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A level Biology > Cellular Control > Flashcards

Cellular Control Flashcards

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1
Q

At what levels can gene expression be controlled at?

A
  • The transcriptional level
  • The post transcriptional level
  • The post-translational level
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2
Q

What controls gene expression at the transcriptional level?

A

Transcription factors

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3
Q

What are transcription factors?

A

Proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription.

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4
Q

What are the 2 types of transcription factors?

A
  • Activators
  • Repressors
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5
Q

What do activators do?

A

they increase the rate of transcription

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6
Q

What do repressors do?

A

They decrease the rate of transcription

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7
Q

What determines whether a transcription factor can bind to DNA or not?

A

The shape of the transcription factor

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8
Q

In eukaryotes, where do transcription factors bind?

A

They bind to specific DNA sites near the start of their target genes.

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9
Q

In prokaryotes, where do transcription factors bind?

A

To operons

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10
Q

What is an operon?

A

A cluster of structural genes that are transcribed together, and also control elements and sometimes a regulatory gene.

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11
Q

What do the control elements include?

A
  • A promoter
  • An operator
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12
Q

What is a promoter?

A

A DNA sequence located before the structural genes that RNA polymerase binds to

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13
Q

What is an operator?

A

A DNA sequence that transcription factors bind to

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14
Q

What does the bacteria E.coli typically respire?

A

Glucose

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15
Q

What can the bacteria E.coli respire if glucose isn’t available?

A

Lactose

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16
Q

Where are the genes that produce the enzymes needed to respire lactose found?

A

On an operon called the Lac Operon.

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17
Q

What happens when lactose isn’t present?

A
  • The regulatory gene produces the lac repressor.
  • The lac repressor is a transcription factor that binds to the operator site when there’s no lactose present.
  • This blocks transcription because RNA polymerase can’t bind to the promoter
18
Q

What happens when lactose is present?

A
  • Lactose binds to the repressor.
  • This changes the repressor’s shape so that the repressor can no longer bind to the operator site.
  • RNA polymerase can now begin the transcription of the structural genes.
19
Q

what structural detail of a polypeptide is altered by gene mutations?

A

the base sequence

20
Q

how is it possible for a mutation to have no effect on the protein produced from that gene?

A
  • Some triplets code for the same amino acid, so the amino acid sequence isn’t altered.
  • Some alternative amino acids will not alter the shape of the protein.
  • The mutation may occur in the intron.
21
Q

How could a mutation alter the protein so that it no longer performs its correct function in the cell?

A
  • An insertion or deletion may result in a frameshift mutation.
  • All triplets downstream will be different.
  • The protein will have a different sequence of amino acids.
  • The tertiary structure of the protein will be different.
22
Q

What do regulatory genes do?

A

code for proteins that control the expression of structural genes.

23
Q

What do the structural genes do?

A

codes for a protein that has a function within a cell

24
Q

How can transcription be controlled in eukaryotes?

A
  • Hormone enters a cell and binds to a transcription factor.
  • The transcription factor will then be activated and will bind to a promoter.
  • This will allow RNA polymerase to bind to the promoter.
25
Q

How can gene expression be regulated after transcription?

A
  • The primary mRNA is modified.
  • Introns are removed to make mature mRNA.
  • Alternative splicing can produce different versions of mRNA.
26
Q

Why are fruit flies chosen for research into genes controlling the development of the body plan?

A
  • There’s less ethical concerns
  • Low cost
  • Rapid reproduction rate
  • The genetics of fruit flies is well understood.
  • They have a simple body plan
27
Q

Why are mice usually used or research into genes controlling the development of the body plan, despite there being some ethical concerns?

A
  • low cost
  • share some genes with humans
  • more than one species is needed to demonstrate the conservation of base sequences.
28
Q

do species that have diverged recently share a similar base sequence?

A

Yes

29
Q

Why do non-coding regions of DNA show more variation?

A

Because they are not selected against

30
Q

Do homeobox genes enable proteins to work as transcription factors?

A

Yes

31
Q

What does RNA polymerase do?

A

makes RNA via transcription

32
Q

What does DNA polymerase do?

A

Allows for DNA replication, where 2 polypeptide strands are produced.

33
Q

What is programmed cell death?

A

Apoptosis

34
Q

What do hox genes do?

A

They determine the identity of embryonic body regions along the anterior-posterior axis (i.e. the head-tail axis)

35
Q

What is a homeobox gene?

A

A homeotic gene that initiates transcription and controls the development of the body plan.

36
Q

Why has there been little change by mutation in homeobox genes?

A

Because these genes are very important so any mutations are likely to be lethal

37
Q

What is the relationship between regulatory genes and structural genes?

A

Regualatory genes control the expression of structural genes

38
Q

How is gene expression regulated at the post-translational level?

A
  • Certain molecules, like hormones, bind to cell membranes and trigger the production of cAMP inside the cell.
  • cAMP then activates proteins inside the cell by altering their 3D structure.
  • Altering the 3D structure can change the active site of an active site, making it more or less active.
39
Q

How does cAMP activate PKA?

A
  • cAMP binds to PKA and causes the shape of the enzymes 3D structure to change, releasing the active subunits.
  • PKA is now active
40
Q

What are the 3 main ways a mutation can occur?

A
  • Substitution
  • Insertion
  • Deletion
41
Q

What can form frameshift mutation?

A

Insertion and deletion

42
Q
A

A level Biology (8 decks)

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