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B12 > Gene Structure and Expression (3.2) > Flashcards

Gene Structure and Expression (3.2) Flashcards

1
Q

Define genes

A

Region of DNA that may be translated into a polypeptide or a functional RNA molecule

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2
Q

State how many nucleotides in length a gene can be

A

Millions of nucleotides in length

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3
Q

Describe the genetic code

A

Set of rules defining how information in nucleic acids is translated

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4
Q

Describe triplet

A

Sequence of three nucleotides in DNA that carries genetic information for an amino acid sequence

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5
Q

Describe codon

A

Sequence of three nucleotides on mRNA that codes for a particular amino acid (or indicates the beginning or end of translation)

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6
Q

State when a triplet is termed ‘codon’

A

DNA triplet is transcribed into mature mRNA

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7
Q

State what a triplet or codon codes for

A

Amino acid

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8
Q

State whether the genetic code is universal.

A

Genetic code is universal

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9
Q

Describe the degeneracy of the genetic code

A

More than one codon may code for a particular amino acid

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10
Q

Describe the process of calculating the total number of codon combination

A

4 nucleotides
3 nucleotides code for an amino acid
Therefore, 4^3 = 64

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11
Q

Describe the benefit of genetic code degeneracy

A

Buffer for gene mutation - a single change in one base may not necessary change the amino acid produced

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12
Q

State 4 structural features common in all eukaryotic genes

A
  1. Stop and start triplet sequences
  2. Promoter regions
  3. Exons
  4. Introns
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13
Q

Provide an alternative term for introns

A

Spacer DNA

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14
Q

State what the start triplet indicates

A

Gene expression will begin

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15
Q

Describe what the start triplet will become when it is transcribed into mRNA

A

Start codon

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16
Q

Describe what the start codon initiates

A

Translation

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17
Q

Provide one example of a start codon sequence and the amino acid it codes for

A

Methionine (AUG)

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18
Q

Describe what the stop triplet indicates

A

Transcription will end

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19
Q

State whether or not the stop triplet codes for an amino acid.

A

Stop triplet does not code for an aino acid

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20
Q

Describe what the stop triplet will become when they are transcribed into mRNA

A

Stop codons

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21
Q

State the 3 unique stop codons

A

UAA, UAG, UGA

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22
Q

Describe the promoter region

A

Sequence of DNA to which RNA polymerase binds

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23
Q

State the 4 major functions/characteristics of the promoter region

A
  1. location where the RNA polymerase attached to the gene
  2. identifies which DNA strand will be transcribed
  3. identifies where transcription of the gene will start
  4. identifies in which direction transcription will occur
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24
Q

State what the promoter region is coded for by in many eukaryotic genes

A

TATA box (sequence of bases TATAAA)

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25
Q

State whether all sections of a gene are translated within eukaryotes. True/false.

A

False

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26
Q

Describe exons

A

Regions of a gene that are usually ‘expressed’ as proteins or RNA

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27
Q

Describe what exons come together for

A

To make up mRNA

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28
Q

Describe introns

A

Non-coding regions of a gene

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29
Q

Describe the process of gene expression

A

Process by which the information stored in a gene is used to synthesis a functional gene product

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30
Q

Provide 2 examples of functional gene products

A
  1. proteins

2. RNA

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31
Q

Describe the regulation of the gene expression process

A

Highly regulated so that proteins or RNA molecules are only produced if and when they are required by a cell

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32
Q

Describe what the regulation of the gene expression process results in

A

Conservation of energy and materials in the cell

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33
Q

State the 3 stages of gene expression leading to protein synthesis in the correct order

A
  1. Transcription
  2. RNA processing
  3. Translation
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34
Q

Describe transcription

A

Production of single-stranded mRNA from DNA

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35
Q

State the location of transcription

A

Nucleus of eukaryotes

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36
Q

Describe the transcription unit

A

DNA segment that undergoes transcription

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37
Q

State the 3 steps of transcription

A
  1. Initiation
  2. Elongation
  3. Termination
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38
Q

