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OCR A BIOLOGY > 6.1 cellular control > Flashcards

6.1 cellular control Flashcards

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1
Q

What is a mutation

A

The change in the sequence of bases in DNA.

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2
Q

what is a point/substitution mutation?

A

when one nucleotide is replaced with a different base, changing that particular codon

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3
Q

what is a deletion muation?

A

when one nucleotide is missing causing every following codon to change

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4
Q

what is an insertion mutation?

A

when one nucleotide is added causing every following codon to change

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5
Q

what types of mutation are frameshift mutations?

A

deletion and insertion

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6
Q

What are the three types of point/substitution mutation?

A
  • Silent
  • nonsense
  • missense.
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7
Q

What is a silent mutation?

A

When the protein doesn’t change due to a mutation in a non-coding region, or coding for the same amino acid,

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8
Q

What is the nonsense mutation?

A

When a stop codon is formed instead of an amino acid, resulting in a shortened non functioning polypeptide.

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9
Q

What is a missense mutation?

A

When a different amino acid is in the primary structure of the protein. these can be silent, beneficial or harmful.

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10
Q

What a conservative mutations?

A

When the new amino acids have similar properties to the original ones,

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11
Q

What are non-conservative mutation?

A

When new amino acids have different properties to the original ones,

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12
Q

What can be the causes of mutation?

A
  • DNA replication
  • spontaneous depurination/depyrimidination
  • X-Rays
  • deaminating agents
  • base analogs
  • viruses
  • alkylating agents.
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13
Q

What are the four types of chromosome mutation?

A
  • Deletion
  • duplication
  • translocation
  • inversion
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14
Q

What is a deletion chromosome mutation?

A

When sections of chromosomes break off or are lost.

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15
Q

What is a duplication chromosome mutation?

A

When sections of chromosomes are duplicated

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16
Q

What is the translocation chromosome mutation?

A

When sections of chromosomes break off and join another non homologous chromosome.

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17
Q

What is an inversion chromosome mutation?

A

When section breaks off and joins in reverse.

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18
Q

What are histones?

A

Proteins with DNA associates with to form a complex called chromatin. The chromatin van coils and condenses to form chromosomes.

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19
Q

What other two types of chromatin

A
  • Heterochromatin
  • euchromatin.
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20
Q

What is heterochromatin

A

Tightly wound DNA causing chromosomes to be visible in cell division. This means transcription is not possible as RNA polymerase can’t access for genes.

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21
Q

What is euchromatin?

A

Loosely wound DNA present during interphase. The genes can be freely transcribed, allowing protein synthesis to occur.

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22
Q

What two ways can histones be modified?

A

By adding an acetyl group or phosphate group.
By adding a methyl group.

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23
Q

How does adding an acetyl group or phosphate group modify a histone?

A

It reduces the positive charge of the histones so dna coils less tightly, allowing certain genes to be transcribed.

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24
Q

How does adding a methyl group modify a histone?

A

It makes the histone more hydrophobic, so they bind more tightly to the DNA. This prevents transcription of genes.

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25
Q

What are operons?

A

A group or a cluster of genes that are controlled by the same promoter. They were first identified in prokaryotic cells.

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26
Q

What is a regulatory gene?

A

The gene, that when expressed leads to the production of a repressor protein.

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27
Q

What is an operator?

A

Where the repressor protein binds in the absence of lactose.

28
Q

What is a promoter?

A

Where the rna polymerase binds to begin transcription?

29
Q

What is a structural gene?

A

They are transcribed to produce enzymes that break down lactose.

30
Q

What is the lac operon

A

A length of DNA with a promoter region operator region and repressive proteins.

31
Q

When may bacteria such as E coli use lactose as respiratory substrate.

A

When glucose is in short supply.

32
Q

What happens on the lac operon when there is no lactose?

A

The regulatory gene codes for the repressor protein, which binds to the operator preventing RNA polymerase binding to the promoter region. This means the genes can’t be transcribed, so the enzymes needed for the metabolism of lactose aren’t made.

33
Q

What happens on the lac operon when there is lactose?

A

The lactose binds to the repressor protein, which changes its shapes of it can no longer bind to the operator. This allows RNA polymerase to bind to the promoter region and transcribed the genes needed to make the two enzymes to metabolise lactose.

34
Q

What is a transcription factor

A

A protein or short non-coding RNA that can combine with a specific site on a length of DNA, and inhibit or activate transcription of the gene.

