20- Gene expression Flashcards
What are the 6 types of mutation?
Addition Deletion Duplication Inversion Substitution Translocation (ADDIST)
What is the inversion mutation?
Inversion=Order of bases are inverted in DNA sequence.
e.g. ATCGTT> TTGCTA
What is the translocation mutation?
Translocation= section of sequence is moved to ANOTHER section
-can be within & across chromosomes-
What is the minimal effect of a mutation on amino acid sequence?
Substitution= Change to only ONE triplet codon
The new codon sometimes codes for the same amino acid and no change occurs in the protein
Effect of addition, deletion, or duplication
ALL base triplets downstream from mutation change (frame shift).
This impacts many amino acids so very likely protein will not function as normal.
Causes of mutation= (2)
- DNA replication (spontaneous)
2. Mutagenic agents
4 main types of stem cell
Totipotent
Pluripotent
Multipotent
Unipotent
Features of totipotent cells
- Can divide & differentiate into ANY type of cell
- occur for LIMITED time in embryonic development
Features of pluripotent cells=
- able to divide into UNLIMITED numbers & produce any type of cell
- TC’s develop into these in embryos
- PC can be used to treat human disorders
Features of Multipotent cells=
- found in mature mammals
- can develop into LIMITED number
of cell types
Features of Unipotent cells=
- found in mature mammals
- can divide to produce only ONE type of cell (cardiomyocytes?)
Which of the 4 types of stem cell is the most UNSPECIALISED
totipotent
which 2 types of stem cell are found in embryos?
totipotent
pluripotent
which 2 types of stem cell are found in mature mammals?
multipotent
unipotent
How are IPS cells produced
somatic cells converted to IPS by activating genes using protein transcription factors
(they then become unspecialised)
Benefits of IPS (2)
- No ethical concerns (as made from patients own body cells)
- Less risk of rejection during transplants (as made from patients own body cells)
Stem cells can be taken from: (3)
- Adult stem cells
- Embryonic stem cells
- Induced pluripotent stem cells (IPS)
Benefits of stem cells use in treating human disorders
- can reduce preventable deaths
2. Can treat conditions that decrease quality of life
Disadvantages of using stem cells in treating human disorders
- Ethical controversy surrounding embryo use (some believe you are depriving a life)
Specific stem cell use= (3)
- Bone marrow transplants
- Drug research
- Developmental biology
What are Transcription factors?
proteins that control gene expression via STIMULATING or INHIBITING transcription.
Transcription factors- ACTIVATORS
TF’s that STIMULATE gene expression
by interacting with enzyme RNA polymerase and allowing it to bind to DNA
Transcription factors- REPRESSORS
TF’s that INHIBIT gene expression
they stop RNA polymerase from binding to DNA, preventing transcription
Role of oestrogen in initiating transcription (4)
- oestrogen is lipid-soluble, passes through PLBL > cytoplasm
- binds to inactive TF which forms receptor-hormone complex & changes shape
- enters and binds to promoter region of DNA
- stimulates T of genes by helping RNA polymerase bind.
How epigenetics controls gene expression
- epigenetic regulation interacts with DNA to control ACCESS to DNA
- controlling access ALTERS gene expression without actually changing the DNA code
Causes of heritable epigenetic changes in gene function= (2)
- Increased methylation
2. Decreased Acetylation
Increased methylation process= (3)
- nucleosome more tightly packed
- when more condensed TF’s cant bind
- genes not transcribed
Decreased Acetylation process= (4)
- Decreased a increases + charge of histones
- Histones bind to DNA (-charged) more TIGHTLY)
- Prevents TF’s binding
- Genes not transcribed
What is chromatin?
DNA & histone combination
What happens if methylation is DECREASED too much?
- Can INCREASE expression of pro-oncogenes (which promotes cell division)
- so cells divide uncontrollably & tumours produced
Impact of RNA interference?
translation of the mRNA produced from target genes is inhibited
^ this prevents gene expression
RNA interference process (2)
- RNAi interferes with mRNA by binding to mRNA molecule & breaking it down
- this means mRNA cannot be translated into a protein
Benign tumour features=
- Not cancerous
- normal nuclei
- Dividing cells cannot spread & invade other tissues
Malignant tumour features= (4)
- Grow rapidly
- Dividing cells can spread & invade other tissues & around the body
- Can be life-threatening
- irregular, enlarged nuclei
Ways tumours can develop=
- Increased methylation of TSGs:
(this inhibits TSG’s which usually inhibit CD so CD) - Oncogenes:
(cause excessive cell division) - Oestrogen
(causes increased expression of genes, which can lead to a tumour developing)
Environmental and genetic factors that can increase likelihood of developing cancer= (4+1)
Environmental=
- radiation exposure
- smoking
- alcohol consumption
- diet high in fat
Genetic=
- Certain alleles (e.g. BRCA1)(e.g. Cancer) when interpreting correlations in graphs what other factors need to be considered?
- Age
- Gender
- Sample size
- variation in lifestyle (e.g. exercise)
- changes in lifestyle provision
Proteome definition=
complete set of proteins expressed by an organism
What are coding genes?
genes that contribute to the proteome (used to produce proteins)
what can genome projects be used for? (3)
- medical advances (identify genes responsible for inherited diseases & target for drug treatment)
- biotechnology
- discover evolutionary relationships
what means that knowledge of the genome cannot easily be translated into the proteome
- Non-coding DNA
- Regulatory genes
