Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cells & Genes > Transcription & Translation > Flashcards

Transcription & Translation Flashcards

1
Q

RNA and DNA differences?

A

Thymine has an extra methyl group compared to uracil which makes it more stable. RNA is usually single stranded whereas DNA is double stranded. Ribose sugar in RNA, deoxyribose sugar in DNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do RNA polymerases copy genes?

A

By recognising promoters and terminators.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a gene?

A

Basic unit of biological information. A specific segment of DNA that encodes an RNA or protein.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a chromosome?

A

Linear or circular molecule, complexed with proteins, containing large numbers of genes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Requirements of RNA Polymerase?

A

Double stranded DNA template. Nucleotide building blocks in the form of NTPs (nucleoside triphosphates). High energy phosphate bonds in the triphosphates are broken to release energy for RNA synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does transcription occur?

A

RNA polymerase unwinds a short stretch of DNA to allow copying, following base pairing rules. RNA is synthesised in the 5’ to 3’ direction. Energy for DNA unwinding and RNA synthesis comes from the pyrophosphate release from nucleotide. RNA polymerase recognises promoter sequences (which show similarities in the -10 to -35 regions) and binds to these.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is pyrophosphate?

A

Oxygen and Phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many nucleotides are synthesised per second by RNA Polymerase?

A

100.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Can genes be simultaneously transcribed?

A

Yes, by multiple RNA Polymerases?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is required for transcription initiation?

A

Sigma subunit is needed for initiation. Gets released after the start of transcription.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What signals the end of translation?

A

A hairpin loop termination signal due to complementary base pairing.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is transcription regulated?

A

It requires a lot of energy, so makes sense to conserve energy by not producing certain proteins in different environments or cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is an inducer?

A

They disable repressors. The gene is expressed because an inducer binds to the repressor. The binding of the inducer to the repressor prevents the repressor from binding to the operator. RNA polymerase can then begin to transcribe operon genes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a transcriptional activator?

A

Protein (transcription factor) that increases gene transcription of a gene. Most are DNA binding proteins that bind to enhancers or promoter-proximal elements.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Example of an activator?

A

The catabolite activator protein (CAP) activates transcription at the lac operon of E.Coli. cAMP is produced during glucose stavation. Binds to CAP, causing a conformational change that allows CAP to bind to a DNA site adjacent to the lac promoter. CAP then makes a direct protein-protein interaction with RNA polymerase that recruits RNA polymerase to the lac promoter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Example of an inducer?

A

Allolactose & lac operon. If lactose is present in the medium then some of it will get converted to allolactose by beta-galactosidase. Allolactose binds to the repressor and decreases the repressor’s affinity for the operator site. When glucose is also available, the lac operon is repressed.

17
Q

What is a repressor?

A

A DNA/RNA-binding protein that inhibits the expression of genes by binding to the operator or associated silencers.

18
Q

How does a DNA binding repressor work?

A

Blocks the attachment of RNA polymerase to the promoter, preventing transcription.

19
Q

How does a RNA binding repressor work?

A

Binds to mRNA and prevents translation of the mRNA into a protein.

20
Q

What is an operator?

A

A segment of DNA to which a transcription factor binds to regulate gene expression. Primarily occur in prokaryotes.

21
Q

What is an enhancer?

A

Short region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. Found in both prokaryotes and eukaryotes.

22
Q

Example of a repressor?

A

Lac operon. LaxZYA transcribes the proteins needed for lactose breakdown. Lacl synthesises the repressor of this gene. The gene Lacl is situated immediately upstream of lacZYA but is transcribed from a different promoter. The lacZYA repressor is constituitively expressed. Always bound to the operator region which interferes with the ability of RNA polymerase to begin transcription.

23
Q

What is a constitutive gene?

A

A gene that is transcribed at a relatively constant level regardless of the cell environmental conditions.

24
Q

What is a facultative gene?

A

Transcribed only when needed.

25
Q

Operon theory?

A

Several genes are controlled by an operon. Forms one mRNA strand.

26
Q

Features of genetic code?

A

Triplet, non-overlapping. 1-6 codons can meant the same amino acid. 3rd position can often be unimportant. Stop codons mean the end of translation. Can be suppressed by tRNA mutations. Almost universal. Allows genes from one organism to be expressed in another.

27
Q

Why is the genetic code degenerate?

A

There are many instances in which different codons specify the same amino acid.

28
Q

How many binding sites do ribosomes have?

A

3 for tRNAs

29
Q

What do ribosomes require for protein synthesis?

A

mRNA amino acyl tRNAs to bring amino acids to the ribosome GTP - energy for synthesis Additional proteins - initiation factors, elongation factors and termination factors.

30
Q

Structure of tRNA?

A

Shape of a 3 leaf clover and has an anticodon as well as an “amino acid arm” where the complementary amino acid binds.

31
Q

How does tRNA get charged up?

A
  1. ATP and the corresponding amino acid bind to the synthetase, releasing two inorganic phosphate molecules.
    Amino Acid + ATP -> Aminoacyl-AMP + PPi
  2. Binds the appropriate tRNA molecule’s D arm and the amino acid is transferred.
    Aminoacyl-AMP + tRNA -> Aminoacyl-tRNA + AMP

Catalysed by a specific aminoacyl-tRNA synthetase. Has recognition sites for both tRNA and the specific amino acid.

32
Q

Steps of protein synthesis?

A
  1. Initiation
    Small ribosomal subunit combines with mRNA and initiator tRNA. Large subunit joins.
    Special initiator tRNA is ued for recognising the start codon (Met) whilst different met-tRNAs are used for recognising internal AUGs.
  2. Elongation
    Internal codons are translated in a series of translocation steps. rRNA catalyses the generation of a peptidyl bond between amino acids. The direction of synthesis is 5’ to 3’.
  3. Termination
    Synthesis stops when stop/termination/nonsense codons are encountered. The large and small subunits dissociate. tRNAs can’t recognise stop codons, instead they are recognised by protein release factors.
    Following release factor association, polypeptide is released and the ribosome is recycled for next translation.
33
Q

Define polysome/polyribosome?

A

Number of ribosomes translating the same mRNA molecule form a polysome.

34
Q

Energy requirements for translation?

A
  1. tRNA charging requires 1 ATP per aminoacyl-tRNA
  2. initiation requires 1 GTP
  3. termination requires 1 GTP
  4. elongation requires 2 GTP per amino acid incorporated
35
Q

Differences between eukaryotic and bacterial protein synthesis?

A
  1. Eukaryotic ribosomes are larger.
  2. Some antibiotics differentially attack bacterial and eukaryotic protein synthesis
  3. In bacteria there can be simultaneous transcription and translation due to no nucleus
  4. Initiator amino acid in eukaryotes is methionine, in bacteria it is N-formyl methionine
36
Q

Examples of antibiotics that are used to attack bacterial translation?

A
  1. Edeine hinders mRNA progression
  2. Tetracycline prevents a-site tRNA binding
  3. Erythromycin blocks protein exit from ribosome
  4. Clindamycin blocks peptide bond formation

Cells & Genes (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions