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OCR A Bio > genetics of living systems > Flashcards

genetics of living systems Flashcards

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Biology 101 flashcards
1
Q

4 ways genes are regulated

A
  • Transcriptional - genes turned on and off
  • post transcriptional -mRNA can be modified which regulates translation of certain proteins
  • translational - can be stopped or started
  • post translational - proteins can be modified after translation in other organelles
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2
Q

TRANSCRIPTIONAL CONTROL

- 3 different methods

A
  • Chromatin remodelling
  • Histone modification
  • trancription factors (lac operon in bacteria)
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3
Q

Chromatin remodelling

what is heterochromatin?

A

HETEROCHROMIN
—> TIGHTLY wound DNA

—>causes chromatin to be visible during cell division

—> no transcription as RNA polymerase cant access genes

—> ensures NO PROTEIN SYNTHESIS DURING DIVISION

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4
Q

Chromatin remodelling

What is euchromatin?

A

EUchromatin
—> loosely wound DNA
—> can be freely transcribed

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5
Q

Chromatin remodelling

why is it used?

A

ensures protein synthesis only occurs during interphase

—> as it is time + energy consuming

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6
Q

Histone modification

A

histones can be modified to increase/decrease degree of DNA packing

histones are positively charged, DNA is negatively charged

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7
Q

how to cause DNA to coil less tighly

A

ACETYLATION- addition if acetyl group

PHOSPHORYLATION- addition of phosphate group

—> these reduce +ve charge on histones
—> increased repulsion

=> allows certain genes to be transcripted

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8
Q

how to cause DNA to be bound more tightly

A

METHYLATION- addition if methyl group

—>makes histones more hydrophobic
—>DNA coils more tighly
—> prevents transcription

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9
Q

what is epigenetics?

A

external control of gene expression by modificstion of DNA

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10
Q

LAC OPERON

type of genes in lac operon

A

structural genes

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11
Q

LAC OPERON

genes in lac operon

A

lacZ - gene codes for enzyme that breaks down lactose

lacY - gene codes for channel protein to allow lactose into bacterium

lacA - idgaf

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12
Q

LAC OPERON

why do bacteria need operons?

A

-more common in prokaryotes as they are more simple/small structure

=> efficient way of saving resources bc if gene products arent needed, all of genes involved in production can be turned off

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13
Q

LAC OPERON

what gene codes for the repressor?

A

regulatory gene —> lacI

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14
Q

repressor gene function

A

codes for repressor protein( transcription factor)

which binds to the OPERATOR

RNA POLYMERASE cant carry out
transcription

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15
Q

LAC OPERON

when lactose is present

A
  • lactose binds to repressor protein which inactivates it
  • repressor cant bind to operator anylonger
  • RNA polymerase can bind to PROMOTER and carry out transcription
  • three structural genes are synthesised
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16
Q

role if Cyclic AMP (cAMP)

A

RNA polymerase carrys out transcription slowly
needs to be increased to prod right amount of proteins

—> cAMP binds to cAMP receptor protein (CRP)
- activates CRP

which increases transcription rate

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17
Q

role of cAMP

when glucose is low

A

high lvls of cAMP produced

  • more cAMP - CRP compexes
  • more freq transcription
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18
Q

POST TRANSCRIPTIONAL CONTROL

splicing

A

after transcription pre mRNA is made
=> cap added to 5’ end
=> poly adenine tail added to 3’ end
HELPS KEEP mRNA STABLE

SPLICING CAN TAKE PLACE
to make multiple different proteins from one gene
—>introns ( non coding parts) cut off and removed
—> exons (coding parts)joined together

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19
Q

POST TRANSCRIPTIONAL CONTROL

RNA editing

A 
change nucleotide base
SAME CHANGES AS MUTATION
- addition
-deletion
- substitution
20
Q

TRANSLATIONAL CONTROL

3 methods

A

mRNA degradation

-more resistant molecule the longer it will last

21
Q

POST TRANSLATIONAL CONTROL

A

modifications to proteins

22
Q

Mutation

A

change in sequence of bases in dna

23
Q

types of mutations

A

substitution

deletion

insertion

24
Q

mutations

substitution?

A

single nucleotide changes in a codon
=>change in codon
=> may cause change in primary structurr
=> degenerate nature of DNA means codon could still code for the same amino acid

25
Q

insertion mutation

A

addition if a nucleotide in a codon

26
Q

deletion mutation

A

nucleotide is removed from codon

27
Q

cause of insertion or deletion mutation?

A

causes a FRAMESHIFT MUTATION

DNA is read in codons and is non overlapping

insertion/deletion moves the reading frame

=> so each successive codon will now be different and code for different amino acids

28
Q

when does insertion/deletion not cause frameshift mutation

A

when multiples of 3 of nucleotides are added/ deleted

multiples of three correspond to full codons
reading frame wont change

only extra/less amino acids will be added

29
Q

causes of mutations

A

spontaneous mutation

mutagens - physical/chemical/biological

depurination/depyramidation - abscence of a base can lead to insertion of incorrect base im DNA replication

Free radicals(oxidising agents)- cam affect structure of nucleotides /can interfere with base pairing

30
Q

physical mutagens

A

ionising radiations eg x-rays

=> break one/both DNA strands

31
Q

chemical mutagens

A

deaminating agents

  • chemically alters bases in DNA

eg converting cytosine to uracil changing base sequence

32
Q

Biological mutagens

A

ALKYLATING AGENTS
—> methyl/ethyl groups attached to bases
—> results in incorrect base pairing

BASE ANALOGS
—> similar structure to bases
—> incorporates in usual place of base during replication
—> change base sequence

VIRUSES
—> viral DNA may insert itself into genome, changing base sequence

33
Q

Effects of mutations

A

silent

nonsense

missense

34
Q

silent mutations

A

when substitution of a nucleotide changes codon

but due to degenerative nature of DNA

the new codon codes for the same amino acid
=> so overall function if the protein isnt changed

35
Q

nonsense mutations

A

codon become a STOP codon instead of coding for an amino acid

  • creates proteins that are too short so non functional
  • usually have negative effects on phenotypes
36
Q

Missense mutations

A

when a new amino acid is incorporated into protein

due to frame shift mutation from deletion/insertion if codons

37
Q

conservative missense mutations

A

when the new amino acid has similar properties to the original

effect of mutation is less severe

38
Q

non-conservative missense mutations

A

new amino acid has different properties than original

dis functional protein

39
Q

beneficail mutations

A

ability to digest lactose

able to drink milk as an adult
=>helps prevent osteoporosis
=>prevent starving during famines

40
Q

chromosome mutations

A

deletion- section of chromosome is broken off

duplication- sections on chromosome duplicated

Translocation- sections of one chromosome breaks off and joins non-homologous chromosome

Inversion- section of chromosome is reversed

41
Q

Homeobox genes

A

codes for a part of a protein the HOMEODOMAIN which binds to DNA and switches genes on and off

IS A TRANSCRIPTION FACTOR

42
Q

how long is a homeobox?

A

180 base pairs long

so codes for 60 amino acids

43
Q

how conserved is the homeobox

A

HIGHLY conserved in plants, aninmals and fungi

44
Q

Hox genes

A

group of homeobox genes only present in ANIMALS

45
Q

what are Hox genes for

A

they are responsible for correct positioning of body parts

46
Q

how are Hox genes found ?

A

found in gene clusters

mammals have 4 clusters on different chromosomes

47
Q

how many hox genes do humans have

A

at least 39

OCR A Bio (4 decks)

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