8.1/2 Mutation Expression Flashcards
(29 cards)
Type of mutation Addition Deletion Substitution Inversion Duplication Translocation
One or more bases are added to a gene
One or more bases are removed from a gene
One or more bases are substituted within a gene
A chromosome mutation in which a section of the chromosome is reversed.
A chromosome mutation in which a section of the chromosome is duplicated.
A chromosome mutation in which a section of one chromosome is removed and becomes attached to a different, non-homologous chromosome.
- What is a silent mutation? Why are some mutations silent?
A silent mutation is when the same amino acid is coded for, even though the base sequence of the gene has been changed.
This happens because the genetic code is degenerate which means that some amino acids are coded for by more than one triplet code.
- What is a mutagenic agent? Name at least 3 examples of mutagenic agents
An agent which makes mutations more likely to occur, e.g.
• High energy radiation, e.g. gamma rays, x-rays, UV light
• Ionising radiation, e.g. alpha or beta radiation
• Chemicals such as benzene or mustard gas
- What is meant by frame shift?
When an addition or deletion of bases occurs such that the reading frame of the gene changes from that point on.
(In other words, all the triplet codes / codons change)
- What sort of mutations can result in frame shift downstream of the mutation?
(What is meant by ‘downstream of the mutation’?)
Additions or deletions of one or more bases. But,if the deletion or addition is a multiple of 3 bases it will not cause frame shift.
Totipotent Pluripotent Multipotent Unipotent Induced pluripotent stem cell Stem cell
Undifferentiated cells which have the ability to divide continuously and mature into any type of body cell
Can divide in unlimited numbers cells and have the ability to give rise to several cell types
Cells which have the ability to divide and give rise to a limited number of cell types (fewer than pluripotent cells)
Cells which can only divide to form one type of cell
Pluripotent cells which are produced by treating unipotent cells with specific protein transcription factors
Undifferentiated cells which can divide continually and can differentiate into any type of cell
- How are induced pluripotent stem cells produced?
4 protein transcription factors are added to unipotent cells (called ‘Yamanaka factors’) and this causes the cells to turn back into pluripotent cells
- Suggest why injecting embryonic stem cells into someone to treat a disorder could cause harm
- The cells could differentiate into the wrong cell types
* The cells could divide out of control, leading to formation of a tumour and possibly cancer
- What is a transcription factor?
- A Transcription factor binds to a gene
- At a specific DNA sequence in the promoter;
- Stimulates RNA polymerase to attach and transcribe the gene (or can prevent transcription)
- How would a transcription factor increase the production of a protein?
- The transcription factor will move from the cytoplasm of the cell to the nucleus
- The transcription factor will bind to the promotor region of a gene
- This will cause RNA polymerase to attach and stimulate transcription to take place
- Therefore, more of the protein will be produced
- What is oestrogen?
A steroid hormone
- Write a flow chart to describe how oestrogen affects gene transcription and draw a labelled diagram to illustrate the process
- Oestrogen binds to the oestrogen receptor (which is found in the cytoplasm)
- This causes the oestrogen receptor to change shape and an inhibitor molecule is released
- This exposes the DNA binding site on the oestrogen receptor
- The oestrogen receptor complex moves into the nucleus via the nuclear pore
- And binds to the specific base sequence in the promotor region of a gene
- This stimulates RNA polymerase to attach and transcription to take place
- What is the function of RNAi?
RNA molecules (such as siRNA or microRNA) inhibit gene expression by ‘neutralising’ specific mRNA molecules so that translation cannot take place. They bind to complementary mRNA sequences either preventing the mRNA from attaching to the ribosome or enabling enzymes to break up the mRNA
- Write a flow chart to describe how RNAi functions? Draw a labelled diagram to illustrate the process.
- Double stranded RNA is produced
- Leaves the nucleus
- One strand of RNAi is bound to RISC, which is a complex with proteins (including RNA hydrolase)
- The RNAi guides the enzyme to mRNA that has a complementary sequence of bases.
- The RNAi binds to the mRNA by complementary base pairing
EITHER
• The enzyme cleaves the mRNA into pieces
OR
• The mRNA is blocked from binding to a ribosome
So either way:
• translation is prevented
- What is epigenetics?
The study of heritable changes in gene function that do not involve changes to their base sequences
- What is DNA methylation?
The addition of methyl groups to DNA bases (usually to cytosine).
- Describe and explain the effect of increased DNA methylation on gene expression
- Increased methylation of DNA in the promoter region of a gene will prevent transcription factors and RNA polymerase from binding
- Transcription of the gene will be inhibited and the gene will be ‘silenced’
- What are histones?
The proteins that DNA is wrapped around
- What is histone acetylation?
The addition of acetyl groups to histone proteins.
- Describe and explain the effect of histone acetylation on gene expression
- Histone acetylation causes DNA to be less condensed;
- Which can reveal the promoter regions of the genes;
- Which can lead to increase binding of transcription factors and RNA polymerase to the promoter regions;
- Which can lead to increase transcription of the gene
- What are the main characteristics of a benign tumour?
A mass of dividing cells which do not break away and invade neighbouring tissue (i.e, do not metastasise)
- What are the main characteristics of a malignant tumour?
A mass of cells which divide uncontrollably and can metastasise, invading other tissues
- What does a proto-oncogene do?
It codes for a protein which stimulates cell division to take place
- What is the consequence of a mutation occurring to a proto-oncogene?
- It forms an oncogene.
* This results in uncontrollable cell division.
