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Grade 12 Biology > Ch. 7 Protein Synthesis > Flashcards

Ch. 7 Protein Synthesis Flashcards

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1
Q

What did Archibald Garrod conclude In what century?

A
  • Early 20th century
  • concluded that enzymes were absent that converted homogentistic acid to break down products for urine -caused alkaptonuria in infants (black urine)
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2
Q

George Beadle and Edward Tatum

A

Studied bread mould

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3
Q

One gene-one enzyme hypothesis and what year?

A

-1941

Proposed by Beadle and Tatum, A single gene controls the production of only one enzyme.

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4
Q

Pauling and Itano

A

Discovered that if 1 amino acid in a particular protein subunit is altered, the function of the entire protein may be altered. This leads to one gene one polypeptide hypothesis

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5
Q

One gene-one polypeptide hypothesis

What year?

A

-1949
Each gene is unique and codes for the synthesis if a single polypeptide.
Restated version of the one gene one enzyme hypothesis.

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6
Q

What is DNA

A

Contains instructions for biological structure and function is carried out by proteins.

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7
Q

Proteins

A

Linear amino acid sequence determines the 3D proteins structure that determines protein function.

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8
Q

Central dogma

A

States that genetic information flows from DNA to RNA to protein.

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9
Q

What are the two major steps of central dogma process

A

Transcription and translation

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10
Q

Differences between DNA and RNA

A

Dna:

  • double stranded
  • adenine pairs with thymine
  • deoxyribose sugar

RNA:

  • single stranded
  • adenine pairs with uracil
  • ribose sugar
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11
Q

How many types of rna are needed for protein synthesis?

List them

A 
3
Messenger rna(mRNA) , transfer rna (tRNA), ribosomal rna(rRNA)
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12
Q

Messenger RNA (mRNA)

A

A working copy (transcript) of DNA sequence about 500-10000 nucleotides long.

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13
Q

Transfer RNA (tRNA)

A

Brings correct amino acid to ribosome as they synthesize proteins. Or 70-90 base pairs long

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14
Q

Ribosomal RNA (rRNA)

A

Combines with proteins to from ribosomes where polypeptides (proteins) are assembled.
Most abundant RNA

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15
Q

Role of rRNA (list 3)

A

-made up of 2 subunits ( large and small)
​​- small subunit is the binding site for mRNA
- large subunit contains 2 binding sites P (peptide) site and A (acceptor) site where tRNA attaches and E site for exit

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16
Q

Role of tRNA

A

​- cloverleaf shaped molecule that contains 2 important sites:
• anticodon
• acceptor site

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17
Q

What is anticodon

A

sequence of 3 bases that recognizes codon of mRNA.

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18
Q

What is acceptor site?

A

carries corresponding amino acid that it codes-> the aminoacyl –tRNA

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19
Q

How does transcription differ from replication in 3 ways

A
  1. only one region of DNA strand (a gene) is used as a template
  2. RNA polymerase is used instead of DNA polymerase
  3. RNA is single-stranded, without thymine; DNA is double stranded.
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20
Q

What is transcription

A

The information encoded in DNA is passed to a complementary mRNA molecule. The code is rewritten using same nucleotides found in DNA except for uracil, which replaces thymine in DNA.

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21
Q

What are the 3 steps of transcription?

A

Initiation, elongation and termination.

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22
Q

What happens in initiation of the transcription process?

A

Transciption begins when RNA polymerase binds to double helix DNA at a promoter region-> TATA box->(Many A’s and T’s around 10) DNA strand is unwound and double helix is disrupted, exposing the template strand.

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23
Q

What happens in the elongation process of transcription?

A

Pre-mRNA is transcribed in the 5’ – 3’ direction along one strand of DNA using RNA polymerase. The opposite strand of DNA not being copied is coding strand.

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24
Q

What happens in the last step of transcription: Termination?

A

Transcription ends when the RNA polymerase reaches termination sequence at the end of gene.
Pre-mRNA and RNA polymerase are released.

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25
Q

What happens in post-transcriptional modifications?

