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MCAT Bio. Chem Ch. 6

Deoxyribonucleic Acid (DNA) Macromolecule that stores genetic information in all living organisms.
Nucleosides Contain a five-carbon sugar bound to a nitrogenous base
Nucleotides Nucleosides with 1 to 3 phosphate groups aded
Nucleotides in DNA contain: Deoxyribose
Nucleotides in RNA contain: Ribose
A Adenine
T Thymine
G Guanine
U Uracil
Watson-Crick Model of DNA's First Part 1. Backbone is composed of alt. sugar and phosphate groups, and is read 5' to 3'.
Watson-Crick Model of DNA's Second Part 2. There are two strands of DNA with antiparallel polarity that are wound into a double helix.
Base-pairing in DNA Purines (A and G) pair with pyrimidines (C, U, T)
In DNA, A Pairs With: T, Thymine via 2 h-bonds
In DNA, C Pairs With: G, Guanine via 2 h-bonds
In RNA, A Pairs With: In RNA, A Pairs With:
Purines and Pyrimidines Are: Biological aromatic heterocycles
Aromatic Compounds Cyclic, planar, conjugated, and contain 4n+2 pi electrons
H├╝ckle's Rule For Amount Of Electrons In An Aromatic Compound 4n+2 pi electrons, where n = any integer
Chargaff's Rules State that purines and pyrimidines are equal in number in a DNA molecule. Also, because of base-pairing, the amount of Adenine equals the amount of Thymine, and the amount of Cytosine equals the amount of Guanine.
Most DNA is: B-DNA that forms a right-handed helix.
When Is Low Conc. Of Z-DNA (zig-zag shape) Seen: With high GC-content or high salt conc.
Denaturation Act of DNA strands being pulled apart
Reannealing Act of DNA strands being brought back together.
Conditions That Cause Denaturation Of DNA Heat, alkaline pH, and chemicals like formaldehyde and urea (removal of these conditions can reanneal the DNA strands)
Amount of Chromosomes in Human Cells' DNA 46 chromosomes
DNA Is Wound Around Histone Proteins (H2A, H2B, H3, and H4) To Form: Nucleosomes which can be stabilized by another histone protein H1
DNA and its associated histones make up: Chromatin in the nucleus
Heterochromatin Dense, transcriptionally silent DNA that appears dark under light microscopy.
Euchromatin Less dense, transcriptionally active DNA that appears light under light microscopy.
Telomeres Ends of chromosomes, which contain high GC-content to prevent unraveling of the DNA.
Telomerase An enzyme that reverses the effect of shortening that telomeres have during replication
Centromeres Located in the middle of chromosomes and hold sister chromatids together until they are separated during anaphase in mitosis. They also contain a high GC-content to maintain a strong bond between chromatids.
Replisome (Replication Complex) Set of specialized proteins that assist the DNA polymerases.
To Replicate DNA: DNA is first unwound at the Origin of Replication by helicases
Unwinding DNA At First Produces: Two replication forks on either side of the origin.
Prokaryotes have a circular chromosome that: Contains only one origin of replication.
Eukaryotes have a linear chromosomes that: Contain many origins of replication.
Single-stranded DNA-binding Proteins Proteins that keep unwound strands from reannealing or being degraded.
Supercoiling Causes torsional strain on the DNA molecule, which can be released by DNA topoisomerase II (DNA gyrase) which creates nicks in the DNA molecule
DNA Replication Is: Semi-conservative meaning that one old parent strand and one new daughter strand is incorporated into each of the new two new DNA molecules.
Primase Puts down a small RNA primer so that DNA can have an adjacent molecule to hook onto to synthesize more DNA.
DNA Polymerase III (Prokaryotes) Synthesize a new strand of DNA by reading the template DNA from 3' to 5' and synthesize the new strand 5' to 3'.
DNA Polymerase Alpha And Gamma (Eukyartoes) Synthesize a new strand of DNA by reading the template DNA from 3' to 5' and synthesize the new strand 5' to 3'.
Leading Strand Requires only 1 primer and can be then synthesized continuously in its entirety.
Lagging Strand Requires many primers and is synthesized in discrete sections called okazaki fragments.
DNA Polymerase I (Prokaryotes) Removes RNA primers and filled in with DNA by DNA Polymerase I
DNA Polymerase I (Prokaryotes) Removes RNA primers and filled in with DNA by DNA Polymerase Alpha
DNA Ligase Fuses two DNA strands together to make one complete molecule.
Oncogenes Develop from mutations of proto-oncogenes and promote cell-cycling. They can lead to cancer or metastasis.
Cacner Unchecked cell proliferation with teh ability to spread by local invasion
Metastasis Migration of cancerous cells to distant sites via the bloodstream or lymphatic system.
Tumor Suppressor Genes Code for proteins that reduce cell cycling or promote DNA repair. Mutations of tumor suppressor genes can also lead to cancer.
During replication, DNA Polymerase: Proofreads its work and excises incorrectly matched bases. The daughter strand is identified by its lack of methylation and corrected accordingly.
Mismatch Repair Occurs during the G2 phase of the cell cycle, using the genes MSH2 and MLH1
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 non-deforming lesions of the DNA helix (such as cytosine deamination) by removing the base, leaving an apurinic/apyrimidinic (AP) site
AP Endonuclease Removes the damaged sequence, which can be filled in with the correct bases.
Recombinant DNA DNA composed of nucleotides from two different sources.
DNA Cloning Introduces a fragment of DNA into a vector plasmid.
Restriction Enzyme (Restriction Endonuclease) Cuts both the plasmid and the fragment, which are left with sticky ends. Once the fragment binds to the plasmid, it can be introduced into the bacterial cell and permitted to replicate, generating many copies of the fragment of interest.
Vectors Contain: An origin of replication, the fragment of interest, and at least 1 gene for antibiotic resistance (to permit for selection of that colony after replication)
After Replciation, Bacterial Cells: Can be used to create a protein of interest, or be lysed to allow for isolation of the fragment of interest from the vector
DNA Libraries Large collections of known DNA sequences
Genomic Libraries Contain large fragments of DNA, including both coding and noncoding regions of the genome. They cannot be used to make recombinant proteins or for gene therapy.
cDNA Libraries (Expression Libraries) Contain smaller fragments of DNA, and only include the exons of genes expressed by the sample tissue. They can be used to make recombinant proteins or for gene therapy.
Hybridization Joining of complementary base pair sequences.
Polymerase Chain Reaction (PCR) Automated process by which millions of copies of a DNA sequence can be created from a very small sample by hybridization.
Agarose Gel Electrophoresis Process in which DNA molecules can be separated by size.
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: Dideoxyribonucleotides, which terminate the DNA chain beause they lack a 3'-OH group. The resulting fragments can be separated by gel electrophoresis, and the sequence can be read directly from teh gel.
Gene Therapy Method of curing genetic deficiencies by introducing a functional gene with a viral vector.
Transgenic Mice Created by integrating a gene of interest into the germ line or embryonic stem cells of a developing mouse.
Chimeras Organisms that contain cells from two different lineages
Ex of Chimera Mice formed by integration of transgenic embryonic stem cells into a normal mouse blastocyst
Transgenic mice can be mated to: Select for the transgene.
Knockout Mice Created by deleting a gene of interest.
Biotechnology Brings Up A Number Of: Safety and ethical issues, which include pathogen resistance and the ethics of choosing individuals for specific traits.
Created by: SamB91