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BIOL 2104 > Final > Flashcards

Final Flashcards

1
Q

What are the six main types of RNA??

A
  1. mRNA: messanger rna - codes for proteins
  2. rRNA: ribosomal rna - structure components of ribosomes
  3. tRNA: transfer rna - amino acid carriers
  4. snRNA: small nuclear rna - transcript processing
  5. Ribozymes
  6. Small rnas: regulatory
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2
Q

What are transcription and translation?

A

Transcription: DNA to mRNA
Translation: mRNA to protein

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3
Q

What are the general components of a gene?

A 
Promoter region 
5' UTR untranslated region (start of mRNA)
Coding sequence of a gene
3' UTR
Terminator
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4
Q

What does the core rna polymerase do?

A

Synthesized RNA but unable to recognize promoters and accurately initiate transcription
Does not contain o70

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5
Q

What does RNA polymerase haloenzyme do?

A

Association with o confers DNA binding and transcription initiation capability, but o is not needed once polymerization process occurs

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6
Q

What are the phases of prokaryotic transcription?

A
  1. Template binding by RNA polymerase (at promoter for accurate initiation of transcription)
  2. RNA chain initiation (closed to open complex)
  3. Chain elongation
  4. Chain termination
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7
Q

What are the three distinct RNA polymerase in the nuclei of eukaryotes ?

A
  1. RNAP I: located in nucléoles, synthesized precursors of most rRNA (except 5S rRNA)
  2. RNAP II: located in nucleoplasm, synthesized mRNA precursors (protein-coding genes), and microRNA
  3. RNAP III: located in nucleoplasm, synthesized small RNAs such as 5S rRNA, tRNAs, snRNAs
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8
Q

What do general transcription factors do?

A

Recognize promoters and recruit RNAP to the transcription start site

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9
Q

Comparé RNA processing in prokaryotes and eukaryotes

A

Prokaryotes:
- transcription and translation are couples
- mRNAs often encode more than one polypeptide
- most mRNAs translated without further modification
Eukaryotes:
- transcription and translation are separate
- primary transcripts generally not functional
- mRNAs generally encode only one polypeptide
- mRNAs undergo extensive modification while still in nucleus

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10
Q

What are the steps to transcription?

A
  1. Addition of cap to 5’-end of nascent transcript (protects rna from degradation and required for translation of mRNA)
  2. Poly(A) tail added to 3’-end (protective function and important for efficient translation of mRNA into protein)
  3. RNA splicing - coding information is fragmented into exons (introns removed)
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11
Q

What define splice site junction?

A

5’GU and 3’AG sequences are necessary and generally sufficient to define a junction

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12
Q

How does splicing occur?

A

Cuts at 5’ and folds over

Cuts 3G’ and is removed forming mature rna and intron is degraded

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13
Q

Describe translation

A

Carried out by a large multiprotein complex involving protein-nucleic acid interactions
Requires accessory factors
Must be exacted with accuracy
Highly energy consuming

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14
Q

What is a peptide bond?

A

Bond formed between OH on carboxyl group of one amino acid and the hydrogen on the amino group of another amino acid resulting in the removal of H2O

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15
Q

What are frameshift mutations?

A

They shift the reading frame for all codons beyond the point of insertion or deletion, almost always abolishing the function of the protein product

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16
Q

What are reading frames?

A

Section of mRNA coding for protein

Can have 3 potential reading frames but usually only one is used

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17
Q

What are some features of the genetic code?

A
  1. All codons have meaning
  2. Code is unambiguous: each codon specifies one amino acid
  3. Code is degenerate: every amino acid coded by more than one codon
  4. Codons representing the same amino acid or chemically similar amino acid tend to be similar in sequence
  5. Genetic code is universal
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18
Q

What are the two required steps for translation?

A
  1. Correct amino acid must be selected for covalent attachment to tRNA by aminoacyl-tRNA synthétase
  2. Correct aminoacyl-tRNA must pair with an mRNA codon via anticodon
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19
Q

What are molecular translators?

A

Aminoacyl-tRNA synthétases are the only molecules that read language of both nucleic acid and protein (amino acid)

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20
Q

What is the wobble rule that Francis crick proposed?

A

First two bases of the codon and the last two bases of the anticodon form canonical A:U or G:C base pairs, but base pairing between third base of codon and first base of anticodon is less stringent
Third position referred to wobble position

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21
Q

What are the functions of ribosomes?

A
  1. Binds mRNA such that codons can be read with high fidelity
  2. Include specific binding sites for tRNA molecules
  3. Médiate interactions with non-ribosomal proteins that promote polypeptide chain initiation, elongation, and termination
  4. Catalyzed peptide bond formation
  5. Undergoes movement so that it can translate sequential codons
22
Q

What is the structure of the ribosome?

A

Small subunit and large subunit and rRNA

23
Q

What are the 3 phases of translation?

A
  1. Initiation: recognition of first codon
  2. Elongation: repetitive addition of amino acids
  3. Termination: at stop codon
24
Q

What are the three steps of the initiation phase of translation?

