Gene expression 8.1 Flashcards
a. mutations b. stem cells c. stimulating +inhibiting transcription+translation d. epigenetics e. cancer
a. Name all types of gene mutations?
-Addition
-Deletion
-Substitution
-Inversion
-Duplication
-Translocation
a. What is the definition of an addition mutation?
the inserting of a base into the base sequence causing a frame shift
a. What is the definition of a deletion mutation?
The removal of a base from a base sequence causing a frame shift
a. What is the definition of substitution?
The change of 1 base to a different base
a. What is the definition of inversion?
A group of bases become separated from the DNA and re-join at the same position but in the inverse order
a. What is the definition of duplication?
One or more bases are repeated causing a frame shift
a. What is the definition of translocation?
A group of bases become separated from the DNA base sequence on one chromosome and become inserted into the DNA base sequence of a different chromosome
b. What are the 4 types of stem cells?
-totipotent
-pluripotent
-multipotent
-unipotent
b. What are stem cells?
Undifferentiated cells that can divide and differentiate into specialised cells by expressing only certain genes in the genome
b. What are totipotent cells?
-Can divide and differentiate and produce any type of body cell
-Only the zygote and first couple of divisions in early mammalian embryos are totipotent
b. What are Pluripotent cells?
-They can divide and differentiate into most types of body cell and can be used to treat human disorders
-found in embryos
b. What are multipotent stem cells?
-Can divide and differentiate into a limited number of cell types
-found in mature mammals
-eg bone marrow stem cells
b. What are unipotent stem cells?
-Can divide and differentiate into only one cell type
-found in mature mammals
-eg cardiomyocytes derived from a small number of stem cells in heart
b. What are induced pluripotent stem cells?iPs
4 points
-produced from unipotent cells in adults
-induce specific transcription factors to express genes not normally expressed
-acquire characteristics of embryonic stem cells (can divide into almost any body cell)
-used to treat disease without ethical issues
c. How do transcription factors stimulate mitosis?
-steroid hormones eg oestrogen move into the cell
-binds to the receptor molecule molecule on a specific transcription factor
-transcription factor moves from cytoplasm to the nucleus
c. How do transcription factors stimulate mitosis?
-steroid hormones eg oestrogen move into the cell
-binds to the receptor molecule molecule on a specific transcription factor activator
-Transcription factor moves from cytoplasm to nucleus
-binds to DNA at a specific promotor sequence
-RNA polymerase is activated starting transcription
c. How does siRNA stop translation?
-A single strand of RNA has a complimentary base sequence to the whole mRNA strand
-The siRNA binds to the mRNA and an enzyme hydrolyses the mRNA by breaking the
phosphodiester bonds in the sugar phosphate backbone
-hydrolysed mRNA cannot be translated into a polypeptide
c. How does miRNA stop translation?
-Only some parts of the miRNA have a complimentary base sequence to the mRNA
-Complimentary regions bind to the mRNA blocking the mRNA from entering the ribosome
-mRNA cannot be translated into a polypeptide
c. What is the difference between miRNA and siRNA?
-siRNA hydrolyses mRNA, miRNA blocks mRNA from entering ribosome
-miRNA only complimentary to to some parts of mRNA, siRNA complimentary to whole base sequence
d. What is the definintion of epigenetics?
Environmental factors that cause heritable changes in gene function without changing the base sequence of DNA
d. How does increased methylation of DNA affect transcription
-acetylation of associated histones decreased
-chromosomes condense
-transcription factors cannot bind to the specific promotor sequence
-DNA cannot be transcribed
d. How does decreased methylation of DNA affect transcription?
- acetylation of associated histones increased
-Chromosomes uncondensed
-Transcription factors can bind to the specific promotor sequence
-DNA can be transcribed
d. What is the epigenome?
Determines the shape of the DNA-histone complex
-inactive genes condensed so can’t be transcribed
-active genes uncondensed so they can be transcribed
e. What is cancer?
-Mutations in the genes that regulate cell division and mitosis can lead to uncontrolled cell division and development of a tumour
-If the tumour metastasises the cancer can form
e. What are benign tumours?
-Cells which break of don’t start new tumours in the body (don’t metastasise)
-Slow growing
-Don’t cause cancer
-Don’t cause damage to other tissues
e. What are malignant tumours?
- Cells can break off and start new tumours in the body (metastasise)
-fast growing
-cancerous
-can cause damage to other tissues
e. How do tumours cause harm to the body?
- may damage the organ that it is growing in
-may cause blockages or obstructions in the blood or lymph vessels
-may exert pressure on other organs
e. What factors increase the risk of abnormal methylation patterns?
-smoking
-caffeine
-asbestos
-gamma radiation
e. What factors can contribute to the development of tumours?
-Mutation of tumour suppressor genes and proto-oncogenes
-abnormal methylation of tumour suppressor and proto-oncogenes
-increased oestrogen concentration can affect development of some breast cancers
e. How does a mutation of the tumour suppressor gene lead to cancer?
-Tumour suppressor genes normally produce protein that slows cell division
-Mutation causes change in base sequence of mRNA
-produces a non-functional tumour suppressor protein that does not slow cell divison
-Cells divide uncrontrollably
e. How does a mutation of the proto-oncogene lead to cancer?.
-Proto-oncogene produce protein that stimulates cell division
-Mutation causes change in base sequence of mRNA
-Changes the 3d tertiary structure of protein produced
-produces an onco-gene which accelerates cell division
-leads to uncontrolled cell division
e. How does increased methylation levels on tumour suppressor genes lead to cancer?
-Increased methylation of tumour suppressor gene
-chromosomes condense
-transcription factors cannot bind to specific promotor sequence so not gene not transcribed
-not translated into protein
-Cell division not slowed leading to uncontrolled cell division
e. How does decreased methylation levels on proto-oncogenes lead to cancer?
-decreased methylation of proto-oncogene
-more uncondensed to transcription factors can bind to promoter and transcription of the onco-gene take place
-more oncoproteins produced
-accelerates cell division leading to uncontrolled cell division
