Gene Expression Flashcards
Give examples of mutagenic agents
High energy ionising radiation
Chemicals
What type of gene mutations are possible
Deletion Substitution Addition Duplication Inversion Translocation
Describe the gene mutation Duplication
One or more bases are repeated
Describe the gene mutation inversión
Base sequence is spliced and reinserted in reverse order
Describe the gene mutation translocation
Base sequence removed from. One chromosome and reinserted into another
Describe the posible outcomes of the gene mutation deletion
Frame shift resulting in non functional DNA
Describe the posible outcomes of the gene mutation substitution
No effect due to degenerate code or in intron
Formation of stop codon or different Amino acid
Describe the posible outcomes of the gene mutation addition
Frame shift resulting in non functional DNA
Describe the posible outcomes of the gene mutation Duplication
Frame shift right resulting in non functional DNA if sequence multiplied is not a multiple of 3
Frame shift to the right
Describe the posible outcomes of the gene mutation inversión
Change to one Amino acid
Or no chnage due to degenerate code
Describe the posible outcomes of the gene mutation translocation
Frame shift resulting in non functional DNA
When do gene mutations occur
During DNA replication
Why is differentiation and specialisation important in cells
No one cell can provide the optimum conditions for every function
How does a zygote divide
By mitosis
How can a zygote produce all the body cells in a human
All cells contain the same genes but some are switched on or off to allow for a particular function
What occurs during differentiation
Certain genes are switched off or on
Why is specialisation more efficient than not having specialised cells
Conserve energy and resources that might go to waste in mechanisms unnecessary for a particular function
Define a stem cell
A cell that retains the ability to become specialised
Why are xylem and red blood cells unable to differentiate
They are so specialised that they don’t have a nucleus and so don’t have the genes that can be turned off or on for specialisation
What general properties do stem cells possess
Able to divide and renew themselves over a long period of time
Unspecialised
Can differentiate into other specialised cells
What are the main sources of stem cells
Bone marrow
Embryo
Umbilical cord blood
Placenta
How are stem cells classified
By their ability tot differentiate
Define totipotent stem cells and give example sof where they are found
Can differentiate into any cell
Early embryo
Define pluripotent stem cells and give example sof where they are found
Can differentiate into almost any cell
embryonic and fetal stem cells
Define multipotent stem cells and give example sof where they are found
Can differentiate into a limited number of cells
Adult stem cells and Umbilical cord blood
Define unipotent stem cells and give example sof where they are found
Can differentiate into one type of cell
Adult tissue
Define the steps to forming a cardiomyocyte
Totipotent cell in Embryo
Pluripotent cell
Multipotent cell able to differentiate into any muscle cell
Unipotent cell only able to differentiate into cardiomyocyte
Cardiomyocyte
What do induced pluripotent cells derive from
Unipotent cells
How are induced pluripotent cells produced
Genes otherwise not expressed are expressed
Induce transcriptional factor synthesis
What do ips cells prove
That all cells contain same genes
How are ips cells different to embryonic stem cells
Able to self renew and unlimited number of times
What is the advantage of ips cells
They can replace embryonic stem cells in research
What disease can be cured using heart cells produced from stem cells
Heart damage
Eg from heart attack
What disease can be cured using skeletal muscle cells produced from stem cells
Muscular dystrophy
What disease can be cured using beta cells produced from stem cells
Type 1 diabetes
What disease can be cured using nerve cells produced from stem cells
Parkinsons Ms Strokes Alzheimers Paralysis
What disease can be cured using blood cells produced from stem cells
Leukemia
Inherited blood diseases
What disease can be cured using skin cells produced from stem cells
Burns and wounds
What disease can be cured using bone cells produced from stem cells
Osteoporosis
What disease can be cured using cartilage cells produced from stem cells
Osteoarthritis
What disease can be cured using retina cells produced from stem cells
Macular degeneration
Pros of using embryonic stem cells
Saves a life of a human already suffering
Embryos from ivf would go to waste anyways
Laws against cloning provide protection against any exploitation
Cons of using embryonic stem cells
Every Embryo has the potential for life
People undermine the respect for life
Move towards reproductive cloning (research knowledge used in other countries with less restrictions)
Embryos are not the only source of stem cells
How is gene expression controlled
Regulation of transcription and translation
Define transcriptional factor
Protein complex with different subunits that binds to DNA and stimulates transcription
Why does each gene have a different transcriptional factor associated with the stimulation of transcription
Each TF has a very specific shape that is only complementary to the promotor region of a specific DNA sequence
How do transcriptional factors stimulate transcription
By binding to the promotor region before a gene, attracting Co factors and stimulating transcription
Define promotor sequence
Base sequence before gene that TF binds to
Describe how inhibitor molecules work
Block DNA binding site preventing action of TF
Competitive inhibition
How do steroid hormones stimulate transcription
Diffuse through bilayer
Bind to TF and activate it
TF changes shape so DNA binding site is comp to promotor region
TF diffuses through nuclear pore into nucleus
Binds to promote region and attracts cofactors
Transcription is stimulated
Give an example of a steroid hormone.
