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Biological Sciences > Lecture 5 - Part 2 - Transcription and translation > Flashcards

Lecture 5 - Part 2 - Transcription and translation Flashcards

1
Q

Why look at transcription and translation

A

It explains how nucleic acids construct proteins

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2
Q

How many chromosomes does each human have

A

46 chromosomes ( 23 pairs )

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3
Q

What is a chromosome and how is it formed

A
  • ## DNA, wrapped up and packaged, wound around other proteins into these X shaped parcels and twisted/further folded
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4
Q

What are histones

A

Proteins that condense/ coil and structure the DNA of eukaryotic cell nuclei into units called nucleosomes

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5
Q

What are the core histones

A

H2A, H2B, H3 and H4 `

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6
Q

What does the histone octamer consist of

A

2 copies of each histone protein

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7
Q

What is the nucleosome core formed of

A

Two H2A-H2B dimers and a

H3-H4 tetramer

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8
Q

How is nucleosome formed and what does each one consist of

A

DNA coils twice aroundtheoctamer

8 histone proteins

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9
Q

What anchors nucleosome together

A

Histone H1

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10
Q

What are nucleotides

A

Building blocks of nucleic acids

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11
Q

What is the structure of nucleotide

A

-Nitrogenous base
-5C sugar can be..
Ribose = RNA
Deoxyribose = DNA
-Phosphate group

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12
Q

What gives the structral element of nucleotide

A

Sugar and phosphate

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13
Q

What does base do

A

Encodes genetic information

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14
Q

What’s the sugar for DNA

A

Deoxyribose

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15
Q

What’s the sugar for RNA

A

Ribose

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16
Q

What is the 5 carbon sugar and how are carbon atoms labelled

A

Pentose ring

Carbon atoms in pentose ring labelled 1-5 clockwise from Oxygen

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17
Q

How is ribose and deoxyribose struucturally different

A

For Ribose -OH group at 2’ postiion

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18
Q

What determines genetic information

A

Sequence of bases on DNA

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19
Q

What carbon number is phosphate group attached to

A

5th carbon

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20
Q

What are the 4 bases in DNA

A

Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

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21
Q

What are bases classed as

A

Purines or Pyrimadines

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22
Q

Which bases are Purines

A

Adenine and guanine

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23
Q

Which bases are Pyrimadines

A

cytosine and thymine

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24
Q

How many interlocking nitrogen-containing rings does purine contain

A

Two

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25
Q

How many interlocking nitrogen-containing rings does pyramidine contain

A

One

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26
Q

What carbon number are bases joined to sugar

A

C1

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27
Q

What bond is formed between phosphate group and ribose sugar

A

Phosphodiester bond

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28
Q

How are DNA bases on strands held together

A

Hydrogen bonds

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29
Q

Which bases are complementary

A

A + T

C + G

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30
Q

How many hydrogen bond between A + T

A

2

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31
Q

How many hydrogen bond between C + G

A

3

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32
Q

Properties of the DNA double Helix

A
  • Two helical polynucleotide chains are coiled around a common axis
  • The chains run in opposite directions – antiparallel
  • Complementary bases are held together by hydrogen bonds on the inside
  • Planes of the Bases are at 90° to axis
  • A phosphate-deoxyribose polymer composes the outside backbone of the DNA = phosphodiester bonds
  • Nitrogenous bases are covalently bonded to the 1’ carbon of the deoxyribose
  • The individual hydrogen bonds are weak but the large number of them confer stability
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33
Q

Is all DNA contained within chromosomes

A

No

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34
Q

What is independent in terms of DNA

A

Mitochondria

They contain their own DNA which encode the mitochondrial proteins and some ribosomal RNA.

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35
Q

How many genes does mitochondria contain

A

37

Essential for normal mitochondrial function

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36
Q

Uses of genes in mitochondria

A
  • Direct the synthesis of enzymes involved in oxidative phosphorylation (ATP production)
  • Synthesis of transfer RNA (tRNA)
  • Synthesis of ribosomal RNA (rRNA)
  • These RNA’s help assemble amino acids into functioning proteins
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37
Q

How does our genetic code translate into what we are

A

By transcription and translation

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38
Q

Summary of transcription and translation

A

The genetic code from DNA is ‘copied’ (transcribed) into shorter sequences (RNA), which are then ‘read’ (translated) by a ribosome which generates a sequence of amino acids, the chains that form proteins.

