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Green > 6.1.1: Cellular control > Flashcards

6.1.1: Cellular control Flashcards

1
Q

Describe a gene mutation

A

Change in base sequence of DNA ( random and during DNA replication(s phase))

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2
Q

What are the overall causes of gene mutations?

A

Mutagenic agents

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3
Q

Give the 3 main types of mutagenic agents

A
  • Physical mutagens
  • Biological mutagens
  • Chemical mutagens
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4
Q

Give an example and how chemical mutagens work

A

Carcinogens in cigarette smoke change base sequence of DNA by chemical altering bases

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5
Q

Give an example and how physical mutagens work

A

Ionising radiation from x-rays breaks DNA strands

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6
Q

Give an example and how biological mutagens work

A

Viral DNA inserted into genome which changes base sequence of DNA

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7
Q

How can depurification/depyrimidation cause a gene mutation ?

A

Lead to the insertion of an incorrect base

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8
Q

How can free radicals cause a gene mutation ?

A

Affect the structure of nucleotide and disrupt base pairing in DNA

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9
Q

What are the 4 types gene mutation ?

A
  • Point mutation
  • Substitution
  • Insertion
  • Deletion
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10
Q

Describe a point mutation

A

1 base is changed in DNA sequence. Changes primary structure and can change tertiary stricture and shape of protein as different amino acid is inserted in ribosome creating a different polypeptide chain

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11
Q

Describe a chromosomal point mutation

A

Length of DNA is doubled which is called duplication

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12
Q

Describe substitution

A

One nucleotide/base is swapped for a different nucleotide/ base in the sequence

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13
Q

Give an example of a disease which involves substitution

A

Sickle cell anaemia

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14
Q

Describe chromosomal substitution

A

Fragment of one chromosome breaks off and attaches to another chromosome which is called translocation

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15
Q

Describe insertion

A

Extra base is added into DNA sequence which can lead to frameshift

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16
Q

Describe chromosomal insertion

A

Length of DNA is repaired but inserted incorrectly and reversed which is called inversion

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17
Q

Describe deletion

A

A base is removed which can cause frameshift

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18
Q

Describe chromosomal deletion

A

Some of the genetic material is broken off

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19
Q

How can insertion and deletion affect a protein ?

A

Can alter the sequence of bases which changes the codon then amino acid , primary structure and folding/ shape of tertiary structure

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20
Q

What are the 3 effects of gene mutation ?

A
  • Neutral
  • Harmful
  • Beneficial
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21
Q

Describe a neutral effect of a gene mutation

A

It is silent as new codon still codes for the same amino acid ( as DNA is degenerate)

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22
Q

Describe a harmful gene mutation

A

Frameshifts change subsequent codons meaning multiple amino acids are incorrectly coded for

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23
Q

Give an example of a harmful gene mutation

A

Tumour suppressor gene is switched off

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24
Q

Describe and give examples of beneficial gene mutations

A

New amino acids are coded for which create benefits such as lactose tolerance or sickle cell trait which means you’re resistant to malaria

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25
Q

Describe non-dysjunction and how it occurs

A

Aneuploidy leads to polypleudY. Occurs in anaphase 1 or 2 when sster chromatids move to same side and if chromosomes don’t seperate the gamete can have 1 extra or be missing a chromosome. More common in plants

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26
Q

Define aneuploidy

A

Presence of abnormal number of chromosomes

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27
Q

Define polypleudy

A

Presence of more than 2 homologous chromosome sets

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28
Q

In what type of organism does lac operon happen in >

A

Prokaryotes

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29
Q

Where was lac operon discovered in

A
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30
Q

At what level does lac operon operate at ?

A

Transcription level from DNA to RNA

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31
Q

Define an operon

A

Group of structural genes that are controlled together

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32
Q

What do bacteria favour ?

A

Glucose as it requires less energy to digest (if lactose is present glucose is absent)

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33
Q

Give the letters within in the lac operon

A

I POZYA

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34
Q

What does the I in lac operon stand for ?

A

Regulatory gene which codes for repressor protein

35
Q

What does the P in lac operon stand for ?

A

Promoter region for RNA polymerase to bind to

36
Q

What does the O in lac operon stand for ?

A

Operator region which switches Z and Y on and off

37
Q

What does the Z in lac operon stand for ?

A

Lac z codes for Beta galactosidase

38
Q

What does the Y in lac operon stand for ?

A

Lac y codes for lactose permease

39
Q

What is the purpose of RNA polymerase ?

A

Transcribes lac z and lac y

40
Q

What is the purpose of beta galactosidase ?

A

Hydrolyses lactose into glucose and galactose to be used as an energy source

41
Q

What is the purpose of lactose permease

A

Membrane carrier protein to transport lactose into bacterial cell

42
Q

Give the sequence of events within lac operon if lactose is absent (glucose present)

A
  • Regulator gene expressed which produces repressor protein
  • Repressor protein binds to operator region ( P+O ) meaning RNA polymerase is prevented from binding so prevents transcription of structural genes
43
Q

Give the sequence of events within lac operon if lactose is present ( glucose absent)

A
  • Inducer molecule lactose binds to repressor protein
  • Repressor protein dissociates from operator region as it can’t bind due to shape change
  • Promoter region is now unblocked meaning RNA polymerase can bind
  • Lac z and y can now be transcribed
  • mRNA is produced along lac operon
44
Q

In which organisms do transcription factors operate ?

