Final Flashcards
What causes fragile X?
Severity of dz correlates w/ # of CGG repeats on the FMR1 gene on the X chromosome. MC inherited form of mental retardation. Expansion from pre- to full mutation only occurs through female meiosis.
XXY results in:
47XYY, masculine men, tall, Alien 3 Syndrome
What is Kleinfelters?
47XXY- hypogonadism, tall in stature, weak bones, may be infertile
What are histones?
They are proteins found in nuclei that package and order DNA into nucleosomes- chief protein component of chromatin- the spools around which DNA winds.
HOw to introns and exons participate in chormatin stage regulation?
Splicing of exons and introns likely occurs co-transcriptionally, with chromatin structure playing a key regulatory role.
Four specific post-translational histone modifications were observed enriched in exons.
What is the significance of CGCG sequences?
Transcriptional regulator Kaiso is a zinc finger protein that specifically binds to methylated CGCG sequences
How do we regulate transcription?
Histone methylations and acetylation
Promoters, enhancers, and exons
How do we regulate RNA transport?
Exportins-transport into the cytoplasm via vesicular transport
How do we regulate translation?
RNA processing and cap 5’/tail 3’
Splicing extrons/intron
Combination of exons = different proteins with different functions
When the poly(A)-binding protein (PABP) interacts with the translation initiation factor bringing the 5’ and 3’ ends of the mRNA together translation is enhanced.
What sex do we see Fragile X syndrome in?
Men
What are protooncogenes?
Normal genes that regulate cell growth and differentiation that when mutated increase growth.
Oncogenes cause cancer by affecting what?
cell growth and differentiation
Tumor suppressor genes require what level of mutation for cancer to develop?
Two-hit (both alleles affected)
If oncogenes take 2 hits do they produce more or less protein?
They are tumor suppressors and they are knocked out producing no regulatory proteins
Where are the locations of modifications marked in epigenomics map?
??
How does proximity interplay with gene linkage?
The closer they are, the more likely they are to be inherited together and less likely to be cross-linked.
What are some DNA polymorphism examples?
- RFLP: Restriction Fragment Length Polymorphisms. The presence or absence of a restriction site produces DNA fragments of varying lengths, reflecting sequence variation
- VNTR: Variable Number of Tandem Repeats. Varying numbers of minisatellite repeats in a specific region of the chromosome. Ranges in size from 20-70 bases each. The repeat is flanked on both sides by a restriction site.
- STRP: Short Tandem Repeat Polymorphisms or Microsatellites. Repeated unit 2-6 base long. Many alleles in the population with each different repeat length at a locus representing a different allele. Mb amplified with a PCR. They are used in paternity testing and in forensic cases as well as in gene mapping.
- SNPs: A single difference in a nucleotide sequence.Typed by PCR amp and ID by sequencing or use of probes on DNA cheps
Why are VNTRs valuable to us?
Variable number tandem repeats. They are used for paternity testing and forensics. Similar between related people.
What is amniocentesis? When is it performed? What percentage do we associate with fetal risk for the procedure?
A test used for prenatal genetic diagnosis in which a small sample of amniotic fluid is collected
Performed at 16 weeks gestation
Risk of fetal demise is from amnio 0.5% CVS is 1%
Risk of infxn, bleeding or damage to amniotic sac, death
BRCA1 is expressed where? What does it do?
BRCA 1 is located on chromosome 17, region 2 band 1, it produces breast cancer type 1 susceptibility protein which is responsible for repairing double strand breaks in DNA or destroying cells that cannot repair. If BRCA 1 is damaged, it is not able to repair DNA, which increases your cancer risk. It is expressed in mammillary cells and other tissues. It interacts with RAD51 to repair. (BRCA2 repairs single strand DNA breaks)
People with BRCA1 and 2 mutations have what condition?
Hereditary breast-ovarian cancer syndrome
What has contributed to failure of gene therapy?
- It’s short lived nature- there have been problems integrating the therapeutic DNA into the genome and the rapidly dividing nature of many cells prevent it from having long term effect, Pt’s would have to have many rounds of gene therapy
- Immune Response- There is always the risk of stimulating the immune system when introducing any foreign material into the body. Especially if the patient needs to have multiple rounds of gene therapy.
- Problems with viral vectors- toxicity, immune and infl response, gene control and targeting issues, may recover its ability to cause disease
- Multigene disorders- most common disease are due to combined effects of variations in many genes
What is RNAi? What can it be used for? What is its importance in human evolution related to parasites and viruses?
- Interference RNA - inhibits gene expression or translation by neutralizing targeted mRNA.
- RNAi is a process within living cells that moderates the activity of their genes. AKA co-suppression, post-transcriptional gene silencing (PTGS) and quelling.
- Has an important role in defending cells against parasitic and viral nucleotide sequences.
- It is a big deal because it is passed down to subsequent generations and means that DNA is not the only form of inheritance.
- Is also important to us because it can be used to shut down each gene in a cell which allows us to identify the component necessary for a particular cellular process or an event such as cell division (knock down studies). This is used to test the effect of mutated genes.
Gene control regulation and expression can be manipulated in which stages?
- CHROMATIN stage - Histone (compact DNA) methylation and acetylation.
- Transcriptional stage - Promoters, exon shuffling.
- Translational stage/RNA transport.
- Post translational control into cytoplasm.
- Post translational modification - folding, cutting, phosphorylation.