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39
Q

What is RNA

A

Sequence of nucleotides

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40
Q

How is RNA different from DNA

A
  • Ribose sugar rather than deoxyribose
  • RNA is single stranded
  • Thymine is substituted for Uracil
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41
Q

What base does Uracil replace

A

Thymine

Cytosine and Uracil - pyramidine - bases joined to C1 of ribose sugar

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42
Q

Transcription and translation flow diagram

A

DNA - mRNA - Polypeptide

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43
Q

What is transcription

A

The production of messenger RNA (mRNA) by the enzyme RNA polymerase, and the processing of the resulting mRNA molecule.

44
Q

What are the 4 steps of Transcription

A

Initiation.
Elongation.
Termination.
Processing.

45
Q

Transcription - Initiation

A

The DNA molecule unwinds and separates to form a smallopen complex. RNA polymerase (enzyme) binds to the promoter of thetemplate strand.

46
Q

What does transcription factors do

A

Bind to the TBP which binds to TATA box (promoter)

47
Q

Transcription - elongation

A

RNA polymerase II moves along the template strand, synthesising an mRNA molecule
Phosphate Group - Joins 3’ to 5’ Carbon with a Phosphodiester bond

48
Q

Transcription - Termination

A

Addition of additional adenine nucleotides at the 3’ of the RNA transcript (a process referred to aspolyadenylation). Creates the poly (A) tail

  • Gets to end of gene that it wants to read
  • Stops reading gene and adds a load of adenine’s ( poly - A - tail to the end of RNA - polyadenylation
49
Q

What’s polyadenylation

A

Addition of adenine nucleotides at the 3’ of the RNA transcript

50
Q

Transcription - Processing

A
  • RNA splicing removes Introns

- mRNA) is produced, this can now leave the nucleus through nuclear pores

51
Q

What are genes composed of

A

Introns and exons

52
Q

What are introns

A

non-coding sequences - not essential for making protein

53
Q

What are exons

A

Coding sequences - are expressed - produce proteins

54
Q

What does splicing do

A

Remove introns - non coding regions from RNA and seal blocks together

55
Q

What’s translation

A

mRNA that has left the Nucleus is used as a TEMPLATE to assemble a chain of amino acids (polypeptide) with a specific sequence.

56
Q

What 2 components does translation require

A
  • Ribosomes

- tRNA

57
Q

What are 4 steps of translation

A

Initiation.
Elongation.
Termination.
Post-translation processing of the protein

58
Q

What does translation involve

A
  • Conversion of the nucleotide sequence of mRNA into an amino acid sequence of a protein
59
Q

What is ribosome made of

A

65% rRNA and 35% protein

60
Q

Where places are ribosome found

A

Nuclear envelope
R.E.R
Free floating in cytosol

61
Q

Function of ribosomes in translation

A
  • Catalyse the assembly of protein chains (they’re enzymes)
  • Read mRNA sequences, and bind tRNA which are bound in turn to an amino acid.
  • Place amino acids next to each other in a sequence that will form the protein read from the mRNA code. You
62
Q

What do ribosomes consist of

A

Large and small subunits

63
Q

What do ribosomes have

A

Binding site for mRNA and 3 binding sites for tRNA
-Combination of R groups sticking out from protein creates environment with 3 specific pockets which will recruit something in, bind to it and pass onto next pocket

64
Q

Function/role of tRNA in translation

A

Helps decode mRNA strand

functioning at the binding sites in ribosomes during translation

65
Q

What are proteins built from

A

Amino acids, specified by 3 nucleotide mRNA sequences called codons

66
Q

What does each codon represent

A

A particular amino acid and each codon is recognised by specific tRNA

67
Q

Structure of tRNA

A
  • 3 hairpin loops
  • One of these hairpin loops contains a sequence – the anticodon – complimentary to the mRNA codon
  • Each tRNA is covalently linked to its corresponding amino acid
68
Q

What happens when tRNA recognises and binds to its corresponding codon in the ribosome

A

The tRNA transfers the appropriate amino acid to the end of the growing amino acid chain

69
Q

What do tRNA and ribosome do

A

Continue to decode the mRNA molecule until the entire sequence is translated into a protein

70
Q

Translation - Initiation

A
  • The small ribosome subunit binds at the 5’ end of the mRNA molecule and moves in a 3’ direction.
  • It keep moving until it reads a start codon (AUG).
  • It then forms a complex with the large unit of the ribosome complex and recruits a tRNA.
71
Q

