Intro To Molecular Diagnostics Flashcards
What is the central dogma of molecular biology?
DNA making RNA and RNA making proteins
An individual’s coded genetic information is hardwired into what?
DNA
What is the coded genetic information hardwired into DNA transcribed into?
Individual transportable pieces of messenger RNA
What synthesis does mRNA direct?
The synthesis of a particular protein based on the code it contains from transcribed genetic material
What is a genotype?
The genetic makeup of an individual.
Another way of saying genetic makeup
Primary nucleotide sequence
How many alleles if a gene are they! What are their sources?
Two. One from mother and ine from father
What do you understand by phenotype?
Phenotype is the expressed physical characteristics of a gene product and its biological function
What determines one’s phenotype?
Their genotype
Do alterations in genotype change phenotype?
They may or may not
What is DNA?
Deoxyribonucleic acid that contains genetic material
What is the structure of a DNA?
A DNA is a polymer of nucleotides
What does a nucleotide consist of?
Deoxyribose sugar
Phosphate residual
Nitrogenous base
What nitrogenous bases are seen in DNA?
A - Adenine
G - Guanine
T - Thymine
C - Cytosine
Identify the two bonds a DNA polymer is assembled by?
Intra-strand phosphodiester bond
Interstrand hydrogen bond
What is the purpose of intra-strand phosphodiester bond in assembling DNA polymers?
It links the 5’ phosphate group of one nucleotide with the 3’ hydroxyl group of the next nucleotide creating the DNA polymers sugar phosphate backbone
What bond is responsible for the sugar phosphate backbone of a DNA polymer?
Intra strand phosphodiester bond
What is the purpose of interstrand hydrogen bonds in assembling DNA polymer?
It gives DNA it’s helical conformation by joining A to T bases with 2 hydrogen bonds and G to C bases with 3 hydrogen bonds
How is RNA different in structure from DNA?
- RNA has ribose sugar structure
- Exists in a single strand folded into complicated 3-D structure for function and integrity
What are the nitrogenous bases seen in RNA?
A - Adenine
U - Uracil
C - Cytosine
G - Guanine
How does RNA differ from DNA in terms of nitrogenous bases?
DNA has thymine that RNA doesn’t and RNA has uracil that DNA doesn’t.
How many pairs of chromosomes are there?
23 pairs, 46 chromosomes in total.
With the help of what are chromosomes highly condensed?
With the help of associated structural proteins, mainly histones.
What is chromatin?
Nuclear DNA in conjugation with associated structural proteins
Define a nucleosome.
The basic level of chromatin organization called beads on a string
In what phase are chromosomes in their most compact state?
Metaphase
How should DNA be during replication and gene transcription?
Unpacked
What are the 3 purposes of chromatin?
- Fit long strands of DNA in nucleus
- Protect delicate DNA from damage
- Inactivation of genes
Is DNA replication conservative?
No, semi conservative
What does is the semi-conservative feature of DNA replication?
Each new dsDNA consists of 1 parent strand (template) and 1 daughter strand (new)
DNA replication is coordinated by?
Several DNA-binding proteins and emzymes
What enzyme separates the two strands of DNA?
Helicase
What is the function of the helicase?
Seperating the two strands of DNA
What enzyme participates in the underwinding of DNA?
Topoisomerase
What is the function of topoisomerase in DNA replication?
It underwinds DNA
How does ss-binding proteins help in DNA replication?
By preventing reannealing of ssDNA
What protein prevents reannealing of ssDNA?
Single stranded binding protein
What is DNA polymerase?
It is the enzyme that synthesizes nucleotides and links them based on template strands
What is the rate at which DNA polymerase synthesizes nucleotides linking them based on template strands?
1000/s
What is the primase in DNA replication?
The enzyme on lagging strand that synthesizes a starting nucleotide primer for Okazaki fragments
DNA polymerase only synthesizes DNA from what prime ends?
5’ to 3’
From what end to what end is the lagging strand?
3’ to 5’
In the lagging strand, how can DNA be synthesized since it is from 3’ to 5’ and DNA polymerase synthesizes from 5’ to 3’?
DNA must be synthesized discontinuously in short segments
What is the function of the ligase?
Enzyme on lagging strand linking Okazaki fragments together
What the most important feature in DNA replication?
Integrity
What are mutations in DNA replication?
Mutations are errors in nucleotide formation.
What property does DNA polymerase have that helps counteract the mutations that happen in replication?
