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Biology > Cellular Control-6.1 > Flashcards

Cellular Control-6.1 Flashcards

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1
Q

What is a somatic mutation?

A

-mutations associated with mitotic division
-may be associated with development of cancerous tumours
-these mutations are not passed on to offspring

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2
Q

What mutations may be inherited by offspring?

A

-mutations associated with meiosis and gamete formation

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3
Q

What are the 2 main classes of DNA mutation?

A

-point/substitution mutation
-insertion or deletion mutation

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4
Q

What is a point/substitution mutation?
List the 3 types of point mutation?

A

-when one base pair replaces (is substituted for) another

3 types
-silent,missense,nonsense

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5
Q

What is a silent mutation?

A

-it is a point/substitution mutation involving a change to the base triplet, where the triplet still codes for the same amino acid
-the primary structure of the protein and therefore the secondary and tertiary structure is not altered

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6
Q

What is a missense mutation?

A

-a change to the base triplet sequence that leads to a change in the amino acid sequence in a protein

-this point /substitution mutation may have a significant effect on the protein produced by altering the primary structure this leads to a change of the tertiary structure of the protein thus altering its shape and preventing it from carrying out its normal function

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7
Q

What is an example of a condition that results from a missense mutation?

A

-sickle cell anaemia

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8
Q

What is a nonsense mutation ?

A

-a point mutation that alters a base triplet so that it becomes a stop triplet
-this will severely disrupt the structure of a protein
-the genetic disease muscular dystrophy is the result of a nonsense mutation

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9
Q

What is an insertion or deletion mutation ?

A

-when one or more nucleotides are inserted or deleted from a length of DNA
-This will cause a frame shift (if not added in multiples of 3) a frame shift will severely disrupt the amino acid sequence. This will alter the primary and therefore the tertiary structure

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10
Q

What do insertions or deletions of a triplet of base pairs result in?

A

-the addition or loss of an amino acid

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11
Q

What is the preferred respiratory substrate for the bacterium E.coli?

A

-glucose is the preferred respiratory substrate
-however if glucose is absent and the disaccharide lactose is present ,lactose induces the production of two enzymes (different enzymes are needed to metabolise lactose then glucose)

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12
Q

What two enzymes are needed to metabolise lactose?

A

-lactose permease- allows lactose to enter the bacterial cell
-β-galoctosidase- hydrolyses lactose to glucose and galactose

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13
Q

What is the operator region on the lac operon?

A

-lacO

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14
Q

What are the structural genes on the lac operon?

A

-lacZ- codes for β-galactosidase
-lacY-codes for lactose permease
-lacA-transacetylase

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15
Q

What is the promoter region on the lac operon?

A

-the promoter region (P) is where the enzyme RNA polymerase binds to begin transcription of the structural genes

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16
Q

What are the control sites on the lac operon?

A

-the operator region and the promoter region

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17
Q

What is lacI ?

A

-lacI is a regulatory gene
-it codes for the represor protein that prevents the transcription of the structural genes in the absence of lactose

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18
Q

What happens at the lac operon if lactose is absent?

A

-the regulatory gene is expressed
-the repressor protein produced binds to the operator
-this prevents RNA polymerase from binding to the promoter region
-the repressor protein therefore prevents the transcription of the structural genes lacZ, lacY and lacA
-TRANSCRIPTION IS PROHIBITED
-the enzymes for the metabolism of lactose are not made

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19
Q

What happens at the lac operon when lactose is present?

A

-lactose binds to lacI the repressor protein
-this alters the shape of the repressor protein’s DNA binding site, this prevents it from binding to the operator
-RNA polymerase can then bind to the promoter region and the transcription of the structural genes take place
-thus lactose induces the enzymes needed to break it down

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20
Q

What is a transcription factor?

A

-a protein or short non-coding RNA that can bind to a specific region (promoter region) on a length of DNA to initiate or inhibit transcription of a gene

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21
Q

What uses transcription factors?

A

-eukaryotes

22
Q

How do transcription factors work?

A

-they slide along a part of the DNA molecule seeking and binding to their specific promoter region
-this may then aid or inhibit the attachment of RNA polymerase to the DNA
-so therefore initiates or inhibits the transcription of the gene

23
Q

What are transcription factors essential for?

A

-the regulation of gene expression in eukaryotes

24
Q

What do housekeeping genes code for?

A

-proteins that are constantly required

25
Q

What do tissue specific genes code for?

A

-proteins which are required to carry out short-lived responses
E.g.hormones

26
Q

What is an exon?

A

-the coding or expressed region of DNA

27
Q

What is an intron?

A

-the non-coding region of DNA

28
Q

Describe the process of editing primary mRNA to produce mature mRNA

A

-all the DNA of a gene is transcribed into primary mRNA both introns and exons
-primary mRNA is then edited and the RNA introns are removed (endonuclease enzyme may be involved in the editing and splicing processes)
-the remaining mRNA exons are joined together- this results in the mature mRNA

29
Q

What happens according to how primary mRNA is spliced?

A

-some genes can be spliced in different ways
-a length of DNA with its introns and exons according to how it is spliced can encode more than one protein

30
Q

What can introns be involved in?

A

-some may encode for proteins
-some may become short non-coding lengths of RNA involved in gene regulation

31
Q

What is the post-translational level of gene expression?

