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Introduction to Genetics & Biochemistry > Bacterial Gene Structure > Flashcards

Bacterial Gene Structure Flashcards

1
Q

Are bacterial genes HAPLOID or DIPLOID?

A

Haploid.

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2
Q

Bacterial genes have how many copies of each gene, on a chromosome of what shape?

A

One copy of each gene on a circular chromosome.

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3
Q

Where are accessory genes encoded for in bacterial cells?

A

Accessory genes are coded for on plasmids, which are extra chromosomes.

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4
Q

Are accessory genes essential?

A

No, they can be shared and used but they are not essential.

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5
Q

Bacteria are unicellular. They don’t have different ………….. that can express different genes so they use …………….. …………….. to switch functions on and off.

A

Tissues, gene regulation.

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6
Q

Gene regulation prevents unwanted ………….. between ………….. .

A

Interactions, functions.

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7
Q

Gene regulation allows bacterial cells to adapt to…?

A

Different conditions.

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8
Q

Name three key features of prokaryotic gene structure.

A

Promoter, transcribed region and terminator sequence.

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9
Q

Name the prokaryotic gene structure:

‘Sequences in a gene that are required for expression and regulation of the gene, but are NOT included in mRNA’.

A

Promoter.

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10
Q

Are promoters included in mRNA?

A

No.

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11
Q

Which feature of prokaryotic gene structure acts like a signal to the cell?

A

Promoter.

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12
Q

Name the prokaryotic gene structure:

‘These sequences can be transcribed into mRNA and turned into a protein’.

A

Transcribed region.

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13
Q

True or false? The transcribed region can include more than one open reading frame or operon?

A

True.

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14
Q

Does the transcribed region feature introns or splicing?

A

No, it is just contiguous open reading frames.

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15
Q

True or false? All mRNA transcribed will be translated into proteins.

A

False. Some mRNA will be translated into proteins, but some mRNA molecules re functional and gene regulation or catalytic events.

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16
Q

Name the prokaryotic gene structure:

‘defines the end of the gene or operon’.

A

Terminator sequence.

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17
Q

What structure does the terminator sequence often take?

A

A stem loop structure.

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18
Q

What is significant about the +1 base and the -1 base? What about 0?

A

The +1 base is the first base that is transcribed into mRNA. The -1 base is the first base that is ot transcribed into mRNA. There is no 0 base!

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19
Q

What is the 5’ UTR?

A

The 5’ UnTranslated Region.

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20
Q

Is the 5’ UTR found before or after the AUG start codon? What is its purpose?

A

The 5’ UTR is found before the AUG start codon. It’s purpose is to signal to ‘follow these instructions to make a protein’.

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21
Q

Each open reading frame starts with …………….. and ……………. ?

A

The start codon and a ribosome binding site.

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22
Q

True or false? Even if there are multiple ope reading frames on one mRNA, there is only one ribosome binding site.

A

False. Each open reading frame has its own ribosome binding site.

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23
Q

Which enzyme synthesises mRNA?

Hint: it is the same in all organisms.

A

RNA polymerase.

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24
Q

What does RNA polymerase bind to to initiate mRNA synthesis?

A

The promoter motif.

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25
Q

What is a motif (as in promoter motif?)

A

A pattern of bases in DNA or mRNA that has been identified to have a known function.

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26
Q

Does translated mRNA require further processing before it can be translated into a protein?

A

No.

27
Q

The coding strand is also known as what? What role does it have in transcription?

A

The coding strand can also be known as the non-template or sense strand. It carries the codons for transcription.

28
Q

Which strand is copied by RNA polymerase - the sense strand, or the anti-sense strand?

A

The anti-sense, or template, strand is copied by RNA polymerase.

29
Q

The bacterial RNA polymerase holoenzyme consists of how many core enzyme subunits? And how many sigma factor subunits?

A

Five core enzyme subunits and one sigma factor subunit.

30
Q

Which sequences of the bacterial promoter does the sigma factor of the RNA polymerase bind to? Why does it do this?

A

The sigma factor binds to the -10 and -35 sequences of the bacterial promoter and identifies the beginning of a gene.

31
Q

What part of RNA polymerase binds to sequences -10 and -35 of bacterial promoters to identify the beginning of a gene?

A

Sigma factor.

32
Q

What part of RNA polymerase makes mRNA? The core enzyme or the sigma factor?

A

The core enzyme.

33
Q

Which proteins control the binding of RNA polymerase to promoters?

