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Biology > 8. DNA, GENES, PROTEIN SYNTHESIS > Flashcards

8. DNA, GENES, PROTEIN SYNTHESIS Flashcards

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1
Q

Describe what a gene’s ‘loci’ is

A

A specific place on a chromosome where the gene is located.

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2
Q

What are introns and exons?

A

Introns are non-coding DNA; exons are coding DNA.

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3
Q

Apart from introns, Where else on a chromosome would you find non-coding DNA?

A

In between genes

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4
Q

Define a gene

A

A short section of DNA that codes for amino acids that join to form polypeptide chains

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5
Q

Name the three types of RNA

A

mRNA, tRNA, rRNA

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6
Q

Recall the four things genes code for

A

mRNA, tRNA, rRNA, polypeptides

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7
Q

The DNA in eukaryotic cells is universal. What does this mean?

A

The DNA of living organisms all contain the same bases.

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8
Q

The DNA in eukaryotic cells is universal. How is this indirect evidence for evolution?

A

All living organisms are made of the same DNA which shows they all have a common ancestor.

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9
Q

The DNA in eukaryotic cells is degenerate. What does this mean?

A

More than one codon can code for the same amino acid.

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10
Q

The DNA in eukaryotic cells is non-overlapping. What does this mean?

A

The same base is not used for two different codons (DNA is read in codons that do not overlap).

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11
Q

What is the purpose of transcription?

A

The production of mRNA from DNA

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12
Q

Where does transcription occur?

A

Nucleus

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13
Q

Why does transcription in prokaryotes not involve pre-mRNA?

A

It does not contain introns.

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14
Q

In a DNA molecule, which strand contains the code for the polypeptide?

A

Sense strand

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15
Q

In transcription, which DNA strand is used as a template to make mRNA?

A

Antisense strand

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16
Q

Name the two enzymes involved in transcription

A

DNA helicase and RNA polymerase

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17
Q

What is the function of DNA Helicase?

A

Unzips DNA by catalysing the break-down of hydrogen bonds between complementary DNA base pairs.

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18
Q

How much of the DNA is unzipped in transcription? Where is it unzipped?

A

Only the section of the DNA at the gene locus is unzipped.

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19
Q

What is a codon?

A

Three bases that code for an amino acid.

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20
Q

How many bases are required to code for a polypeptide containing 103 amino acids?

A

103 x 3 = 309

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21
Q

There are 64 different possible codons the code for amino acids. Show and explain how this is calculated?

A

There are 4 bases, and each codon has 3 bases. The bases could all be the same so 4 x 4 x 4 = 64

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22
Q

Explain why there are only 20 amino acids, but 64 possible codons

A

Multiple codons can code for the same amino acid.

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23
Q

From this strand of DNA, write a complementary DNA sequence: TAC-TTT-TCA-AAG-GAT

A

ATG-AAA-AGT-TTC-CTA

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24
Q

From this strand of DNA, write a complementary mRNA sequence: TAC-TTT-TCA-AAG-GAT

A

AUG-AAA-AGU-UUC-CUA

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25
Q

How is the start and end of the gene signalled?

A

By a start and stop codon.

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26
Q

Describe how the complementary mRNA strand is formed

A

Free RNA nucleotides attach to their exposed complementary base pairs on the antisense strand of DNA through hydrogen bonding

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27
Q

What is the function of RNA Polymerase?

A

Catalysing the formation of phosphodiester bonds between adjacent RNA nucleotides to produce pre-mRNA

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28
Q

How is mature mRNA formed from pre-mRNA?

A

Introns are spliced out and exons join to form mature mRNA.

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29
Q

Once mature mRNA is formed from pre-mRNA,, what happens to the mRNA?

A

mRNA travels out of the nucleus out of a nuclear pore to the cytoplasm.

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30
Q

What is the purpose of translation?

A

To make a polypeptide chain (happens in the cytoplasm)

31
Q

Where are ribosomes found?

A

Cytoplasm

32
Q

What are ribosomes made of?

A

Mostly protein, but also some rRNA

33
Q

Describe the structure of ribosomes

A

Two sub-units, one large sub-unit one smaller sub-unit.

34
Q

How does the ribosome know where the start of the mRNA is?

A

By the start codon at the start of the mRNA sequence

35
Q

Describe the structure of a tRNA

A
36
Q

Describe the structure of tRNA

A

A clover-shaped strand of RNA held together by hydrogen bonds between complementary base pairs. It has an anticodon on one end, and the complementary amino acid on the other end.

37
Q

What is the function of tRNA?

