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Biology - Module 6 > 6.1.1 - Cellular Control > Flashcards

6.1.1 - Cellular Control Flashcards

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1
Q

What is a gene mutation?

A

A change in the DNA’s base sequence which can occur spontaneously during DNA replication

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2
Q

What are mutagenic agents?

A

Outside factors which increase the rate of mutations

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3
Q

What are the 3 types of gene mutation?

A
  • Deletion
  • Substitution
  • Insertion
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4
Q

What is deletion?

A

When a nucleotide is removed from a DNA sequence causing a frameshift which is a change to the sequence of triplets. A deletion of 3 bases will not cause a frameshift but an amino acid will be missing from the polypeptide.

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5
Q

What is the effect on the polypeptide of deletion?

A

This changes the sequence of amino acids which are coded for and results in a large change to the primary structure of the resulting protein meaning it may be non-functional

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6
Q

What is substitution?

A

When a base is swapped out for a different one. This only affects a single triplet in the DNA sequence.

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7
Q

What is the effect on the polypeptide of substitution?

A
  • Non-sense: the new sequence is a STOP codon so the polypeptide would be truncated
  • Mis-sense: the triplet codes for a different amino acid having a different effect depending on the substituted amino acid and where in the protein it is found
  • Silent: the substituted nucleotide still codes for the same amino acid having a neutral effect
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8
Q

What is insertion?

A

When one or more nucleotides are added to a DNA sequence. This either results in a frameshift or in the addition of an extra amino acid.

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9
Q

What is the effect on the polypeptide of insertion?

A

If a frameshift occurs the polypeptide will be disrupted with a different amino acid sequence. The resulting protein may be non-functional.

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10
Q

Why might gene mutations be harmful?

A

Mutations which do change the protein’s primary structure alter the bonds within its tertiary structure. This can result in a non-functional protein which may be harmful for the organism.

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11
Q

Why might gene mutations be beneficial?

A

Mutations which do change the protein’s primary structure alter the bonds within its tertiary structure. This can result in a new protein which is beneficial for the organism.

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12
Q

What are the 3 levels of gene expression?

A
  • Transcriptional
  • Post-transcriptional
  • Post-translational
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13
Q

What is an active gene?

A

A gene which is transcribed and translated resulting in a polypeptide

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14
Q

What is a structural gene?

A

A gene which codes for a protein that has a function within the cell

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15
Q

What is a regulatory gene?

A

A gene which codes for a protein that controls structural genes

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16
Q

What is a promoter?

A

A promoter enables the transcription of structural genes because its the binding site for the enzyme that carries out transcription which is RNA polymerase.

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17
Q

How is gene expression controlled at the transcriptional level in prokaryotes?

A
  • The regulatory gene produces a repressor protein
  • The repressor protein binds to the operator
  • RNA polymerase is then unable to bind to the promoter
  • RNA polymerase can’t transcribe structural genes
18
Q

What is an operon?

A

A cluster of structural genes that is under the control of one promoter

19
Q

When is the lac operon active?

A

When lactose is present

20
Q

How is the lac operon activated?

A
  • Regulatory gene produces repressor protein
  • Lactose binds to repressor protein and changes its tertiary structure
  • Repressor protein unable to bind to operator
  • RNA polymerase binds to promoter
  • RNA polymerase transcribes structural genes
21
Q

How is the lac operon inactivated?

A
  • Regulatory gene produces repressor protein
  • Repressor protein binds to operator
  • RNA polymerase unable to bind to promoter
  • RNA polymerase can’t transcribe structural genes
22
Q

Why isn’t the lac operon always on?

A

The structural genes coding for lactose digestion are only active when lactose is present which ensures that ATP isn’t wasted on expressing the genes coding for lactose digestion when lactose isn’t present.

23
Q

What does a DNA sequence in a eukaryotic cell not contain?

A

An operator

24
Q

How do transcription factors in eukaryotes stimulate gene expression?

A
  • Regulatory gene produces transcription factor which stimulates gene expression
  • Transcription factor binds to promoter
  • Transcription factor enables RNA polymerase to bind to promoter
  • RNA polymerase transcribes structural genes
25
Q

How are transcription factors activated?

A

A hormone enters the cell and diffuses into the nucleus. It then binds to the inactive transcription factor and activates it.

26
Q

What does control at the post-transcriptional level describe?

A

The changes primary mRNA goes through after transcription to ensure it is ready for translation

27
Q

What changes does primary mRNA go through to ensure it is ready for translation?

A

RNA splicing occurs where the non-coding introns are removed and RNA editing occurs where some RNA bases are substituted, deleted or added in. This creates a mature mRNA which is ready for translation.

28
Q

What does control at the post-translational level describe?

A

The changes a protein goes through after translation to ensure the protein is ready to perform a specific function in the cell. After translation a protein needs to be activated.

29
Q

How are proteins activated?

A
  • Cyclic AMP binds to and activates an enzyme called protein kinase
  • Protein kinase then phosphorylates the protein which changes the protein’s tertiary structure and activates it
  • The activated protein can now perform a specific function in the cell
30
Q

What is an organism’s body plan?

A

The observable, spatial arrangement of an organism’s body parts including any symmetry in the way the body parts are arranged

31
Q

What is a homeobox gene?

A

A type of regulatory gene which controls the initial development of an organism’s body plan

32
Q

When are homeobox genes active?

A

During the embryonic stage

33
Q

What do homeobox genes contain?

A

A DNA sequence called a homeobox

34
Q

What do homeoboxes do?

A

It codes for the homeodomain which is the transcription factor’s DNA binding site

35
Q

Why do biologists say homeobox genes and homeoboxes are highly conserved by natural selection?

A

This is because the homeobox found in all plants, animals and fungi is very similar

36
Q

What is a hox gene?

A

A type of homeobox gene that is only found in animals

37
Q

Which 2 cellular processes control the development of body plans?

A

Mitosis and apoptosis

38
Q

What does mitosis do?

A

Produces new cells for growth, repair and reproduction

39
Q

What does apoptosis do?

A

Removes old cells or cells that are no longer needed

40
Q

What are mitosis and apoptosis controlled by?

A

Hox genes which respond to internal stimuli such as DNA damage or external stimuli such as stress

Biology - Module 6 (6 decks)

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