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Biology Module 2 > 3.8-3.10 Nucleic Acids, DNA Replication, Extraction, Synthesis > Flashcards

3.8-3.10 Nucleic Acids, DNA Replication, Extraction, Synthesis Flashcards

1
Q

What are nucleic acids?

A

Large polymers formed from monomers called nucleotides. They are found in the nucleus of a cell

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2
Q

Where are nucleic acids found?

A

In the nucleus of a cell

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3
Q

What are the 3 components of a nucleic acid?

A

Phosphate group, pentose sugar and an organic/nitrogenous base

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4
Q

What is a phosphate group?

A

An inorganic molecule that is acidic and negatively charged

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5
Q

What is a nitrogenous base?

A

A complex organic molecule containing one or two carbon rings in its structure, as well as oxygen.

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6
Q

What are the two types of nucleic acids?

A

Deoxyribonucleic acid and Ribonucleic acid

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7
Q

What are nucleic acids used for?

A

Storage and transfer of genetic information needed to make proteins

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8
Q

What elements do nucleic acids contain?

A

Oxygen, Hydrogen, Nitrogen and Phosphorus

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9
Q

How are nucleotides linked together?

A

The phosphate group at the fifth carbon of the pentose sugar of one nucleotide forms a covalent bond with the hydroxyl group at the 3rd carbon of the pentose sugar of an adjacent nucleotide

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10
Q

What type of reaction links nucleotides together?

A

Condensation reaction

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11
Q

What type of bond links nucleotides together?

A

Phosphodiester bond

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12
Q

What does a condensation reaction between nucleotides form?

A

A polynucleotide connected by phosphodiester bonds, with a long, strong sugar-phosphate backbone.

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13
Q

What is the difference between the sugars deoxyribose and ribose?

A

Deoxyribose has one less oxygen atom than ribose.

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14
Q

What are the two groups of nitrogenous bases?

A

Pyrimidines and Purines

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15
Q

What is the difference between a pyrimidine and a purine?

A

Pyrimidine bases have a single ring, purines have a double ring

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16
Q

What are pyrimidines and purines?

A

The two groups of nitrogenous bases

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17
Q

Which bases are pyrimidines?

A

T, C and U

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18
Q

Which bases are purines?

A

A and G

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19
Q

Which base does Uracil replace?

A

T

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20
Q

Which bases pair with eachother?

A

A-T, and C-G

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21
Q

Where is the U base found?

A

In RNA

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22
Q

What is DNA made up of?

A

Two antiparallel polynucleotide chains (strands)

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23
Q

How are the two strands of polynucleotide chains held together?

A

By hydrogen bonds between the bases.

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24
Q

How many hydrogen bonds are there between a C-G?

A

3

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25
Q

How many hydrogen bonds are there between an A-T?

A

2

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26
Q

What do the hydrogen bonds do in DNA?

A

They hold the two antiparallel polynucleotide chains together, and make the molecule stable.

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27
Q

How does the sense strand in DNA run?

A

From 5’ to 3’ (5 prime to 3 prime, downwards)

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28
Q

What is an alternative name for the sense strand?

A

The coding strand

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29
Q

What does the sense strand contain?

A

The sequences of bases that codes for the proteins to be synthesised.

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30
Q

How does the anti-sense strand run?

A

From 3’ to 5’ (3 prime to 5 prime, upwards)

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31
Q

What are the alternative names for the anti-sense strand?

A

Non-coding strand, template strand

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32
Q

What does the anti-sense strand do?

A

Does not code for the production of protein, is a complementary copy of the sense strand. Used as the template for mRNA.

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33
Q

What does RNA do?

A

Plays an essential role in the transfer of genetic information from DNA, to the proteins that make up the enzymes and tissues in our body.

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34
Q

What does one mRNA molecule contain?

A

The transcription a complementary strand of one gene in DNA.

35
Q

Why can mRNA molecule only contain a complementary strand of a small amount of DNA?

