2.3 DNA

Question 1

What kind of acid is DNA?

Answer 1

Nucleic acid

Question 2

What is a nucleotide?

Answer 2

A molecule with:
-phosphate
-five-carbon sugar (Pentose)
-nitrogenous base

Question 3

What is a poly nucleotide?

Answer 3

Large molecule containing many nucleotides

Question 4

What elements do nucleotides contain?

Answer 4

C N O H P

Question 5

What pentose is in DNA?

Answer 5

DEOXYribose

Question 6

What pentose is in RNA?

Answer 6

Ribose

Question 7

Which is more polar, RNA or DNA?

Answer 7

RNA
because it has OH
Which makes it less stable

Question 8

What groups are the four bases divided into?

Answer 8

Purines and pyrmidines

Question 9

Which bases are smaller?

Answer 9

Pyrimidines
They have a single carbon ring structure

Question 10

What is the structure of a pyrimidine like?

Answer 10

Single carbon ring

Question 11

Which bases are pyrimidines?

Answer 11

Thymine, cytosine and uracil

Question 12

Which bases are the bigger ones?

Answer 12

Purines

Question 13

What structure do purines have?

Answer 13

Double carbon ring structures

Question 14

Which bases are purines?

Answer 14

Adenine and Guanine

Question 15

When nucleotides are formed, what kind of reaction happens when the sugar and base join?

Answer 15

Condensation reaction
Molecule of water is produced
The product is a nucleoside

Question 16

What happens when phosphoric acid joins the nucleoside?

Answer 16

Creates a nucleotide and water
It forms a phosphoester bond between OH group on acid and the OH on C-5 of the sugar

Question 17

How do nucleotides form polynucleotides?

Answer 17

Condensation reaction
The phosphate group of one nucleotide joins with a sugar of another nucleotide
This forms a phosphodiester bond

Question 18

What is a phosphodiester bond?

Answer 18

2 phosphoester bonds
Phosphate to 2 sugars

Question 19

How do you know which end is 3’ or 5’?

Answer 19

C5 will be closest to the top
C3 will be closest to the bottom

Question 20

How do you break down polynucleotides?

Answer 20

Hydrolysis reactions

Question 21

How do the two strands of DNA join together?

Answer 21

By hydrogen bonds between the bases

Question 22

What kind of pairing happens between bases?

Answer 22

Complementary pairing

Question 23

Which bases join together?

Answer 23

• A + T (U in RNA)
• G + C

Question 24

How do the strands run to one another?

Answer 24

Anti parallel

Question 25

What does it mean when DNA strands run anti parallel to one another?

Answer 25

It means they run in opposite directions

Question 26

How many H bonds between C and G?

Answer 26

3

Question 27

How many H bonds between A and T?

Answer 27

2

Question 28

Which protein allows DNA to be packed up tightly?

Answer 28

Histone

Question 29

How many base pairs in one full turn of DNA?

Answer 29

10 base pairs

Question 30

What kind of proteins are Histones?

Answer 30

Globular proteins

Question 31

What makes up ATP?

Answer 31

3 phosphate groups Ribose Adenine

Question 32

What can be said about the bonds between the phosphates?

Answer 32

Unstable bonds so are easily broken

Question 33

how do two strands of DNA run?

Answer 33

anti parallel to one another

Question 34

why must DNA be tightly coiled and packaged?

Answer 34

so that it can fit in the nucleus

Question 35

what does ATP stand for?

Answer 35

adenosine triphosphate

Question 36

how is ATP suited to the transfer of energy?

Answer 36

-it is small and soluble -releases energy in small quantities -has an unstable phosphate bond -easily regenerated

Question 37

what is DNA replication?

Answer 37

semi conservative

Question 38

what does the enzyme helicase do?

Answer 38

helicase separates the 2 DNA strands (where the strands are seperated is called the replication fork)

Question 39

what do single stranded binding proteins do? SSB proteins

Answer 39

the 2 DNA strands are held seperate by them

Question 40

where do the nucleotides that form the new strand come from?

Answer 40

they are free floating in the nucleus

Question 41

which direction does DNA polymerase read DNA strands from?

Answer 41

3' to 5'

Question 42

what does DNA polymerase do?

Answer 42

reads the sequence and adds the free floating nucleotides to form new strands

Question 43

what is the name of the strand which is formed continuously?

Answer 43

the leading strand

Question 44

what does DNA polymerase catalyse?

Answer 44

it catalyses the joining of nucleotides with phosphodiester bonds

Question 45

what is the name of the strand that is formed in a discontinuous way?

Answer 45

the lagging strand

Question 46

what are the sections that are formed by the addition of complementary bases called?

Answer 46

Okazaki fragments

Question 47

which enzyme is requred to fill the gaps between the okazaki fragments?

Answer 47

DNA ligase

Question 48

what does DNA ligase do?

Answer 48

it is an enzyme required to seal the gaps between the okazaki fragments

Question 49

how many bases does it take to make one amino acid?

Answer 49

3 bases

Question 50

each gene codes for a specific ...?

Answer 50

polypeptide

Question 51

is a triplet code overlapping?

Answer 51

no, non ever lapping

Question 53

What are the four bases?

Answer 53

Adenine Thymine Cytosine Guanine Uracil

Question 54

Is DNA a macromolecule?

Answer 54

Yes

Question 55

What does each DNA nucleotide consist of?

Answer 55

-a phosphate group -pentose - deoxyribose -a nitrogenous base

Question 56

In DNA, What kind of bond is between the sugar and phosphate group?

Answer 56

It’s a covalent bond It’s a phosphodiester bond

Question 57

What is transcription?

Answer 57

The process of making mRNA from a DNA template

Question 58

What is translation?

Answer 58

Formation of a protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from DNA to the ribosome by mRNA

Question 59

What are the three forms of RNA?

Answer 59

mRNA - messenger tRNA - transfer rRNA - ribosomal

Question 60

How much of an organisms dry mass does protein account for?

Answer 60

75% of the organisms dry mass

Question 61

What comes first translation or transcription?

Answer 61

Transcription then translation