Final

Question 1

What are the six main types of RNA??

Answer 1

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

Question 2

What are transcription and translation?

Answer 2

Transcription: DNA to mRNA
Translation: mRNA to protein

Question 3

What are the general components of a gene?

Answer 3

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

Question 4

What does the core rna polymerase do?

Answer 4

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

Question 5

What does RNA polymerase haloenzyme do?

Answer 5

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

Question 6

What are the phases of prokaryotic transcription?

Answer 6

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

Question 7

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

Answer 7

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

Question 8

What do general transcription factors do?

Answer 8

Recognize promoters and recruit RNAP to the transcription start site

Question 9

Comparé RNA processing in prokaryotes and eukaryotes

Answer 9

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

Question 10

What are the steps to transcription?

Answer 10

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)

Question 11

What define splice site junction?

Answer 11

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

Question 12

How does splicing occur?

Answer 12

Cuts at 5’ and folds over

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

Question 13

Describe translation

Answer 13

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

Question 14

What is a peptide bond?

Answer 14

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

Question 15

What are frameshift mutations?

Answer 15

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

Question 16

What are reading frames?

Answer 16

Section of mRNA coding for protein

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

Question 17

What are some features of the genetic code?

Answer 17

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

Question 18

What are the two required steps for translation?

Answer 18

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

Question 19

What are molecular translators?

Answer 19

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

Question 20

What is the wobble rule that Francis crick proposed?

Answer 20

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

Question 21

What are the functions of ribosomes?

Answer 21

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

Question 22

What is the structure of the ribosome?

Answer 22

Small subunit and large subunit and rRNA

Question 23

What are the 3 phases of translation?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What happens in the elongation phase of translation?

Answer 26

Addition of amino acids to C-terminus of polypeptide | Charged tRNAs ushered into A site by elongation factors

Question 27

Describe polyribosome

Answer 27

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

Question 28

Describe the termination phase of translation

Answer 28

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

Question 29

What are the possible posttranslational processing of proteins?

Answer 29

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

Question 30

What are the 4 types of transition or transversion mutations?

Answer 30

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

Question 31

Define genetic selection

Answer 31

Establish conditions in which only the desired mutant will grow

Question 32

Define genetic screen

Answer 32

Examiné each colony for a particular phenotype

Question 33

Describe the typical bacterial genome

Answer 33

One circular chromosome | Condensed by supercooling and looping

Question 34

What are small transposable elements?

Answer 34

``` 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 ```

Question 35

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

Answer 35

Prevents transcription of entire gene by interrupting gene

Question 36

What are plamids?

Answer 36

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

Question 37

What are R plasmids?

Answer 37

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

Question 38

What are the three ways bacteria exchange DNA?

Answer 38

Transformation Conjugation Transduction

Question 39

Describe transformation

Answer 39

Donor cell lysis and released DNA into medium | Donor cell is taken up by recipient

Question 40

Describe conjugation

Answer 40

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

Question 41

Describe transduction

Answer 41

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

Question 42

What are the steps to the artificial transformation of bacteria?

Answer 42

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

Question 43

What are restriction enzymes?

Answer 43

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

Question 44

Explain the steps to restriction mapping

Answer 44

1. Divide solution containing cloned DNA into three portions | 2. Load each digested sample into gel, along with size markers in a fourth lane

Question 45

What are some features of coloning vectors?

Answer 45

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

Question 46

What are the ingredients to PCR?

Answer 46

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

Question 47

What are the steps to PCR?

Answer 47

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

Question 48

What are some other uses of PCR?

Answer 48

``` 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 ```

Question 49

What is automated DNA sequencing?

Answer 49

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

Question 50

Describe how the lac operon is an example of negative regulation

Answer 50

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

Question 51

What are structural gene mutations?

Answer 51

Affect function of just one enzyme