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Biology A level > 1.5 Nucleic Acids > Flashcards

1.5 Nucleic Acids Flashcards

1
Q

What are the functions of DNA?

A

Carries the genetic code for protein synthesis
Replication for making new cells

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2
Q

What is mRNA?

A

Messenger RNA

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3
Q

What is rRNA?

A

Ribosomal RNA

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4
Q

What is tRNA?

A

Transfer RNA

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5
Q

What is a monomer of nuclei acids called?

A

Nucleotide

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6
Q

What is a polymer of nucleotides called?

A

Polynucleotide

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7
Q

How is a polynucleotide formed?

A

Condensation reaction between two nucleotides with a phosphodiester bond

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8
Q

How many polynucleotide chains does DNA have?

A

2 found in the nucleus

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9
Q

How many polynucleotide chains does RNA have?

A

1 found in the ribosomes and in the nucleus

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10
Q

Describe the structure of a general nucleotide

A

Nitrogenous base attached to c1
Pentose sugar so ribose/ deoxyribose
Phosphate group attached to c4
All bands between atoms are covalent bonds

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11
Q

What are the 5 different bases?

A

Thymine
Guanine
Cytosine
Uracil
Adenine

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12
Q

Which pentose sugar is present in DNA?

A

Deoxyribose

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13
Q

What are purine bases?

A

Double ring structure bases

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14
Q

What are the two purine bases?

A

Adenine and guanine

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15
Q

What are pyrimidine bases?

A

Single ring structured bases

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16
Q

What are the 3 pyrimidine bases?

A

Thymine
Cytosine
Uracil

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17
Q

How many H bonds are between C and G?

A

3

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18
Q

How many H bonds are between A and T/U?

A

2

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19
Q

What nitrogenous bases are present in ribose?

A

Adenine and uracil
Guanine and cytosine

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20
Q

How is a molecule of DNA formed?

A

Condensation reaction = the pentose sugar of one nucleotide and the P group of another
Phosphodiester bond forms
Repeated condensation reactions = a single chain of repeating nucleotides = polynucleotide
It has a strong sugar-phosphate back bone
The chains run anti-parallel
H bonds between bases Which joins the polynucleotides

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21
Q

How would you describe the polynucleotide chains in DNA?

A

They run antiparallel to each other
One running 3’ to 5’ and the other running 5’ to 3’

22
Q

What is the role of the sugar-phosphate backbone in DNA?

A

Gives strength to the DNA molecule

23
Q

What is the hydrogen bonds between chains in DNA role for DNA replication?

A

H bonds are weak so the chains can be separated for transcription and replication

24
Q

What is the role of DNA coiled structure?

A

Protects H bonds therefore reducing corruption of genetic code

25
Q

What is the role of many weak H bonds in DNA?

A

Makes DNA a stable molecule

26
Q

What is the role of sequencing of DNA bases in DNA?

A

It allows info to be stored

27
Q

What is the role of DNA being a long molecule?

A

Can store a lot of genetic information (genes)

28
Q

Describe DNA’s structure

A

A double helix structure of 2 polynucleotides which are joined together on a condensation reaction and form a strong sugar-phosphate backbone

29
Q

What are the 3 fundamentals in DNA replication?

A

Complementary base pairing
DNA has to unzip itself = break h bonds and separate chains
The new polynucleotides would use the original polynucleotide as a template

30
Q

What are the 3 hypotheses for DNA replication?

A

Conservative
Semi-conservative
Dispersive

31
Q

What is conservative DNA replication?

A

The original double helix will unzip
Produces 2 DNA molecules one with the new synthesised DNA with two new polynucleotide chains
And the other is a direct replication of the original DNA double helix

32
Q

What is semi-conservative DNA replication?

A

The DNA strands unzip which provides the template for the new DNA
Produces 2 new DNA molecules both have one strand of the newly synthesised polynucleotide and one strand of the original DNA

33
Q

What is dispersive DNA replication?

A

Regions of the original DNA double helix and regions of newly synthesised double helix are present in the two molecules of DNA produced

34
Q

Who carried out the DNA replication experiment to prove the hypotheses?

A

Meselson and stahl

35
Q

Why did meselson and stahl use E.coli?

A

It has a short generation time
It’s DNA is not bound by a nuclear membrane

36
Q

What is N14?

A

Light nitrogen

37
Q

What is N15?

A

Heavy nitrogen

38
Q

Why is nitrogen used in the DNA replication experiment?

A

Nitrogen is used to synthesise nitrogenous bases to form DNA

39
Q

What are the first steps of M and S experiment?

A

They cultured 2 populations
One on N14 agar and the other on N15 agar

40
Q

What did M and S do after putting the bacteria on the N14 and N15 agar?

A

Bactria that had only been on N14 and N15 had their DNA extracted
Other bacteria was transferred to N14 agar and the samples were removed after different generations 1,2 and 3

41
Q

What happened to the DNA after being extracted from the bacteria in M and s experiment?

A

The DNA extract was suspended in a special solution which was then placed in a centrifuge

42
Q

What was shown in the test tube In The M and S experiment after N15 placed on N14 for 1 generation?

A

There was a mix of DNA strands
1 N14 and 1 N15

43
Q

What hypothesis does M and S experiment prove and how?

A

Semi-conservative = both new DNA double helixes contain the original polynucleotide and the new polynucleotide

44
Q

Describe DNA replication (semi-conservative)

A

Both original polynucleotide chains act as a template
Both new DNA double helixes contain the original polynucleotide the original polynucleotide of one new polynucleotides

45
Q

Describe the process of semi-conservative replication in DNA

A

DNA helicase unwinds and unzips (h bonds broken) the double helix
The 2 polynucleotides have exposed bases that act as a template
Free DNA nucleotides in the nucleoplasm align themselves against each template strand
H bonds form between complementary base pairings
DNA polymerase
Enzymes rewind DNA molecules back into a double helix
Each newly formed DNA molecules has 1 original and 1 new strand

46
Q

What is the role of DNA polymerase in semi-conservative replication?

A

Joins adjacent DNA nucleotides
catalyses condensation reactions for the formation of phosphodiesther bonds between adjacent nucleotides

47
Q

What would the 3rd generation on N14 display after DNA extraction?

A

There would be a thicker band of N14 synthesised DNA than the 2nd generation

48
Q

What are 2 differences of an ATP molecule and an RNA molecule?

A

RNA only has 1 phosphate group, triphosphate in ATP
RNA has 4 different nitrogenous bases, there is only adenine in ATP

49
Q

How does ATP carry out its role as an energy donor?

A

Hydrolyses the bond between the 2nd and 3rd phosphate group by ATP hydrolase
This is n exogonic reaction

50
Q

Describe the structure of DNA

A

Polymer of nucleotides

Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous base

Phosphodiester bonds (between nucleotides);

Double helix/2 strands held by hydrogen bonds;

(Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine;

51
Q

How is a phosphodiesther bond formed?

A

Condensation (reaction)/loss of water;

(Between) phosphate and deoxyribose;

(Catalysed by) DNA polymerase;

52
Q

What are features of DNA which aids semi-conservative replication?

A

weak H bonds - allows strands to be separated
two stands- both act as templates
comp pairing - accurate replication

Biology A level (34 decks)

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