Describe the initiation process of transcription

A

RNA polymerase binds to the promoter and separates the DNA strands

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39
Q

State what is required for RNA polymerase to attach to DNA in transcription

A

Transcription factors

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40
Q

Describe how RNA polymerase unzips DNA molecules

A

Breaking the weak hydrogen bonds between the two strands to expose the bases

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41
Q

Describe the elongation process of transcription

A

RNA polymerase ‘reads’ DNA template and builds an RNA molecule out of complementary nucleotides - chain grows 5’ to 3’

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42
Q

Describe what transcription factors combine with during the initiation process of transcription

A

Transcriptions factors combine with the promoter

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43
Q

Describe the approximate number of base pairs covered by an RNA polymerase molecule in transcription

A

30 base pairs

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44
Q

State approximately how many base pairs are uncoiled in one region of RNA polymerase cover

A

approx. 15/30 base pairs

45
Q

State the direction of mRNA synthesis

A

5’ to 3’ direction

46
Q

State which end of mRNA nucleotides are added to during transcription

A

3’ end

47
Q

Describe what mRNA is termed after it has been transcribed

A

primary RNA transcript

48
Q

State whether or not DNA strands located behind the transcription bubble recoil

A

Yes. DNA strands located behind the transcription bubble are coiled again

49
Q

Describe what the primary RNA transcript is processed into during transcription

A

Mature mRNA

50
Q

Describe the termination process of transcription

A

Terminators signal completion of RNA transcript. Transcript is released from the RNA polymerase.

51
Q

State when transcription ends

A

RNA polymerase reaches the termination site of the gene

52
Q

State what the termination site of a gene contains

A

Stop triplet code

53
Q

Describe the function of the stop triplet code in transcription

A

Binds release factors that signal termination

54
Q

State the term used to describe the strand of DNA that is transcribed to the mRNA

A

Template strand

55
Q

State the term used to describe the complementary strand of DNA

A

Coding strand

56
Q

Does mRNA carry the same base sequence as the coding strand?*

A

Yes. mRNA carries the same base sequence, however it contains uracil in place of thymine

57
Q

Describe RNA processing

A

Primary RNA transcript undergoes processing before it is translated

58
Q

Describe the 3 stages of RNA processing

A
  1. addition of 5’ cap
  2. addition of poly-A-tail
  3. splicing
59
Q

Describe the 5’ cap

A

Cap added to the 5’ of the primary RNA transcript during RNA processing

60
Q

Describe the structure of the 5’ cap

A

Consists of methylguanosine triphosphate

61
Q

Describe the poly-A-tail

A

Chain is added to the 3’ end of the primary RNA transcript during RNA processing

62
Q

Describe the structure of the poly-A-tail

A

Consists of up to 250 adenine nucleotides

63
Q

Describe the benefit of the 5’ cap modification

A

Aids the binding of the ribosome to the mRNA at the beginning of translation

64
Q

Describe the benefit of the poly-A-tail modification

A

Increase stability and prevent degradation

65
Q

Describe splicing

A

Spliceosome removes the introns from the primary RNA transcript and joins the exon sections to make mature mRNA

66
Q

Describe where the mature mRNA exits the nucleus

A

Via the nuclear pore

67
Q

Describe splicing in prokaryotes

A

Most prokaryotes only contain exons and therefore splicing is not required

68
Q

Describe the structure of mature mRNA composed during splicing

A

Single-stranded

69
Q

Describe alternative splicing

A

Unique splicing can result in alternative mature mRNA strands from a single gene and thus different proteins

70
Q

State the major function of alternative splicing

A

Reason why 21000 genes of humans can produce many more than 21000 proteins

71
Q

Describe what introns were referred to as in early gene structure research

A

‘Junk DNA’

72
Q

Describe translation

A

Codons on mRNA are translated into a sequence of amino acids which compose a polypeptide

