the conservative DNA theory

Answer 34

new DNA is both copied from old DNA as template

Question 35

what was the dispersive DNA theory

Answer 35

DNA is a mixture of old and new nucleotides

Question 36

DNA purification

Answer 36

place ethanol in freezer for 24hours crush sample using mortar and pestle to disrupt membrane mix detergent (breaks down membrane) and salt (clumps DNA) in water to make a lysis buffer mix solution and sample in clean test tube aand heat at 60C for 5 min add 3 drops of protease (breaks down histone proteins to uncoil DNA) slowly pour chilled ethanol (shows as DNA is not soluble in alcohol) down side of tube DNA forms at top of test tube