A
  1. A “methyl cap” is added to 5’ end of pre-mRNA. Made of methyl guanosine to help bind mRNA to ribosome.
    ​2. A “poly A tail” is added to 3’ end of pre-mRNA. Made of 200 adenine nucleotides. Protects pre-mRNA from destruction once in cytoplasm.​
  2. snRNPs bind to introns and signals to be removed from pre-mRNA sequence by spliceosomes. Introns are regions of gene that do not code for anything. They exist between coding regions of genes called exons.
    Once mRNA has been modified, it can leave the nucleus, enter the cytoplasm and be used in translation.
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26
Q

What is the first stage of translation?

A

Initiation:
• the small rRNA subunit attaches to mRNA at its 5’ end exposing the first codon.
• the tRNA come into place to pair with the initiation/start codon
• larger rRNA subunit then attaches to the small subunit with the P site locked over the tRNA.

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27
Q

What is the second stage of translation?

A

Elongation:
• the next tRNA position over the A site.
• a peptide bond is catalyzed between the first 2 a.a.’s ( in P & A site)
• the first tRNA is released- from E site.
• the ribosome move down the mRNA to the next codon to repeat this process.

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28
Q

What is the last stage of translation?

A

Termination:
• near the end of the mRNA, the codon for “stop” is reached.
• polypeptide chain is released into the cytoplasm for further processing in the Golgi bodies.
• A ribosome assembles amino acids into polypeptide chain

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29
Q

What is a polysome complex?

A

A complex that is formed when multiple ribosomes attach to the same mRNA molecule in order to facilitate rapid translation.
Happens in elongation stage of translation.

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30
Q

2 mechanism control system used by cells?

A
  1. Negative control system

2. Positive control system

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31
Q

What is a negative control system?

A

A regulatory protein binds to the dna to block transcription. It can be removed by an inducer —> lac operon

32
Q

What is a positive control system

A

A regulatory proteins binds to the dna to promote initiation of transcription —> trp operon

33
Q

What is prokaryotic gene control mechanism l?

A

Lactose and tryptophan

34
Q

What is the operon model include

A

• a promoter – signals the start of the gene
• an operator – helps in gene regulation
• structural gene (s) – the sequence of DNA for protein
• Transcription of structural genes depends on action of “repressor protein”. If this protein binds to the operator, it blocks the promoter and prevents transcription of the structural gene
• If repressor protein is removed, transcription can begin.
The repressor is affected by specific substance that can activate or inactivate it by changing its shape (an allosteric effector)

35
Q

What is a repressor protein

A

A protein that binds to the operator to repress gene transcription

36
Q

Which enzyme in bacteria cell breaks lactose into monosaccharide

A

In bacteria, β-galactosidase enzyme breaks lactose into monosaccharide used as an energy source.

37
Q

What happens when there is absence of lactose in regulation of the lac operon

A
  • When lactose is not available, no need for β-gal
  • the lacl repressor protein binds to the lac operator site, covering the promoter, RNA polymerase cannot bind to promoter, and thus, blocking transcription.
38
Q

What happens when there is a presence of lactose in the lac operon?

A

In the presence of lactose, lactose binds to the lacl repressor protein, changing its shape so it no longer remains to the lac operator site and RNA polymerase can bind to the promoter and transcription occurs and structural genes are expressed . . making β-gal.

39
Q

What is inducer

A

A signal molecule that triggers the expression of an operon’s genes

40
Q

What is the lac operon known as

A

It is known as the indicible operon.

High levels of lactose induce the operon

41
Q

What happens when there is a lack of tryptophan?

A

Lack of tryptophan inactivates the repressor and transcription proceeds

42
Q

What does tryptophan act as?

A

Tryptophan acts as a corepressor and binds to the tryptophan repressor. The complex can now bind to the trp operator and transcription is blocked.

43
Q

What is corepressor

A

A signal molecule that binds to a regulatory protein to reduce the expression of an operon’s genes

44
Q

What happens when there is highl level of trp(tryptophan)

A

High levels of tryptophan repress the operon.

45
Q

What are the four categories that fall into the control mechanisms on eukaryotes

A

Transcriptional
Post-transcriptional
Translational
Post-translational

46
Q

What happens in transcriptional control?

A

Transcriptional control regulates which gene are transcribed and/or the rate at which transcription occurs.

47
Q

What happens in post-transcriptional?

A

Forms of post-transcriptional control include alternative splicing of exons, introns, masking proteins binding mRNA and the rate of degradation of mRNA

48
Q

What happens in translational control?

A

Translational control involves how often and how rapidly mRNA is translated.

49
Q

What happens in post-translational?