A

Because the DNA of each eukaryotic chromosome is very long, and is unable to leave the nucleus for protein synthesis.

36
Q

What are the 2 differences between RNA nucleotides and DNA nucleotides?

A

-The pentose sugar in RNA is ribose, the pentose sugar in DNA is deoxyribose
-The thymine base in DNA is replaced by the Uracil base in RNA

37
Q

What happens to the RNA molecules after protein synthesis?

A

They are degraded in the cytoplasm. Phosphodiester bonds are hydrolysed, RNA nucleotides are released and re-used.

38
Q

How do RNA nucleotides form polymers?

A

The same way as DNA: They form phosphodiester bonds in condensation reactions between nitrogenous bases.

39
Q

What is the process of DNA replication?

A

The process of producing 2 new strands of DNA that are identical to the original.

40
Q

What are the products of DNA replication?

A

2 new molecules of DNA, each one consisting of one old strand of DNA and one new strand.

41
Q

Why is DNA replication considered to be “semi-conservative”?

A

Because the each new DNA molecule contains one old strand of DNA and one new strand.

42
Q

What two enzymes control DNA replication?

A

DNA helicase and DNA polymerase

43
Q

What does DNA helicase do?

A

Catalyses reaction that break the H bonds between complementary base pairs. This causes the DNA to unwind and the 2 strands to separate.

44
Q

What does DNA polymerase do?

A

Catalyses the formation of phosphodiester bonds between nucleotides, forming a DNA strand.

45
Q

What is Genetic Code?

A

The sequence of amino acids that DNA codes for.

46
Q

What is an example of a replication error?

A

Sequences of bases not always matched correctly, leading to an incorrect sequence being produced in the newly-copied strand.

47
Q

When do replication errors occur?

A

Randomly and spontanteously

48
Q

What do replication errors lead to?

A

A change in the sequence of bases, AKA a mutation

49
Q

Why is DNA considered a triplet code?

A

Because DNA is read in sets of 3. 3 bases = codon. Each codon codes for an amino acid.

50
Q

What is a codon?

A

3 bases

51
Q

What does each codon code for?

A

An amino acid.

52
Q

What is the first step in DNA replication?

A

-Hydrogen bonds are broken between the base pairs (catalysed by DNA helicase)
-Both strands act as templates to make new strands

53
Q

What is the second step in DNA replication?

A

-DNA Helicase completes the separation of the strand.
-Free nucleotides float in the nucleoplasm, they are attracted to complementary bases, and form complementary base pairs with exposed bases on each strand.

54
Q

What is the third step in DNA replication?

A

-Activated nucleotides line up, bases joined by hydrogen bonds.
-DNA polymerase catalyses the reaction/formation of phosphodiester bonds between nucleotides

55
Q

What is the fourth step in DNA replication?

A

-All the nucleotides are joined to form a complete poly-nucleotide chain.
-Two identical molecules of DNA are formed
-Each new molecule of DNA is composed of one original strand and one newly-formed molecule

56
Q

What is a gene?

A

The section of DNA that contains the complete sequence of bases (codons) to code for an entire protein

57
Q

What does “genetic code is universal” mean?

A

All organisms use the same code of C, G, A and T bases.

58
Q

What does “genetic code is degenerate” mean?

A

-Many amino acids can be coded for by more than one codon
-Different combinations of bases can code for the same amino acid. This is so that if there is a mutation, it might not make a difference.

59
Q

What are the steps for DNA extraction?

A

-Grind sample in a pestle and mortar
-Mix sample with water, detergent and salt
-Heat at 60°C for 15 minutes in a water bath
-Cool the mixture for 5 minutes
-Add protease enzyme
-Add a layer of ethanol on top of the sample
-The DNA will be seen as white strands forming between the layer of sample and layer of alcohol.

60
Q

Why should you grind a sample in a pestle and mortar for DNA extraction?

