L1- Genetic Material Flashcards
What are the chemical parts of a nucleotide? A nucleoside?
Nucleotides contain a base, a sugar and a phosphate(s). Nucleosides contain only a base and a sugar.
What is the chemical difference between the second carbons of RNA and DNA?
RNA has a 2’ OH group. DNA has an H at this position.
What is the direction in which DNA and RNA are read and written?
5’ to 3’.
The terms ‘denaturation’ and ‘annealing’ of double stranded oligos and primers refer to what physical change?
Strand separation (denaturation) and strand association (annealing).
Which class of enzymes relaxes positive and negative DNA supercoils?
Topoisomerases.
How many chromosomes do diploid human cells have?
46
How many base pairs does the haploid human genome contain, approximately?
About 3 billion.
What percent of human DNA codes for proteins?
1-2%
How many proteins do human genes encode, roughly (not including splice variants)?
About 30,000.
The average protein is about __ amino acids long.
About 400
What process often leads to more than one form of mature RNA being formed from a given transcript?
Alternative RNA splicing.
Functionally related genes that appear close to each other in the genome belong to the same ____.
Gene cluster (i.e. beta globin gene cluster).
What is a pseudogene?
A piece of DNA homologous to a coding segment that does not code for a protein.
Compared to pseudogenes, processed psudogenes lack ____.
Introns.
What is a provirus?
DNA copies of ancient viruses that have integrated themselves into the genome. There are about a thousand proviruses integrated into the human genome, and they make up about 8% of our DNA.
What is a transposable element?
A piece of DNA that can insert copies of itself in a new location within the genome.
What percent of our genome is composed of short interspersed repeat elements (SINEs)?
About 10%. Note that SINEs are inserted into the genome via reverse transcription.
What percent of our genome encodes long (>500 nt) interspersed repeat elements (LINEs)?
About 20%.
What is a transposase?
An enzyme that allows movement of a transposable DNA element. Note that some elements encode their own transposase.
Name two types of SSRs (simple sequence repeats).
Microsatellites (very short repeats) and minisatellites (14-500 base pair repeats).
What is the function of telomeres?
They protect the end of chromosomes from degradation.
Where are telomeres found and what is their base sequence?
Telomeres are found at the ends of chromosomes. They contain 1000-1700 copies of the hexameric sequence TTAGGG.
What is meant by the term mitotic clock?
It refers to the loss of 50-200 nucleotides from the ends of chromosomes every time a cell divides. When the telomeres are sufficiently shortened, the cell is no longer able to divide.
Name two drugs that inhibit topoisomerases.
Camptothecin and mAMSA.
What polymerase is often activated in cancer cells?
Telomerase - this enzyme rejuvenates the telomeres and circumvents the mitotic clock.
How is DNA packaged in nucleosomes?
DNA is wrapped around histone octomers. These are packed together to form chromatin fibers.
Telomerase is a ____ (type of enzyme).
Reverse transcriptase (it uses an RNA template).
What type of enzyme is encoded by LINEs?
A reverse transcriptase. This is involved in introducing additional copies of the LINE into the genome.
What is a single nucleotide polymorphism (SNP)?
It is a common single base substitution between individuals. Rare single base substitutions are called mutations.
Why are simple sequent repeats (SSRs) used as biomarkers?
SSRs tend to be highly polymorphic, so the number of copies varies from one individual to another. This allows them to be useful biomarkers.
