Biological Molecules (DNA+RNA)

Question 1

What does DNA stand for

Answer 1

Deoxyribonucleic acid

Question 2

What is the monomer of a deoxyribonucleic acid (DNA polymer)

Answer 2

Nucleotides

Question 3

What is a DNA nucleotide made up of

Answer 3

A phosphate group
A deoxyribose pentose sugar
A nitrogen containing base

Question 4

What are the 4 nitrogen bases

Answer 4

Adenine
Thymine
Cytosine
Guanine

Question 5

What is a polynucleotide

Answer 5

A polynucleotide is when nucleotides join by condensation reactions forming phosphodiester bonds

Question 6

In a polynucleotide, where do the phosphodiester bonds form

Answer 6

Between the phosphate group of one nucleotide and the deoxyribose pentode sugar of another
–> adjacent nucleotides

Question 7

Due to the strong covalent bonds in the phosphodiester bond, a polynucleotide is said to have a….

Answer 7

A sugar phosphate backbone

Question 8

Give the complimentary base pairs

Answer 8

Adenine is complimentary to Thymine
Cytosine is complimentary to Guanine

Question 9

What do two polynucleotide strands that run anti parallel to each other form when twisted together

Answer 9

Form a DNA double helix

Question 10

Describe the 4 steps of semi conservative replication

Answer 10

1) Double helix unwinds

2) the hydrogen bonds between complimentary base pairs are broken by the DNA helicase enzyme so DNA unzips to form template strands

3) complimentary base pairing means free floating DNA nucleotides are attracted to their complimentary exposed bases on each template strand

4) condensation reactions occur to join adjacent nucleotides which forms phosphodiester bonds, catalysed by the DNA polymerase enzyme

—> forms 2 DNA molecules- one strand on each DNA molecule is original and the other is newly synthesised

Question 11

What is the bond between specific complimentary base pairs and how many form between them

Answer 11

Held by hydrogen bonds
Adenine and Thymine has 2 hydrogen bonds between them
Guanine and cytosine has 3 hydrogen bonds between them

Question 12

Explain how the structure of DNA is related to its function

Answer 12

Sugar phosphate backbone - provides strength and stability by protecting bases and hydrogen bonds

Large molecule - can store lots information

Double helix - compact

Complimentary base pairs - identical copies can be made during semi conservative replication

Weak hydrogen bonds - DNA can easily unzip

Many collective hydrogen bond - provides strength

Double stranded so replication can occur semi conservativley to form two template strands

Question 13

What did Watson and Cirk discover

Answer 13

The structure of DNA

Question 14

What was the 3 hypothesis theories of DNA replication

Answer 14

Semi conservative replication - each replicated DNA molecule contains one of the original DNA strands and a newly synthesised strand

Conservative replication - original DNA is fully conserved and replicated so the other replicated DNA molecule contains 2 newly synthesised strands

Dispersive replication - Half of each of the replicated molecules are original and half is newly synthesised

Question 15

What did Meselson and Stahl intend to do with their experiment

Answer 15

Figure out which of the 3 theory’s of DNA replication was true
–> found out it was semi conservative

Question 16

What were the 2 isotopes used in Meselson and Stahl’s experiment

Answer 16

Nitrogen -15 (15N) and Nitrogen- 14 (14N)

Question 17

Which of the 2 nitrogen istotopes ( 14 and 15) is heavier and denser

Answer 17

Nitrogen - 15 is heavier and denser than nitrogen-14

Question 18

Describe the Meselson and Stahl experiment

Answer 18

1) E coli is left to grow in a growth medium only containing nitrogen-15
2) DNA is then spun in a centrifuge - position of it is looked at
3) E coli bacteria is then taken and put in a growth medium containing nitrogen-14
4) Spun in centrifuge again
5) Bacteria left for many generations to replicate

Question 19

Describe position of DNA in centrifuge after G0 (generation 0)

Answer 19

DNA is in bottom band as 100% of DNA is nitrogen-15.
–> nitrogen-15 is denser than nitrogen-14 so it sinks

Question 20

Describe position of DNA in centrifuge after G1

Answer 20

DNA is in middle band as 50% of it is nitrogen-15 and 50% nitrogen-14

Question 21

Describe the position of DNA in centrifuge after G2

Answer 21

DNA is in middle band - 50% of DNA is nitrogen-15 and nitrogen-14

DNA is also in top band - 50% of DNA nitrogen-14 and nitrogen-14

Question 22

Describe the position of DNA in centrifuge after G3

Answer 22

DNA is in top band - 75% of DNA is nitrogen-14 and nitrogen-14.

DNA is also in middle band - 25% of DNA is nitrogen-15 and nitrogen -14

Question 23

How can you tell there is 75% of DNA in a centrifuge

Answer 23

The band is thicker

Question 24

DNA and RNA are both examples of…

Answer 24

Nucleic acid

Question 25

What is a RNA nucleotide made up of

Answer 25

A phosphate group
A ribose sugar
A nitrogenous base

Question 26

What are the 4 bases in RNA

Answer 26

Adenine
Cytosine
Guanine
Uracil

Question 27

Give three differences between DNA and RNA

Answer 27

DNA is double stranded (double helix) whereas RNA is single stranded
DNA is very stable whereas RNA is unstable and breaks up quickly
DNA is only found in the nucleus whereas RNA is found in both nucleus and cytoplasm

–> extra: ribose sugar in RNA, deoxyribose sugar in DNA