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Biology > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

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1
Q

What bonds are present between bases?

A

Hydrogen bonds

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2
Q

What bonds are present between the sugar and phosphate group?

A

Phosphodiester bonds

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3
Q

What does a nucleotide consist of?

A

A nitrogenous base
A pentode sugar
A phosphate group

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4
Q

What does the backbone of a DNA molecule consist of?

A

A phosphate group

A deoxyribose sugar

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5
Q

How are phosphodiester bonds broken?

A

Hydrolysis

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6
Q

What is the structure of ATP?

A

Composed of an adenine base, a ribose sugar and 3 phosphate groups
ATP + H20 -> ADP + Pi + energy (hydrolysis)
Properties = small and water soluble

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7
Q

Give 4 reasons why ATP is useful

A

1- Releases energy in small amounts
2- Broken down in a single reaction, releasing energy quickly
3- Adds phosphate to other molecules, makes them more reactive
4- Easily resynthesised

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8
Q

What are pyrimidines?

A

Contain single carbon ring structures (hexagon)
Made up of carbon and nitrogen
Thymine and Cytosine

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9
Q

What are purines?

A

Contain double carbon ring structures (hexagon and pentagon)
Made up of carbon and nitrogen
Adenine and Guanine

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10
Q

How many hydrogen bonds are between adenine and thymine?

A

2 h bonds

Complementary base pairing

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11
Q

How many hydrogen bonds are between cytosine and guanine?

A

3 h bonds

Complementary base pairing

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12
Q

Base pairing

A
  • Adenine and Thymine (2 h bonds)
    Cytosine and Guanine (3 h bonds)
  • Small pyrimidine bases always bind to larger purine bases (parallel)
  • Means that DNA always has equal amounts of all bases
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13
Q

What is a gene?

A

A section of DNA that contains the complete sequence of DNA to code for an entire protein

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14
Q

How is the genetic code degenerate?

A

There are more possible codes than there are amino acids (20)
Same amino acid can be coded for by more than one triplet

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15
Q

How is the genetic code universal?

A
  • Codes for the same a.a in all living organisms

All organisms use this same code - all life on earth has common ancestory

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16
Q

How is the genetic code non-overlapping?

A

Each DNA triplet and gene is separate from each other

17
Q

Describe semi conservative DNA replication

A
  • DNA helicase unwinds DNA by breaking H bonds
  • Both strands act as templates
  • Free DNA nucleotides attach by complementary base pairing
  • DNA polymerase joins nucleotides, forming phosphodiester bonds
  • H bonds reform
  • DNA replication is semi conservative (new DNA contains one old strand and one new strand)
18
Q

What is the function of DNA helicase?

A

Unwinds DNA by breaking H to bonds

19
Q

What is the function of DNA polymerase

A

It catalyses the condensation reaction between the nucleotides in a DNA strand
It forms phosphodiester bonds between adjacent nucleotides

20
Q

What is the function of DNA Ligase?

A

Seals up the fragments in the sugar-phosphate backbone to form continuous DNA

21
Q

What does primase do?

A

Makes a small piece of RNA called a primer

21
Q

Describe Meselsohn-Stahl experiment

A
  • population cultured in a growth medium containing heavy nitrogen (15N) only
  • When centrifuged, only 1 heavy band is observed
  • Cells transferred to a medium with only light nitrogen (14N)
  • After 1 replication the DNA band was intermediate (twice the thickness)
  • After 2 replications, intermediate and light bands were observed
22
Q

Where does transcription take place?

A

Nucleus

24
Q

Why is transcription important?

A

Makes a shorter mRNA molecule so that it can leave the nucleus and travel to the ribosomes

25
Q

What is the process of transcription?

A
  • DNA helicase unwinds strands by breaking H bonds
  • Free RNA nucleotides attach to template strand
  • Complementary base pairing
  • RNA polymerase joins nucleotides together
  • H bonds reform
  • Once the mRNA strand is formed, it can move out of the nucleus and travel to the ribosomes (either free or those on the RER)
26
Q

What are introns?

A

Non-coding sections of DNA

27
Q

What is splicing?

A

Removing introns

29
Q

What is the process of translation?

A
  • Ribosome binds onto the mRNA at a start codon
  • Codon is matched to an anticodon by complementary base pairing
  • Ribosome holds tRNA in place
  • Amino acids are joined together with a peptide bond
  • Only 2 tRNA molecules can do this at a time
  • Once the bond is formed, it moves onto the next 2 until it has a chain of amino acids (primary structure of a protein/polypeptide)
30
Q

Where does translation take place?

A

Cytoplasm

36
Q

Describe the method of purifying DNA by precipitation

A

1- Break open cells, e.g. blender
2- Mix: washing up detergent (break down nuclear membrane), table salt (Clump together pieces of DNA) and distilled water
3- Mix in cell mixture and wait 10 mins
4- Keep ice cold (stop enzymes breaking down DNA)
5- Filter mixture
6- Slowly pour cold ethanol to form a layer on top
7- Wait 10 mins
8- DNA forms a white precipitate
9- Remove DNA (tweezers/centrifuge)

37
Q

What is a codon?

A

Triplet of bases on mRNA that codes for a specific amino acid

38
Q

What is an anticodon?

A

Triplet of bases that is complementary to codon on mRNA

39
Q

Describe tRNA

A
  • Polynucleotide
  • Folded by H bonds
  • Anticodon is specific to amino acid that it carries
40
Q

What is the DNA antisense strand?

A
  • Template stand
  • Acts as the template for mRNA
  • Complementary to genes on sense strand
41
Q

What is the DNA sense strand?

A
  • Contains the genes

- Doesn’t act as the template for mRNA

42
Q

What is the primary mRNA?

A

Same as DNA sense strand except U replaces T

43
Q

What is the locus?

A

Location of gene on a chromosome

Biology (19 decks)

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