Chapter 13 Flashcards
The molecular Basis of Inheritance (aka DNA Replication)
Who was Fredrick Griffth?
he discovered the phenomenum of “transformation” (mouse experiment)
What are Chargaff’s Rules?
1)DNA composition varies between species
2) for each species, %of A matches %of T, and %of C matches %G
What was the Hershey-Chase experiment?
found that DNA was genetic material (tagged proteins and DNA on viruses and let them infect E. Coli)
What is a baceriophage?
viruses that infect bacteria
What is a virus
an infection particle incapable of replicating outside of a cell
explain the structure of a DNA double helix
-the helix makes a full turn every 3.4 nM
-the bases are stacked .34nM apart
-every ten ‘rungs’, the helix creates a full turn
How are nucleic acids unique in comparison to other organic molecules?
nucleic acids have the ability to dictate their own replication from monomers
DNA replication is
the process by which a DNA molecule is replicated
(1 in 10,000,000,000 nucleotide pairs have an error)
What are the models of DNA replication? Which one is the most supported?
conservative model - a parent molecule creates an identical copy while remaining intact, resulting in 3 new daughter molecules and the original parent molecule
semiconservative model - a strand from the parent goes to each of the direct daughters, who then replicate again, so there are 4 new daughter molecs with 2 of those having a strand of the original parent in them (MOST SUPPORTED IN EXPERIMENTATION)
dispersive model - all of the resulting 4 daughter molecs have parts of the parent, in a mosaic fashion
origin of replication
stretch of DNA with a specific sequence of nucleotides that dictate where replication should occur
-eukaryotes have thousands of these to spread up the process of DNA replication
replication fork
a Y-shaped region on replicating DNA molecule where the parental strands are being unwound and new strands are synthesizing
Helicase
an enzyme that untwists the double helix of DNA at replication forks by breaking the nitrogenous base’s H-bond
Single-strand binding protiens
a protein that binds to the unpaired DNA strands during DNA replication, stabilizing and holding them apart while serving as templates for the synthesis of complementary strands of DNA
topoisomerase
a protein that breakers, swivels, and rejoins DNA strands (relieve strain in the double helix ahead of the replication fork)
what is a RNA primer?
a short polynucleotide with a free 3’ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotide during DNA replication
what is primase?
a enzyme that joints RNA nucleotide to make a primer during DNA replication, using the parental DNA strand as a template
what is DNA polymerase
an enzyme that catalyzes the elongation of new DNA by the addition of nucleotides to the 3’ end of an existing chain
what is the lagging strand? what are Okazaki fragments?
the lagging strand is a discontinuously synthesized DNA strand that elongates by menas of OKazaki fragments in a 5’ -> 3’ direction (away from the replication fork)
Okazaki fragments are short segments of DNA synthesized away from the replication fork on a template strand during DNA
what is DNA ligase?
an enzyme that catalyzes the covalent bonding of the 3’ end of one DNA fragment to the 5’ end of another DNA fragment
what is the process of mismatch repair?
the cellular process that uses specific enzymes to remove and replace incorrectly paired enzymes
what is nuclease?
an enzyme that cuts DNA or RNA, either removing one or a few bases, or hydrolyzing the DNA or RNA completely into its component nucleotides
what is nucleotide excision repair?
a repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide
what are telomeres?
the repetitive DNA at the ends of eukaryotic chromosome’s DNA molec; protects genes from being eroded during successive rounds of replication
what is a nucleoid?
dense regions of DNA in a bacterium that are not surrounding with a nuclear envelope
what are chromatin?
complex regions of DNA and proteins fitting into the nucleus of a eukaryotic cell
what is a nucleosome>
the basic, bead-like unit of DNA packing in eukaryotes, consisting of a segment of DNA wound around a protein core composed of 2 copies of each of 4 types of histone
histone
small proteins with a high proportion of positively charged amino acids that bind to the negatively charged DNA and play a key role in chromatin structure
what is a heterochromatin?
eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed
what is a euchromatin?
the less condensed form of eukaryotic chromatin that is available for transcription
what is nucleic acid hybridization?
the process of base pairing between a gene and a complementary sequence on another nucleic acid molecule
-bases of genetic engineering
what is DNA cloning?
the production of multiple copies of a specific DNA segment
what are plasmids?
small, circular, double stranded DNA molecs that carry away genes separate from those of a bacterial chromosome
-used as vectors
what is a recombant DNA molc?
a DNA molc made in vitro with segments form different sources
what is a cloning vector?
a DNA molc that can carry foreign DNA into a host cell and replicate there (includes plasmids)
what is gene cloning?
the production of multiple copies of a gene
what are restriction enzymes?
a type of enzymes that recognizes and cuts DNA molcs (at restriction sites) that are foreign to a bacterium
what is a restriction site?
a specific sequence on a DNA strand that is recognized and cut by a restriction enzyme
what are restriction fragments?
a DNA segment that results from cutting of DNA by restriction enzymes
what is the sticky end of a restriction fragments?
a single-stranded end of a double-stranded restriction fragments that forms H-bonds with other sticky ends
what is gel electrophoresis?
a technique for separating nucleic acids/proteins on the base of their size and electrical charge, both of which affect their rate of movement through an electric field in a gel made of agrose of other polymer
what is a polymerase chain reaction? the steps?
a polymerase chain reaction is a technique for amplifying DNA in vitro by incubating it with specific primers, a heat-resistant DNA polymerase, and nucleotide
1) rxn mixture is heated to denature the DNA strands
2) rxn mixture is cooled to allow hybridization of primers complementary to sequences on opposite strands at each end of the target segment
3) DNA polymerase extends primers in the 5’ -> 3’ direction
what is DNA sequencing? what was the first procedure and who developed it?
DNA sequencing is determine the order of nucleotide base in a gene of DNA fragment
-first procedure : dideoxy sequencing
-developed by : Fredrich Sanger
what is the CRISPR-Cas 9 system
a technique for editing gens in living cells, involving a bacterial proteins (Cas 9) associated with a guide RNA complementary to a gene sequence of interest
what is gene drive?
a process that baises inheritance such that a particular allele is more likely to be inherited than another allele
What is DNA polymerase III?
an enzyme that performs base pairing using the parent strand as a template
(requires RNA primer to attach at the Origin of Replication, is an ancient molecule, replicates leading and lagging strand at the same time, is highly conserved)
What is DNA polymerase I?
an enzyme that proofreads and repairs mis-paired nucleotides during replication
also removes the RNA primers
what nitrogenous bases are are purines? which are pyrimidines? what number of hydrogen bases are shared?
pyrimidines - thymine and cytosine (one ring)
purines - guanine and adenine (two rings)
A+T share 2 H-bonds
G+C share 3 H-bonds
how can you identify the 3’ and 5’ end of a DNA molecule?
3’ end is at the OH group
5’ end is at the carbon that connects directly to the phosphate group
