DNA, RNA, and DNA replication Flashcards
James Watson is…
a sexist asshole that stole info from people
What did Rosalind Franklin do?
used X-ray diffraction data
what are the purines?
adenine and guanine
what are the pyrimidines?
cytosine, uracil, and thymine
What are the complementary base pairs in DNA?
adenine-thymine (2 hydrogen bonds)
guanine-cytosine (3 hydrogen bonds)
what is Chargaff’s rule?
A pairs to T and G pairs to C
What is the basic chemical composition of DNA?
sugar phosphate backbone and a base combine to form a nucleotide
-nucleotides form to make a DNA strand
-make a double stranded DNA
-form a double helix
What is a gene?
a unit of heratity
How is DNA organized in prokaryotes?
linear or contiguous fashion
Can transcription and translation occur on the same strand at the same time in prokaryotic organisms?
yes, because there is no nucleus , there is no separation between transcription and translation
What are exons?
regions of DNA that will give rise to the protein sequence
What are introns?
regions of DNA that do not code for protein
What are UTR?
untranslated regions that are on the 5’ and 3’ ends of the DNA
What is the process of removing introns from a transcript?
splicing
Is there only one way to splice a transcript?
no, there are other regulatory elements that can alter the splicing (alternative splicing)
-this can create multiple proteins that can be made from one transcript
How is DNA condensed in prokaryotes?
by a set of polyamines and proteins in back and forth loops
(look like a bobby pin)
How is DNA condensed in eukaryotes?
first condensed with nucleosomes (involve about 200 bp each) and a set of core proteins
-nucleosomes looks like beads on a string and are packages together to give chromatin fiber structure
What is euchromatin?
more relaxed structure and transcriptionally active
What is heterochromatin?
more highly condensed and generally not transcriptionally active
What are the even more condensed that heterochromatin form of DNA?
solenoids and then supersolenoids and then into chromosomes
How were chromosomes arranged and numbered?
by size
-biggest is chromosome 1
-smallest chromosome 22 (or the Y chromosome)
What is the DNA entity in bacteria called?
plasmids
How many protein coding genes are in the human genome?
around 20,000-25,000
How much of the DNA is made up of coding genes?
1%
how many isoforms does the average gene give?
8
How long is the average gene?
27,000 bp
What is the proteome?
the complete set of proteins in an organism
(more complex than the average estimate)
How many bp is the human genome?
around 3.2 billion
What is the smallest mutation that can cause disease?
1 bp
What is the difference between siblings?
around 1-2 million bp
What is the difference between unrelated humans?
around 6 million bp
Base pair difference between humans and chimps?
around 50 million bp
Base pair difference between humans and mice?
around 100 million bp
Is only one strand of DNA able to be used for replication?
no, both strands are able to be used for replication
What is the central dogma of genetic information flow?
DNA -> RNA -> protein
What does DNA polymerase do?
makes new strand of DNA in the 5’ - 3’ direction
-requires a template strand and a strand to build off of with a free 3’ OH group
-has 5’-3’ polymerase activity and 3’-5’ exonuclease activity
Which direction is DNA made?
5’-3’
What are the origins of replication rich in?
AT regions
What is the active region of replication?
replication fork
How many replication forks on a circular chromosome?
two replication forks moving in opposite directions
What is the leading strand of DNA?
daughter strand that is synthesized continously
What is the lagging strand of DNA?
daughter strand that is synthesized discontinously
What are the fragments created on the lagging strand of DNA replication?
Okazaki fragments
Why are Okazaki fragments created?
since DNA replication happens 5’-3’, there are small fragments made that are then ligated together
what attaches Okazaki fragments?
DNA ligase
*requires ATP
What are the general steps of DNA replication?
-DNA rich in A-T pairs (replication origin)
-local opening of DNA helix
-RNA primer synthesis
-leading strand DNA synthesis begins
-RNA primers start lagging strand synthesis
How fast is DNA polymerase in bacteria?
500 nt/sec
How fast is DNA polymerase in eukaryotes?
50 nt/sec
What enzyme makes the RNA primers for DNA replication?
DNA primase
-creates a new polynucleotide chain
How long is the RNA primer?
10 nt
Why is the RNA primer needed for DNA synthesis?
DNA polymerase is not able to start their own nucleotide chains
Steps of lagging strand synthesis:
-RNA primer made by DNA primase
-DNA polymerase adds to new RNA primer to start new Okazaki fragment
-DNA polymerase finished DNA fragment
-old RNA primer erased and replaced by DNA
-nick sealing by DNA ligase joins new Okazaki fragment to the growing chain
What enzyme seals that broken phosphodiester bond?
DNA ligase
Is DNA replication accurate?
yes, there are a lot of mechanisms in place that remove the chance for a lot of mutations to cause huge harm
-only 3 nucleotide changes at each time of cell division
What is DNA helicase?
enzyme that moves along DNA strand and break any portions that are double stranded
What do single strand DNA binding proteins do?
bind to exposed DNA strands
-unable to open DNA strands themselves, but aid helicases by stabilizing unwound helix
-binding coats and straightens out regions of single-stranded DNA on the lagging strand template
-prevent formation of short hairpin helix
What does the sliding clamp do for DNA replication?
holds DNA polymerase on the DNA
What is Werner syndrome?
premature aging disease
-cells divide more slowly
-allow DNA damage to accumulate
-impair normal cell activities and cause health problems
How do retroviruses replicate?
use reverse transcriptase to turn their RNA into DNA that can be inserted into the human genome
