DNA transcription, replication and translation Flashcards

wk 11

1
Q

What are two similarities in the structure of DNA and RNA?

A

Phosphates always attached to 5’ and 3’ carbon of each sugar

Nitrogenous bases always attached to 1’ carbon of each sugar

bases = purine or pyrimidine

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2
Q

Where is the Nitrogenous bases always attached to?

A

1’ carbon of each sugar

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3
Q

Describe the structure of purines vs pyrimidines.

A

Purine = double ring structure

Pyrimidine = single ring structure

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4
Q

In which direction can polynucleotides of DNA and RNA only be synthesised?

A

Polynucleotides

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5
Q

Where are additional nucleotides added in RNA and DNA?

A

3’ end

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6
Q

What enzyme adds the precursor (nucleotide triphosphate) to DNA and RNA?

A

polymerase

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7
Q

Transcription

A

When the code of DNA is temporarily transferred to RNA (Copying of DNA –> RNA)

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8
Q

What enzyme is responsible for unwinding and separating DNA in replication

A

Helicase

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9
Q

What enzyme is responsible for reading strand template and inserting complementary bases in replication

A

polymerase

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10
Q

How is the leading strand of DNA produced?

A

continuously due to the polarity of 5’-3’

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11
Q

How is the lagging strand of DNA produced?

A

discontinuously replicated. Therefore is synthesized as Okazaki fragments

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12
Q

What enzyme seals the gap between Okazaki fragments?

A

DNA Ligase

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13
Q

What is the role of RNA Polymerase?

A

Required to make RNA from free nucleoside triphospates

moves along DNA from 3’ end to 5’ end inserting complementary bases

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14
Q

What are the three steps of transcription? Explain

A

Initiation – RNA polymerase moves to precursor and starts to unwind DNA

Elongation – RNA polymerase reads DNA (3’-5’) and produces RNA transcript adding nucleotides in a (5’-3’) direction.

Termination – RNA polymerase reaches termination site, RNA transcpit set free and polymerase dissociates

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15
Q

What is an example of gene regulation?

A

TATA box: DNA sequence where genetic sequence can be rad and decoded = promoter sequence that specifies where transcription begins.

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16
Q

What occurs in the transcription initiation step and act as important control.

A

Transcription factors
promoter sequences
regulatory sequences
enhancer sequence

17
Q

What are the non coding regions of eukaryotic DNA and how are they removed?

A

Introns

via mRNA splicing

18
Q

What are the seven regions of Eukaryotic DNA?

A

Gap

2- 5’-non coding region

3- start codon (AUG)

4- Coding region/ open reading frame

5- Stop codon (UGA)

6- 3’ non coding region

7- ply A tail

19
Q

What is the code for start codon?

20
Q

What is the code for end codon?

21
Q

What are the five steps in mRNA Processing?

A

1- 5’ capped with modified Guanine reside

2- 3’ polyadenylated (add strong of A)

3- Poly A tail of mRNA generated

4- spliced

5- transported to cytoplasm

22
Q

Outline main differences in prokaryotic and eukaryotic DNA.

A

Prokarotic are coded in a continous blcok where as Eukaryotic have exons (coding) and introns (non coding)

E undergoes mRNA processing (cap, tail) and mRNA slicing but P does not

23
Q

General overview of translation

A

After mRNA is exported from nucleus it becomes bound to a ribosome which reads mRNA and uses tRNA to assemble a polypeptide.

Amino acids selected, collected and carried to ribosome by tRNA

TRNA enters ribosome and mind to mRNA chain

24
Q

What three steps are used in both transcription and translation?

A

Initiation
Elongation
Termination

25
What are the 4 steps of translation elongation?
Codon recognition (incoming tRNA anticodon pairs with mRNA codon) Peptide bond formation- ribosome catalyses bond formation between amino acids Translocation- tRNA leaves P site of ribosome, ribsome moves down mRNA 3 bases Repeat as required
26
What occurs in translation elongation?
Reaches stop codon which does not bind to any anticodons of tRNA Release factor binds to stop codon to promote hydrolysis of peptide bond between polypeptide and tRNA at P site.
27
What are the different types of point mutations?
Silent, nonsense and missense
28
Describe silent mutations
base change but codon does not alter AA sequence
29
Describe nonsense point mutations
Base change creates a stop codon translation ends prematurely = mutant protein
30
Describe missense point mutation. Define Conservative and non-conservative ones.
base change resulting in new AA C= properties of new AA similar = normal protein function NC= new AA different properties = loss of protein function
31
What is a frameshift mutation?
Insertion / deletion of base that alters sequence of codon
32