A

-post-translational regulation of gene expression involves the activation of proteins
-many enzymes are activated by being phosphorylated

32
Q

How are proteins activated by cyclic AMP?

A

1-A signalling molecule binds to a receptor on the plasma membrane of the target cell.
2 -This activates a transmembrane protein which then activates a G protein.
3 -The activated G protein activates adenyl cyclase enzymes.
4 -Activated adenyl cyclase enzymes catalyse the formation of many molecules of cyclic AMP from ATP.
5 -cyclic AMP activates PKA (protein kinase A).
6 -Activated PKA catalyses the phosphorylation of various proteins, hydrolysing ATP in the process. This phosphorylation activates many enzymes in the cytoplasm
7 -PKA may phosphorylate another protein (CREB protein, cAMP response element binding).
8 -This then enters the nucleus and acts as a transcription factor, to regulate transcription.

33
Q

What is a homeobox gene sequence?

A

-a section of DNA that is 180 base pairs (excluding introns) encoding for a 60-amino acid sequence (Homeodomain sequence ) within a protein
-they code for transcription factors that bind to DNA to regulate transcription by switching genes on and off when they are required at particular stages of development

34
Q

What are 2 features of homeobox gene sequences?

A

-they are similar in plants,animals and fungi
-they are highly conserved

35
Q

What are hox genes?

A

-a subset (type) of homeobox genes
-found only in animals
-involved in formation of anatomical features in correct locations of body plan

36
Q

Suggest 2 characteristics that researchers should look for when choosing an organism for research into how genes control development
(2 marks)

A

-small
-short life cycle

37
Q

What is the role of hox genes?

A

-regulate development of embryos along the anterior-posterior (head-tail) axis
-control which body parts grow where
-arranged in clusters each cluster can contain up to 10 genes
-There is a linear order to the Hox genes in each Hox cluster and this order is directly related to the order of the regions of the body that they affect

38
Q

What can happen if Hox genes are mutated?

A

-abnormalities can occur
-e.g. Drosopila developing legs instead of antennae on head

39
Q

What is a mutagenic agent?

A

-increases likelihood of mutations

40
Q

Mitosis is part of the________ that is _________ with the help of _______ and _________ genes.
It ensures that each new _______ cell contains the full _______ and is a ______ of the parent cell.
During cell differentiation some of the genes in a particular type of cell are _________ __ and not _________.

A

-cell cycle
-regulated
-homeobox
-hox
-daughter
-genome
-clone
-switched off
-expressed

41
Q

What is the Hayflick constant?

A

-the limited number of times a body cell divides before dying

42
Q

State the steps of apoptosis

A

1-enzymes break down the cell cytoskeleton
2-the cytoplasm becomes dense with tightly packed organelles
3-the cell surface membrane changes and small protrusions called BLEBS form
4-chromatin condenses,the nuclear envelope breaks and DNA breaks into fragments
5-the cell breaks into vesicles that are ingested by phagocytic cells (so that cell debris does not damage any other cells or tissues)

43
Q

What is apoptosis?

A

-programmed cell death

44
Q

How is apoptosis controlled?

A

-many cell signals help to control apoptosis e.g.cytokines,hormones,growth factors,nitric oxide
-some of these signalling molecules may be released by cells when the GENES REGULATING THE CELL CYCLE AND APOPTOSIS RESPOND TO INTERNAL CELL STIMULI AND EXTERNAL CELL STIMULI e.g.stress

45
Q

What are some examples of apoptosis controlling the development of the body form ?

A

-during limb development apoptosis causes digits to separate from each other
-removes ineffective or harmful T-lymphocytes during the development of the immune system

46
Q

What should the rate of cells dying through apoptosis be equal to?

A

-the rate of cells produced by mitosis:

47
Q

What are the consequences of not enough or too much apoptosis ?

A

-NOT ENOUGH leads to the formation of tumours
-TOO MUCH leads to cell loss and degeneration

48
Q

An enzyme such as amylase, has a specific 3-dimensional shape
Explain how DNA structure determines the specific shape of enzymes
(4 marks)

A

-DNA codes for protein / polypeptide
-transcription and translation occurs
-an enzyme is a globular protein
-sequence of bases determines sequence of amino acids (primary structure)

49
Q

State what is meant by a homeobox gene
(2 marks)

A

-regulatory/homeotic gene
-initiates transcription/ switches genes on and off

-codes for homeodomain on protein
-control of development

50
Q

Homeobox genes show ‘astonishing similarity across widely different species of animal’
Explain why there has been very little change by mutation in these genes
(2 marks)

A

-these genes are very important
-mutations would have big effects /alter body plan

-many other genes would be affected
-mutation likely to be lethal

51
Q

Much of the _____ in cells contain sequences called genes.
Many genes code for _______________that fold to make enzymes.
Often, enzymes are kept in an _______ form until needed.
These enzymes may then be activated by cAMP which involves changes in their __________ ________

A

-DNA
-inactive
-polypeptides
-tertiary structure shape

52
Q

Describe how a nucleotide base sequence in a gene is used to synthesise a polypeptide

(7 marks)

A
  • DNA transcribed into mRNA
    -free activated RNA nucleotides
    -line up be complementary base pairing
    -catalysed by RNA polymerase

-mRNA moves to ribosomes
-tRNA molecules bind to mRNA
-anticodons bind to codons
-formation of peptide bond between amino acids

Biology (11 decks)

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