CMB Week 2 Flashcards
In sickled cells, valine causes a … that polymerizes when Hb is …
In sickled cells, valine causes a hydrophobic patch that polymerizes when Hb is deoxygenated.
In HbS, when RBCs rupture, the vessels become …
In HbS, when RBCs rupture, the vessels become occluded (trapped cells).
Vaso-occlusion is a complex event involving - - - - leading to tissue damage from ….
Vaso-occlusion is a complex event involving - endothelial activation - leukocyte and red cell adhesion - hemoglobin polymerization - ischemia and infarction leading to tissue damage from necrosis.
The sickle cell trait provides a … in areas where falciparum malaria is endemic
The sickle cell trait provides a survival advantage (balanced polymorphism) in areas where falciparum malaria is endemic
Three tests used to diagnose sickle cell disease
1) Solubility test 2) Hemoglobin electrophoresis 3) DNA analyses (Restriction Fragment Length Polymorphism)
Solubility test for sickle cell disease
- blood is added to a solution with high ionic strength (2% sodium metabisulfite) - Deoxyhemoglobin S has a low solubility in this solution whereas deoxyhemoglobin A is soluble - this test cannot distinguish the trait from the disease state
Hemoglobin Electrophoresis
- agarose gel using a citrate buffer pH 6.0 - larger molecules will migrate more slowly - HbS will move more slowly than normal HbA - AS (sickle cell trait) will show as two pieces, with heavier HbS at the top - HbF - smallest, will run quickest
DNA analyses: Restriction Fragment Length Polymorphism (RFLP)
- more sensitive method that can be used to detect the DNA mutation in HbS - RFLP based on the ability of restriction endonucleases to cleave specific sites within the DNA sequences - if the cleavage site contains a mutation, the restriction endonucleases can no longer cleave at that site leaving a larger DNA fragment compared to the DNA with the normal sequence
One method for prevention of crises in sickle cell anemia is partial exchange …, although this is only used in select cases due to the complication of ….
One method for prevention of crises in sickle cell anemia is partial-exchange blood transfusion, although this is only used in select cases due to the complication of iron overload (transfusion-induced hemosiderosis)
transfusion-induced hemosiderosis
- iron overload - there is no excretory pathway in the body for eliminating excess iron and its accumulation can result in organ failure.
Besides blood transfusions, what are two other forms of treatment for sickle cell anemia?
- bone marrow transplantation to repopulate the patient’s bone marrow with normal donor cells - induction of HbF synthesis
Why would increase levels of HbF help in sickle cell disease?
- HbF has been shown to inhibit sickling - inhibits Hb polymerization - in individuals who express higher levels of HbF, the RBCs do not become as deformed and vaso-occlusive crises do not occur
What drug increases the expression of HbF
hydroxyurea
If a proline is substituted into the alpha helical region of hemoglobin, an unstable hemoglobin can arise because:
Prolines are helix breakers and the breaking of an α-helical segment can cause an unstable hemoglobin
Hemoglobinopathies of increased oxygen affinity are often characterized by … anemia and ….
Hemoglobinopathies of increased oxygen affinity are often characterized by hemolytic anemia and Heinz body formation.
Patients with higher than 10% of HbM will show …
Patients with higher than 10% of HbM will show cyanosis
Patients with higher than 35% of HbM will have clinical symptoms such as …
Patients with higher than 35% of HbM will have clinical symptoms such as headache and weakness.
A higher than 80% of HbM is not …
A higher than 80% of HbM is not compatible with life.
The deficiency of the enzyme … that can reduce the ferric iron back to the ferrous state can also result in …
The deficiency of the enzyme diaphorase that can reduce the ferric iron back to the ferrous state can also result in methemoglobinemia.
