Genetics Flashcards
what does aneuploidy mean?
a whole missing chromosome
what does balanced mean?
all chromosomal material is present
what are positives and negatives of chromosome microarray?
+
can detect any size of imbalance
can detect tiny changes
quicker, cheaper, more sensitive (than karyotyping)
-
cannot detect BALANCED arrangements
what is somatic mosaicism?
as a cell develops, variation occurs as cell divides
all cells suffer mutation as they divide
(repair mechanisms exist)
what is the recurrence risk of a child being mosaic if one parent is?
high
what is the difference between PCR & Next Generation Sequencing?
PCR allows amplification of one small piece of the human genome
Next generation sequencing can sequence entire genome or exome
when can new mutation occur?
in gametogenesis
very rare
spontaneous
what does polymorphism mean?
any variation in a human genome that has a population frequency of greater than 1 %
does not cause disease in own right, but may predispose to common disease
what does penetrance mean?
likelihood of having a disease if you have a gene mutation
100% penetrance means you will always get the disease if you have the mutation
what is a missense mutation?
point mutation (change in single base) results in a change of amino acid sequence
usually by substitution
most likely to directly activate an oncogene
what does c. mean?
the change in mature mRNA sequence
what does p. mean?
the change in the peptide (protein) sequence
what is the variant classification 1-5?
1- definitely a polymorphism
2- probably a polymorphism
3- unclassifiable
4- probably pathogenic
5- definitely pathogenic
what is a frameshift mutation?
addition or deletion of a single base (or 2)
what is a missense mutation?
results in a change of amino acid sequence
can change protein function
what does de-novo mean?
the process by which new genes evolve from DNA sequences that were ancestrally non-genic.
novel genes, and may be protein-coding or instead act as RNA genes
what is a mendelian disorder?
examples?
a disease that is commonly caused by a change in a single gene (high penetrance)
autosomal dominant & recessive
X-Linked
examples of non-mendelian inheritance?
methylation/ Imprinting
Mitochondrial Inheritance
Mosaicism
what is the presentation of a female with one pathological allele and normal allele in X-Linked inheritance?
does not show major clinical features of disease
(a male with a single faulty gene allele will be fully affected)
what is SNP?
single nucleotide polymorphism
not high penetrance
exerts effects not in themselves a disease, but effects through gene function make you more prone to disease
most SNPs have no effect
what is the common variant common disease hypothesis?
predicts that common disease-causing alleles, or variants, will be found in all human populations which manifest a given disease.
