8-20 Gene expression Flashcards
What is an addition mutation?
When extra bases are inserted into the sequence
Causes a frameshift to the right
The whole sequence is affected
If three bases are added, there will not be a frameshift
What is a duplication mutation?
One or more bases are repeated, frameshift to the right
What is an inversion mutation?
Where a group of bases become separated from the DNA sequence and rejoin at the same position but back to front (inverse order)
Affects the amino acid sequence
What is a translocation mutation?
Where a group of bases becomes separated from the DNA of one chromosome and become inserted into the DNA sequence of a different chromosome
This leads to an abnormal phenotype
What are the causes of mutations?
Some are spontaneous with no outside interference
High energy ionising radiation e.g. xrays and UV
Chemicals e.g. nitrogen dioxide which alters DNA structure
What are totipotent cells?
Cells which can become any type of cell
What are stem cells?
Cells which retain the ability to differentiate into other cells
Which type of cells can redifferentiate?
Plant cells which allows them to develop once again into another completely different cell
What are pluripotent cells?
Cells found in embryos which can differentiate into almost anything
What are multipotent cells?
Cells found in adults which can differentiate into a limited number of specialised cells
What are unipotent cells?
Cells which can only differentiate into a single cell
They’re derived from multipotent cells and are made into adult tissue
What is epigenetics?
The study of markers on DNA
This allows us to understand what switches on genes
What is the epigenome?
All of the epigenetic markers in a cell or organism
What happens if a gene is not expressed?
No protein is made
What is chromatin?
The DNA molecule wrapped around histones
What determines whether the genes are expressed?
The interaction between DNA molecules and histones
What does the epigenome determine?
The shape of the DNA - histone complex
What is epigenetic silencing?
A tightly packed arrangement of the DNA-histone complex which makes a gene inactive
What is the addition of methyl groups called?
Methylation
What is the addition of acetyl groups called?
Acetylation
How do you express an addition or removal of methyl of acetyl groups?
Hyper- = more Hypo- = less
What are the environmental factors which affect the epigenome?
Stress and diet affect the epigenome which affects whether genes are expressed or not
What is the process of methylation?
Methyl group attaches to cytosine
This prevents the binding of transcriptional factors to the DNA
This attracts proteins to the gene which removes acetyl groups from the histones
Histones become more positively charged
DNA is negative
Association is stronger
This makes DNA become more tightly wrapped around the histone
This stops transcription because it is too tightly wound to reach the DNA
What does decreased acetylation cause?
A more condensed DNA histone complex
Chromatin: heterochromatin
No access for transcriptional factors
The gene becomes inactive
