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A level Bio OCR A > 6.1.1 Cellular control > Flashcards

6.1.1 Cellular control Flashcards

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1
Q

gene mutations - substitution

A

one or more bases are swapped for another

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2
Q

gene mutations - deletion

A

one or more bases are removed

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3
Q

gene mutations - addition

A

one or more bases are added

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4
Q

what is mutation

A

the order of DNA bases in a gene determines the order of amino acids in a particular protein

a mutation could change the primary structure of a protein and alter its function
- changed find 3D shape

a mutation could be neutral

mutations could also affect whether or not a protein is produced
- eg. if a mutation occurs at the start of the gene so RNA polymerase cant bind to it and begin transcription, the protein will not be made

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5
Q

Neutral mutation

A

the mutation changes a base in a triplet, but the amino acid the triplet codes for does not change
- because some amino acids are coded for by more than one triplet

mutation could change the amino acid BUT the amino acid is chemically similar to the original so it functions like the original amino acid so neutral effect on the protein

the mutated triplet codes for an amino acid not involved with the proteins function
- far away from active site

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6
Q

Beneficial mutation

A

have an advantageous effect on an organism - increase chance of survival

eg. some bacteria break down certain antibiotics which make them antibiotic resistant

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7
Q

Harmful effects

A

have a disadvantageous effect on an organism - decrease chance of survival

eg. cystic fibrosis can be cause by a deletion of three bases that code for the CFT regulator protein so it folds incorrectly so its broken down, leads to excess mucus production

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8
Q

what is gene expression?

A

switching genes on and off

all cells carry the same genes but the structure and function of cells differ because not all the genes are expressed - they are selectively switch on or off

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9
Q

where is gene expression controlled?

A

transcriptional

post-transcripitional

post-translational

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10
Q

gene expression at transcriptional level - what controls it

A

TRANSCRIPTION FACTORS - proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription

  • activators increase
  • repressors decrease
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11
Q

Transcription factors

A

control rate of transcription

the shape of transcription factors determines whether it can bind to DNA or not
- this can be altered by binding of molecules (hormones/sugars)

the number of certain molecules in a cell can control the synthesis of some proteins by affecting transcription factors binding

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12
Q

gene expression at transcriptional level - eukaryotes

A

transcription factors bind to specific DNA sites near the start of their target genes

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13
Q

gene expression at transcriptional level - prokaryotes

A

often involved transcription factors binding to operons

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14
Q

gene expression at transcriptional level - operons

A

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

structural genes - code for useful proteins (enzymes)

control elements:
promoter - a DNA sequence located before the structural gene that RNA polymerase binds to)
operator - a DNA sequence that transcription factors bind to

regulatory gene - codes for an activator or repressor

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15
Q

gene expression at transcriptional level - the Lac operon in E. coli

A
  1. E.coli is a bacterium that respired glucose but can use lactose if glucose is not available
  2. the genes that produce the enzymes needed to respire lactose are found on the lac operon
  3. the lac operon has 3 structural genes - lacZ, lacY and lacA, which produce proteins that help the bacteria digest lactose (B-galactoside and lactose permease)
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16
Q

gene expression at transcriptional level - the Lac operon function

A

Lactose NOT present:
the regulatory gene (lacI) produces the lac repressor, which is a transcription factor that binds to the operator site when there is no lactose present
- this blocks transcription because RNA polymerase cant bind to the promoter

lactose PRESENT:
when lactose is present it binds to the repressor, changing the repressors shape so it can no longer bind to the operator site
- RNA polymerase can now bind to the promoter and begin transcription of the structural genes

17
Q

gene expression at post-transcriptional level

A

mRNA is edited
1. genes in eukaryotic DNA contain sections that don’t code for amino acids - INTRONS (exons do code)

  1. during transcription the introns and exons are both copied onto mRNA
    - mRNA strands with introns and exons are PRIMARY mRNA TRANSCRIPTS
  2. introns are removed from primary mRNA strands by SPLICING
    - introns are removed and exons joined, forming MATURE mRNA strands

this takes place in the nucleus

  1. the mature mRNA then leaves the nucleus for translation
18
Q

gene expression at the post-translational level

A

cAMP activates some proteins

  1. some proteins arent functional straight after they have been synthesized
    - they need to be activated to work
  2. proteins activation is controlled by molecules (hormones and sugars)
  3. some of these molecules work by binding to cell membranes and triggering the production of CYCLIC AMP inside the cell
  4. cAMP then activates proteins inside the cell by altering their 3D structure
    - this could change the active site of an enzyme making it more or less active
19
Q

gene expression at the post-translational level - cAMP and protein kinase A (PKA)

A

PKA is an enzyme made of four sub-units

when cAMP isn’t bound the four units are bound together and are inactive

when cAMP binds, it causes a change in the enzymes 3D structure, releasing the active subunits

PKA in now active

20
Q

what is a body plan

A

the general structure of an organism

  • how the body parts are arranged
21
Q

what controls the development of body plan?

A

proteins

help set up the basic body plant so that everything is in the right place

22
Q

what codes for the proteins that control body plan development?

A

hox genes

23
Q

why are similar hox genes found in animals, plants and fungi?

A

because body plan development is controlled in a similar way

hox genes have regions called homeobox sequences which are highly conserved
- they have changed very little during the evolution of different organisms

24
Q

How do hox genes control development?

A

HOMEOBOX SEQUENCES - code for part of the PROTEIN called the HOMEODOMAIN

the HOMEODOMAIN binds to specific site on DNA, enabling the protein to work as a transcription factor

the protein binds to DNA at the start of developmental genes, activating or repressing transcription, and so altering the production of proteins involved in the development of the body plan

25
Q

what processes are involved in the development of body plans

A

mitosis and apoptosis

26
Q

what is apoptosis?

A

programmed cell death

  1. enzymes inside the cell break down important cell components, proteins in cytoplasm and DNA in nucleus
  2. as the cells contents are broken down its begins to shrink and break up into fragments
  3. the cell fragments are engulfed by phagocytes and digested
27
Q

what is mitosis?

A

part of the cell cycles where one cell divides to form two genetically identical daughter cells

28
Q

how does apoptosis and mitosis control body plan development?

A

mitosis and differentiation create the bulk part of the body parts

apoptosis then refines the parts by removing unwanted structures
eg. when hands and feet are first developed the digits are connected and are only separated when the cells in the connecting tissue undergo apoptosis

29
Q

how is apoptosis and mitosis controlled?

A

during development genes that control apoptosis and the genes that control mitosis are switched on and off in appropriate cells

this means some cells die whilst some new cells are produced

and the correct body plan develops

30
Q

can genes that control apoptosis and mitosis respond to stimuli?

A

the genes that regulate apoptosis and progression through the cell cycle (mitosis) can respond in internal and external stimuli

internal:
DNA damage - if detected this can result in the expression of genes that cause the cell cycle to be paused and can even trigger apoptosis

external:
stress by a lack of nutrient availability - could result in genes expression that prevents cell from undergoing mitosis.
attack of a pathogen - triggers gene expression which leads to apoptosis

A level Bio OCR A (12 decks)

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