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Microbio Exam 2 > Lecture 7 (DNA replication, Transcription, Translation) > Flashcards

Lecture 7 (DNA replication, Transcription, Translation) Flashcards

1
Q

When does the cell replicate/duplicate its DNA?

A

Before cell division (binary fission)

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2
Q

How much of the DNA is replicated before cell division?

A

All of it (including the plasmids)

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3
Q

What is the enzyme that replicates DNA in both eukaryotes and prokaryotes?

A

DNA polymerase

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4
Q

Where does DNA replication occur in prokaryotes?

A

Cytoplasm

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5
Q

Where does DNA replication occur in eukaryotes?

A

Nucleus

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6
Q

Central Dogma

A

DNA –(RNA polymerase)–> RNA –(ribosomes)–> protein

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7
Q

What does DNA polymerase help produce?

A

DNA

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8
Q

Transcription

A

DNA –> RNA (via RNA polymerase)

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9
Q

Translation

A

RNA –> protein (via ribosomes)

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10
Q

Where does transcription occur in prokaryotes?

A

Cytoplasm

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11
Q

Where does transcription occur in eukaryotes?

A

Nucleus

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12
Q

Where does translation occur in prokaryotes?

A

At the ribosomes in the cytoplasm

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13
Q

Where does translation occur in eukaryotes?

A

At the ribosomes on the rough ER or in the cytoplasm

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14
Q

The DNA molecule is a continuous chain of _____ ______.

A

base pairs

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15
Q

What is a triplet?

A

1) 3 base pairs
2) How the DNA sequence is interpreted

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16
Q

Each DNA triplet is transcribed to three bases of mRNA, also known as a ______.

A

codon

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17
Q

T/F: Chains of amino acids (polypeptides) are folded into mature proteins

A

T

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18
Q

Where is the RNA polymerase binding sight in the gene promoter?

A

-35

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19
Q

Where in the gene promotor does the RNA polymerase unwind DNA?

A

-10

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20
Q

What 3 structures make up the gene?

A

1) Gene promoter
2) Gene
3) Termination sequence

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21
Q

What occurs at the gene promoter?

A

Conserved AT-rich sequences direct the RNA polymerase toward the gene where it will bind and then facilitate the unwinding

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22
Q

What occurs during stage 1 of transcription (initiation)?

A

The sigma factor and RNA polymerase bind to the promoter and RNA polymerase unwinds the DNA helix

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23
Q

What are sigma factors?

A

1) In bacteria
2) a cytoplasmic protein that binds to RNA polymerase and helps it find promoters
3) subunits of RNA polymerase

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24
Q

What are the main differences between transcription in prokaryotes and eukaryotes?

A

Prokaryotes: 1 RNA polymerase, sigma factors (primary and alternative)
Eukaryotes: 3 types of RNA polymerases, transcription factors (general and inducible)

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25
Q

What is a primary sigma factor?

A

1) Constitutively active (random)
2) Aid in the transcription of most housekeeping genes

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26
Q

What is an alternative sigma factor?

A

1) Activity is increased in response to stress conditions
2) Promte expression of “stress response” genes (nutrient acquisition, virulence)

27
Q

What is a transcription factor?

A

1) An accessory protein that binds to DNA and aids in RNA polymerase 2
2) General TF and Inducible TF

28
Q

What is a general transcription factor?

A

1) Involved with transcription in most RNA polymerase II (Constitutively expressed genes)

29
Q

What is an inducible transcription factor?

A

1) Activated at specific times, often in response to stress conditions

30
Q

What happens during the 2nd stage of transcription, elongation?

A

RNA polymerase moves the bubble forward and brings in nucleotides complementary to the DNA template

31
Q

What direction does RNA polymerase synthesize?

A

5’ -> 3’ (reads 3’ -> 5’)

32
Q

What happens during the 3rd stage of transcription, termination?

