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Biology AS Rafa > 2.3 Nucleic Acids > Flashcards

2.3 Nucleic Acids Flashcards

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1
Q

What are nucleotides?

A

monomer from which nucleic acids are made

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2
Q

Give examples of phosphorylated nucleotides?

A

ADP and ATP.

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3
Q

What is a nucleotide made from?

A
  • phosphate group
  • five carbon sugar
  • nitrogenous base
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4
Q

What’s the covalent bond between the sugar residue and the phosphate group also known as?

A

Phosphodiester bond.

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5
Q

What type of reaction joins the sugar residue, base and phosphate group?

A

Condensation reaction.

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6
Q

Which bases are purine?

A

Adenine and guanine.

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7
Q

Which bases are pyramidine?

A

Thymine or cytosine.

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8
Q

Which bases are one ring bases?

A

Thymine and cytosine.

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9
Q

How are the two antiparallel DNA strands joined together?

A

Hydrogen bonds.

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10
Q

How made hydrogen bonds does an A-T pairing have?

A

Two hydrogen bonds.

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11
Q

How many hydrogen bonds does a C-G pairing have?

A

Three.

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12
Q

What is each DNA molecule wound around to make a chromosome?

A

Histone protein.

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13
Q

In semi-conservative replication, which enzyme catalyses the double helix untwist?

A

Gyrase enzyme.

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14
Q

In DNA replication, which enzyme catalyses the unzipping of the molecule?

A

DNA helicase breaks hydrogen bonds.

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15
Q

In DNA replication, which enzyme catalyses the addition of new nucleotide bases?

A

DNA polymerase.

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16
Q

Which direction does DNA polymerase add nucleotide bases?

A

5’ to 3’ direction.

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17
Q

What is semi-conservative replication?

A

How DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand.

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18
Q

What enzyme joins the lagging strand fragments in DNA replication?

A

Ligase.

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19
Q

How do the loops of DNA in prokaryotes replicate?

A

A bubble sprouts from the loop and this unwinds and unzips, and the complementary nucleotides join to the exposed nucleotides.

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20
Q

What is the replication fork?

A

The point at which the two strands are separated.

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21
Q

How is RNA structurally different from DNA?

A
  • the nitrogenous base, uracil, which is a pyramidine, replaces the pyramidine base thymine
  • RNA is usually a single stranded polynucleotide chain
  • RNA polynucleotide chain is shorter
  • there are three forms of RNA
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22
Q

Why is the genetic code described as degenerate?

A

Because, for all amino acids, except methionine and trypotophan, there is more than one bass triplet.

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23
Q

What is a codon?

A

A triplet of bases in a length of mRNA.

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24
Q

What is an anticodon?

A

A triplet of bases on a tRNA molecule.

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25
Q

What is used to show the distribution of DNA and RNA with cells? How?

A

Methyl green-pyronin.
DNA stained blue-green in nuclei
RNA stained red in cytoplasm.

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26
Q

Define double helix.

A

shape of DNA due to coiling of the two sugar phosphate backbone strands into a right handed spiral configuration

27
Q

Define nucleotide

A

Molecule consisting of a five carbon sugar, phosphate group and a nitrogenous base

28
Q

Define DNA polymerase

A

Enzyme that catalyses formation of DNA from activated deoxyribose nucleotides, using a single stranded DNA as a template

29
Q

Define helicase

A

Enzyme that catalyses the breaking of hydrogen bonds between the nitrogenous pairs of bases in a DNA molecule

30
Q

Define semi conservative replication

A

How DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand. One old strand is conserved in each new molecule

31
Q

Define gene

A

Length of DNA that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression

32
Q

Define polypeptide

A

A polymer made of many amino acid units joined together by peptide bonds

33
Q

Define protein

A

A large polypeptide of 100 or more amino acids

34
Q

Define transcription

A

The process of making messenger RNA from a DNA template

35
Q

Define translation

A

Formation of a protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from DNA to the ribosome by mRNA

36
Q

What are ADP and ATP?

A

Phosphorylated nucleotides

37
Q

What elements do nucleotides contain?

A

C H O N P

38
Q

Whats the sugar in DNA called?

A

Deoxyribose

39
Q

How many carbon-nitrogen rings do purines have?

A

Two

40
Q

How many carbon-nitrogen rings do pyramidines have?

A

One

41
Q

What is the base in ADP and ATP?

A

adenine

42
Q

Where is energy stored in a molecule of ATP?

A

In the phosphate bond

43
Q

What does a phosphodiester bond consist of?

A

phosphate group and two ester bonds

44
Q

Why is the double helix twisted?

A

Because the two strands are antiparallel

45
Q

How can you purify DNA using a precipitation reaction?

A
  • Blend cells to break them up
  • Make solution of detergent (eg washing up liquid), salt and distilled water
  • add cells to beaker with detergent solution
  • incubate beaker for 15 mins at 60 degrees in waterbath
  • cool in ice bath
  • filter + transfer to clean boiling tube
  • add protease enyzmes and RNAase
  • dribble cold ethanol down side so it forms a layer
  • leave for a few mins, DNA will form a white precipitate which you can remove using a glass rod
46
Q

What does the detergent in the purifying DNA experiment do?

A

Breaks down cell membranes

47
Q

What does salt in the purifying DNA experiment do?

A

Binds to DNA and causes it to clump together

48
Q

Why do you incubate the DNA purification solution?

A

To stop the enzymes in the cells from working properly and breaking down DNA

49
Q

Why is it important that DNA replication is very accurate?

A

To make sure genetic information is conserved

50
Q

Describe the nature of the genetic code?

A

Universal
Degenerate
Non-overlapping

51
Q

Why is the genetic code described as universal?

A

Because in almost all living organisms the same triplet of bases codes for the same amino acid

52
Q

Why must DNA be copied into mRNA?

A

Because it is too large to leave the nucleus

53
Q

Describe mRNA

A
  • made in nucleus

- carries genetic info from nucleus to cytoplasm

54
Q

Describe tRNA

A
  • found in cytoplasm
  • has an amino acid binding site at one end and a sequence of three bases at the other end
  • carries amino acids
55
Q

Where is the anticodon?

A

on tRNA

56
Q

Describe rRNA

A
  • forms the two subunits of a ribosome

- helps to catalyse the formation of peptide bonds between the amino acids

57
Q

Explain how the structure of DNA allows replication

A
  • double stranded
  • each strand = template
  • H bonds break easily
  • complementary base pairing
  • purine only binds with pyrimidine
58
Q

Why is complementary base pairing important in DNA replication?

A
  • DNA can be replicated without error
  • reduces occurrence of mutation
  • allows reformation of hydrogen bonds
59
Q

Describe how DNA replicates

A
  • semi conservative replication
  • helix untwists
  • hydrogen bonds break
  • each strand acts as template
  • free DNA nucleotides complementary base pairing
  • hydrogen bonds reform
  • sugar phosphate backbone forms
  • DNA polymerase joins
  • each has 1 old 1 new
60
Q

Why is mRNA shorter than DNA?

A

only copies one gene/section

DNA has many genes

61
Q

How can a protein be affected by changing the sequence of DNA nucleotides?

A
  • different sequence of amino acids
  • different protein
  • different function
62
Q

How many base pairs are there in one full turn of the DNA double helix?

A

10

63
Q

What technique was used to determine the double helical structure of DNA?

A

X-ray crystallography

Biology AS Rafa (13 decks)

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