ABB HCLD Molecular Diagnostics Flashcards
Molecular Diagnostics is a universal Technology affecting what areas?
Genetics, Infectious Disease, Heme Oncology, Identity Testing
What is an infectious disease impacted by molecular diagnostics?
TB and other hard to culture organisms. These could take weeks to culture.
What is a diploid genome?
Two sets of chromosomes
How many pairs of chromosomes?
23 pairs, 22 pairs autosomes, 2 sex chromosomes
How many bases make up the human Genome?
3 billion
How many genes in the human genome?
22,000
How much of the human genome codes for proteins?
10%
Heterochromain
Densely packed region of chromosomes, like centromeres, not transcribed
Euchromain
Less densely packed region of chromosomes, transcribed
Chromosomes are characterized based on the position of the centromere.
Telocentric = centromere is located at the proximal end or tip of the chromosome
Acrocentric = centromere is located at one end of the chromosome, resulting in a very short arm and a very log arm (named after grasshoppers).
Sub-metacentric = centromere is located near but not exactly at the center of the chromosome (majority of human chromosomes).
Metacentric = centromere is located exactly at the center of the chromosome, leading to 2 equal size arms (seen in primitive organisms, amphibians) (human chromosomes 1 and 3).
Describe the centromeres of chromosomes.
Centromeres are variable in size, humans and plants are megabases and budding yeast are only 125bp. Centromeres are rich in repetitive AT sequences and are essential for mitosis and meiosis. The chromatin structure is unique because histone H3 is replaced by centromere specific histone H3, CENP-A which may affect DNA binding ability.
Antiparallel structure
5’ - 3’ and 3’ - 5’
A NUCEOTIDE is made up of :
A 5-carbon sugar, a phosphate and a nitrogenous base
Pyrimidine
A 6-member ring, Cytosine, Thymine, Uracil
Purine
Fused 5 and 6-member rings, Adenine, and Guanine
Difference between deoxyribose and ribose
Deoxyribose is missing an hydroxyl group in lower right corner
Mitochondrial DNA, how many bases and how many genes?
16.5K bases, 37 genes
What are some mitochondrial genes?
rRNA, tRNA, cytochrome C and ATP synthase
What do the large and small subunits of ribosomes do during translation?
The small subunit (40S) decodes the genetic message. The large subunit (60S) catalyzes the peptide bond formation. Both subunits are composed of rRNA and other proteins.
What is a locus?
The location of the gene on the chromosome
What is an allele?
Version of the gene present at any locus
Polymorphism
Benign change in the genome, almost everyone has them
Mutation
Present in a low percentage of people, role in disease
How often do SNP’s occur in the genome?
Every 300bp or 10 million per genome
What is a synonymous polymorphism?
A silent variant, the substitution does not change the amino acid.
What is a non-synonymous polymorphism?
The substitution does change the amino acid.
What is a somatic mutation?
Mutation that is acquired in non-germline cells, not inheritable,
What is a germline mutation?
Mutations occur in germline cells, they are inheritable,
What are structural mutations?
Translocations, Rearrangements, gene amplifications
What are molecular mutations?
Insertions, deletions, point mutations, nucleotide repeats
What does an exonuclease do?
Exonucleases are enzymes that cleave DNA sequences in a polynucleotide chain from either the 5’ or 3’ end, one at a time. DNA polymerase I exonuclease activity plays a role in correcting polymerase errors. Also, in replication they work with RNA pol II to degrade RNA primes which are replaced with DNA nucleotides.
The venom of snakes and lizards contains which group of enzymes?
Exonucleases are present in their toxins leading to cleavage of DNA molecules which code for essential proteins.
What is aneuploidy?
Whole chromosome loss or gain
What is a duplication?
An area of gene sequence is repeated, can visualize with FISH
What does a chromosome microarray show you?
Virtual or digital karyotype, millions of probes on a chip highlight areas of the chromosome where there could be abnormalities. Allows you to look for gains or losses in the genome.
What is a Duplication?
An area of gene sequence is repeated, visualize with FISH.
What is a Translocation?
An area of one chromosome is transferred to another chromosome, like BCR-ABL. Visualize with FISH or real-time PCR or NGS.
What is a point mutation?
A single nucleotide substitution, insertion or deletion.
What is a transition mutation?
A purine is substituted for a purine. A pyrimidine is substituted for a pyrimidine.
What is a transversion mutation?
A purine is substituted for a pyrimidine. A pyrimidine is substituted for a purine.
What is a missense mutation?
A base substitution that alters the codon resulting in a different amino acid.
What is a nonsense mutation?
A base substitution that alters the codon resulting in a stop codon.
What is a silent mutation?
Alters the codon, but not the amino acid
What is a neutral mutation?
Alters the amino acid to a similar amino acid which does not disrupt the protein.
What is a frameshift mutation?
Insertion or deletion of one or more bases which alters the codon reading frame changes protein structure
Sickle cell anemia is caused by:
A single point mutation in the hemoglobin gene
What is a splice site mutation:
Mutation alters the exon intron splice site, leads to exon skipping or intron inclusion
What is the universal genetic code?
The different codons that form the amino acids.
What a loss of function mutation?
Leads to complete or partial loss of protein function. Frequently recessive.
What a gain of function mutation?
Causes an entirely new trait which can appear in inappropriate tissue or at inappropriate time in development. Frequently dominant.
Quantity of DNA from UV Spectrophotometry?
(A260-A320) * dilution factor * 50 ug/mL
Quantity of RNA from UV Spectrophotometry?
(A260-A320) * dilution factor * 40 ug/mL
Quality of DNA by UV Spectrophotometry?
(A260/A280) = purity
(A260-A320) / (A280-A320)
1.7-2.0 = good quality
<1.7 = too much protein
How to look at quality of DNA/RNA with respect to size?
Gel electrophoresis
Maxam - Gilbert sequencing
Used a toxic chemical and never really caught on
Sanger sequencing technique
Chain termination sequencing using dideoxy method
Difference between deoxy and dideoxy
Dideoxyribonucleic acid is missing a hydroxl group and more dNTP’s cant add on so chain terminates
Capillary Sequencing Technique
Separate bands in the gel capillary, excite fluorescent tag with Argon laser, Fluorescent light is shown through a prism to separated the colors.
How does Ion Torrent Sequencing work?
Tagged DNA fragments are mixed with oil droplets, inside each oil droplet there is a sphere with DNA sequences that match the adaptors. Fragments bind to sphere and are PCR amplified inside the oil droplet. Each sphere is spun down into the chip. Sequencer floods the chip with a certain dNTP and measures the pH.
How does Illumina work?
Seguencing by synthesis. Adapters cause DNA fragments to bind to the surface of the flow cell. Adapter at other end of the fragment bends over and binds forming a bridge. Synthesis occurs and amplifies the fragments, makes many copies and you visualize fluorescence.