2.1.3 Nucleotides and nucleic acids

Question 1

Is a purine or pyrimidine base two ringed?

Answer 1

purine

Question 2

How do two nucleotides join together?

Answer 2

condensation reaction btwn sugar of one and phosphate of another

Question 3

difference btwn dna and rna

Answer 3

DNA has a deoxiribose sugar, RNA has a ribose sugar

Question 4

what bond is formed between 2 nucleotides in a condensation reaction?

Answer 4

3’ to 5’ phosphodiester bond

Question 5

condensation or hydrolysis to break a phosphodiester bond?

Answer 5

hydrolysis

Question 6

Structure of ATP

Answer 6

3 phosphate groups, ribose sugar, adenine base

Question 7

reaction to break ATP to ADP?
condensation or hydrolysis?

Answer 7

ATP + H2O -> ADP + iorganic phosphate + energy

Question 8

structure of DNA

Answer 8

2 antiparallel nucleotide strands, 5’3’ strand and 3’5’ strand held by phosphodiester bond
double helix
complementary bases

Question 9

which two bases have 3 H bonds

Answer 9

C + G

Question 10

Which two bases have 2 H bonds

Answer 10

A + T

Question 11

purine always bind to

Answer 11

pyrimidine

Question 12

DNA replication (7PNTS)

Answer 12

1) helicase enzyme breaks hydrogen bonds
2) double helix unwinds
3)each strand acts as a template
4) free nucleotides in cytoplasm align next to complementary base pairs
5)hydrogen bonds reform between bases
6)DNA polymerase joins nucleotides forming a new sugar phosphate backbone
7)2 new strands of DNA

Question 13

Why is DNA replication semi-conservative?

Answer 13

each new DNA molecule contains one old and one new strand

Question 14

Meselson and stahl experiment?
8pnts

Answer 14

• grew e.coli in a N15 medium
• as cells reduplicate, they create new DNA
• DNA nitrogenous base has N15 in
• took e.coli out + centrifuged=V N115 heavy
• took e.coli out and put it in N14
• so when dna replicated in N14 , one trand N14, one N15
  -mix of heavy N-15 and lighter N 14 so appears in middle of test tube
• new DNA’s means thicker disc not new ones

Question 15

how manny directions is the DNA strand read in?

Answer 15

ONE

Question 16

what’s meant by non-overlapping dna?

Answer 16

3 bases read, then move onto the next three

Question 17

DNA is degenrate meaning

Answer 17

some amino acids have more than one triplet code

Question 18

DNA is universal means?

Answer 18

used across all organisms

Question 19

How to purify DNA by precipitation?
5 pnts

Answer 19

1) crush piece of fruit to break cell wall
2) add detergent to dissolve cell surface/plasma membrane
3) add a protease enzyme to break dwn histones associated w/DNA
4) add salt to help DNA clump 2gether
5) pour cold alcohol into mixture, DNA is insoluble in alcohol so should float 2 top

Question 20

steps of protein synthesis

Answer 20

1) bases code for sequence of amino acids in polypeptides
2) DNA helicase used to break Hbonds
3) free RNA nucleotides form mRNA (copy of DNA coding strand)
4) RNA polymerase helps form phosphodiester bonds btwn RNA nucleotides
5) mRNA leaves nucleus thru nuclear pore
6) mRNA attaches to a ribosome made of 2 subunits of RNA
7) anticodon on tRNA bringing a specific amino acid w/it
8) amino acids joined by peptide bonds 2 give primary structure (then goes on 2 secondary,tertiary,e.t.c)