A

1) Inverted repeats in DNA termination sequences cause a hairpin to form in the mRNA, and for a tail of U’s to follow the hairpin
2) mRNA detaches and RNA polymerase releases the DNA template

33
Q

T/F: Multiple copies of RNA are simultaneously transcribed in both eukaryotes and prokaryotes

A

T

34
Q

T/F: Prokaryotic mRNA needs to be processed

A

F (eukaryotic mRNA needs to be processed)

35
Q

What are the 3 steps for eukaryotic mRNA processing?

A

1) 5’ end capping
2) 3’ end polyadenylation
3) splicing

36
Q

Why does eukaryotic mRNA need to be processed?

A

Aids in eukaryotic mRNA stability and export from the nucleus

37
Q

Where does mRNA capping occur?

A

Nucleus

38
Q

What is the mRNA cap made of?

A

7-methylguanosine linked to mRNA via a triphosphate bridge attached to the 5’ end of mRNA

39
Q

What does the mRNA cap help with?

A

Aids in mRNA stability and transport to the cytoplasm

40
Q

What is polyadenylation (polyA tail)?

A

The addition of several hundreds of A nucleotides to the 3’ ends of mRNAs

41
Q

Why is the polyA tail important?

A

For nuclear export, stability and initiation of translation

42
Q

Eukaryotic mRNA contains ______ and ______.

A

Introns, extrons

43
Q

What do the introns have?

A

Noncoding regions within genes (they do not code for a function, “nonsense”)

44
Q

What do the extrons have?

A

The coding regions on the genes

45
Q

During what process are introns removed from the mRNA?

A

mRNA splicing

46
Q

Are the introns or extrons removed during mRNA splicing?

A

introns

47
Q

What complex performs mRNA splicing?

A

Spliceosomes

48
Q

What is translation?

A

Using instructions encoded in the mRNA to make protein

49
Q

Where does translation occur in prokaryotes?

A

On ribosomes on the cytoplasm

50
Q

Where does translation occur in eukaryotes?

A

On ribosomes in the RER and the cytoplasm

51
Q

What happens during translation?

A

1) mRNA codons are read by ribosomes and translated into amino acids
2) amino acids join to form peptides, which form proteins
3) All elements needed to synthesize protein are brought together on the ribosome (mRNA, tRNA, and amino acids)

52
Q

T/F: Multiple codons may code for 1 amino acid

A

T (redundancy)

53
Q

What role does transfer RNA (tRNA) serve?

A

During translation, tRNA helps convert mRNA into protein

54
Q

What is tRNA’s structure?

A

1) single-stranded RNA that is folded into hairpin loops (secondary structure)
2) Anticodon
3) Amino acid attachment site

55
Q

T/F: The cytoplasm has a wide array of tRNAs with correct amino acids attached

A

T

56
Q

What are ribosomes made of?

A

ribosomal RNA (rRNA) and protein

57
Q

What are the subunits of the prokaryotic ribosome (70s)?

A

50s and 30s

58
Q

What are the subunits of the eukaryotic ribosome (80s)

A

60s and 40s

59
Q

What does the ribosome do during translation?

A

1) Small ribosomal subunit binds to mRNA
2) Large subunit contains enzymes that catalyze the formation of peptide bonds (protein synthesis)
3) All protein synthesis machinery assembles on the ribosome

60
Q

What are the 4 steps of translation?

A

1) Small subunit binds to the 5’ end of mRNA and pulls it into the ribosome
2) Ribosome scans the mRNA codons
3) Appropriate tRNAs enter with their amino acids
4) Peptide bonds are formed between amino acids to generate peptide chain

61
Q

T/F: Protein synthesis happens faster in prokaryotes than in eukaryotes

A

T (in 30 seconds or less in prokaryotes)

62
Q

Why is protein synthesis quicker in prokaryotes compared to eukaryotes?

A

1) Ribosomes can bind to mRNA as it is being transcribed
2) Everything happens in the cytoplasm

63
Q

What are polyribosomal complexes?

A

1) They enable many proteins to be synthesized from one mRNA transcript
2) Formed in both prokaryotes and eukaryotes
3) Shows that one gene can result in many proteins

Microbio Exam 2 (5 decks)

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