Operon
cluster of genes that code for proteins involved in a particular metabolic pathway
An operon is made up of several structural genes arranged under a … and regulated by a …
An operon is made up of several structural genes arranged under a common promoter and regulated by a common operator
The lactose operon is an example of …
inducible operon
The lactose operon contains genes that
encode enzymes responsible for lactose metabolism
What are the 3 structural genes in lac operon?
lac Z, lac Y, and lac A
lac Z
- gene that codes for the enzyme beta-galactosidase - beta-galactosidase breaks down lactose into glucose and galactose
lac Y
- gene that codes for the enzyme permease - permease transports lactose into the cell
lac A
gene that codes for the enzyme transacetylase
In addition to the structural genes, the lac operon has:
- promoter (P) - Operator (O) - CAP binding site (catabolite gene activator protein) - repressor gene (lac I)
The repressor gene in lac operon binds to:
lac I: lac repressor binds a) to DNA of the operator region, prevents RNA pol advancing along the operon, and transcription does not occur b) binds to lactose
In the absence of lactose (i.e. in the presence of glucose)
- lac I gene is transcribed and translated, producing the lac repressor protein - lac I binds to the operator and blocks RNA pol - no transcription - enzymes for lactose metabolism are not synthesized
If there is lactose in the environment and a small amount of the lactose gets into the cell:
- lac repressor is constitutively synthesized - lac I binds to the lactose, which induces conformation change in lac I and is now unable to bind to the operator region - RNA pol can transcribe the genes of the operon
When both glucose and lactose are available in the cell:
-transcription of the operon is negligible - adenylate cyclase is deactivated - no cAMP produced
… is active in the absence of glucose, producing … that binds to CAP. This further promotes …
Adenylate cyclase is active in the absence of glucose, producing cAMP that binds to CAP. This further promotes transcription of structural genes.
Repressible operon
- transcription of the operon normally takes place (operon is ON) - activated repressor protein binds to operator and prevents transcription
The tryptophan (trp) operon is an example of a …
repressible operon
If there is plenty of trp around, and no more is needed, the operon is …. If there is no trp around, it needs to be synthesized, and the operon is …, allowing the production of the enzymes for trp synthesis
If there is plenty of trp around, and no more is needed, the operon is repressed. If there is no trp around, it needs to be synthesized, and the operon is transcribed, allowing the production of the enzymes for trp synthesis
Regulation of transcription in response to lack of amino acids (prokaryotes)
- Uncharged tRNA binds to the A site of the large ribosome subunit, activating stringent factor ReIA - ReIA synthesizes polyphosphorylated guanosine (ppGpp) - Results in selective inhibition of transcription (protein synthesis is inhibited), until AAs are available
Hereditary persistence of fetal hemoglobin (HPFH)
a benign condition in which significant fetal hemoglobin production continues well into adulthood, disregarding the normal shutoff point after which only adult-type hemoglobin should be produced
As HbF switches to HbA, the activation of β chain acts to …
As HbF switches to HbA, the activation of β chain acts to down regulate the production of gamma and delta goblins
In HbSC, the individual is … and …
In HbSC, the individual is heterozygous for the sickle cell trait and heterozygous for the HbC disease.
Common motifs in proteins that bind DNA and regulate transcription
- helix-turn-helix - leucine zipper - zinc finger
Cis-acting regulatory elements (CREs)
specific regulatory DNA sequence that binds trans-acting protein factors
Nuclear receptors mostly sense small hydrophobic molecules such as ….
Nuclear receptors mostly sense small hydrophobic molecules such as steroid and thyroid hormones.
Apolipoprotein B is a protein that carries fat molecules around in the body. The ApoB mRNA is made in the ….
Liver
In the intestine, on ApoB-100 protein, the C residues in the codon CAA (glutamine) is deaminated to U, making a nonsense codon; creating a shorter protein Apo B-48. This is an example of
mRNA editing
Chylomicrons
- a large plasma lipoprotein particle - transports neutral lipids from the intestine to the tissues by way of the lymph.