Trancription - Elongation

A
  • Following codons of the mRNA chain determine which tRNA molecule next is recruited into the ribosome. This enters binding site A as the first tRNA moves into site P.
  • A new peptide bond is formed between amino acids at other end of tRNAs
  • The small subunit moves a distance of a codon along the mRNA chain ejecting the spent tRNA molecule
  • The next tRNA molecule binds to the A-site on the ribosome
  • Steps continue and create a polypeptide
72
Q

Translation - Termination

A
  • vTranslation in terminated when the ribosomal complex reads a stop codon (either UAA, UAG, UGA).
  • This codon binds a release factor and results in hydrolysis of the last amino acid (–COOH) when the ribosomal release factor is read
  • The release factor disconnects the polypeptide from the tRNA in the P-site
  • The ribsome dissociates into its two separate subunits
73
Q

Gene expression

A
  • Multiple identical RNA copies can be made from the same gene
  • Each RNA molecule can direct the synthesis of many identical protein molecules
  • Each gene can be transcribed and translated with different efficiency
  • RNA polymerase requires transcription factors - genes are up or down regulated by transcription factors
  • Transcription and translation are regulated
74
Q

Controlling gene expression - Transcription control

A
  • The most common type of genetic regulation
  • Turning on and off of mRNA formation
  • The rate at which DNA is being read and turned into RNA
  • Regulated by availability of transcription factors
75
Q

Controlling gene expression - Post - Transcription control

A

Regulation of the processing of a pre-mRNA into a mature mRNA
- Regulation of splicing enzymes

76
Q

Controlling gene expression - Translational Control

A

Regulation of the rate of Initiation - availability of ribosomes, tRNA - limit how much RNA into protein

77
Q

Controlling gene expression - Post Translational Control

A

Regulation of the modification of an immature or inactive protein to form an active protein
i.e. how it processes through golgi and modified with lipids and sugars

78
Q

What happens to genetic material ( chain )

A

It’s split up into 20,000 different regions - each one = gene - contains genetic code to make one protein

79
Q

What does TATA box represent

A

Binding/promoter region of genetic code

80
Q

What do transcription factors do

A

Recruit enzyme - RNA polymerase II

81
Q

What does RNA polymerase II do

A
  • Opens up DNA and starts transcription process - starts reading of genetic code and produce RNA chain
  • Binds to the promoter of thetemplate strand
82
Q

What does RNA polymerase II do in elongation

A

Unwinds double helix and reads 1 chain of DNA and recruits in free floating nucleotides and pieces in complementary base. e.g. C and G

83
Q

What happens once the nitrogenous base has binded to its complementary base

A

Creates a chain of RNA which is complementary to DNA sequence

84
Q

How are RNA’s binded together

A

Condensation reaction

85
Q

What does splicing produce

A

mRNA - template strand

86
Q

What does mRNA bind with during translation

A

Ribosome

87
Q

What is mRNA used for in translation

A

A template to produce protein

88
Q

What does ribosome recruit

A

tRNA

89
Q

What is gene

A

Sequence of bases

90
Q

How are bases read

A

In groups of 3 - codon - triplet

91
Q

What are triplets of bases referred to in mRNA

A

Codons

92
Q

What is each codon specific for

A

Certain amino acid

93
Q

Where is RNA produced

A

Nucleus

94
Q

What creates the hairpin loops in tRNA

A

Hydrogen bonding

95
Q

What is anticodon

A

Sequence of 3 bases in a row which then specific sequence.

96
Q

How many different types of tRNA’s

A

64

97
Q

What is start codon for every protein in body

A

AUG

98
Q

What happens when start codon is read

A

Ribosome brings in tRNA and starts translation

99
Q

When does termination happen

A

When there’s a stop codon

100
Q

What do stop codon’s represent

A

Not amino acid, instead its represents tRNA not bind to amino acid

101
Q

What is post translation processing of protein

A

Can be modified afterwards

Go into golgi apparatus - add sugars

102
Q

Why regulate gene expression ( transcription and translation)

A

Don’t need every protein identified in genetic material being produced at the same rate all the time - inefficient

103
Q

What is one way of regulating gene expression

A

Binding of transcription factors - change rate at which RNA is being produced and therefore rate at which protein is being produced from that

104
Q

How are transcription factors activated

A
  • Cleaving off region

Phosphorylating/dephosphorylating

105
Q

What happens when transcription factors are active

A

Migrate into nucleus and bind to DNA and initiate transcription

Biological Sciences (27 decks)

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