Gene expression Flashcards
Inversion mutation
short sequence of nucleotides detach and rejoin the wrong way around
Duplication mutation
nucleotide is repeated causing frame shift to right
Translocation mutation
short section of nucleotides detaches + reinserted on a different gene (possibly chromosome), significantly impact gen expression -> phenotype
Key properties of stem cells
Self-renewal (divided whilst remaining undifferentiated), potency (can diferentiate)
Name 4 types of stem cells
Totipotent: early embryo, into any cell (limited time)
Pluripotent: fetal, almost any type of cell (not placenta)
Multipotent: adult/umbilical blood, limited no. of cells
Unipotent: derived from multipotent/adult tissue, one type of cell
Induced pluripotent stem cells
Unipotent stem cells genetically altered to have characteristics of pluripotent s. cells/embryonic stage
- induce genes + transcriptional factors in cell to express themselves
capable of self-renewal, could replace embryonic stem cells in research (overcome ethical issue)
Role of transcriptional factor
Binds to specific base sequence of DNA in nucleus, begins transcription of this sequence -> expressing gene
Effect of oestrogen on transcription
- Oes. lipid soluble so diffuses across cell membrane
- binds to receptor site on TF as complementary
- shape of DNA binding site changes on TF
- TP diffuses into nucleus + binds w/ DNA beginning process of transcription
Effect of siRNA on translation
- double stranded RNA is hydrolysed by enzyme into siRNA
- one of the two strands of single siRNA combines w/ enzyme
- siRNA strand pairs w/ complementary bases on mRNA strand
- enzyme cuts mRNA into smaller sections
What is the epigenome?
multitude of compounds that can instruct the genome, flexible + so responds to env. changes activating or inhibiting genes
Effect of methyl
Increase inhibits transcription
binds to cytosine base, attracts proteins that condense DNA histone complex so TF cannot bind
Effect of acetyl
Decrease inhibits transcription
increasing + charge on histones which increases attraction of phosphate groups in DNA so stronger association (tighter)
-> TF cannot bind
What are the two types of chromatin?
heterochromatin: tightly packed so inaccessible to promoters + enzymes
euchromatin: loosely packed so readily accessed by enzymes
What is cancer?
Group of diseases caused by damage to genes regulating mitosis which can lead to a tumour
How do primary tumours spread?
- early tumour enlarges + develops blood + lymphatic vessels
- tumour cells enter blood + lymphatic vessels
- circulating tumour cells adhere to blood vessel walls, squeeze through to form distant metastases
OR
metastasis in lymph node
2 ways oncogene can cause excessive cell division
- receptor protein on cell surface overexpressed so permanently activated
- oncogene may code for growth factor which is produced excessively stimulating division
- hypomethylation
How can tumour suppressor genes be involved in causing cancer?
hypermethylation in promoter region inhibits transcription so tumour suppressor gene switched off
-> inactivated so uncontrolled cell division
Role of oestrogen in development of some breast cancers
post menopause fat cells of breast produce more oestrogen, tumour cells increase oest., w.b cells drawn in also increase oest
oest. activates gene by binding to a gene which promotes transcription
so can cause proto-oncogenes in breast cells to develop into oncogenes
How many genes are in human genome?
20,000, over 3 billion base pairs
What is WGS?
Whole Genome Shotgun
cutting DNA into smaller easily sequenced sections then using computer algorithm to align overlapping segments, assembling entire genome
*methods constantly being updated
What is SNP and why is it important?
single nucleotide polymorphism, single base variations in genome that are associated w/ disease
allows quick identification of potential medical problems for early intervention, can est. evol. relationships
Why is determining proteome of simpler organisms easier?
- prokaryotes don’t have introns so genome can directly sequence proteins derived from their genetic code
- most have just one piece of circular DNA not associated w/ histones
Why might knowledge of a proteome pathogen help control disease it causes?
Helps identify antigens so that they can be used to create a vaccine which provides immunity