RNA interference (RNAi)
mechanism of gene silencing through decreased expression of mRNA, either by repression or by increased degradation
RNA interference (RNAi) is mediated by
microRNA (miRNA), a short 22 bp non-coding RNA
endonuclease DICER cleaves double-stranded RNA creating
endonuclease DICER cleaves double-stranded RNA creating short double-stranded RNA fragments called small interfering RNA (siRNA) and microRNA
RISC – RNA-induced silencing complex
a multiprotein complex, specifically a ribonucleoprotein, regulates mRNA expression
RISC associates with …, which acts as a …
RISC associates with one strand of siRNA or miRNA, which acts as a template for RISC to recognize the complementary sequence on mRNA
Once RISC has recognized the target mRNA, RISC can …
Once RISC has recognized the target mRNA, RISC can repress the translation of the target mRNA
Slicer/Argonaute/Ago are proteins found in RISC that can …
Slicer/Argonaute/Ago are proteins found in RISC that can cleave the target mRNA leading to degradation.
Phosphorylation of Eukaryotic Initiation Factor 2 (eIF2)
inhibits its function and inhibits translation at the initiation step.
On DNA, histone proteins are covalently modified at their … terminal end by … or …. to influence …
On DNA, histone proteins are covalently modified at their NH2 terminal end by acetylation or phosphorylation to influence gene expression.
Methylation modifies the … of the DNA, typically acting to …
Methylation modifies the function of the DNA, typically acting to suppress gene transcription.
Which two DNA nucleotides can be methylated?
adenine and cytosine
Adenine DNA mythelation only occurs in …
prokaryotes
CpG islands
unmethylated CpGs are often grouped in clusters called CpG islands
In many disease processes, such as cancer, gene promoter CpG islands acquire …, which results in …
In many disease processes, such as cancer, gene promoter CpG islands acquire abnormal hypermethylation, which results in transcriptional silencing.
Chromatin remodeling:
Chromatin remodeling is the modification of chromatin architecture to allow access to the condensed genomic DNA, influencing gene expression.
Chromatin remodeling relaxes the …
the nucleosome
Transposons
mobile segments of DNA that move in random manner from one site to another, on the same or different chromosome
Direct transposon movement, …
Direct transposon movement, cuts out and then inserts the transposons at a new site.
In replicative transposon movement, the transposon is … elsewhere while the original …
In replicative transposon movement, the transposon is copied and the copy is inserted elsewhere while the original remains in place.
Transcriptional factors are of clinical significance for at least two reasons:
1) mutations can be associated with specific diseases 2) they can be targets of medications
Oncogene
a gene that has potential to cause cancer
Many transcription factors are either … or … so mutations or aberrant regulation of them is associated with …
Many transcription factors are either tumor suppressors or oncogenes, so mutations or aberrant regulation of them is associated with cancer.
Three groups of transcription factors important in human cancer
1) the NF-kappaB and AP-1 families (2) the STAT family (3) the steroid receptors
Mutations in the … transcription factor are associated with Rett syndrome, a …
Mutations in the MECP2 transcription factor are associated with Rett syndrome, a neurodevelopmental disorder
A rare form of diabetes called MODY (Maturity onset of diabetes of the young), can be caused by mutations in … or …
A rare form of diabetes called MODY (Maturity onset of diabetes of the young), can be caused by mutations in hepatocyte nuclear factors (HNFs) or insulin promoter factor 1 (IPF1)
Mutations in the … transcription factor are associated with …, a disease in which individuals are unable to produce the finely coordinated movements required for speech
Mutations in the FOXP2 transcription factor are associated with developmental verbal dyspraxia, a disease in which individuals are unable to produce the finely coordinated movements required for speech
Mutations in the … transcription factor cause the autoimmune disease called IPEX, which leads to a …
Mutations in the FOXP3 transcription factor cause autoimmune disease called IPEX, which leads to a dysfunction in regulatory T-cells
Li-Fraumeni syndrome is a rare hereditary disorder, leading to …, caused by mutations in the … gene
Li-Fraumeni syndrome is a rare hereditary disorder, leading to cancer predisposition, caused by mutations in the tumor suppressor p53 gene.
The STAT family of transcription factors are associated with …
The STAT family of transcription factors are associated with breast cancer.
A variety of cancers are associated with the … of transcription factors.
