2.1 Structure of DNA and RNA

Question 1

What does RNA stand for

How many strands does it have

Answer 1

Ribonucleic acid

One strand

Question 2

What does DNA stand for

Answer 2

deoxyribonucleic acid

Question 3

What is DNA made up of and what is the structure of DNA called

Answer 3

Its double helix structure

Nucleotides that have 3 basic components

Question 4

What is the nucleotide structure

Answer 4

. A pentose sugar (so called because it has 5 carbon atoms)

. A phosphate group

. A nitrogen containing organic base (ATCG)

Question 5

What are the names of the bases

A
T
C
G

Answer 5

Adenine

Thymine

Cytosine

Guanine

Question 6

What base is In RNA that isn’t in DNA

Answer 6

Uracil (U)

Question 7

What type of reaction occurs between a pentose sugar, phosphate group, and organic base

Answer 7

Condensation reactions to form a single nucleotide
(mononucleotide)

Question 8

How are mononucleotides joined and what’s the new name

What’s the bond called

Answer 8

Condensation reactions also between the deoxyribose sugar of one mononucleotide, and phosphate group of another

Dinucleotide

A phosphodiester bond is formed

Question 9

What is a polynucleotide

Answer 9

Multiple mononuclotides joined together forming a long chain

Question 10

What is the shape of the symbol for…

Phosphate

Pentose sugar

Answer 10

. Circle

. Pentagon

Question 11

What base does uracil replace in RNA from DNA

Answer 11

Thymine

Question 12

Describe the structure of ribonucleic acid

Answer 12

. Ribonucleic acid is a polymer made up of nucleotides

. Single, short chain where the pentose sugar is ALWAYS ribose

. Bases are always Adenine, Cytosine, Guanine, and Uracil
so they have no thymine

Question 13

What are the 3 types of RNA

MRNA
Ribosomal RNA
Transfer RNA

Answer 13

. Messenger RNA: Transfers genetic info from nucleus to ribosomes

. Ribosomal RNA: Ribosomes are made from this type of RNA

. Transfer RNA: Involved in protein synthesis

Question 14

Who worked out the structure of DNA and when

Answer 14

1953

James Watson and Francis Crick worked out the structure

Rosalind Franklin also found X ray diffraction patterns of DNA

Question 15

What is the pentose sugar in DNA

What are the bases

Answer 15

Deoxyribose

Adrenine
Thymine
Cytosine
Guanine

Question 16

Structure of DNA

Answer 16

Made up of two strands of nucleotides (polynucleotides).

Each strand is extremely long

Strands are joined together by hydrogen bonds formed between certain bases

Question 17

What does Adenine pair to

What does Guanine pair to

Answer 17

Thymine

Cytosine

Question 18

What is complimentary base pairing

Answer 18

. The bases attach to a specific one with hydrogen bonds, that hold the two strands together.

Question 19

How do the quantities of bases vary in DNA

Answer 19

The quantities of A and T in DNA are always the same, and so are the quantities of C and G

However, the ratio of AT to CG varies between species

Question 20

What is the name of the structure of DNA

Explain it

Answer 20

Double helix

Ladder like arrangement of two polynucleotide chains being twisted

Uprights of phosphate and deoxyribose wind around each other to form double helix

It forms the backbone of the DNA molecule

Question 21

What ways do the uprights run in DNA

Answer 21

They go different directions ( Antiparallel)

Question 22

How is DNA a stable molecule

Answer 22

. Phosphodiester backbone protects the more chemically reactive organic bases inside the double helix

. hydrogen bonds link the organic base pairs forming bridges between the phosphodiester uprights.
As there are three hydrogen bonds between C and G, the higher the proportion of these pairings, the more stable the DNA molecule

There are other interactive forces between base pairings, holding molecule together

Question 23

How many hydrogen bonds are there between cytosine and guanine

What about between adenine and thymine

What do these bonds do

Answer 23

3 between c and g

2 between a and t

They hold the two chains together forming bridges.

Question 24

What is the function of DNA

Answer 24

. To contain Hereditary material responsible for passing genetic info from cell to cell and generation to generation

Question 25

There are around 3.2 billion base pairs in the DNA of a typical mammal cell

What does this mean

Answer 25

There is an almost infinity variety of sequences of bases along the length of a DNA molecule

Question 26

Why is DNA being stable very important for its function

Answer 26

. It’s a very stable structure which passes down generations without significant change.

Most mutations are repaired, so persistent mutations are rare

Question 27

Why is it good that DNA has only hydrogen bonds joining the two strands together

Answer 27

Its two strands are joined only by hydrogen bonds between the nitrogenous based which allow them to separate during DNA replication and protein synthesis

Question 28

How is the DNA molecule adapted to carry out it’s function:

Its large

Answer 28

Its an extremely large molecule so carries an immense amount of genetic info

Question 29

How is the DNA molecule adapted to carry out it’s function:

Has base pairs within helical cylinder of the deoxyribose phosphate backbone

Answer 29

By having base pairs within the helical cylinder of deoxyribose phosphate backbone, the genetic info is to some extent protected from being corrupted by outside chemical and physical forces

Question 30

How do base pairings help DNA transfer information

Answer 30

Base pairings lead to DNA being able to replicate and to transfer information as MRNA

Question 31

How are carbon atoms in pentose molecules numbered

Answer 31

. Labelled from 1 to 5

3 prime carbon has hydroxyl group

5 prime carbon has the attached phosphate group

They are labelled starting from 1, from the clockwise direction from the O in it.

Question 32

What ways do the strands run in DNA

Answer 32

. One strand runs in 5’ to 3’ direction, whilst the other runs in the opposite 3’ to 5’ direction.

The two strands are said to be antiparallel

Question 33

Why can nucleic acids only be synthesised in Vivo

Answer 33

This is the 5’ to 3’ direction, because the enzyme DNA polymerase that assembles nucleotides into a DNA molecule can only attach nucleotides to the hydroxyl group on 3’ carbon molecule.