Exonuclease activity
What does the exonuclease activity of DNA polymerase achieve?
- Recognizes and cuts out wrong nucleotide. (Proof-reading)
How are mutations reduced after proof reading function of DNA polymerase?
One nucleotide error happens every 10^5 nucleotide incorporated, but with proof reading of DNA polymerase, one error happens per 10^9/10 nucleotides replicated
How many errors are seen per cycle after proof reading?
0.3 to 3
Why are mutations dangerous?
Mutations of important genes like GI,or surprises or genes or proto-oncogenes may lead to cancer
What cells are prone to grow cancer? And why?
Cells with increased exposure to carcinogens. They have a high turnover rate, so more cell cycles and more chance for errors to happen
What is PCR?
Polymerase chain reaction. An artificial replication technique that is fast and inexpensive used to copy and amplify specific DNA fragments
This fast and inexpensive technique is used to copy and amplify specific DNA fragments.
PCR
What are the components in PCR system?
DNA polymerase
Primers
dNTPs
What component of the PCR systems makes it require high levels of heat to function?
DNA polymerase which is heat resistant
What are primers in PCR and what is their use?
Short, manufactured single strings of nucleotides used to define a specific DNA segment for amplification
What is the use of dNTPs?
Nucleotide building blocks used to synthesize new DNA
How many cycles does the PCR system have? How many steps?
30-40 cycles. 3 steps
Describe the three steps in PCR?
Denaturation: separating double strand at high temp (94-98)
Annealing: primers binding to single strand template (50-65)
Extension: DNA polymerase makes new DNA strands (70-80)
What is the end product of PCR?
Large amount f specific DNA fragments of target
What is the difference between DNA and protein that calls for transcription?
DNA stored genetic information but protein carries out the function
How is RNA necessary for transcription?
RNA is a necessary intermediate messenger carrying specific instructions to the factories that synthesize proteins
Define transcription.
Transcription is the provess of transferring sequence information from DNA to RNA
How is transcription initiated?
Transcription starts by binding transcription factors to promoter regions
What are promotors?
Regulatory region of a gene where transcriptional factors bind to activate gene transcription
What is the regulatory region of a gene where transcription factors bind to activate gene transcription?
Promoter region
What are transcription factors?
Series of protein cofactors that bind to promotors and RNA polymerase II and start transcription from DNA to mRNA
What is the difference between an exon and intron?
An exon is the coding region of a gene that contributes to AA sequence while an intron is the no coding sequence between exams of a gene
What is the expressed sequence of a gene
Exon
What is the intervening sequence of a gene?
Intron
The 5’ end of RNA is modified with what!
A protective cap
What does the cap do aside replacing the 5’ end of RNA?
Initiates recognition and protein synthesis later on
The 3’ end of RNA is modified by addition of what?
Multiple adenine bases. Poly (A) tail
What is the necessity of the poly (A) tail I’m mRNA transcripts?
Translation and protecting mRNA from degradation
What us RNA slicing?
This is the process of converting a newly transcribed RNA (pre mRNA) into a mature mRNA
In what process are intron sequences sequences removed and exon sequences connected together?
RNA splicing
What does a mature RNA consist of?
5’ cap
3’ poly (A) tail
Spliced sequence
What is translation?
It is the process in which mRNA sequences direct the amino acid sequences to synthesize proteins
Where does translation take place?
On ribosomes (rRNA) using tRNA to match mRNA
A codon is a how many nucleotide sequence?
3 nucleotide sequence a
Each amino acids have how many codons!
At least one
What is the initial codon where protein synthesis begins?
AUG
Identify the stop codons
UGA
UAG
UAA
Specific amino acids are delivered to mRNA by
tRNA
What are genetic events related to?
Changes in actual DNA sequences
Identify some genetic events
Gene mutation
Translocation
Deletions etc
Epigenetic events are related to what?
Processes that don’t alter DNA sequences but still have effects in gene function
What is the difference between genetic and epigenetic events?
In genetic events, there’s actual change in DNA sequence but in epigenetic events, processes alter gene function without a,tearing DNA sequence
List some epigenetic events
DNA methylation
Histone modification
ncRNA regulation (non-coding RNA)
Chromatin remodeling
These events affect the access to genetic code without affecting genetic code itself
Epigenetic events
What is DNA methylation?
A biological process by which methyl groups are added to a DNA molecule by binding it to cytosine
How does DNA methylation inhibit transcription?
Methylated cytosine prevents binding of RNA polymerase II to get access to DNA sequence
