Genetics

Question 1

what does aneuploidy mean?

Answer 1

a whole missing chromosome

Question 2

what does balanced mean?

Answer 2

all chromosomal material is present

Question 3

what are positives and negatives of chromosome microarray?

Answer 3

+
can detect any size of imbalance
can detect tiny changes
quicker, cheaper, more sensitive (than karyotyping)
-
cannot detect BALANCED arrangements

Question 4

what is somatic mosaicism?

Answer 4

as a cell develops, variation occurs as cell divides
all cells suffer mutation as they divide
(repair mechanisms exist)

Question 5

what is the recurrence risk of a child being mosaic if one parent is?

Answer 5

high

Question 6

what is the difference between PCR & Next Generation Sequencing?

Answer 6

PCR allows amplification of one small piece of the human genome
Next generation sequencing can sequence entire genome or exome

Question 7

when can new mutation occur?

Answer 7

in gametogenesis
very rare
spontaneous

Question 8

what does polymorphism mean?

Answer 8

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

Question 9

what does penetrance mean?

Answer 9

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

Question 10

what is a missense mutation?

Answer 10

point mutation (change in single base) results in a change of amino acid sequence
usually by substitution
most likely to directly activate an oncogene

Question 11

what does c. mean?

Answer 11

the change in mature mRNA sequence

Question 12

what does p. mean?

Answer 12

the change in the peptide (protein) sequence

Question 13

what is the variant classification 1-5?

Answer 13

1- definitely a polymorphism

2- probably a polymorphism

3- unclassifiable

4- probably pathogenic

5- definitely pathogenic

Question 14

what is a frameshift mutation?

Answer 14

addition or deletion of a single base (or 2)

Question 15

what is a missense mutation?

Answer 15

results in a change of amino acid sequence
can change protein function

Question 16

what does de-novo mean?

Answer 16

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

Question 17

what is a mendelian disorder?
examples?

Answer 17

a disease that is commonly caused by a change in a single gene (high penetrance)
autosomal dominant & recessive
X-Linked

Question 18

examples of non-mendelian inheritance?

Answer 18

methylation/ Imprinting
Mitochondrial Inheritance
Mosaicism

Question 19

what is the presentation of a female with one pathological allele and normal allele in X-Linked inheritance?

Answer 19

does not show major clinical features of disease

(a male with a single faulty gene allele will be fully affected)

Question 20

what is SNP?

Answer 20

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

Question 21

what is the common variant common disease hypothesis?

Answer 21

predicts that common disease-causing alleles, or variants, will be found in all human populations which manifest a given disease.