73
Q

Describe the 3 steps of translation

A
  1. Initiation
  2. Elongation
  3. Termination
74
Q

Describe the initiation process of translation

A

Ribosome combines with mRNA and the first tRNA so translation can begin

75
Q

Describe the elongation process of translation

A

Amino acids brought to the ribosome by tRNAs and link together to form a chain

76
Q

Describe the termination process of translation

A

Finished polypeptide is released to function in the cell

77
Q

Describe how protein synthesis begins

A

Ribosomal subunit attaches to the 5’ end of an mRNA strand

78
Q

Describe the function of tRNA molecules in the initiation process of translation

A

tRNA carries anticodon to the mRNA codons, attaching the codon and anticodon by complementary base pairing

79
Q

State what attaches to the tRNA and ribosomal subunit in the initiation process of translation

A

Large ribosomal subunit

80
Q

State what the binding of the large ribosomal subunit results in

A

Formation of three binding sites for tRNA

81
Q

State the 3 binding sites of tRNA

A
  1. aminoacyl site (A)
  2. peptidyl site (T)
  3. exit site (E)
82
Q

Describe where that attachment of amino acids to their corresponding tRNA molecules occurs

A

Cytosol

83
Q

State whether or not the initiation process of translation is catalysed by enzymes

A

Yes. The initiation process is catalysed by enzymes.

84
Q

Describe the bond that forms between deposited amino acids

A

Peptide bonds

85
Q

State whether or not the tRNA molecules of translation can be reused

A

Yes. tRNA molecules can be reused throughout translation

86
Q

State what halts the attachment of amino acids during translation

A

Reaching of a stop codon

87
Q

State what happens to the polypeptide chain when a stop codon is reached

A

Released from the ribosome into the cytoplasm or endoplasmic reticulum

88
Q

Describe what happens to proteins of quaternary structure

A

Associate in the cytoplasm or the Golgi apparatus to form the fully functional protein

89
Q

Describe the benefit of translating the same, single strand of mRNA at the same time

A

Enables many polypeptide chains to be produced simultaneously

90
Q

State what happens to the polypeptide chains once they are fully functional

A

Remain in cell or are exported via exocytosis for use somewhere else within the organism

91
Q

Describe the process of transcription and translation in prokaryotes

A

Continuous process, as all cellular processes occur within the cytosol

92
Q

Describe whether or not splicing is required during transcription and translation in prokaryotes and suggest a reason why this might be

A

Prokaryotic DNA only contains exons, therefore splicing is not required

93
Q

State how many protein synthetic initiation factors prokaryotes have

A

3 initiation factors

94
Q

State how many protein synthetic initiation factors eukaryotes have

A

10 initiation factors

95
Q

State whether or not a 5’ cap and poly-A-tail is added to prokaryotic mRNA

A

No 5’ cap or poly-A-tail is added to mRNA in prokaryotes

96
Q

Describe when protein synthesis begins in prokaryotes

A

During transcription

97
Q

Provide a term used to describe the beginning of protein synthesis during transcription in prokaryotes

A

Coupled transcription-translation

98
Q

State why coupled transcription-translation can occur in prokaryotes

A

Ribosome and DNA are both found in the cytosol together

99
Q

Describe when protein synthesis begins in eukaryotes

A

During translation

100
Q

mRNA contains the coding sequence of ________ ________ in prokaryotes

A

Several genes

101
Q

mRNA contains the coding sequence of ________ _________ in eukaryotes

A

One gene

102
Q

State how many prokaryotic ribosomal subunits are involved in protein synthesis

A

30S-50S ribosomal subunits

103
Q

State how many eukaryotic ribosomal subunits are involved in protein synthesis

A

40S-60S ribosomal subunits

104
Q

State in what direction RNA polymerase runs along DNA template

A

3’-5’

105
Q

State whether the methyl cap is added to the 3’ or 5’ end of the synthesised mRNA strand

A

3’ end

106
Q

State whether the poly A tail is added to the 3’ or 5’ end of the synthesised mRNA strand

A

5’ end

107
Q

State in what direction the mature mRNA strand enters the ribosome for translation

A

3’ end (methyl cap)

108
Q

State why new nucleotides are added to the 3’ end of DNA backbone

A

OH allows for binding of nucleotide compared to phosphate which does not

B12 (41 decks)

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