Ch 6: DNA and Biotechnology Flashcards
Nucleosides
contain a 5-carbon sugar bound to a nitrogenous base
nucleotides
nucleosides w 1-3 phosphate groups added
___ in DNA contain deoxyribose and in RNA contain ribose
nucleotides
Nucleotides are abbrev A,C,G,T,U
adenine cytosine guanine thymine uracil
Watson-Crick model says backbone of DNA is
organized alternating sugar and phosphate groups and is always read 5-3’
purines
A and G
pyrimidines
C,U,T
A pairs with
T or U
G three hydro bond with
C
purine and pyrimidines are biologically aromatic heterocycles meaning
aromatic - cyclic, planar, conjugated, 4n+2pi electrons (Huckels rule where n needs to come out 0 or positive even integer when set equation equal to numb pi electrons in molecule)
heterocycles - ring structure that contains at least two different element in the ring
Chargaff’s rule
purines and pyrimidines are equal in number in a DNA molecule and that because of base pairing the amount of adenine equals the amount of thymine,and C=G
most DNA is ___ which forms righ handed helix
B-DNA
low concentrations of DNA are in ___ with a zig zag shape, may be seen with hgih GC-content or high salt concentration
Z-DNA
What can denature DNA and then allow it to reanneal when gone
heat, alkaline pH, chemicals like formaldehyde and urea can cause denaturation of DNA
DNA organized into ___ chromosomes in the human cells
46
in eukaryotes, DNA is wound around ____ to form ____ which may be stabilized by another ____
histone proteins (H2A, H2B, H3, H4) nucleosomes histone protein (H1)
DNA and its associated histones as a whole make up ____ in the nucleus
chromatin
heterochromatin
dense, transcriptionally active DNA that appears dark under the light microscopy
euchromatin
less dense, transcriptionally active DNA that appears light under the light microscopy
telomeres
end of chromosomes; high GC content to prevent unraveling of DNA
during replication, telomeres are slightly shortene. although this can partially be reversed by the enzyme telomerase
centromeres
located in the middle of chromosomes and hold sister chromatids together until they are seperated during anaphase in mitosis. they also contain a high GC content to maintain a strong bond between chromatids
replisome (replication complex)
is a set of specialized proteins that assist the DNA polymerases
Origin of replication
when DNA is replicated it is unwound here by helicases
this produces two replication forks on either side of the origin
prokaryotes - circular chromosome with one OOR
eukaryotes - linear chromosome with many origin of replication
unwound strands are kept from reannealing or being degraded by
single-stranded DNA-binding proteins
__causes torisonal strain on the DNA molecule, which can be released by ____, which creates nicks in the DNA molecule
supercoiling
DNA topoisomerase II (DNA gyrase)
DNA replication is ___ for one old parent strand and one new daughter strand are incorporated into each of the two new DNA molecules
semiconservative
DNA cannot be synthesized without ____ so a small RNA primer is put down by ____
an adjacent nucleotide to hook onto
primase
DNA polymerase 3 (prokaryotes) or DNA polymerase alpha and gamma (eukaryotes)
can then synthesize a new strand of DNA
read DNA temple 3 -5’ and synthesize new strand 5-3
leading strand needs only
one primer and can by synthesized continuously
lagging strand needs
many primers and synthesized in sections called Okazaki fragments
RNA primers can be removed later by ____ and filled in with DNA by _____
DNA polymerase 1 (prok) or RNase H (euk)
DNA polymerase 1 (prok) or DNA polymerase gamma (euk)
DNA ligase
can fuse the DNA strands together to create one complete molecule
Oncogenes
develop from mutations of proto-oncogenes and promote cell cycling. they may lead to cancer which is unchecked cell proliferation with the ability to spread by local invasion or metastasize
Tumor suppressor genes
code for proteins that reduce cell cycling or promote DNA repair
during replication, _____ proofreads its work. the ____ is identified by its lack of ____ and corrects accordingly
DNA polymerase
daughter strand
methylation
Mismatch repair also occurs during ___ of the cell cycle and uses genes MSH2 and MLH1
G2
Nucleotide excision repair fixes
helix-deforming lesions of DNA (such as thymine dimers) via a cut-and-patch process that requires an excision endonuclease
Base excision repair fixes
nondeforming lesions of the DNA helix (such as cytosine deamination) by removing the base, leaving an apurinic/apyrimidinic (AP) site. An AP endonuclease then removes the damaged sequence which can be filled in with the correct bases
Recombinant DNA is
DNA composed of nucleotides from two different sources
DNA cloning introduces a fragment of DNA into a
vector plasmid
building of the cloning, ____ cuts both the plasmid and the fragment, which are left with sticky ends. once a fragment binds to the plasmid, it can be introduced into a bacterial cell and permitted to replicate, generating many copies of the fragment of interest
Restriction enzyme
vectors contain
OOR, fragment of interest, one gene of antibodic resistance to permit for selection of that colony after replication
once replicated bacterial cells can be used to create a protein of interest or can be lysed to allow for isolation of the fragment of interest from the vector
DNA libraries
large collections of known DNA sequences
genonmic and cDNA libraries are two examples
Genomic libraries
contain large fragments of DNA including both coding and non coding regions of the genome. They CANT be used to make recombinant proteins or for gene therapy
cDNA libraries (expression libraries)
contain smaller fragments of DNA and only include the exons expressed by the sample tissue. CAN be used to make recombinant proteins or for gene therapy
Hybridization
is the joining of complementary bp sequences
automated process by which millions of copies of a DNA sequence can be created from a very small sample by hybridization
Polymerase Chain Reaction (PCR)
DNA molecules can be seperated by size using
agarose gel electrophoresis
Southern Blotting
can be used to detect the presence and quantity of various DNA strands in a sample. After electrophoresis, the sample is transferred to a membrane that can be probed with single-stranded DNA molecules to look for a sequence of interest
DNA sequencing uses____ which terminate the DNA chain bc they lack a 3’-OH. The resulting fragment can be seperated by _____ and the sequence can be read directly from the gel
dideoxyribonucleotides
gel electrophoresis
method of curing genetic deficiencies by introducing a functional gene with a viral vector
gene therapy
created by integrating a gene of interest into the germ line of the embryonic stem cells of a developing mouse
transgenic mice
and they can be mated to select for the transgene
chimeras
are organisms that contain cells from two different lineages (such as mice formed from integration of transgenic embryonic stem cells into a normal mouse blastocyst)
created by deleting a gene of interest
knockout mice
