Genetics Flashcards
What 2 factors add together to produce disease?
- environment
- genes
Explain DNA structure
- double stranded
- anti-paralel
- deoxyribose sugar
- A-T , C-G
What is the name of the protein DNA wraps around to produce chromosomes?
- histone
How many bonds between cystosine and guanine?
- 3
How many bonds between adenine and thymine?
- 2
Which direction is DNA read and replicated?
- 5’ –> 3’
What are the steps of the cell cycle?
- G1
- S
- G2
- M
At which stage in the cell cycle does DNA synthesis occur?
- S phase
What is mitosis?
- 1 diploid parent produces 2 identical diploid cells
What is meiosis?
- 1 diploid parent produces 4 haploid cells
what occurs during meiosis?
- crossing over
- gamete production
What is the differences in RNA compared to DNA
RNA:
- single stranded
- ribose sugar
- uracil replaces thymine
Explain the processes from DNA to protein
- DNA transcribed to pre mRNA
- pre mRNA spliced to mRNA
- mRNA translated to protein
- protein modified and moved around cell
What is the definiton of a polymorphism?
- any variation in the human genome with a population frequency of greater than 1%
- doesnt cause disease in own right, but can predispose
What is the definition of a mutation?
- a gene change that causes a genetic disorder
What causes variations within genes?
- changes in promotor sequences
- changes in exon sequences
How are chromosomes recognised?
- banding patterns
- length
- position of the centromere
What is the name given to a chromosome where the short arm doesnt really matter?
- acrocentric
Define balanced chromosomal arrangement
- all chromosomal material is present
Define unbalanced chromosomal arrangement
- extra or missing chromosomal material
Define anueploidy
- whole extra or missing chromosome
Define transloaction
- rearrangement of chromosomal material
Down syndrome genetic makeup?
- trisomy 21
- 47XY + 21
What is a robertsonian translocation?
- two afrocentric chromosomes stuck end-to-end
Turners syndrome genetic make up?
45 X
Edwards syndrome genetic make up
47 XY + 18
- trisomy 18
Klinefeleter syndrome genetic make up
47 XXY
What is the 1st line chromosome test?
- microarray CGH (aCGH)
what is a disadvantage of aCGH?
- Doesn’t detect balance rearrangements
Define mosaicism
- different cells have different genetic constitution
What 2 chromosomal abnormalities may cause cancer?
- activation of oncogenes
- deletion of tumour suppressor genes
What are the functions of introns?
- non-coding regions
- regulation of genes
- spacing out of genes
What is a mutation?
- a genetic variation that causes disease
What is a polymorphism?
- a genetic variation that may not cause disease in its own right
What is a point mutation?
- a single nucleotide base is changed, inserted or deleted
What does “>” represent on the c.
- substitution
What does “c.” represent when describing mutations?
- change to the mature mRNA
What does “p.” represent when describing mutations?
- change to the peptide (protein) sequence
What does “wild type” mean?
- the “normal”
Define penetrance
- the likelihood of having a disease if you have the gene mutation
- 100% penetrance = 100% you will have the disease
Define mendelian disorders?
- caused by a change in a single gene
What are examples of non-mendelian disorders?
- methylation/imprinting
- mitochondrial inheritance
- mosaicism
autosomal dominant mutations are seen in ____ generation(s)
- all generations
If a parent is affected with an autosomal dominant mutation, what is the risk that a child will also be infected?
- 50% risk of child being infected
Autosomal recessive mutations require ___ copies of the gene to cause disease
- 2 copies
In autosomal recessive mutations usually ____ generation(s) are affected.
- one generation
What is the risk of a child being affected if both parents are a carrier of an an autosomal recessive mutation?
- 25% risk
Explain X linked recessive diseases?
- gene fault lies on the X chromosome
- female may be carrier but will show no sign of disease (except if X inactivated)
- 1/2 of male children effected
- 1/2 of female children carriers
If an affected male, with X linked recessive mutation has 2 children, boy and a girl. What are their individual risks?
- Male - 0% (no male-to-male transmission)
- all of female children will be affected
What are SNPs?
- Single Nucleotide Polymorphism
- most have no/little effect
Cancers can be described as genetic disease at a ____ level
- somatic
Methylation usually occurs on the ___ bases just before the ____ bases
- cytosine
- guanine
What are oncogenes activated by?
- point mutations
- translocations
- gene amplifications
Name an example of an oncogene?
- RAS
- MYC
Tumour supressor mutations are ___
dominant or recessive?
- recessive
Examples of tumour supressors?
- pRb
- p53