A

Post-translational control regulates when proteins become fully functional, how long they are functional, and when they are degraded.

50
Q

What is the key to mutation

A

GENETIC VARIABILITY

51
Q

What are the 3 ways a species can maintain genetic variability?

A

1) ​sexual recombination
2) ​genetic recombination
3) ​ mutations

52
Q

What are 2 types of mutations

A

1) point mutation

2) frameshift mutation

53
Q

What is a point mutation

A

change in chromosome at a single nucleotide within a gene

Example: substitution of one base for another (missense)

54
Q

What is a frameshift mutation

A

the number of nucleotides inserted or deleted is not a multiple of 3, thus resulting in improper grouping into codons.

55
Q

What three types are involved in frameshift mutation?

A

Substitution
Insertion/deletion of a single base pair
Inversion of two adjoining base pairs

56
Q

Effects of point mutations

A
  • missense mutations alter the codons, but the new codons still code for amino acids and thus make ‘sense’. The effect depends on importance of a. a. to the protein.
  • nonsense mutations alters amino acid codon to a stop signal. This results in shorter polypeptide and nearly always non functional.
  • silent mutations - have no effect due to the redundancy of the gene code ie. several types of codons code for the same amino acid.
57
Q

Effects of a frameshift mutation

A

are more disastrous effect than point mutations on polypeptide (protein) being encoded because all the nucleotides that are ‘downstream’ from the error will be improperly grouped into codons.
produce a nonfunctional protein.

58
Q

No mutation

A

This is the normal condition

59
Q

What does large scale mutations include

A

Translocation and inversion

60
Q

Define Translocation

A

movement of genes from one chromosome to another chromosome

61
Q

Example of translocation

A

Down syndrome

62
Q

2 causes of genetic mutations

A

1) spontaneous – error in DNA replication

2) mutagens - chemical and physical agents that interact with DNA to cause mutations

63
Q

What are examples of physical mutagens

A
  • X-rays

- UV radiation

64
Q

What are examples of chemical mutagens

A

a) base analogues
b) reactive chemicals
c) intercalating chemicals

65
Q

What is base analogue

A

chemicals that are similar to normal DNA bases but pair incorrectly. eg. bromouracil normally replaces thymine but can incorrectly pair up with guanine later

66
Q

What is a reactive chemical

A

chemicals that add or remove chemical groups to or from normal bases leading to mispairing during DNA synthesis.
e.g. nitrous acid deaminates nitrogenous bases (replaces amino NH2 group with keto group) thus changing the hydrogen bonding properties of the base.

67
Q

What is intercalating chemicals

A

chemicals which attach between stacked bases in the double helix leading to small insertions or deletions during DNA synthesis.
eg. proflavin is a flat molecule that can insert between stacked bases.

68
Q

Types of mutation compared with

1) X-rays
2) Ultraviolet rays
3) Base analogues
4) Reactive chemicals
5) Intercalating chemicals

A

1) Frameshifts
2) point & Frameshifts
3) point
4) point
5) Frameshift

69
Q

What is a microsatellites(VNTR’s)

A

Variable Number Tandem Repeats – repeating sequences of TAG TAG TAG TAG TAG

70
Q

What are the repetitive DNA sequences found near centromere?

A

LINEs (Long Interspersed Nuclear Elements)
SINEs (Short Interspersed Nuclear Elements)
Transposons – small sequence of DNA that can move and insert into different position in the genome.
Pseudogenes – a sequence of DNA that is similar to an existing gene but does not code for proteins
- Mutated version of the older genes, vestigial genes that have lost their evolutionary adaptive value
Promoter region – sequence of DNA that binds RNA polymerase upstream of a gene.

71
Q

What is a retrovirus

A

A virus that uses reverse transcriptase for replication

72
Q

Example of a application of viral vector

A

Transduction

73
Q

What is transduction

A

Transduction is the use of viral vectors to introduce new genetic material into an existing cell.

74
Q

What is a virus

A

Viruses have small genomes that consist of only RNA or DNA. They rely on their host’s genetic machinery to replicate themselves.

75
Q

What is the enzyme called when the viral dna is incorporated into the host’s genome?

A

The viral DNA is then incorporated into the host’s genome by an enzyme call integrase, then transcribed and translated to produce virus proteins and viral RNA. These proteins and RNA are used to assemble new virus particles.

Grade 12 Biology (2 decks)

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