Mutations and Gene Expression (Topic 8A) Flashcards
a mutation is…
any change to the base nuleotide sequence of DNA
substitution is when…
one or more bases are swapped for another
deletion is when…
one or more bases are removed
addition is when…
one or more bases are added
duplication is when…
one or more bases are deleted
inversion is when…
a sequence of bases is reversed
translocation is when..
a series of bases is moved from one location in the genome to another
some mutations can cause genetic mutations…
genetic mutations
why don’t all mutations affect the order of amino acids?
the genetic code is degenerate
mutagenic agents are…
things that increase the rate of mutations
what ways do mutagenic agents increase the rate of mutations?
- acting as a base
- altering bases
- changes the structure of DNA
what two types of gene control cell division?
tumor supressor genes
proto-oncogenes
when functioning normally what do tumor supressor genes do?
slow cell division by producing protiens that stop cells dividing or cause them to self destruct
when functioning normally what do proto-oncogenes do?
stimulate cell division by producing proteins that make cells divide
a mutated proto-oncogene is called an….
oncogene
malignant tumors are…
cancers
bengin tumors are not….
cancerous
how do malignant tumors spread to other parts of the body?
cells break off the tumors and spread to other parts of the body in the bloodstream
how do tumor cells differ from normal cells?
- nucleus is larger and darker
- irregular shape
- don’t produce all the proteins they need to function correctly
- have different antigens
- they divide more frequently
methylation is…
adding a CH3 group onto something
methylation can control wether…
a gene is transcribed is transcribed and translated
hypermethylation is when….
methylation happens too much
hypomethylation is when…
methylation happens too little
abnormal methylation can cause…
tumors
over exposure to oestrogen is thought to….
increase a womens chance of bresat cancer
the two types of risk factor are…
genetic
environmental
screening can be used to..
look for cancer causing mutations in a persons DNA
stem cells are…
unspecialised cells that can develop into other types of cell
totipotent cells can…
mature into any type of body cell in an organism
pluoripotenet cells can…
mature into any type of cell in the body but not cells that make up the placenta
multipotent cells can…
differentiate into a few different types of cell
unitpotent cells can…
differentiate into only one type of cell
a cardiomyocyte is…
heart muscle cells that make up a lot of tissue in our heart
bone marrow transplants can be used to….
replace the faulty bone marrow in patients that produce abnormal blood cells
bone marrow transplamts can be used to treat…
leukaemia and lymphoma
bone marrow contains…
stem cells that can become specialised to form any type of body cell
what are the 3 sources of stem cell?
- adult stem cells
- embryonic stem cells
- induced pluoripotent stem cells
pros and cons of adult stem cells
pros
obtained from simple operation
cons
can only specialise into a limited type of cells (multipotent)
embryonic stem cells are obtained from…
embryos at an early stage of development
how old are the embryos when embryonic stem cells were obtained from then?
4 to 5 days
pros and cons of embryonic stem cells
pros
can divide an unlimited amount of times and develop into all types of body cell
cons
ethical beliefs about killing an embryo
induced pluripotent cells (iPS) are created in…
the lab
how are iPS cells developed?
adult cells are made to express a series of transcription factors associated with stem cells that cause them to express genes associated with pluripotency
the benefits of stem cell therapy are
they could save lives
they can improve quality of life
could be used to grow a tissue or organ that the body won’t reject
transcription factors are…
protein molecules that control the transcription of genes
the site where transcription factors bind to DNA is….
the promoter
transcription factors control expression by….
controlling the rate of transcription
activators are…
transcription factors that stimulate or increase the rate of transcription
repressors are….
transcription factors the inhibit or decrease the rate of transcription
how do activators stimulate or increase the rate of transcription?
they help RNA polymerase bind to the start of the target gene and activate transcription
how do repressors inhibit or decrease the rate of transcription?
they bind to the start of the target gene, preventing RNA polymerase from binding, stopping transcription
oestrogen binds to a transcription factor called an…..
oestrogen receptor
when oestrogen binds to a oestrogen receptor what is formed?
an oestrogen - oestrogen receptor complex
after an oestrogen-oestrogen receptor complex forms what happens?
it moves from the cytoplasm into the nucleus where it binds to specific DNA sites near the strat of the target gene
the oestrogen-oestrogen receptor complex can act as…
a repressor of transcription
and an activator of transcription
RNAi molecules are…
small lengths of non-coding RNA
RNA interference is abbriviated to…
RNAi
what does RNAi do?
stops mRNA from target genes being translated into proteins
What does miRNA and siRNA stand for?
Micro RNA
Small interfering RNA
How do miRNA and siRNA Differ?
miRNA isn’t fully complementary to the mRNA, because it less specific than siRNA it can target more than one mRNA molecule
epigenetics is…
the process by which environmental factors cause heritable changes in gene function without changing DNA base sequence
what are the 2 epigenetic mechanisms used to control gene expression?
increased methylation of DNA
decreased acetylation of histones
how does methlyation of DNA cause a gene to not be expressed?
increased methylation changes the DNA structure so the transcriptional machinery can’t interact with the gene
histones are…
proteins that DNA wraps around to form chromatin which makes up chromosomes
how condensed the chromatin is affects the…
accessibility of the DNA and wether or not it can be transcribed
how can histones be epigenetically modified?
by addition or removal of acetyl groups
when histones are acetylated…
the chromatin is less condensed so the transcriptional machinery can access the DNA allowing genes to be transcribed
when acetyl groups are removed from histones…
the chromatin becomes highly condensed and genes in the DNA cannot be transcribed because the transcriptional machinery cannot physically access them
what enzyme is responsible for removing acetyl groups?
histone deacetylase
are epigenetic changes reversible?
yes
phenotype is…
the observable characteristics of an organism that is a result of the genotype and its environment