Oestrogen
How can gene expression be reduced
Using small interfering RNA
Explain how small interfering RNA works
An enzyme cuts a large double stranded RNA into smaller sections
One of the two strands combines with an enzyme which is activated using ATP
SiRNA forms hydrogen bonds with the mRNA via comp base pairing
Enzyme cuts mRNA into small sections
No more translation of MRNA
Define epigentics
When environmental factors cause heritable changes in gene expression or function without changing the DNA base sequence
What environmental factor might affect the epigenome
Diet
Exercise
Light exposure
Hormon levels
How do tags affect gene. Expression
Determine shape of DNA histone complex
How does the shape of a DNA histone complex affect transcription
Less condensed or compact = easier binding of transcriptional factors and RNA polymerase
More transcription
How does acetyl action affect transcription
More acetyl groups = less condensed = more transcription
Make histones less positive so repel DNA
What do acetyl groups attach to
Histones
How does methylation affect transcription
More methylation = more condensed = less transcription
Methyl groups prevent binding of transcriptional factors and RNA polymerase.
Attract proteins that condense DNA histones complexes by inducing deacetylation
What occurs to epigenetic tags in the early stages of Embryo development
Most tags are erased but some remain
What two genes play the largest role in cancer development
Tumor suppressor genes and protooncogenes
How can epigenetic therapy be used
Inhibit enzymes involved in methylation to reactivate genes to treat cancer
Diagnostic tests to determine levels of methylation and acetylation
Why must epigenetic therapy be very targeted
Because normal cells will turn cancerous if also treated
How do malignant tumors differ from benign ones
They grow larger
Cancerous
Grow rapidly
Have large dark nuclei due to more DNA
Unspecialised cells as opposed to specialised ones
No adhesion molecules produced so metastasis
No dense tissue capsule so fingerlike projections extend into neighbouring tissue
More likely to be lifethreatening
Systemic affects not localised
Must use radio or chemotherapy to remove not surgery
More frequent reoccurances
Describe how metastasis occurs
Tumor enlarges and grown lymphatic vessels
Tumor cells squeeze into blood and lymphatic vessels
Tumor cells circulate in blood, adhere to blood vessel walls and squeeze into healthy tissue and metastasis
Tumor cells circulate via lymph and metastasis within lymph Nodes
What ways can tumors circulate around the body
Blood lymph
How does one cell cause a tumor
Single cell mutates to have uncontrolled cell division
Cell in lineage mutates again causing differences in appearance and growth
Define oncogene
Mutated proto oncogene causing genes that stimulate cell division to be permanently switched one
How can an oncogene lead to cancer
Permanently switch on receptor protein for growth factors so cell division occurs despite lack of growth factors
May code for growth factor protein which is produced in excess amounts
Lead to uncontrolled cell division
How do growth factors lead to gene transcription
Growth factor binds to cell receptor
Causes transcriptional factor to be activated
Transcriptional factor enters nucleus and Activates transcription
Define tumor suppressor gene
Gene to slow down cell division, repair mistakes in DNA and initiate apoptoisis
How can mutated tumor suppressor genes lead to cancer
Causes gene to be silenced
Non functional growth factor protein produced
Lead to uncontrolled cell division
Define hypermethylation
Over methylation
Define hypomethylation
Under methylation
How can hypermethylation lead to cancer
Hypermethylation of tumor suppressor gene in promotor region
Gene is inactivated (DNA histone complexes more compact)
How does hypomethylation lead to cancer
Less methylation of oncogenes occurs
DNA histone complexes are less compact so more transcription
Uncontrolled cell growth
How is oestrogen produced in post. Menopausal women
Not produced in ovaries
More produced in fat cells of breast
Why is the risk of breast cancer higher in post menopausal women
More oestrogen produced by fat cells in breast
Oestrogen causes activation of transcriptional factors
If the transcriptional factor is complementary to a proto oncogene then tumor occurs
So higher risk of tumor
Tumor occurs = even more oestrogen produced
White blood cells drawn to tumor so more oestrogen produced
What occurs during a genome project
DNA is mapped out
Genes are mapped onto chromosomes
Define bio informatics
Science of celle ting and analysing complex biological data
How is DNA sequenced
Using whole genome shotgun sequnceing
DNA is cut into smaller pieces so more easily sequenced
Algorithms align overlapping segments to assemble entire genome
How has DNA sequnceing been used for medical advances
Single nucleotide polymorphisms detected and associated with certain diseases
Medical screening for snps for early diagnosis and intervention
How has DNA sequnceing been used
Genome sequnceing
Medical advances
Identification of evolutionary links
Define proteome
All proteins coded for by genome
Define complete proteome
All proteins coded for in particular organism at certain time and conditions
Define cellular proteome
All proteins coded for in particular cell at certain time and condition
How can DNA technology be used in simple organisms
Genome exploited and use to help cure and provide knowledge about disease
Genes from extreme files used to clean environment
Why is the determination of a simple organisms genome easy
No histones
Only one piece of circular DNA
No intorns
Why is the determination of a complex organisms genome hard
Intorns
Genes used in the control of other genes expression
What is the main dilemma when sequcing the human genome
Who’s DNA should be used
How do tumor suppressor genes work
They code for a protein that activate apoptoisis or control mitosis
What affects do transcriptional factors have
Activate RNA polymerase
