Control of Gene Expression Flashcards
Out of the human genome,how many genes are actually expressed ?
In any given cell, only 10,000 genes are expressed
Where are totipotent cells found?
In zygotes
What is β thalassaemia?
Group of genetic blood diseases caused by insufficient expression of β-globin reducing haemoglobin production
What is the genotype?
The genetic makeup of cells and organisms determining characteristics
What are the different translational control mechanisms in the body?
- Early embryogenesis
- Environmental stress
- 5’ UTR
- Fe starvation
- 3’ UTR
- Small non coding RNAs
What is differential gene expression?
The expression of different genes in different cells at different times giving the cell its functions
What is the role of miRNAs?
Control part of the post-transcriptional regulations of 1/3 of all human genes by regulating several target genes
How does β thalasaemia differ from sickle cell disease?
In β thalasaemia, the β globin protein is structurally normal
How are intracellular iron levels controlled?
Via translation of Ferritin
How does the genome differ from cell to cell?
It doesn’t, the genome is identical in every cell
How is the miRNA able to target genes?
Single stranded miRNA searches for complementary mRNA on target proteins
- If an extensive match is found: mRNA is rapidly
degraded and RISC released - If a less extensive match is found: mRNA translation is
reduced; mRNA sequestered and eventually degraded
How is gene expression controlled in early embryogenesis?
During the first 4-8 cell divisions no genes are expressed
After blastocyst formation the 1st genes are expressed
- due to up regulation of maternally derived preformed mRNA translation
What is a pluripotent cell?
A cell that can give rise to all cell types except placental cells
What role does the 5’ UTR play in translation control?
Determines how efficiently the ribosome initiates translation e.g.
- Globin: very efficient
- Ferritin: very inefficient
How many small non coding RNAs are present in the human genome?
Human genome encodes 500+ small non coding RNAs transcribed by RNA Pol II
How is differential expression regulated in time?
- During development (i.e in an embryo vs. adult)
- In response to hormones, infections and other signals
How many forms of β thalasaemia are there?
There are multiple independently arising forms of the disease
How is differential expression regulated tightly in space?
Different tissues and cell types express different genes (i.e. brain vs. muscle cells)
How does environmental stress control gene expression in humans?
Exposure to heat shock or pathogens can cause global translation changes
How does Ferritin help maintain the bodies cellular iron levels?
Ferritin binds iron and retains it in the cytoplasm as an excess store
Ferritin is only required when iron levels are in excess
What is the result of β thalassaemia caused by the single base change at the intro-exon junction?
CACAGCTCCT -> CACGGCTCCT
Deletion causes intron to not be spliced
Gene not exported to cytoplasm
What is the translational control of gene expression?
The regulatory mechanisms of the rate at which proteins are formed
What are small non coding RNAs?
RNA molecules that aren’t translated into proteins e.g. miRNA
What is meant by a totipotent cell?
A cell that can differentiate into every cell type
