Flashcards for AQA A Level Biology Chapter 20- Gene Expression
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Course
Chapter 20- Gene Expression
Institution
AQA
Contain all you need to know for this chapter of the course. Are detailed and concise, and work best with Anki, but can be used with quizlet. They are in the form of a txt document that can be imported into anki or quizlet. Some images are missing due to the format, so these images will have to be ...
What are the new kinds of gene mutation?
Duplication<div>Inversion </div><div>Translocation</div>
What happens in inversion? A group of bases is separated from the DNA and
rejoins in the inverse order
What happens in translocation of bases? A group of bases gets separated from one
chromosome and is inserted in the base sequence of another chromosome
What are the typical causes of mutation? Ionising radiation<div>Chemicals like
benzopyrene </div>
What are stem cells? Unspecialised cells
What is the process by which stem cells turn into specialised cells?
Differentiation
What makes a specialised cell specialised? It has a special structure or
organelle distribution that makes it fit for its purpose
How is a cell differentiated? Different genes are turned on and off. For example,
in a beta cell, the gene that codes for insulin production is switched on, and in
other cells it will be switched off
What are the four kinds of stem cell? Totipotent- can differentiate into any
kind of cell<div>Pluripotent- can differentiate into almost any kind of
cell</div><div>Multipotent- can differentiate into a limited number of types of
cell</div><div>Unipotent- can only differentiate into one kind of cell</div>
What is an induced pluripotent cell? A unipotent cell that is genetically
altered into a pluripotent stem cell, allowing for it to be used for medical
purposes
What is the mechanism by which transcription is started? Transcriptional factors
bind to the promoter of the gene<div>This allows mRNA polymerase to bind to the DNA
and for an mRNA strand to be formed</div>
How do transcriptional factors contribute to the turning genes on and off? When
transcriptional factors are bound or are able to bind, the gene is said to be
turned on<div>When transcriptional factors cannot be bound, the gene is switched
off</div>
How does oestrogen interact with transcription? Oestrogen can bind with a site on a
receptor molecule of a transcriptional factor<div>This receptor molecule will be
complementary and specific in shape to the oestrogen</div><div>This changes the
shape of the transcriptional factor, allowing it to bind to the promoter region of
the gene, triggering the transcription of the gene </div>
What is the epigenome? DNA is wrapped around histones. These histones are covered
in chemical tags which determine how tightly coiled the chromatin complex is. How
tightly some genes are coiled determines whether transcriptional factors can bind
or not. If a gene is very tightly coiled due to chemical tags it cannot be
transcribed, and if it is more loose, it can be
How is the epigenome determined? Cells receive signals determined by its
environment, with factors like stress and diet affecting it, which cause the
epigenome to change, and switch off and switch on certain genes
Can the epigenome be inherited? Yes
What are the two ways the epigenome can be changed? A change in the acetylation
of the histones<div>A change in the methylation of DNA</div>
What does decreased acetylation of histones cause? This increases the positive
charge of the histones, and so increases their attraction to the negative phosphate
groups in DNA<div>This makes chromatin more tightly coiled, and so switches off
genes </div>
What does increased methylation of DNA cause? Adding methyl groups to DNA
prevents the binding of transcriptional factors
How can epigenetics cause disease? It can turn off important genes, like proto-
oncogenes and tumour suppressor genes
How can epigenetics be used to cure disease? Treatments can be used to alter the
epigenome, switching off harmful enzymes that may cause disease
How can translation be interfered with? Using something called siRNA:<div>An
enzyme cuts large double stranded RNA into smaller sections of single stranded RNA
called siRNA</div><div>One of these strands binds with an enzyme</div><div>The
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