Nucleic Acids

Question 1

Structure of a nucleotide

Answer 1

phosphate, sugar (pentose) and a base

Question 2

Differences between DNA and RNA

Answer 2

Sugar, double/single stranded. thymine/uracil, size

Question 3

Pyramidines

Answer 3

Single carbon ring
Thymine and cytosine

Question 4

Purines

Answer 4

Double carbon rings
Adenine and Guanina

Question 5

How many hydrogen bonds between thymine and adenine?

Answer 5

2

Question 6

Semi conservative replication

Answer 6

Each new DNA molecule consists of an old strand of DNA and one new strand

Question 7

DNA Helicase

Answer 7

breaks hydrogen bonds, seperating helix

Question 8

DNA polymerase

Answer 8

Catalyses the formation of phosphodiester bonds between nucleotides

Question 9

Triplet code

Answer 9

A sequence of three bases called a codon. Each codon codes for an amino acid

Question 10

How does ATP release energy

Answer 10

The terminal phosphate breaks apart after a hydrolysis reaction

Question 11

Properties of ATP

Answer 11

Small
Water soluble
Releases energy in small quantities
Easily regenerated

Question 12

Phosphate group

Answer 12

acidic
negatively charged

Question 13

Synthesis of polynucleotides

Answer 13

condensation reactions
phosphate group and carbon 3 of OH join

Question 14

How many hydrogen bonds between cytosine and guanine

Answer 14

3

Question 15

Structure of the double helix

Answer 15

two strands held together by hydrogen bonds
antiparallel

Question 16

Translation

Answer 16

Anticodon binds to complementary codon on mRNA
tRNA molecules carry an amino acids corresponding to codon
codons and anticodons bind together forming the primary structure of the proteins

Question 17

How does bonding occur between complimentary bases?

Answer 17

Purines pair with pyrimidines
Two hydrogen bonds between A&T
Three hydrogen bonds between C&G

Strands are antiparallel because they run in opposite directions

Question 18

Explain DNA replication

Answer 18

DNA is untwisted and uzipped by DNA helicase
H bonds between bases break
Both strands acts as templates
Free DNA nucleotides go to their complimentary bases
Hydrogen bonds reform
Sugar phosphate backbone is joined by DNA polymerase forming phosphodiester bonds

Question 19

What is a gene?

Answer 19

A sequence of DNA nucleotides that code for a polypeptide

Question 20

Characteristics of the genetic code

Answer 20

Triplet code: three bases code for an amino acid
Degenerate: All amino acids bar one have more than one code
Some codes don’t code for amino acids but instead are stop codons
Universal: Same in all organisms

Question 21

Definition of the genetic code

Answer 21

The sequence of bases on a gene is a code with instructions for the construction of proteins

Question 22

How can mutations be beneficial, neutral or harmful

Answer 22

Beneficial:
Changes the sequence of amino acids and therefore phenotype but this could be advantageous

Neutral:
could occur in a non coding section of DNA
Silent mutation - still codes for same amino acid

Harmful:
Changes sequence of amino acids and therefore phenotype but this can be harmful, such as: paler skin in hotter environments