A

Eukaryotes

45
Q

What do transcription factors control ?

A

Up and down regulation of genes

46
Q

What are transcription factors made from ?

A

Proteins or short sections of RNA

47
Q

How do transcription factors work ?

A

Suppress or enhance transcription from DNA to mRNA and control protein synthesis by binding to a different base sequence on DNA to initiate transcription

48
Q

Describe the function and give an example of an enhancer

A

Increases the expression of a gene e.g. a transcription factor as it helps RNA polymerase to bind to promoter

49
Q

What is post transcriptional control ?

A

Pre mRNA is modified before it binds to a ribosome and codes for the synthesis of a protein

50
Q

Give the process of transcriptional control

A

Introns are spliced out and exons remain which creates mature mRNA

51
Q

Define introns

A

non-coding DNA/ sequences of bases which don’t code for amino acids

52
Q

Define exons

A

Coding DNA/ sequences of bases which code for amino acids

53
Q

What is alternative splicing ?

A

Results in multiple mRNA molecules being produced from 1 gene as mRNA is spliced in different ways forming different proteins

54
Q

What is post translational control ?

A

Activation of proteins after translation on a ribosome

55
Q

Give the 5 steps of post translational control

A
  • Signalling molecule e.g. hormone glucagon binds to receptor on cell surface membrane on target cell
  • Transmembrane protein activates another protein
  • This protein activates adenyl cyclase enzyme
  • Enzyme catalyses the formation of cAMP ( secondary messenger molecule) from ATP
  • cAMP activates pKA which catalyses the phosphorylation and activation of proteins
56
Q

Define the function of homeobox genes

A

A subset of homeotic genes which control other genes which control body plan

57
Q

In which organisms are homeobox genes found ?

A

Multicellular ( animals, plants, fungi )

58
Q

What is the homeobox sequence ?

A

A 180bp sequence that is highly conserved ( same bp order as mutations haven’t occured) Codes for a specific sequence of 60 amino acids in a polypeptide synthesised protein called a homeodomain

59
Q

How does a homeodomain operate ?

A

Folds into 3 alpha helix’s. Helix turn helix between 2nd and 3rd helix which shape allows protein to bind to DNA to up and down regulate the transcription of nearby genes.

60
Q

What does the homeodomain act as ?

A

A transcription factor as it can help RNA polymerase to bind to the promoter and control the expression of genes

61
Q

What are hox genes ?

A

subset of homeobox genes which control body plan development

62
Q

Where are hox genes only found?

A

In bilaterian animals ( symetrical)

63
Q

What are the 2 types of linearity within hox genes ?

A

Spatial and temporal linearity

64
Q

What is spatial linearity?

A

Order of genes along chromosome matches the expression pattern along embryo for the body plan

65
Q

What is temporal linearity ?

A

Expression of genes occur in temporal order, firstly expression of anterior hox genes

66
Q

What is spatial and temporal linearity combined called ?

A

Colinearity

67
Q

Where are hox gene found ?

A

Next to eachother on chromosomes in clusters

68
Q

Why do humans have more hox genes than fruit flies ?

A

They are more complex

69
Q

What are homeotic mutations ?

A

Hox gene is mutated and body develops incorrectly

70
Q

When are hox genes expressed ?

A

In early development along the anterior-prosterior axis of organism

71
Q

What happens when a hox gene is expressed ?

A

It codes for a protein/ transcription factor

72
Q

What can hox genes act as by controlling the expression of other genes ?

A

Regulatory genes by regulating cell growth and cell specialisation

73
Q

How do hox genes control the development of the human body plan ?

A

Coding for protein synthesis that is essential for embryonic development

74
Q

Why is the cell cycle controlled by genes ?

A

To ensure new cells are only made when they are needed for GROWTH and REPAIR to preserve energy and prevent tumour formation

75
Q

How do tumour suppressor genes operate ?

A

Make proteins that stop the cell cycle from continuing

76
Q

How is the cell cycle initiated ?

A

Proto-oncogens which produce proteins to initiate it

77
Q

What internal stimuli can affect hox genes ?

A

Hormones of psychological stress

78
Q

What external stimuli can affect hox genes?

A

Temperature

79
Q

What do different rates of transcription of a gene determine ?

A

The rate of protein production and therefore the rate for enzymes involved in cell division production

80
Q

What can genes which regulate the cell cycle respond to ?

A

Chemical stimuli

81
Q

What is apoptosis ?

A

Programmed cell death

82
Q

What are blebs ?

A

Evidence the cytoplasm is shrinking in

83
Q

Give the 4 stages of apoptosis

A
  • Nucleus condenses as cell shrinks
  • Blebs form
  • Blebs form apoptic bodies as nucleus fragments
  • Phagocyte engulfs apoptic bodies
84
Q

How do activated genes help promote the correct development of each body segment ?

A

By regulating genes in mitosis, apoptosis and cell differentiation by switching on or suppressing genes

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