genetics + body plans Flashcards

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1
Q

what is a mutation

A
  • changes in sequence of bases in DNA
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2
Q

describe substitution

A
  • mutation
  • one or more bases are swapped for another
  • E.g ATGCCT becomes ATTCCT
  • changes the codon
  • new codon could code for a different amino acid
  • this changes the primary structure of the protein
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3
Q

describe deletion + insertion

A
  • one or more bases are removed/added
  • E.g ATGCCT becomes ATCT/ATGCCT becomes ATGACCT
  • leads to a frameshift mutation
  • shifts the reading frame of the sequences (added/removed)
  • so changes every consecutive codon from the point of mutation
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4
Q

effects of different mutations

A
  • no effect :
  • on phenotype because normal proteins are still synthesised.
  • Damaging :
  • phenotype is affected in a negative way - proteins aren’t being synthesised/synthesised in a non-functioning way.
  • interferes with essential processes.

Beneficial :

  • new and useful characteristic in the phenotype
  • due to synthesis of protein
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5
Q

what increases rate of mutation

A
  • mutagens
  • chemical, physical or biological agent which causes mutations
  • radiation (break strands of DNA)
  • viruses (inserts into a genome changes base sequence)
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6
Q

describe how chromosome mutations occur

A
  • affect the whole chromosome / no. of chromosomes
  • caused by mutagens
  • during meiosis
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7
Q

how can chromosome mutations affect its structure

A
  • deletion : section of the chromosomes breaks of and is lost
  • translocation : part of one chromosome break off and joins another non-homologous chromosome
  • inversion : section of C breaks off, is reversed and then joins back onto C
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8
Q

what are housekeeping genes

A
  • these are always expressed

- the products (e.g enzymes) of these genes are always required to allow the cell to grow

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9
Q

what ways can genes be regulated

A
  • transcriptional : genes turned on/off
  • post-transcriptional : mRNA is modified and regulates translation and the proteins produce
  • translational : translation can be stopped/started
  • post translational : modifying proteins after synthesis, changing their function
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10
Q

describe chromatin remodelling

A
  • transcriptional control
  • transcription isn’t possible when DNA is tightly wound
  • RNAP cant access the genes
  • heterochromatin is tightly wound DNA
  • euchromatin is loosely wound DNA
  • genes in euchromatin transcribed during interphase between cell divisions
  • ensure necessary proteins are synthesised
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11
Q

describe histone modification

A
  • negative DNA coils around positive histones
  • histones can be modified to increase/decrease degree of packing
  • acetylation/phosphorylation causes histone to become more negatively charged so DNA coils less tightly
  • allows transcription of certain genes
  • methylation causes histones to be more
    positive so DNA coils more tightly and prevents transcription
  • Epigenetics = term used to describe this control of gene expression
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12
Q

describe lac operon

A
  • if glucose is in short supply, lactose can be used as a respiratory substrate
  • regulatory gene lacI codes for a repressor gene
  • prevents transcription of structural genes in absence of lactose (down regulation)
  • binds to operator
  • prevents RNA polymerase binding to promoter region

When lactose present:

  • binds to repressor protein
  • changes shape
  • repressor proteins can’t bind to operator
  • RNA polymerase can bind to promoter
  • three structural genes transcribed
  • enzymes are synthesised
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13
Q

why is glucose preferred over lactose

A
  • easier to metabolise
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14
Q

what is an operon + lac operon

A
  • group of genes that are under the control of same regulatory mechanism + expressed at the same time
  • LO is a group of 3 structural genes (lacY, lacZ, lacA) - code for enzymes
  • lacI is a regulatory gene located near the operon.
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15
Q

what increases rate of trancription

A
  • up regulated
  • cAMP receptor proteins (CRP)
  • only possible when CRP binds to cAMP
  • transport of glucose into E.coli decreases levels of cAMP
  • ## decreases rate of transcription for metabolism of lactose
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16
Q

describe post transcription regulation of gene expression

A
  • RNA processing:
  • product of transcription = pre-mRNA
  • modified to form mature mRNA
  • binds to ribosomes and codes for specific protein
  • A cap (modified nucleotide) added to 5’ end
  • tail (chain of adenine nucleotides) added to 3’ end
  • stabilise mRNA
  • delay degradation in the cytoplasm
  • cap aids binding of mRNA to ribosomes
  • splicing = DNA cut at specific point (introns removed , exons joined)

RNA editing:

  • mRNA nucleotide sequence can be modified through base addition, deletion or substitution
  • same effect as point mutations
  • synthesis of diff protein = diff function
  • increases range of proteins produced from mRNA mol
17
Q

What are:

  • introns
  • exons
A
  • non-coding DNA

- coding DNA

18
Q

what regulates the process of protein synthesis

A
  • degradation of mRNA : more resistant mol, longer in the cytoplasm, more protein can be synthesised
  • inhibitory proteins binding to mRNA to prevent it from binding to ribosomes and synthesise proteins
  • activating initiation factors which help mRNA bind to ribosomes
19
Q

describe protein kinases

A
  • enzymes
  • catalyse addition of P to proteins
  • addition of phosphate changes tertiary structure
  • changes function of protein
  • enzymes activated by phosphorylation
  • PK important regulators of cell activity
  • PK activated by cAMP
20
Q

describe post translational control

A
  • modifies proteins that have been synthesised
  • adding non-proteins groups (lipids, carb)
  • folding / shortening proteins
  • modifying amino acids and bond formation (disulphide)
  • modification by cAMP (lac operon cAMP binding to cAMP receptor protein t increase rate pf structural gene transcription)
21
Q

body plan

A

general structure of an organism that is arranged in a particular way

22
Q

homeobox gene

A
  • genes containing a homeobox
  • homeobox : section of DNA 180 base pairs long
  • codes for part of a protein 60 amino acids long
  • that is highly conserved in plants animal and fungi
  • regulatory genes
  • switch genes on/off
23
Q

hox gene

A
  • one group of homeobox genes
  • only in animals
  • responsible for correct positioning of body parts