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College Biology > Review 3 > Flashcards

Review 3 Flashcards

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1
Q

What is a gene?

A

A sequence of DNA the codes for a functional product such as a protein.

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2
Q

What is the central Dogma of Biology?

A

DNA to RNA to protein to function.

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3
Q

What is the process that is used to go from DNA to RNA?

A

Transcription.

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4
Q

What is the process to go from RNA to proteins?

A

Translation.

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5
Q

Name 3 types of RNA?

A
  1. Messenger RNA (mRNA)
  2. Ribosomal RNA (rRNA)
  3. Transfer RNA (tRNA)
  4. Small nuclear RNA (snRNA)
  5. Signal recognition particle RNA (SRP RNA)
  6. Small RNAs (miRNA and siRNA)
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6
Q

What is required for Transcription?

A
  1. Transcription unit within the template DNA (including a promoter, start site, and termination site)
  2. RNA polymerase creates RNA
  3. RNA nucleotides, which are the building blocks of RNA
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7
Q

Describe the function of the promoter.

A

Region just upstream of the start site, used to recruit the RNA polymerase.

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8
Q

What happens in the initiation stage of Transcription?

A
  1. The holoenzyme binds the promoter at the -10 and -35 positions
  2. The Sigma factor loads the RNA polymerase onto the DNA
  3. The RNA polymerase uses its helicase activity and unwinds the DNA at the start site
  4. The sigma factor leaves the complex
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9
Q

What happens in the elongation stage of transcription?

A

The RNA polymerase progresses with the transcription bubble in a 5’ to 3’ direction and adds a RNA base to the growing RNA molecule based on the base pair rules and which base is next in the DNA. (C with G and T with U)

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10
Q

What causes termination of transcription?

A

A hairpin.

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11
Q

What are the 3 different types of Eukaryotic RNA polymerases and what type of RNA do they make?

A
  1. RNA polymerase I - transcribes RNA
  2. RNA polymerase II - transcribes mRNA
  3. RNA polymerase III - transcribes tRNA
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12
Q

What is the difference between Eukaryotic and Prokaryotic Transcription?

A
  1. The initiation stage in Eukaryotic transcription is more complex with more general transcription factors forming an initiation complex
  2. In prokaryotes transcription happens in the cytoplasm and can happen at the same time as translation
  3. In prokaryotes a single mRNA may have several genes on it
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13
Q

What are the 3 types of mRNA modifications?

A
  1. Addition of a 5’ cap, which protects from degradation and is involved in translation initiation
  2. Addition of a 3’ poly-A tail, which are created by poly-A polymerase and protects from degradation
  3. Removal of introns
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14
Q

What are introns and exons?

A
  1. Introns - non-coding sequences will not be translated
  2. Exons - coding sequences that will be translated into proteins
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15
Q

Describe splicing.

A

Small ribonucleoprotein particles (snRNPs) recognize the intron-exon boundaries, snRNPs cluster with other proteins to form spliceosome.

  1. The snRNPs bind to the end of the 1st exon and the branch point in the intron
  2. The intron at the boundary of the exon is cut and then attached to the branch point
  3. The 2nd exon is removed from the intron and attached to the 1st exon and the intron is now a lariat structure that will float away and recycled
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16
Q

What is alternative splicing?

A

Single primary transcript can be spliced into different mRNAs by including different sets of exons.

17
Q

What is the genetic code?

A

The way that information in DNA is converted into proteins, this is using codons which are a block of 3 DNA nucleotides corresponding to an amino acid.

18
Q

What are the special codons and what are they used for?

A
  1. Stop codons and Start codon
  2. They signal the ribosome where/when to stop or start translation
19
Q

Why are tRNAs key to the function of the genetic code?

A

tRNAs use an anticodon to connect to a specific codon and then bring the correct amino acid to the growing protein.

20
Q

What is the enzyme that adds the amino acid to the tRNA?

A

Aminoacyl-tRNA synthetase.

21
Q

Describes the sites in the ribosome.

A
  1. P site - protein site
  2. A site - acceptor site
  3. E site - exit site,
22
Q

What does the P site do?

A

Protein site, binds the tRNA attached to the growing peptide chain.

23
Q

What does the A site do?

A

acceptor site, binds the tRNA carrying the next amino acid

24
Q

What does the E site do?

A

exit site, binds the tRNA that carried the previous amino acid added

25
Q

Describe initiation of translation.

A
  1. In prokaryotes - mRNA has a ribosome binding sequence (RBS). The small ribosome binds the RBS in the mRNA and is positioned at the start codon. The fmet-tRNA binds the start codon. This complex is the initiation complex.
    - Then the large subunit binds and the fmet-tRNA is positioned into the P site of the ribosome and everything is ready to go on to eleongation.
  2. Same Eukaryotes met-tRNA and 5’ cap instead of RBS
26
Q

Describe elongation of translation.

A

The ribosome has the tRNA in the P site with the amino acid chain attached to it. The a new tRNA enters the ribosome at the A site based on what codon is there on the mRNA. The ribosome then transfers the amino on the tRNA in the P site to the amino on the tRNA in the A site. Then the ribosome undergoes translocation and moves to the next codon. The tRNAs move from P to E and A to P. Then the tRNA in the E site can exit and we start over.

27
Q

Describe termination of translocation.

A

The ribosome elongates until it reaches the stop codon. Then the release factor enters the A site and releases the protein and disperses everything.

28
Q

What is an operon?

A

Operons are blocks of genes controlled together.

29
Q

What does the operator do in an operon?

A

It is a DNA sequence that is bound by the regulator.

30
Q

What is a regulator?

A

It is a protein that binds the operator and regulates transcription of the genes.

31
Q

Describe the lac operon in relation to lactose.

A
  1. Negative inducible operon
  2. Without lactose the regulator binds the operator and stops transcription
  3. with lactose the regulator binds lactose and then can’t bind the operator, then transcription can happen.
  4. With a lot of glucose there is a low level of cAMP so CAP can’t bind the CAP binding
32
Q

Describe the lac operon in relation to glucose levels.

A
  1. With low glucose levels there is high cAMP levels. CAP binds the cAMP and then it can bind the CAP binding site. The CAP is an activator and activates transcription at a high level.
  2. With a lot of glucose there is a low level of cAMP so CAP can’t bind the CAP binding, so transcription is at low level.
33
Q

Describe the trp operon.

A
  1. Negative repressible operon
  2. Without trp the regulator doesn’t bind trp and then can’t bind the operator, so transcription happens
  3. With trp the regulator binds trp and the binds the operator and stops transcription
34
Q

Why are operons regulated by a input or product in their genes pathway?

A

As a way of controlling the efficiency of the pathway so it is only on when it is needed. Example = only need lactose when there is lactose present. So only turn it on when there is lactose.

35
Q

What are the types of specific transcription factors?

A
  1. Transcription activator proteins (activators) - Activate and bind DNA
  2. Coactivators - Activate and bind activators
  3. Transcription repressor proteins (repressors) - repress and bind DNA
  4. Corepressors - Repress and bind Repressors
36
Q

What is an enhancer?

A

Sequence that activators bind.

37
Q

Where can a silencer or enhancer be located?

A

Can be about anywhere
- 5’ of gene
- 3’ of gene
- in introns

38
Q

Name 2 of the other types of regulation of gene expression?

A
  1. DNA level - chromatin structure, euchromatin v. heterochromatin, histone modifications, DNA methylation
  2. RNA level - Alternative splicing, RNA degradation, miRNA, siRNA, RNA editing, RNA transport
  3. Protein level - protein stability, miRNA
39
Q
A

College Biology (24 decks)

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