Nucleic Acids

Question 1

what are polymers made up of

Answer 1

Both DNA and RNA are polymers that are made up of many repeating units called nucleotides

Question 2

what is each nucleotide made up of

Answer 2

A phosphate group - circle
deoxyribose pentose sugar- hexagon
A nitrogen-containing organic base - rectangle

Question 3

what are the components of an RNA nucleotide

Answer 3

phosphate group
ribose sugar with hydroxyl group at 2’
one of the bases (uracil)

Question 4

difference between rna and dna

Answer 4

RNA is single-stranded while DNA is double-stranded. RNA contains uracil while DNA contains thymine. RNA has the sugar ribose while DNA has the sugar deoxyribose.

Question 5

how are nucleotides joined

Answer 5

via condensation reactions
These condensation reactions occur between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide forming a phosphodiester bond

Question 6

how are DNA molecules arranged

Answer 6

two polynucleotide strands lying side by side, running in opposite directions – the strands are said to be antiparallel

Each DNA polynucleotide strand is made up of alternating deoxyribose sugars and phosphate groups bonded together to form the sugar-phosphate backbone

Question 7

what does the phosphodiester bonds link

Answer 7

5-carbon of one deoxyribose sugar molecule to the phosphate group from the same nucleotide, which is itself linked by another phosphodiester bond to the 3-carbon of the deoxyribose sugar molecule of the next nucleotide in the strand

Question 8

how are the two antiparallel DNA polynucleotide strands held

Answer 8

held together by hydrogen bonds between the nitrogenous bases

Question 9

is RNA shorter or DNA

Answer 9

RNA polynucleotide chains are relatively short compared to DNA

Question 10

what are the sugar phosphate bonds called

Answer 10

covalent bonds known as phosphodiester bonds

Question 11

difference and similarities between transcription and DNA replication

Answer 11

both form polynucleotides and form phosphodiester bonds and involve the unzipping using DNA helicase

(DNA nucleotides) dna replication uses dna nucleotides and transcription uses (RNA polymerase) RNA nucleotides

transcription produces single stranded DNA and DNA replication produces double stranded DNA

Question 12

how does insertion or removal of nucleotides produce leptin w shorter primary structures

Answer 12

changes the triplet code so it will introduce a new start or stop codon which will code for a short sequence of amino acids

Question 13

three differences between replication and transcription

Answer 13

replication produces double stranded DNA molecules whereas transcription produces a single stranded
RNA molecule (1)
replication uses DNA polymerase whereas transcription requires
RNA polymerase (1)
replication produces identical copies whereas transcription produces a complementary
cop

Question 14

how does deletion and substitution have different affects on protein structure

Answer 14

deletion could affect every codon (on the mRNA) / substitution will only affect one codon (1)
deletion more likely to affect the position of { stop codon / start codon } (1)
deletion results in a different sequence of amino acids / substitution may not affect the sequence of amino acids (1)
substitution may code for the same amino acid (1)
(same amino acid) due to the degenerate nature of the genetic code (1)

Question 15

how does CFTR protein ensure right consistency of mucus in lungs

Answer 15

chloride will leave cell by CFTR channel proteins and sodium will follow increase solute concentration in mucus and water will leave cell by osmosis into mucus

Question 16

Describe the process of protein synthesis that occurs in the cytoplasm.

Answer 16

reference to ribosome (attaches to mRNA) ;
idea that tRNA carries an amino acid;
idea of {anticodon codon interaction / complementary base pairing } between tRNA and mRNA;
formation of hydrogen bonds (between the tRNA and mRNA);
reference to peptide bond (between amino acids) ;
(peptide bond) formed by a condensation reaction;
idea that tRNA released from {mRNA / ribosome} ;
idea that ribosome {attaches to / detaches from / eq} {sequence / eq} on mRNA;

Question 17

Explain how the expression of a gene mutation in a person with cystic fibrosis
causes a build-up of mucus in their respiratory system.

Answer 17

reference to CFTR {protein / channel} / eq ;
2. idea of a different {amino acid / sequence of amino acids /
primary structure / eq} ;
3. {shape / function} of {CFTR / protein/ channel / eq}
changed / eq ;
4. role of protein in transporting chloride ions / eq ;
5. (chloride) ions not {moving out of cells / going into
mucus} / eq ;
6. water does not move out (of cells) / water moves in (to
cells) / eq ;
7. reference to osmosis ;
8. mucus (on cell surface) {is not diluted / becomes thicker /
becomes stickier} / eq ;
9. (thickened mucus) cannot be moved by {cilia / coughing}

Question 18

What is meant by non overlapping

Answer 18

{triplet is discrete / each base
is only used once in a triplet

Question 19

Describe how DNA is organised in a bacterial cell.

Answer 19

(large) circular DNA (1)
 DNA not associated with histone proteins (1)
 (small / several ) plasmids (1)
 located in the cytoplasm / not inside a nucleus