paper 1: Nucleic Acids and DNA Replication

Question 1

what does DNA stand for

Answer 1

deoxyribonucleic acid

Question 2

what does RNA stand for

Answer 2

ribonucleic acid

Question 3

what does DNA do in the body

Answer 3

holds genetic information which codes for proteins

Question 4

what does RNA do in the body

Answer 4

transfers genetic information from DNA to ribosomes

Question 5

draw the structure of a DNA/ RNA nucleotide

Answer 5

Question 6

what is the difference between the structure of DNA and the structure of RNA

Answer 6

• the pentose sugar for DNA is deoxyribose, for RNA it’s ribose
• the bases for DNA can be A, C, G, T but for RNA its A, C, G, U.

Question 7

what are the names of the organic bases in DNA

Answer 7

adenine, thymine, cytosine, guanine

Question 8

what are the names of the organic bases in RNA

Answer 8

adenine, uracil, cytosine, guanine

Question 9

describe the formation of polynucleotides

Answer 9

• nucleotides join together by condensation reactions
• to form a phosphodiester bond between the phosphate group of one nucleotide and the pentose sugar of another
• to make the sugar-phosphate backbone
• which is strong and stable

Question 10

what is the word used to describe the phosphate backbones running in opposite directions

Answer 10

anti-parallel

Question 11

what does the 3’ and the 5’ relate to

Answer 11

the carbon number of the deoxyribose

Question 12

describe an RNA strand

Answer 12

relatively short, single stranded polynucleotide strand

Question 13

why must DNA be replicated accurately

Answer 13

so each daughter cell recieves an exact copy of DNA

Question 14

when does DNA replication take place

Answer 14

• during cell division

Question 15

describe the 3 stages of DNA replication

Answer 15

stage 1: DNA helicase breaks hydrogen bonds between complimentary bases in the polynucleotide strand. this causes the DNA helix to unwind and separate

stage 2: new DNA nucleotides are attracted to exposed bases on the template strands and hydrogen bonds form between complimentary bases.

stage 3: DNA polymerase joins the adjacent nucleotides together via a condensation reaction to form phosphodiester bonds.

Question 16

why is DNA replication described as semi-conservative

Answer 16

a strand from the original DNA molecule acts as a template which joins a new strand

Question 17

why does DNA polymerase run in opposite directions

Answer 17

• the active site of DNA polymerase is only complimentary to the 3’ end of nucleotides so runs in opposite directions along the 2 template strands

Question 18

how does the structure of DNA allow it to carry out its function

Answer 18

• sugar-phosphate backbone and double helix structure: provides strength and stability, protects bases and hydrogen bonding between bases
• long molecule: can store lots of information
• helix structure: compact
• base sequence: codes for amino acids and therefore proteins
• double stranded: allows for semi conservative replication
• complimentary base pairing: allows accurate replication
• weak hydrogen bonds between bases: allows unwinding of strands for replication
• many hydrogen bonds in the whole molecule: strong and stable molecule

Question 19

describe the function of DNA helicase

Answer 19

breaks hydrogen bonds between complementary bases which causes the double helix to unwind

Question 20

describe the function of DNA polymerase

Answer 20

joins adjacent nucleotides via a condensation reaction to form phosphodiester bonds