HOX family
Most Osteogenesis Imperfecta (OI) cases are caused by
type I collagen mutations
Severity of OI disorders from most severe to mildest
Most severe: OI type II ➡️ type III ️ ➡️ type IV ➡️ type I (mildest)
OI type I is the most …. It is an autosomal … Features include:
OI type I is the most mild and most common. It is an autosomal dominant inherited disorder. Features include: - blue sclerae, mild to moderate bone fragility before puberty. - hearing loss, which progresses to severe as adults - mitral valve prolapse - easy bruising - large joints are hyperextensible
OI type IA has no …, while type IB does.
dentinogenesis imperfecta
Dentinogenesis imperfecta (DI) is a
genetic disorder of tooth development.
OI type II is the … form of the disease, and leads to … due to … The disease is caused by new … Characteristics:
OI type II is the most severe form of the disease, and leads to death in utero or in the perinatal period due to respiratory failure. The disease is caused by new dominant mutations. Characteristics: - multiple utero fractures - triangular face flat mid face - small beaked nose - bluish-gray sclerae
OI type III is a progressively … and is the most … Most are caused by .. mutations, but … mutations have been reported. Many die in childhood or adulthood due to …. Characteristics include:
OI type III is a progressively deforming OI and is the most severe form compatible with life beyond infancy. Most are caused by dominant mutations, but recessive mutations have been reported. Many die in childhood or adulthood due to respiratory, cardiac or neurological complications. Characteristics include: - macrocephaly (increased head circumference) - triangular flat mid face - bluish sclerae which lighten with age - long bone and spine deformities
OI type IV includes a variety of … forms of …. inherited disorders, with mild to moderate … Characteristics include:
OI type IV includes a variety of moderately severe forms of dominantly inherited disorders with mild to moderate bone fragility. Characteristics include: - prenatal fractures - osteoporosis - macrocephaly - scloliosis -short stature
OI type IVA has no …, while type IVB does.
dentinogenesis imperfecta
When recombinant DNA encoding a protein is introduced into a host organism, the recombinant protein will …. Expression of foreign proteins requires the use of …
When recombinant DNA encoding a protein is introduced into a host organism, the recombinant protein will not necessarily be produced. Expression of foreign proteins requires the use of specialized expression vectors.
Recombinant DNA (rDNA) are:
Recombinant DNA (rDNA) are formed by laboratory methods, and are sequences generated from multiple sources, creating DNA that would not otherwise be found in biological organisms.
Vector (DNA)
Any molecule that has the ability to replicated inside the host
Vectors are generally derived from ….
plasmids and viruses
Plasmid:
Plasmid is a small DNA molecule within a cell that is physically separated from a chromosomal DNA and can replicate independently. They are most commonly found in bacteria as small, double stranded molecules.
Bacterial protein expression systems, such as … and …. are commonly used in molecular cloning because they are …, …., and ….
Bacterial protein expression systems, such as E. coli and plasmids, molecular cloning because they are easy to culture, grow fast, and produce high yields of recombinant proteins.
What type of vectors are used if the DNA segment being cloned is exceptionally large?
- bacteriophages - retroviruses - bacterial or yeast artificial chromosomes
Recombinant DNA: Explain cloning (using plasmids)
After the vector (plasmid) is inserted inside the bacteria (host), the plasmid replicates as the host replicates. The plasmid contains a selectable marker, often an antibiotic. After replication, there are multiple products, some with the gene of interest, some without. Next, antibiotics are added to this mixture, and only the bacteria with the antibiotic resistant plasmids will survive.
Eukaryotic multi-domain proteins expressed in bacteria are often …, because bacteria are prokaryotes, and they are not equipped to …
Eukaryotic multi-domain proteins expressed in bacteria are often non-functional, because bacteria are prokaryotes, and they are not equipped to perform post-translational modification or molecular folding.
Eukaryotic Recombinant Protein production: mammalian in vivo expression systems usually produce …., but …
Eukaryotic Recombinant Protein production: mammalian in vivo expression systems usually produce functional proteins, but yield is low, it’s time consuming, and costly.
Explain gene therapy
In gene therapy, a viral vector containing DNA encoding the functional gene is inserted into the target cells. Virus unloads its genetic info, the functional gene is translated to functional proteins that restores the target cells into their normal state.