35
Q

What is an exon?

A

The coding or expressed region of DNA

36
Q

What is an intron?

A

a non-coding region of DNA

37
Q

What is an example of a transcription factor?

A

cAMP binding to CRP which leads to an increase in transcription of the Lac Operon structural genes

38
Q

How did transcription factors work?

A

Some transcription factors bind to the promoter region of the gene which will allow or prevent transcription. Therefore the rate of transcription will either increase or decrease.

39
Q

What is splicing?

A

The removal of introns from pre mRNA molecules and the fusing together of exons to form mature mRNA. This ensures that only the coding sections of the mRNA are used to form proteins.

40
Q

What makes up post transcriptional modification?

A
  • splicing
41
Q

What is apoptosis?

A

Programmed cell death.

42
Q

What is the homeobox sequence?

A

The sequence of 180 base pairs excluding introns found within genes were involved in regulating patterns of anatomical development in animals, fungi and plants.

43
Q

What are Hox genes

A

A subset of homeobox genes found only in animals involved in formation of anatomical features in correct locations of body plans.

44
Q

What are homeobox genes?

A

A group of genes that contain a homeobox, which is a section of DNA, 180 base pairs long, and is highly conserved, found in plants, animals and fungi.

45
Q

What are examples of post translational control?

A
  • addition of a non-protein group
  • modifying amino acids, forming bonds like disulfide bridges
  • folding or shortening proteins
  • modification by cAMP
46
Q

How is gene expression controlled in transcription?

A
  • chromatin structural changes
  • transcription factors
  • epigenetics
  • operons
47
Q

How does epigenetics control transcription

A

There are changes that affect how the genetic code is read. For example, acetylation of histones increases the rate of transcription, whereas methylation of histones stops the transcription.

48
Q

How can gene expression be controlled post transcription?

A
  • mRNA processing
  • mRNA editing
49
Q

What is mRNA processing?

A

The removal of introns from pre mRNA molecules and the fusing together of exons to form mature mRNA. This ensures that only the coding sections of the mRNA are used to form proteins.

50
Q

What is mRNA editing?

A

The addition, deletion or substitution of nucleotides which increases the range of proteins that can be produced from a single mRNA molecule or gene.

51
Q

How can gene expression be controlled during translation

A

through the control of mRNA binding:
- degredation of mRNA
- inhibitory proteins
- initiation factors

52
Q

How can the degradation of mRNA control translation?

A

The molecules are more resistant to being broken down by Enzymes will last longer in the cytoplasm So a greater quantity of protein can be synthesised.

53
Q

How can inhibitory proteins control translation?

A

They bind to mRNA to prevent it binding to ribosomes, stopping protein synthesis.

54
Q

How can initiation factors control translation

A

They aid the binding of mRNA to ribosomes.

55
Q

How can gene expression be controlled post translation

A

Polypeptide modification.

56
Q

How can polypeptide be modified?

A
  • addition of a non-protein group
  • modifying amino acids, forming bonds like disulfide bridges
  • folding or shortening proteins
  • modification by cAMP
57
Q

What is apoptosis?

A

Programmed cell death.

58
Q

What are conserved genes?

A

genes that have remained unchanged throughout the evolution of different descendant species.

59
Q

How is the homeodomain sequence folded?

A

Two helices connected by one turn. Which allows the protein to bind to DNA.

60
Q

What is a homeotic mutation?

A

When a mutated body part ends up developing in the wrong place on the body,

61
Q

When are hox genes expressed?

A

In early embryonic development along their head-tail axis of the organism.

62
Q

what are hox genes regulated by.

A

gap genes and pair-rule genes.

63
Q

What is mitosis regulated by and why?

A

It is regulated by homeobox and hox genes to ensure that each new daughter’s cell contains the full genome.

64
Q

What is the process of apoptosis?

A
  1. Enzymes break down cytoskeleton
  2. Cytoplasm becomes dense with tightly packed organelles.
  3. cell surface membrane changes in small protrusions form.
  4. Chromiting condenses the nuclear envelope and DNA breaks into fragments
  5. cell breaks into vehicles that are ingested by phagocytes
65
Q

What molecules control apoptosis?

A

signalling molecules such as cytokines, hormones, growth factors, and nitric oxide.

66
Q

how can apoptosis be seen in the development of the human body.

A
  • The separation of the digits from each other
  • the removal of ineffective or harmful T cells during the development of the immune system.

OCR A BIOLOGY (21 decks)

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