A

To break down the cell walls

61
Q

Why should you mix a sample with detergent for DNA extraction?

A

To break down the cell membrane, releasing the cell contents (including DNA) into the solution.

62
Q

Why should you add salt to a sample for DNA extraction?

A

To break down the hydrogen bonds between the DNA and water molecules, shielding the negatively-charged phosphate groups of the DNA molecules.

63
Q

Why should you heat the sample at 60°C for DNA extraction?

A

DNase enzymes, which would otherwise start to cut the NDA into fragments, are denatured.

64
Q

Why should you cool down the sample for 5 minutes for DNA extraction?

A

To slow down the breakdown of DNA/denaturing of enzymes

65
Q

Why should you add protease to the sample for DNA extraction?

A

This will break down the histones associated with the DNA in the nuclei, allowing the DNA to uncoil

66
Q

Why should you add a layer of ethanol on top of the sample for DNA extraction?

A

Alcohol causes the DNA to precipitate out of solution, making it more visible.

67
Q

What are the names of the 2 stages of protein synthesis?

A

Transcription and translation

68
Q

Where is DNA contained?

A

Within a double membrane, the nuclear envelope, which encloses the nucleus and protects the DNA from being damaged in the cytoplasm

69
Q

Why does transcription have to take place?

A

Because a chromosomal DNA molecule is too large to leave the nucleus, so the base sequences of genes have to be copied and transported to the site of protein synthesis

70
Q

Describe the stages of transcription in protein synthesis.

A

-DNA helicase causes one gene in the DNA molecule to unwind. The start codon signals the starting point of the gene
-Free RNA nucleotides will base pair with the exposed nucleotides of the antisense strand. This is catalysed by RNA polymerase. This forms an mRNA strand.
-The mRNA detaches from the DNA template and exits the nucleus through a nuclear pore.
-The DNA double helix reforms.

71
Q

What is an exon?

A

A part of the DNA that codes for proteins

72
Q

What is an intron?

A

A non-coding part of the DNA

73
Q

What type of cells contain exons and introns?

A

Eukaryotic cells

74
Q

What is the name of the process where introns are removed by enzymes from mRNA?

A

Splicing

75
Q

What does mRNA stand for?

A

Messenger Ribonucleic Acid

76
Q

What does tRNA stand for?

A

Transfer Ribonucleic Acid

77
Q

What does rRNA stand for?

A

Ribosomal Ribonucleic Acid

78
Q

Describe the process of splicing. in the context of protein synthesis.

A

-During transcription, mRNA nucleotides are joined by phosphodiester bonds in a reaction catalysed by RNA Polymerase
-Before the mRNA leaves the nucleus, it is processed.
-The introns are cut out of the mRNA by the enzyme spliceosome, and the exons are joined together
-Newly formed mRNA detaches from the DNA and leaves the nucleus.

79
Q

What is the name of the enzyme that cuts introns from mRNA?

A

Spliceosome

80
Q

What is tRNA?

A

A single-stranded nucleotide chain made up of about 80 base pairs, folded up into a clover shape.

81
Q

Describe the process of translation.

A

-mRNA binds to a ribosome
-A tRNA molecule with an anticodons that is complementary to the first mRNA codon binds with the mRNA.
-The tRNA delivers the correct amino acid to the ribosome, as specified by the mRNA codon
-Working along the mRNA in a 5’ to 3’ direction, each codon in translated in this way, and the amino acids are joined by peptide bonds to form a polypeptide chain.
-The forming of the peptide bonds is catalysed by peptidyl transferase
-The final polypeptide chain is modified and folded in the golgi apparatus

82
Q

What enzyme catalyses the reaction of amino acids being joined by a peptide bond?

A

Peptidyl transferase

83
Q

What is the anti-codon sequence of tRNA complementary to?

A

The codon on mRNA, and the amino acid attached to the tRNA.

Biology Module 2 (19 decks)

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