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OCR A Level Biology- module 6 > Chapter 1- Cellular Control > Flashcards

Chapter 1- Cellular Control Flashcards

1
Q

What does an increase in transcription do?

A

Produce more mRNA.

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2
Q

What can more mRNA be used for?

A

Make more proteins.

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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 transcription factors called that increase rate of transcription?

A

Activators.

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5
Q

What are transcription factors called that decrease rate of transcription?

A

Repressors.

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6
Q

What does the shape of a transcription factor determine?

A

Whether it can bind to DNA or not.

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7
Q

What can the shape of transcription factors be altered by?

A

Binding of certain molecules, e.g sugars and hormones.

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8
Q

Where do transcription factors bind to in Eukaryotes?

A

They bind to specific DNA sites near the start of their target genes- the genes they control the expression of.

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9
Q

Where do transcription factors bind to in Prokaryotes?

A

In prokaryotes, the control of gene expression often involves transcription factors binding to operons.

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10
Q

What is an Operon?

A

A section of DNA that contains a cluster of structural genes, that are transcribed together, as well as control elements and sometimes a regulatory gene.

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11
Q

What are structural genes?

A

Genes that code for useful proteins such as enzymes.

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12
Q

What are control elements?

A

promoter (DNA sequence located before structural genes that RNA polymerase binds to) and operator (DNA sequence that transcription factors bind to).

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13
Q

What does regulator gene code for?

A

activator and repressor.

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14
Q

What is the Lac Operon in E. Coli?

A
  • E. coli respires glucose, but can use lactose if glucose isn’t readily available.
  • Genes that produce enzymes needed to respire lactose are found on an operon known as the Lac Opero.
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15
Q

What are the 3 structural genes found on the Lac Operon, and what proteins do they produce to help bacteria to digest lactose?

A

Lac A- unknown
Lac Z- Beta Galactosidase
Lac Y- Lactose permease

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16
Q

What happens when lactose is not present in the Lac Operon?

A

The regulatory gene (Lac L) produces the lac repressor, which is a transcription factor that binds to the operator site when there’s no lactose present. This blocks transcription as RNA Polymerase cannot bind to the promoter.

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17
Q

What happens when lactose is present in the Lac Operon?

A

When lactose is present, it binds to the repressor, changing the repressor’s shape so it can no longer bind to the operator site. RNA Polymerase can now begin the transcription of the structural genes.

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18
Q

How is mRNA edited at a post-transcriptional level?

A

1) Genes in Eukaryotic DNA contain sections that don’t code for amino acids (introns).
2) During transcription, introns and exons (sections of DNA that do code for amino acids) are both copied into mRNA.
3) mRNA strands containing introns and exons are known as primary mRNA transcripts (pre-mRNA).
4) Introns are removed from pre- mRNA via a process known as splicing- introns removed and exons joined, forming mature mRNA.
5) This takes place in nucleus
6) Mature mRNA leaves nucleus for next stage of protein synthesis- translation.

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19
Q

How does cAMP activate proteins at the post-translational level?

A

1) protein activation is controlled by molecules such as hormones and sugars.
2) Some of these molecules work by binding to cell membranes and triggering the production of cyclic-AMP inside the cell.
3) cAMP then activates proteins in the cell by altering their 3D structure.
4) This can alter the active site of an enzyme, making it more or less active.

20
Q

How does cAMP activate protein Kinase A (PKA)?

A

1) PKA = enzyme made of 4 subunits
2) when cAMP isn’t bound, the 4 bound subunits are inactive
3) when cAMP binds, it causes a change in enzyme’s 3D structure= releases sub units= PKA becomes active.

21
Q

What is a body plan?

A

The general structure of an organism that are arranged in a particular.

22
Q

What molecules control the development of a body plan?

A

Proteins.

23
Q

What are homeobox genes?

A

a DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development.

24
Q

What can happen with a mutation in a homeobox gene?

A

Mutations in a homeobox may change large-scale anatomical features of the full-grown organism.

25
Q

What are Hox genes?

A

genes that code proteins that control the development of a body plan.

26
Q

What organisms have similar hox genes?

A

Plants
Animals
Fungi

27
Q

What does it mean if organisms have similar hox genes?

A

Body plan development is controlled in a similar way.

28
Q

What are the highly conserved regions on a hox gene called?

A

homeobox sequences.

29
Q

What do homeobox sequences show?

A

sequences have changed very little during the evolution of organisms that possess homeobox sequences.

30
Q

How do Hox genes control development?

A

1) homeobox sequences code for a part of a protein known as the homeodomain.
2) homeodomain binds to specific sites on DNA, enabling protein to work as a transcription factor.
3) The proteins bind to DNA at the start of developmental genes, activating or repressing transcription and so altering the production of proteins involved in the development of body plan.

31
Q

What is apoptosis?

A

a highly controlled process that is also known as programmed cell death.

32
Q

Once apoptosis has been triggered, how is a cell broken down?

A

1) enzymes in cell break down important cell components such as proteins in cytoplasm and DNA in nucleus.
2) As the cell’s contents are broken down it begins to shrink and break up into fragments.
3) cell fragments are engulfed by phagocytes and digested.

33
Q

What does apoptosis do after mitosis and differentiation?

A

apoptosis refines body parts that have been created via mitosis and differentiation by removing unwanted structures.

34
Q

Examples of apoptosis

A

tail cells of tadpoles removed when they start to grow into frogs
connective tissue between fingers and toes undergos apoptosis to separate the digits.

35
Q

Apoptosis and response to internal stimulus:

A

internal stimulus may be DNA damage. if damage is detected then cell cycle may stop, or pause due to the expression of genes. This could then trigger apoptosis.

36
Q

Apoptosis and response to external stimulus:

A

external stimulus such as stress caused by lack of nutrient availability, could result in gene expression that prevents the cell from undergoing mitosis. Gene expression which leads to apoptosis being triggered can also be caused by external stimulus such as attack of a pathogen.

37
Q

Substitution

A

one or more bases swapped for another

38
Q

deletion

A

one or more bases removed

39
Q

insertion

A

one or more bases added.

40
Q

What is a frameshift?

A

when the base sequence shifts left or right due to insertion or deletion.

41
Q

what does the order of DNA bases in a gene determine?

A

the order of amino acids in a particular protein.

42
Q

What effect does a mutation have on a protein?

A

the primary structure (amino acid chain) of the protein it’s coding for may be altered. This may change the final 3D shape of the protein so it doesn’t work properly. e.g active sites in enzymes may not form properly, meaning substrates can’t bind to them.

43
Q

What is a neutral mutation?

A

Also known as a silent mutation. Changes a base in a triplet, but the amino acid that it codes for remains the same. This is because amino acids are coded for by more than one triplet code (degenerate)

44
Q

What is a beneficial mutation?

A

A mutation that has an advantageous effect on an organism- increase chance of survival.

45
Q

What is a harmful mutation?

A

A mutation that has a disadvantageous effect on an organism- decrease chance of survival.

OCR A Level Biology- module 6 (3 decks)

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