Mutations and Gene Expression Flashcards
define stem cells?
cells that can divide and differentiate to become diff types of cell
totipotent stem cells
can divide and differentiate into any type of specialised cell
- very early mammalian embryos
- can form placenta cells
pluripotent stem cells
can differentiate into MANY types of specialised cell
- embryo and adult cells
- cant make placenta cells
multipotent stem cells
can differentiate into FEW types of specialised cell
unipotent stem cells
can differentiate into ONE type of specialised cell
what can a change in the internal enviro do?
affect expression of genes
cells = specialised (cant be reversed)
conditions within cells control what?
which genes expressed (transcribed and translated)
into proteins
what does RNAi do?
control gene expression by preventing translation
what is siRNA?
- small interfering RNA
- short stranded RNA
- combines with proteins to = siRNA-protein complex
what does siRNA do?
- siRNA = single stranded
- has complementary base sequence to target mRNA
- siRNA-protein complex breaks down mRNA into pieces
- prevents translation
- mRNA pieces recycled
what does microRNA do?
- combines with protein = microRNA-protein complex
- binds to mRNA by comp base pairing
- less specific than siRNA - works on more than one mRNA
- prevents translation - prevents ribosome attaching
- mRNA stored / recycled
what are transcription factors
proteins that control the rate of protein synthesis by switching some genes on and other genes off
what are promoter regions
short sequence of DNA at start of gene
how transcription factors work?
- TF move from cytoplasm to nucleus
- binds to promoter region
- activators - help RNA polymerase bind to gene (TRANSCRIBED)
- repressors - prevent RNA polymerase binding to gene (NOT TRANSCRIBED)
what can transcription factors also be turned on / off by?
second messenger
cAMP
controlling TF
oestrogen example
- oestrogen = steroid hormone
- binds to receptor called oestrogen complex
- forms oestrogen-oestrogen complex
define epigenetics?
changes to gene expression caused by enviro factors ( without changing base sequence of DNA)
what does epigenetics do?
- controls gene expression by preventing transcription
- can be inherited between gen
- helps organisms respond to changes in enviro
More Methylation =
Terminates Transcription
what are CpG sites
where C and G next to each other in DNA
what do methylated CpG sites prevent?
transcription enzymes attaching (RNA polym)
transcription prevented
less acetylation of histones =
Terminates Transcription
what are histones
proteins that supercoil DNA into chromatin
what does acetylation do?
- acetyl groups make histones space out
- allows transcriptional enzymes (RNA polym) attach
- gene expressed
- enzymes remove acetyl groups
- prevent transcription
bone marrow transplant
- contains multipotent stem cells
- can differentiate into RBC and WBC
- replace faulty bone marrow with new bone marrow = forms new healthy cells
growing new organs
- no donor needed
- induced pluripotent stem cells
- iPS have same antibodies - no organ rejection
advantages of growing new organs and transplants
- saves lives
- improves quality of life
- prevents suffering
ethical issues to growing new organs and transplants
- stem cells taken from IVF embroys which could develop into embryos if implanted
- from fertilisation zygote has right to life
(as you use unfertilised eggs which are triggered to divide)
- adult stem cells not pluripotent
iPS may be future sol
what can transcription be controlled by
methylation
hypermethylation
- TSG
- protein not transcribed
- uncontrolled cell division
hypomethylation
- proto-oncogenes
- more proteins transcribed
- uncontrolled cell division
describe benign tumours
- non-cancerous
- grow slowly
- harmless
- can become malignant
describe malignant tumours
- grow quickly
- destroy tissue
- can break up and spread to blood / lymphatic system
describe what tumour cells look like
- mitosis - more cells dividing
- nuclei - large and odd shaped - more than 1
- cell shape = irregular
- function - loss of normal function
- arrangement - disorganised
how can high levels of oestrogen cause some types of breast cancer
- binds to proteins = transcription factor
- called oestrogen-oestrogen receptor complex
- increases rate of cell division
- inc rate of dna rep
- inc chance of mutations
- inc chance of cancer
define mutation
change to base sequence of DNA
no change to amino acid sequence
- amino acid coded for by more than triplet
- DNA = degenerate
change to single amino acid
- changes one DNA triplet
- changes translation of amino acid
- changes primary structure
- changes hydrogen/ionic bonding
- changes tertiary structure of protein
change to many sequence of amino acids
- frame shift changes sequence of all following dna triplets
- changes all following amino acid sequence
- changes primary structure
- changes hydrogen/ionic bonding
- changes tertiary structure
mutations that change sequence of DNA
- addition
- duplication
- deletion
define induced pluripotent stem cells
treating unipotent stem cells with transcription factors that make them pluripotent
iPS
- use modified virus as vector
- virus inserts TF genes from pluripotent stem cells into DNA of unipotent stem cells
- TF expressed
- make totipotent stem cells this way
embryonic stem cells
- embryos made in lab by IVF
- pluripotent stem cells removed after few days
- embryo destroyed
- pluripotent stem cells differentiate into all types of body cells
adult stem cells
- taken from adults in operation
- adult stem cells = multipotent
- less useful for medicine as cant form every type of cell
how do mutations occur
spontaneous mistakes during dna rep
what do mutagenic agents do
increase rate of mutations
base analogs
chemical that can substitute for normal nucleotide base
SUBSTITUTION MUTATION
radiation
change structure of dna
UV, IONISING
change dna bases
chemicals that react with dna to change its structure
SUB / DELETION
define substitution
one base swapped for another
(no change, dna = degenerate)
define addition
extra base added
define deletion
base removed
- causes frame shift
- all following triplets in sequence affected
define inversion
sequence of bases reversed
- no change
- change few AA
- no frame shift
define duplication
one / more bases repeated
define translocation
sequence of DNA moved from one part of genome to another part of genome
(in same chromosome / to diff chromosome)
