9-1-05 Molecular Medicine

Front 1

A DNA sequence variation may or may not be pathogenic

Back 1

Mutation

Front 2

an allele present in more than 1% of the general population

Back 2

polymorphism

Front 3

G2983>A means what?

Back 3

a nucleotide exchange of guanine for adenine at position 2983

Front 4

What does C282Y mean?

Back 4

a missense mutation C is original amino acid, the position, and the new amino acid (tyrosin)

Front 5

What does W1282X mean?

Back 5

nonsense mutation original, position, folowed by X

Front 6

what does 711+1G->T

Back 6

mutation in intron/splicing site 1 is the 5' donor splice site

Front 7

What is a point mutation?

Back 7

a single base pair change in DNA

Front 8

What is missense mutation?

Back 8

changes in amino acid.

Front 9

What is silent mutation?

Back 9

does not change Amino acid

Front 10

what is conservative?

Back 10

changes to an amino acid with simliar properties

Front 11

What is a nonsense mutation?

Back 11

creates a stop codon Very deletarious to the protein!

Front 12

What are RNA splicing mutations?

Back 12

they disrupt the consensus sequences from splicing, or create alternative sites (pathogenic)

Front 13

What are small insertions/deletions?

Back 13

Will change reading frame (frameshift) if not in multiples of 3. (pathogenic)

Front 14

What is loss of function?

Back 14

reduces or eliminates the amount of funstional protein. ie. CF

Front 15

What is gain of function?

Back 15

increases production of a normal protein ie Anchondroplasia

Front 16

What are novel property mutations?

Back 16

changes function of the protein ie sickle cell anemia no effect on O2 transport, Huntington disease

Front 17

What is dominant negative?

Back 17

An allele that disrupts the function of the wild type allele in the same cell. Its worse than having none. Osteogenesis imperfecta.

Front 18

What are triplet repeat expansions?

Back 18

unstable mutations in which have expansion of a segment of DNA that contains 3 nucleotides
-lead to abnormalities of gene expressionandfunction
-repeats can be anywhere in gene even in intron
Huntington, fragile X, spinal cerebellar ataxis, Freidreichs ataxias, myotonic dystrophy

Front 19

What is anticipation?

Back 19

degree of expressivity or penetrance changes, usually increases, from one generation to the next

Front 20

What is parental bias?

Back 20

tenedency for a repeat to expand differs from a male vs. female

Front 21

important concepts of mitochondrial genetics

Back 21

-own genome
high mutation rate
-maternal origin
-variable inheritance and expression (diff phenotypes even in same family)
-heteroplasmy (diff tissue have diff levels)
-segregate as mendelian traits

Front 22

Couple key ideas about Real time PCR

Back 22

very rapid and sensitive 1/100,000
-use melting point analysis mutation destablizes and reduces melting point. Heterozygotes have 2 Tm's.

Front 23

What is RFLP?

Back 23

Restriction fragment length polymorphism use restriction enzymes to cut DNA at specific sites palindromic sequences
-good if mutation adds or deletes a site so get change in pattern

Front 24

What are "ARMS"?

Back 24

-Allele specific PCR amplification
-good if mutation doesnt change restiction site
-faster than PCR RFLP
-design primers specific to mildtype and mutated sequence
-needs 3' end to add and wildtype primer will extend
-score for absence/presence of a band)

Front 25

What is ASO or Dot Blot?

Back 25

-allele specificoligonucleotide hybridization
-short probes if perfect match will hybridize
-useful if no informative restriction site
-if probe binds you get color
-can be adapted for high throughput by spotting oliogos and probing patients labelled DNA (reverse dot blot)

Front 26

What is microarray?

Back 26

ASO for known mutations probes can be spotted onto chip, fluoresce labeled patient DNA will bind to mutant or WT or both. Mismatches wont bind.

Front 27

Southern Blotting +/-/

Back 27

can see large scale duplications and deletions expansions
-disadvantages: takes forever , expensive

Front 28

DNA sequencing

Back 28

incorporates random ddNTPs that dont allow pol to extend
+speels out DNA seq (gold standard)
-expensive laborious

Front 29

Newer DNA sequencing

Back 29

automated, uses fluorescence read by laser/CCD camera
should be 1 peak/position.
overlapping (go over)

Front 30

What are microsatellites?

Back 30

short tandem repeats
-zygosity testing
-maternal cell conamination
-UPD testing
-linkage
-paternity

Front 31

What is locus heterogeneity?

Back 31

more than one locus associated with a specific clinical phenotype (lots genes, 1 disease)

Front 32

Modifier gene

Back 32

gene that alters phenotype associated with mutations in a non allelic gene (thalassemia and sickle cell interaction)

Front 33

Clinical or Phenotype heterogeneity

Back 33

association of more than one phentype with mutations at a single locus. 1 gene, variable disease CF)

Front 34

Allelic heterogeneity

Back 34

multiple alleles at a locus ( many possible mutations in 1 gene, CF)

Front 35

Diagnostic Testing

Back 35

having a diagnosis is important to know recurrence risk, access support groups, avoid other invasive $$ procedures

Front 36

Predictive testing

Back 36

asymptomatic patients want to know. Counseling

Front 37

Carrier testing

Back 37

most informative when familial mutation is known disouraged in children

Front 38

Prenatal testing

Back 38

familys specific mutation should be known before testing offered

Front 39

______ is used for biochemical disorder testing

Back 39

enzyme assay

Front 40

When family history of a disease, should______________
then subsequent at risk people can have very informative test for only that mutation

Back 40

Affected person tested

CF carrier screening,ehthnicity matters!