A

Regulatory proteins.

34
Q

Why do regulatory proteins control the binding of RNA polymerase to promoters?

A

To switch genes on and off as needed.

35
Q

……………… ………………. binds to the -10 and -35 promoter boxes. Then it brings in the complex protein …………. ……………. ……….. enzyme.

A

Sigma factor, RNA polymerase core.

36
Q

Describe how negative gene regulation works.

A

When a regulatory protein binds to the operator region, RNA polymerase is prevented from transcribing the full mRNA.

37
Q

In E.Coli, the binding of the inducer changes the lacl repressor shape, allowing transcription of the full mRNA encoding structural genes. If, in this case, the inducer is sugar in the environment, what does this allow E.Coli to do?

A

E.Coli can respond to the presence of sugar in the environment and turn sugar uptake on and off.

38
Q

What is a ‘weak motif’?

A

A weak motif is one that RNA polymerase cannot bind to without help (from an activator).

39
Q

What do activator proteins do?

A

Activator proteins ‘locks’ sigma factor into place so it stays there to bring in the core enzyme.

40
Q

When an activator helps RNA polymerase to bind to a ‘weak’ motif, this is an example of …………………… gene regulation.

A

Positive.

41
Q

-10 to +1 of the DNA strand is known as the…?

A

Discriminator region.

42
Q

True or false? Sequences upstream of -35 have no role in gene regulation.

A

False. The modern view is that the -40 to -60 region can have things binding to it which can affect RNA polymerase binding, especially if activators or repressors are present.

43
Q

In the initiation of transcription, what is formed first? The open complex or the closed complex?

A

The closed complex is formed when the holoenzyme assembles on the promoter. The open complex is then formed when core enzymes split dsDNA.

44
Q

Describe the three steps of the initiation of transcription.

A
  1. The closed complex is formed when the holoenzyme assembles on the promoter.
  2. The open complex is formed when core enzymes split dsDNA.
  3. Transcription is initiated at the +1 site.
45
Q

True or false? RNA polymerase can intiate transcription without a primer.

A

True.

46
Q

What are the two types of termination of transcription?

A
  1. Intrinsic / rho-independent termination.
  2. Rho-dependent termination.
47
Q

Which type of termination of transcription occurs in around 99% of bacterial genes?

A

Rho-independent termination.

48
Q

What process does this describe:

‘Involves an inverted repeat (palindrome) in the gene, followed by an polyA region (polyU in mRNA).’

A

Rho-independent termination.

49
Q

What is rho?

A

An additional terminator protein.

50
Q

How does rho act to terminate transcription?

A

Rho pulls RNA out of the transcription complex as it acts as a molecular motor, running along the new RNA molecule to the RNA polymerase.

51
Q

Where does transcription AND translation occur in bacteria?

A

In the cytoplasm.

52
Q

What is the start codon for protein synthesis?

A

ATG / AUG.

53
Q

If the start codon is ATG, what is always the first amino acid to be produced?

A

Methionine.

54
Q

Approximately how many nucleotides upstream of the start codon is the ribosomal binding site?

A

8 - 10 nucleotides.

55
Q

Sets of related genes can be organised into an…?

A

Operon.

56
Q

True or false? Usually, one operon = one promoter.

A

True.

57
Q

What is the name for one mRNA which encodes multiple open reading frames?

A

Polycistronic mRNA.

58
Q

True or false? Translation can start before transcription is complete.

A

True.

59
Q

What does ‘coupled’ transcription and translation mean?

A

That translation can start before transcription has ended.

60
Q

Multiple ribosomes can bind to one transcript in the nucleoid. What is this called?

A

A polyribosome.

61
Q

Polyribosomes are when multiple ribosomes bind to one transcript in the nucleoid. What does this mean for how many copies of a new protein are produced from one RNA molecule?

A

Multiple copies of the new protein can be produced from one RNA molecule.

62
Q

What type of mutations occur when a new terminator is introduced, so that a shorter mRNA is made, switching off expression of downstream genes?

A

Polar mutations.

63
Q

True or false? The basic model of protein synthesis is the same in prokaryotes and eukaryotes.

A

True. There are some differences in accessory factors but the process is the same.

64
Q

Are the ribosomal subunits in prokaryotes the same as in eukaryotes?

A

No.

Small - 30s.
Large - 50s.
Total - 70s.

Introduction to Genetics & Biochemistry (21 decks)

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