Genetics Yr13 Flashcards
What is a gene mutation?
A change in one or more nucleotide base or change in sequence of bases
What are the two types of mutations?
Gene mutation
Chromosome mutation
What is polyploidy?
3 or more sets of chromosomes
What is non-disjunction?
When homologous pairs fail to separate during meiosis
What is substitution?
Nucleotide base is replaced with a different nucleotide with a different base
What are the three possible outcomes of substitution?
Stop codon formed
Different amino acid formed
Different codon produced but codes for same amino acid
What does it mean if a stop codon is formed in substitution?
Polypeptide formation stopped prematurely
What does it mean if a different amino acid is formed in substitution?
Polypeptide different by one amino acid
Active different shape
What does it mean if a different codon is produced but codes for same amino acid in substitution?
Degenerate
No effect
What is deletion?
Nucleotide base has been removed from the sequence
What will deletion cause?
Frame shift (left) So all amino acids are different
How can the effect of deletion be made worse?
If deleted base is at beginning of sequence
What is the effect of adding a base?
Frameshift (right)
What happens if three bases are added to the sequence?
= no effect as no frameshift
What is the effect of duplicating a base?
Frameshift
What is inversion?
A group of bases separate from the sequence + re-join sequence in some place BUT in inverse order
What is translocation?
Group of bases separate from one chromosome + joins the other
What does translocation between chromosome 9 and 22 cause?
Leukaemia
What does translocation cause?
Marked effect
Is translocation a mutation?
YES
Is crossing over a mutation?
NO
Why is translocation a mutation?
Change in genetic information between non-homologous chromosomes
Why isn’t crossing over a mutation?
Swaps genetic material BUT homologous chromosomes unchanged
What are the causes of mutations?
Spontaneous = no outside factors
During replication
Natural mutation rate - 1 or 2 per 100,000 genes/ generation
What can mutagenetic reagents cause?
Natural mutation rate to increase
What are some mutagenetic reagents?
Chemicals - NO2 + benzopyrene
High energy ionising radiation - Alpha, beta, X-rays + UV
What does NO2 + benzopyrene do?
NO2 = affect transcription Benzopyrene = inactivates tumour suppressor gene
What is differentiation?
The process by which cells develop special structures needed to carry out specific role
What do multicellular organisms require?
Specialised cells to carry out specific functions
What are stem cells?
Undifferentiated cells that can divide into any cell
What is self-renewal?
The ability to go through numerous cycles of cell division while maintaining the undifferentiated state
Where do you find stem cells?
Embryonic - flexible
Adult tissues - non-flexible
Specific to tissue/organ ^^^
What are totipotent stem cells?
Can produce all cell types (embryo + placenta)
Only present during 1st few cell divisions
What are pluripotent stem cells?
Can become any body cell in embryo
BUT not placenta
Why are pluripotent used in medicine?
Can divide in unlimited numbers
What are multipotent stem cells?
Found in adults
Give rise to different types of specialised cells
BUT restricted to certain organs/tissue types
What are unipotent stem cells?
Found in adults
Make only one type of cell
Why are embryonic cells important?
Differentiate into any type of cell
What males a cell become specialised?
Different gene expressed
So only some DNA translated to proteins
Do all body cells make all the products they are genetically capable of?
No = waste resources unfavourable
How is gene expression controlled?
Some permanently expressed
Some never expressed
Some switch on + off
How are genes prevented from expressing themselves?
Prevent transcription
Breakdown of mRNA before translation
What are cardiomyocytes?
heart muscle cells
That can be replaced by unipotent stem cells when damaged
What is myocardial infraction?
Heart attack when coronary arteries are blocked
What impact does myocardial infraction have?
No blood flow = cells die
How do cardiomyocytes help with myocardial infraction?
Inject into damaged area = regenerate them when differentiate
How are embryonic stem cells used?
Cells taken from early stages of embryo
Grown in vitro
Induced to develop into tissues
What can embryonic stem cells be used for?
Burns Parkinson's disease Nerve damage Diabetes Heart disease Cancer
What are iPS cells?
Type of induced pluripotent cell that is produced from unipotent cells
How are iPS cells created?
Genetically modified in a lab
To make them acquire characteristics of embryonic stem cells
Need to induce gene + transcriptional factors to turn genes that were off on
What does iPS cells show since they can be reactivated?
They retain the same info present in the embryo
What is interesting about iPS cells?
Capable of self-renewal
Very flexible
Potentially divide to provide limitless supply
How could iPS cells be useful?
Could replace embryonic stem cells in medicine + research
= overcome ethical issues
Do plants have stem cells?
YES
Mature plants have totipotent stem cells = them to form clones of single cells
What are the arguments for stem cells?
Cure debilitating diseases
Wrong to allow suffering when it can be relieved
Embryos created for IVF so why not stem cells
Legislation in place to stop risk with research
Embryos less than 14 days not recognised as human
Adult stem cells not as suitable
What are the arguments against stem cells?
Potential human life Deserves same respect as adult human Could lead to cloning humans Undermines respect for life Adult stem cells = available alternative so research should be directed towards them
What are the basics of gene expression?
Transcription has to occur
pre-mRNA spliced
Translation has to occur
What do protein hormones do?
Help in gene expression
Act via 2nd messenger
What do lipid-soluble hormones do?
Act directly
Regulate transcription + translation