nucleic acids and cell division

Question 1

nucleotide structure

Answer 1

consists of:

a pentose sugar (either ribose or deoxyribose)
a phophate group
a nitrogenous base

Question 2

purines

Answer 2

adenine and guanine

2 carbon rings

Question 3

pyrimidines

Answer 3

cytosine and thymine/uracil

1 carbon ring

Question 4

structure of atp

Answer 4

adenosine triphosphate

• ribose sugar
• adenine nitrogenous base
• 3 phosphate groups

(ribose+adenine= adenosine)

Question 5

structure of polynucleotides

Answer 5

sugar phosphate backbone

phosphodiester bonds between carbon3 and phosphate/ carbon5 and phosphate

Question 6

dna structure

Answer 6

• 2 antiparallel strands (double helix)
• two strands held together by hydrogen bonds
• adenine pairs w guanine (3 hydrogen bonds)
• thymine pairs with cytosine (2 hydrogen bonds)

Question 7

purifying DNA

Answer 7

1. break up cells
2. add to solution of detergent and salt
3. place in water bath at 60*
   (detergent breaks down cell membranes, high temp denatures enzymes, salt causes DNA to clump together)
4. place in ice bath to cool down
5. filter and add protease enzymes (breaks down proteins bound to dna)
6. slowly dribble cold ethanol down side, forming a layer of dna-detergent mixture
7. wait until dna forms white precipitate

Question 8

what is semi-conservative dna replication

Answer 8

each polynucleotide strand acts as a template for new strand
one molecule of dna is used to make two identical copies
each new dna molecule contains one old strand and one new strand

Question 9

outline process of transcription in protein synthesis

Answer 9

1. DNA helicase unwinds and unzips dna molecule by breaking hydrogen bonds betw nucleotides
2. free activated (phosphorylated) rna nucleotides pair with exposed dna bases on dna template strand
3. phosphodiester bonds form betw sugar and phosphate groups
4. mRNA molecule made which passes through nuclear pore out of nucleus

Question 10

outline process of translation in protein synthesis

Answer 10

1. mRNA molecule attaches to a ribosome
2. tRNA with anti-codon enters ribosome and forms hydrogen bonds betw complementary bases
3. second tRNA enters and attaches to second codon, carrying specific amino acid
4. peptidontransferase forms peptide bonds between amino acids
5. first tRNA leaves, ribosome moves along mRNA by 3 bases and third tRNA can enter
6. process continues until there is a stop codon, no complementary tRNA molecules so translation terminated