Examples of virus types that are used as gene therapy vectors
- retroviruses - adenoviruses - adeno-associated viruses - herpes simplex viruses
Retrovirus
a single-stranded RNA, invades the host cell, and uses reverse transcriptase to transcript its RNA into DNA. The viral DNA is integrated into the host cell’s DNA
Adenovirus
- has double stranded DNA - can cause respiratory problems (common cold)
Adeno-associated virus
small, single-stranded DNA virus that can insert its genetic material at a specific site on chromosome 19
Herpes simplex virus
double-stranded DNA virus that infect neurons
Two nonviral options for delivery in gene therapy
- Direct introduction of the therapeutic DNA into the target cells. Can only be used with certain tissues and requires a large amount of DNA 2. Creation of an artificial lipid sphere (liposome) with an aqueous core, which can carry the therapeutic DNA trough target cell’s membrane
What factors have kept gene therapy from becoming an effective treatment for genetic disease?
- short-lived nature of gene therapy - immune response (attack of foreign invader) - problems with viral vectors (toxicity, virus regaining its function, inflammatory responses) - multigene disorders - most diseases arise from mutations in more than a single gene.
Gene knockdown
experimental technique where expression of one or more of an organism’s genes are reduced.
Knockout mutation
replacement of a gene segment by homologous recombination that results in a nonfunctional or null allele
Knock-in mutation
point mutation that results in a partially functional or nonfunctional allele
Northern Blot
- Isolate the RNA of interest 2. Gel electrophesis - RNA fragments are separated by size on the gel 3. Blotting - the RNA fragments are transferred to a membrane (something more stable than gel) 4. Hybridization - A probe is used to identify the RNA of interest. Probe is usually fluorescent, complimentary DNA (cDNA) 5. Wash off excess probe 6. Visualization (radiography)
Southern Blot
- DNA is cleaved into several smaller fragments. 2. Gel electrophesis - DNA fragments are separated by size on the gel 3. Blotting - the DNA fragments are transferred to a membrane (something more stable than gel) 4. Hybridization - A probe is used to identify the DNA of interest. Probe is usually radioactive, complimentary DNA (cDNA) 5. Visualization (radiography)
What are two main difference between Northern Blot and Southern Blot?
Southern Blot uses DNA fragments, while Northern Blot uses RNA. In Southern Blot, before analysis, the DNA has to be cleaved by enzymes, in Northern Blot, the RNA is not cleaved.
In Southern Blot, before analysis, the DNA has to be cleaved by enzymes, in Northern Blot, the RNA is not cleaved. Why?
RNA not cleaved because it is already short.
Polymerase Chain Reaction (definition)
technique used to amplify a DNA sequence - creating thousands to millions of copies of the sequence
What are the main components required for PCR:
- template (DNA sample) - DNA polymerase (a thermally stable enzyme for replication of DNA) - primers (small single-stranded DNA sequences complimentary to either end of the region being amplified) - buffer - mixture of nucleotides (G, A, C, T) - thermocycler (automated heating/cooling device)
Steps of PCR
- DNA is denatured - temp. increased to 95 degrees C. The two strands separate 2. Cool down mixture to allow primers to anneal to each DNA strand. 3. Temp brought to 72 degrees C, add nucleotides and DNA pol can now replicate the DNA 4. Repeat steps 1-3 to amplify the DNA
Potential yield from PCR calculated by
Yield = (2^n)x, n = number of cycles, x = original copies of DNA
In situ hybridization (ISH) is a ….
In situ hybridization (ISH) is a type of hybridization that uses a labeled complementary DNA, RNA or modified nucleic acids strand (i.e., probe) to localize a specific DNA or RNA sequence in a portion or section of tissue (in situ)
DNA microarray analysis
- method for simultaneous evaluation of multiple genes - can only be used for known genes and their products
Differential expression analysis by differential display
Purpose of these techniques is to compare two different RNA populations (normal vs diseased, one tissue type vs another, control vs treated)
Body Mass Index (BMI)
determines the relative weight for stature of an individual
BMI is calculated by
(weight kg)/(height meters)^2 (703) X (weight lb)/(height inches)^2
Range of BMI for healthy individual
19.5 - 25
Range of BMI for overweight individual
25.1 - 29.9