A

To bring the complimentary amino acid to the ribosome during translation

38
Q

Make five comparisons between mRNA and tRNA

A

tRNA has complementary base pairing, whereas mRNA doesn’t.
tRNA has hydrogen bonding, whereas mRNA doesn’t.
tRNA has an amino acid binding site, whereas mRNA doesn’t.
mRNA has codons, and tRNA has anticodons.
mRNA can be different lengths, whereas tRNA is always the same length.

39
Q

What happens before translation can begin?

A

mRNA binds to the ribosome

40
Q

Describe how mRNA and tRNA interact during translation

A

tRNA with the complementary anticodon binds to the mRNA codon

41
Q

How many binding sites are there in a ribosome?

A

2

42
Q

Name the bonds that form between the amino acids in translation

A

Peptide

43
Q

From a strand of mRNA, write the tRNA sequence: AUG-AAA-AGU-UUC-CUA

A

UAC-UUU-UCA-AAG-GAU

44
Q

Use an amino acids reference table to transcribe the mRNA sequence into amino acids: AUG-AAA-AGU-UUC-CUA

A

Met-Lys-Ser-Phe-Leu

45
Q

How does the ribosome know to stop translating?

A

It reaches a stop codon on the mRNA

46
Q

What happens to the polypeptide made after translation?

A

The polypeptide is coiled and folded into its tertiary structure. It may also bond with other subunits to form a quaternary protein.

47
Q

Explain how many polypeptides can be translated from one mRNA at once

A

Many ribosomes can attach to the same mRNA (at different places) at once.

48
Q

Define what alleles are

A

Versions/forms of a gene

49
Q

How do most alleles arise?

A

Through mutations

50
Q

Define what a gene mutation is

A

Any change to the quantity or sequence of the DNA in a gene

51
Q

When do gene mutations arise spontaneously?

A

During DNA replication

52
Q

When can mutations be inherited?

A

When they occur during gamete formation (meiosis)

53
Q

Describe the effect of mutagenic agents

A

They increase the rate of genetic mutations

54
Q

Name some mutagenic agents

A

Tar, radiation (UV, X-Rays, Gamma Rays), Nitrogen Dioxide

55
Q

Define mutation

A

A sudden change in the amount or the arrangement of the genetic material in the cell

56
Q

State what a gene mutation is

A

A change to one or more nucleotide bases in DNA resulting in a change in genotype which may be inherited

57
Q

State what substitution mutation is

A

A type of gene mutation in which a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base

58
Q

Describe how gene mutation arise from deletion

A

A nucleotide is lost from the normal DNA sequence

59
Q

Name the different types of mutation

A

Substitution, insertion, deletion

60
Q

Define what a base substitution is

A

A nucleotide in a gene is replaced with another nucleotide with a different base

61
Q

Why might a base substitution not result in a different sequence of amino acids?

A

Because DNA is degenerate, so the mutated codon might code for the same amino acid as the original codon

62
Q

Why might one different amino acid not cause a change in the 3D shape of the protein?

A

Because the amino acid that has changed might not play a role in forming tertiary bonds

63
Q

Define a deletion mutation

A

A nucleotide is lost from the normal DNA sequence

64
Q

Describe how deletion mutations cause a change in the tertiary shape of the protein

A

A deletion causes a frame shift to the left. Therefore all codons after the deletion are read differently. This causes all amino acids after the frame shift to change.

65
Q

Define an insertion mutation

A

A nucleotide is inserted into the normal DNA sequence.

66
Q

Describe how Insertion can cause frameshift mutations

A

An insertion causes a frame shift to the right. Therefore all codons after the insertion are read differently. This causes all amino acids after the frame shift to change.

67
Q

Describe the structure of a chromosome

A

A long molecule of DNA wound around proteins called histones. This complex is called chromatin.

68
Q

Describe the structure of eukaryotic DNA

A

Linear, contains introns, is long and is associated with histones.

69
Q

Describe the structure of prokaryotic DNA

A

Circular, does not contain introns, is short and is not associated with histones.

70
Q

Mitochondrial and chloroplast DNA is similar in structure to which type of DNA?

A

Prokaryotic

71
Q

Describe the difference in the shape of DNA in prokaryotes and eukaryotes.

A

Eukaryotic DNA is linear, whereas prokaryotic DNA is circular.​

72
Q

Describe the difference in the contents of DNA in prokaryotes and eukaryotes.

A

Eukaryotic DNA contains introns, whereas prokaryotic DNA does not.​

73
Q

Describe the difference in the length of DNA in prokaryotes and eukaryotes.

A

Eukaryotic DNA is longer than prokaryotic DNA.​

74
Q

Describe the difference in the final structure of DNA in prokaryotes and eukaryotes.

A

Eukaryotic DNA is associated with proteins and coiled into chromosomes, whereas prokaryotic DNA is not.​

Biology (26 decks)

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