Genetics Flashcards
In what direction is DNA replicated?
5’ to 3’
What does the 5’ indicate?
the carbon number that the bond is attached to
Which DNA bonds are strongest?
C-G
What is the most common DNA mutation?
C-T
How is DNA kept?
tightly wound round proteins such as histones and condensed in the nucleus
how many bases are there in the human genome?
3 billion
How many genes are there in the human genome?
30,000
What are the 5 phases to the cell cycle?
G0 - resting phase S - synthesis for replication G2 - checkpoint for mitosis Mitosis G1 - final check point for new cell
What are the implications of DNA damage and repair mechanisms?
DNA repair mechanisms can be damaged thus preventing them from occurring
what is mitosis?
the splitting of one cell into almost identical daughter cells which are diploid
What is meiosis?
the splitting of a parent cell into 4 haploid cells and contains two episodes of cell division.
crossing over and DNA recombination occurs
DNA errors more likely to occur
what does splicing involve?
the removal of introns
How is splicing initiated?
through gene sequence motifs that indicate a need for splicing or insertions
What is the process of protein production?
DNA - premRNA (spliced) - mRNA - protein
What can cause variations in the human genome?
changes in promoter sequence
changes in exon sequence
SNP
Larger deletions or duplications
What is a polymorphism?
a variation that has a population frequency of >1% and does not cause disease - may still pre-dispose to a disease
What is a mutation?
a gene that causes a genetic disorder
What is FGFR3?
an achondraplasia mutation that causes a form of dwarfism - one or two mutations cause it
Why is FGFR3 achondraplasia relatively common?
because spermatids that have this mutation have a selective advantage over normal spermatids
What are the short arm and long arms of chromosomes also referred to as?
short (p)
long (q)
What are acrocentric chromosomes?
chromosomes where the short arm does not exist but is not typically required i.e. 21
what is a balanced chromosome rearrangement?
when all chromosome material is present
What is an unbalanced chromosome rearrangement?
where extra or missing chromosome material is present i.e. 1 or 3 copies
what is aneuploidy?
having a whole extra or missing chromosome
What is translocation?
rearrangement of chromosomes
what are microdeletions?
deletions that cant be seen in a microscope - need to be 5m bp to be seen
What is the likely cause of Downs Syndrome?
extra 21 sneaking into the egg
what are the likely changes from maternal and paternal transmission?
maternal is more likely to be chromosomal
paternal is more likely to be gene changes
what is a robertsonian translocation?
where two acrocentric chromosomes are passed on through translocation i.e. mother has one normal 21 and a 21 attached to 14 therefore child gets normal from mother and father and extra from mum
What occurs with trisomy 18?
Edward Syndrome
What is the notation for Turners syndrom?
45X
What is the notation for Triple X?
47 XXX
What is the notation for Klinefelter syndrome?
47 XXY
why is having one X ok?
because one X is only ever active in cells
Why are bigger translocations better?
Child will either have normal or balanced chromosomes - although potential risk for reproduction
What does the FISH technique allow?
the staining of protein or gene in a cell to see if production is normal, heightened or lessened i.e. HER2 gene
What is somatic mosaicism?
where all cells suffer mutations but those mutations are variable throughout the body
What is next generation sequencing?
DNA with exons cut out and compared to a reference frame
What is an SNP?
a genetic variation that is prevalent in the population and not, in itself, disease causing
