Nucleic Acids

Question 1

What does DNA stand for

Answer 1

Deoxyribonucleic aci

Question 2

What does RNA stand for

Answer 2

RiboNucleic acid

Question 3

What does DNA and RNA do

Answer 3

They are important information carrying molecules
DNA holds genetic information that codes for proteins
RNA transfers genetic information from DNA ribosomes

Question 4

What does the structure of DNA contain

Answer 4

Phosphate group
Deoxyribose sugar
Nitrogenous base (Adenine thymine cytosine and guanine)

Question 5

What does the structure of RNA contain

Answer 5

Phosphate group
Ribose sugar
Nitrogenous base (Adenine Uracil Cytosine Guanine)

Question 6

What are the differences between DNA and RNA

Answer 6

DNA has 2 polynucleotide strands but RNA has 1
DNA is long but RNA is short
DNA is shaped like a double helix whereas RNA is shaped linear or clover leaf

Question 7

Differences between DNA and RNA (2)

Answer 7

DNA has deoxyribose sugar but RNA has ribose sugar
DNA contains thymine but RNA has uracil
DNA has hydrogen bonds whereas RNA doesnt

Question 8

What is the overral structure of a polynucleotide

Answer 8

It is formed by the condensation of many repeating nucleotides
A phosphodiester bond forms between the phospate group of one nucleotide and the pentose sugar of another nucleotide molecule
These bonds make up a sugar phosphate backbone
2 polynucleotide chains are held together by hydrogen bonds between complimentary base pairs
Adenine bonds with thymine and cytosine bonds with guanine

Question 9

How is DNA antiparallel

Answer 9

Each end is labelled with a 5’ end and a 3’ end
they become important when making proteins
is also important during DNA replications as DNA polymerase only has a complimentary active site to the 3’ end of the molecules

Question 10

How does having a sugar phospate backbone relate to DNA function

Answer 10

It provides strength and stability
Protects bases and hydrogen bonding between bases

Question 11

How does DNA being a long molecule relate to its function

Answer 11

It can store a lot of information

Question 12

How does DNA having a helical structure relate to its function

Answer 12

It makes it more compact

Question 13

How does DNA having a base sequence relate to its function

Answer 13

It can code for amino acids and therefore proteins

Question 14

How does DNA being double stranded relate to its function

Answer 14

It allows for semiconservative repliaction to occur

Question 15

How does DNA having complimentary base pairing

Answer 15

It allows for accurate replication

Question 16

How does hydrogen bonding between the bases help DNA

Answer 16

The hydrogen bonds can be broken easily so strands can replicate

Question 17

How does many hydrogen bonds in the structure of dna allow it to relate to its function

Answer 17

It creates a strong and stable molecule

Question 18

What is the process of DNA replication

Answer 18

1) The enzyme DNA helicase attaches and moves along the DNA molecule breaking the hydrogen bonds between complimentary bases
2) The 2 strands seperate and both strands act as a template

Question 19

What is the process of DNA replication (2)

Answer 19

3) New individual DNA nucleotides are attracted to exposed complimentary bases and template strands and bind by complimentary base pairing
4) DNA Polymerase joins the DNA nucleotides together via a condensation reaction to form many phosphodiester bonds

Question 20

Why is DNA decribed as semi conservative

Answer 20

Each strand in the original molecule acts as a template
each new DNA molecule contains one strand from the original molecule and one new strand

Question 21

What is the importance of semi conservative replication

Answer 21

It ensure genetic continuity between generations of cells`

Question 22

How did the Meselson and Stahl experiment prove that DNA replication was semi conservative

Answer 22

Bacteria was grown in a medium containing N15 a heavy form of nitrogen
Bacteria used the nitrogen atoms to create bases to make their own DNA

Question 23

How did the Meselson and Stahl experiment prove that DNA replication was semi conservative (2)

Answer 23

This DNA was extracted and centrifuged in a test tube
Causes substances to separate due to their different densities
Denser substances settle at the bottom of the tube and less dense substances will rise to the top

Question 24

How did the Meselson and Stahl experiment prove that DNA replication was semi conservative (3)

Answer 24

The bacteria were then transferred to a medium containing N14 a light form of nitrogen
The bacteria now use these nitrogen atoms when replicating DNA

Question 25

How did the Meselson and Stahl experiment prove that DNA replication was semi conservative (4)

Answer 25

After each cell division the DNA was extracted and centrifuged. This was repeated for 3 cell divison

Question 25

How does the experiment prove that DNA was semi conservative

Answer 25

The DNA from generation 1 forms a band midway between the position of “heavy” and “light” DNA
This shows that the molecules have one “heavy” strand from the original DNA molecule and one new “light” strand

Question 26

How does the Hershey and Chase experiment prove that DNA is the hereditary material not proteins

Answer 26

Bacteriophage-virus that infects and replicates within bacteria
Phages repoduce by attacking the bacterial cell wall and infecting the bacteria with their DNA- instructs the bacteria to create a new generation of phages

Question 27

How does the Hershey and Chase experiment prove that DNA is the hereditary material not proteins (2)

Answer 27

Viruses were used bc they are only made up of DNA+proteins
Radioactive S used to label proteins to allow it to be monitored
No radioactive sulphur was foind in the next generation of phages. Therefore none of the proteins was passed onto the next generation

Question 28

How does the Hershey and Chase experiment prove that DNA is the hereditary material not proteins (3)

Answer 28

Then radioactive phosphorus was used to label DNA as its found in DNA but not protein. Radioactive phosphorus was found in the next generation of phages showing that DNA was the hereditary material

Question 29

How does the Griffiths experiment prove that DNA was hereditary

Answer 29

He used mice and the bacteria that caused pneumonia the first mouse was injeced with a safe strain of bacteria

Question 30

What was the 2nd 3rd and 4th mice injected with

Answer 30

2nd- Injected with a harmful form of bacteria
3rd- Injected with the harmful form of the bacteria that was heatkilled
4th- Injected with both the heat killed harmful strain and the safe strain

Question 31

How did this prove that DNA was hereditary

Answer 31

Pneumonia is caused by a toxin. The harmful strain of bacteria has the DNA coding for the toxin
The heat killed strain has the DNA to make the toxin but cant make it as its dead
3rd mouse didnt die but 4th did
THEREFORE the info for how to be “harmful” mustve been passed to the live bacteria from the heat killed bacteria

Question 32

why dont mutations always cause a change in the encoded polypeptide amino acid sequence

Answer 32

Because the genetic code could be degenerate
Mutation could be to non coding DNA

Question 33

Why might there be DNA in from cancer cells in blood plasma

Answer 33

When cancer cells die they can break open. This releases DNA into the blood plasma

Question 34

What is the difference between the effects of the changes in the two types of nucleic acids?

Answer 34

DNA is the genetic material that is passed from parent cells to daughter cells to future generations