A
  1. Small ribosomal subunit binds mRNA
  2. Initiator tRNA is positioned in P site and then
  3. The large ribosomal subunit binds
25
Q

What is the fundamental difference between imitation in prokaryotes and eukaryotes?

A

Prokaryotes: small ribosomal subunit recognizes the shine-dalgarno sequence of the mRNA - these can be internal
Eukaryotes: the small ribosomal subunit recognizes the 5’ cap structure on the mRNA and translation generally initiates from the closest aug

26
Q

What happens in the elongation phase of translation?

A

Addition of amino acids to C-terminus of polypeptide

Charged tRNAs ushered into A site by elongation factors

27
Q

Describe polyribosome

A

Simultaneous synthesis of many copies of a polypeptide from a single mRNA

28
Q

Describe the termination phase of translation

A

No tRNAs carry anticodons for the stop codon
Release factors bind to the stop codons
Causes release of ribosomal subunits, mRNA and polypeptide

29
Q

What are the possible posttranslational processing of proteins?

A
  1. Cleavage may remove an amino acid
  2. Cleavage may split a polyprotein
  3. Chemical constituent addition may modify a protein
30
Q

What are the 4 types of transition or transversion mutations?

A

Synonymous: altered codon specifies the same amino acid
Missense (conservative): altered codon specifies a chemically similar amino acid
Missense (nonconservafive): altered codon specifies a chemically dissimilar amino acid
Nonsense: altered codon signals chain termination

31
Q

Define genetic selection

A

Establish conditions in which only the desired mutant will grow

32
Q

Define genetic screen

A

Examiné each colony for a particular phenotype

33
Q

Describe the typical bacterial genome

A

One circular chromosome

Condensed by supercooling and looping

34
Q

What are small transposable elements?

A 
700-5000bp length 
Inverted repeats at ends
Carry transposase gene
Can move to other locations in genome
Can disrupt genes by insertion into coding region
35
Q

What does the insertion of an insertion sequence do to the lacZ gene?

A

Prevents transcription of entire gene by interrupting gene

36
Q

What are plamids?

A

Smaller circles of DNA separate from the bacterial chromosome
Beneficial but usually not essential to the host

37
Q

What are R plasmids?

A

Résistance plasmids
Carry genes that make host cells resistant to antibiotics and other antibacterial drugs
Multiple antibiotic resistance often due to composite IS/transposons éléments on a plasmid

38
Q

What are the three ways bacteria exchange DNA?

A

Transformation
Conjugation
Transduction

39
Q

Describe transformation

A

Donor cell lysis and released DNA into medium

Donor cell is taken up by recipient

40
Q

Describe conjugation

A

Donor DNA is transferred directly to recipient through a connecting tube
Contact and transfer are promoted by a specialized plasmid in donor cell

41
Q

Describe transduction

A

Bacteriophage infects a cell
Donor cell lysis and bacteriophages containing donor DNA are released
Donor DNA is transferred when phage particle infects recipient cell

42
Q

What are the steps to the artificial transformation of bacteria?

A
  1. Expose bacteria to a salt solution and apply heat shock in the presence of foreign DNA
  2. Expose bacteria to electric current in presence of foreign DNA
43
Q

What are restriction enzymes?

A

Endonucleases that recognize and cleave specific DNA sequences
Produced by bacteria for protection against viruses

44
Q

Explain the steps to restriction mapping

A
  1. Divide solution containing cloned DNA into three portions

2. Load each digested sample into gel, along with size markers in a fourth lane

45
Q

What are some features of coloning vectors?

A

have an origin of replication so that DNA can be replicated in host cell
Handled easily
Unique restriction sites for cloning DNA fragments
Selectable markers for determining whether the clone has been transferred into cells and verify foreign DNA has been inserted into vector

46
Q

What are the ingredients to PCR?

A
  1. DNA template with at least some sequence known
  2. Primers (oligonucleotides) complementary to sequence flanking the region to be amplified
  3. Four deoxyribonucleotides
  4. DNA polymerase
  5. Buffer with appropriate salt
47
Q

What are the steps to PCR?

A
  1. Heat (92-95) used to denature DNA strands
  2. DNA cooled (50-60) to allow primers to anneal (primers are in vast excess over template)
  3. Heated again (72) to allow thermostable DNA polymerase to replicate DNA
48
Q

What are some other uses of PCR?

A 
PCR fragments can be labelled to produce hybridization probes and can be sequenced 
Used in recombinant DNA technology
Genotype detection and gene mapping
Markers for molecular breeding
DNA barcoding
49
Q

What is automated DNA sequencing?

A

Each ddNTP is labeled with a different colour fluorescent dye and all four are used in a single synthesis reaction
All four reactions are run in a single lane on a gel
After electrophoresis, fragments flow through a fluorescence detector and the colour is digitally recorded

50
Q

Describe how the lac operon is an example of negative regulation

A

When no lactose is present, repressive protein is bound to operator so Z, Y, A genes can’t be expressed
When there is plus lactose, inducer binds to receptor preventing it from binding to oporagkr so genes can be expressed and promoter region is accessible

51
Q

What are structural gene mutations?

A

Affect function of just one enzyme

BIOL 2104 (2 decks)

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