3.1.5 - Nucleic acids are important information-carrying molecules

Question 1

what are DNA and RNA both types of?

Answer 1

nucleic acid

Question 2

what does DNA stand for?

Answer 2

deoxyribonucleic acid

Question 3

what is DNA used for?

Answer 3

to store your genetic information

Question 4

what does RNA stand for?

Answer 4

ribonucleic acid

Question 5

what is the RNA structure similar to?

Answer 5

similar in structure to DNA

Question 6

RNA function

Answer 6

transfer genetic information from the DNA to the ribosomes.

Question 7

RNA and ribosomes

Answer 7

ribosomes read the RNA to make polypeptides during translation

Question 8

what are molecules of DNA and RNA polymers of?

Answer 8

molecules of DNA and RNA are polymers of nucleotides

Question 9

what components make up a nucleotide?

Answer 9

• pentose sugar (5 C atoms)
• a nitrogen containing organic base
• phosphate group

Question 10

what forms when many nucleotides join together

Answer 10

many nucleotides join together to form polynucleotide strands (or chains)

Question 11

how do the nucleotides join up to form a polynucleotide?

Answer 11

the nucleotides join up via a condensation reaction

Question 12

condensation reaction forming polynucleotides

Answer 12

condensation reaction between the phosphate group of one nucleotide and the sugar of another

Question 13

bond formed in condensation reactions to form polynucleotides

Answer 13

this forms a phosphodiester bond (phosphate group and 2 ester bonds). chain of phosphates and sugars is known as the sugar-phosphate backbone

Question 14

DNA structure

Answer 14

double helix structure

Question 15

what are the strands in the DNA double helix

Answer 15

polynucleotides

Question 16

DNA’s structure and use

Answer 16

DNA molecules are very long/coiled up very tightly so lots of genetic information can fit into a small space in the cell nucleus

Question 17

DNA nucleotide structure

Answer 17

a DNA nucleotide is made from a phosphate group, the pentose sugar deoxyribose and a nitrogen containing organic base

Question 18

DNA nucleotide structure :
sugar/phosphate

Answer 18

each DNA nucleotide has the same sugar and phosphate

Question 19

DNA nucleotide structure :
nitrogen containing organic base

Answer 19

the organic base can either be adenine (A), thymine (T), guanine (G) or cytosine (C)

Question 20

what do 2 DNA polynucleotide strands join together by

Answer 20

2 DNA polynucleotide strands join together by hydrogen bonds between the bases

Question 21

what is complementary base pairing

Answer 21

each base can only join with one particular other base = complementary base pairing

Question 22

what are the complementary base pairs in DNA?

Answer 22

adenine pairs with thymine
cytosine pairs with guanine

Question 23

what does complementary base pairs result in, in terms of amount of bases in DNA

Answer 23

there will always be equal amounts of adenine and thymine and equal amounts of cytosine and guanine

Question 24

how many hydrogen bonds form between the complementary bases pairs in DNA?

Answer 24

• two hydrogen bonds form between adenine and thymine
• three hydrogen bonds form between cytosine and guanine

Question 25

RNA structure

Answer 25

RNA is made of nucleotides that contain a sugar, a phosphate group and one of four different bases

Question 26

RNA structure what do the nucleotides form

Answer 26

the nucleotides form a polynucleotide strand with a sugar-phosphate backbone

Question 27

RNA structure what is the sugar in RNA nucleotides

Answer 27

the sugar in RNA nucleotides is a ribose sugar which is a pentose sugar

Question 28

RNA structure bases

Answer 28

Uracil (U, a pyrimidine) replaces thymine as a base. Uracil always pairs with adenine in RNA

Question 29

RNA structure polynucleotide strands

Answer 29

nucleotides form a single polynucleotide strand, not a double one

Question 30

RNA structure RNA strand length

Answer 30

RNA strands are much shorter than most DNA polynucleotides

Question 31

why did scientists initially have doubts about DNA carrying the genetic code

Answer 31

DNA was 1st observed in the 1800s, lots of scientists then doubted it could carry the genetic code as it had a relatively simple chemical composition

Question 32

what did some scientists initially think carried genetic code

Answer 32

some scientists thought genetic information must be carried by proteins which are much more chemically varied

Question 33

when was it discovered that DNA was the carrier of the genetic code

Answer 33

by 1953, experiments had shown that DNA was the carrier of the genetic code

Question 34

when was DNA's double helix structure discovered

Answer 34

in 1953, Watson and Crick discovered DNA's double helix structure

Question 35

why does DNA replicate

Answer 35

DNA copies itself before cell division so that each new cell has the full amount of DNA

Question 36

what is the name for the DNA copying itself before cell division

Answer 36

it is called semi-conservative replication

Question 37

why is it called semi-conservative replication

Answer 37

as half of the strands in each new DNA molecule are from the original DNA molecule

Question 38

what does the semi-conservative replication of DNA ensure

Answer 38

means there's genetic continuity between generations of cells

Question 39

what happens in the 1st stage of DNA replication?

Answer 39

enzyme DNA helicase breaks the hydrogen bonds between bases on the 2 polynucleotide DNA strands. this makes the helix unwind to form 2 single strands

Question 40

what happens in the 2nd stage of DNA replication?

Answer 40

each original strand acts as a template for a new strand. complementary base pairing means that free floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand - A with T, C with G

Question 41

what happens in the 3rd stage of DNA replication?

Answer 41

condensation reactions join the nucleotides of the new strand together, catalysed by the enzyme DNA polymerase. hydrogen bonds form between the bases on the original and new strands. each new DNA molecule contains 1 strand from the original DNA molecule and 1 new strand

Question 42

3' (3 prime) and 5' (5 prime) ends of DNA

Answer 42

each end of a DNA strand is slightly different in its structure, one end is called the 3' end and the other is called the 5' end

Question 43

the action of DNA polymerase

Answer 43

in DNA replication, DNA polymerase's active site is only complementary to the 3' end of the newly forming DNA strand, so the enzyme can only add nucleotides to the new strand at the 3' end so the new strand is made in a 5' to 3' direction and the DNA polymerase moves down the template strand in a 3' to 5' direction

Question 44

DNA polymerase working on a double stranded DNA molecule

Answer 44

as the strands in the double helix are antiparallel, the DNA polymerase working on 1 of the template strands moves in the opposite direction to the DNA polymerase working on the other template strand

Question 45

who came up with the theory of semi-conservative DNA replication?

Answer 45

watson and crick

Question 46

what validated watson and crick's theory of semi-conservative DNA replication?

Answer 46

Meselson and Stahl's experiment a few years later validated their theory