Chapter 6 - DNA & Biotechnology Flashcards
DNA Libraries
large collections of known DNA sequences
Genomic Libraries
contain large fragments of DNA and include both coding (exon) and noncoding (intron) regions of the genome
cDNA Libraries
constructed by reverse-transcribing processed mRNA, lacks noncoding regions, only includes genes that are expressed in the tissue
Hybridization
joining complementary base pair sequences (DNA-DNA or DNA-RNA), uses 2 single strands, vital part of PCR and Southern blot
Restriction Enzymes (Restriction Endonucleases)
enzymes that recognize specific palindromic double-stranded DNA sequences, once a sequence is identified, restriction enzyme can cut through the backbones of the double helix
Southern Blot
used to detect the presence and quantity of various DNA strands in a sample
Transgenic Mice
altered at their germ line by introducing a cloned gene into fertilized ova or into embryonic stem cells
Transgene
cloned gene that is introduced into transgenic mice
Nucleosides
five-carbon sugar (pentose) bonded to a nitrogenous base and are formed by covalently linking the base to C-1’ of the sugar
Ribose vs. Deoxyribose
ribose has —OH at C-2; deoxyribose has —H
Pyrimidines
CUT the PYe (cytosine, uracil, thymine)
Purines
As Gold (adenine and guanine)
Aromaticity
- compound is cyclic
- compound is planar
- compound is conjugated
- Compound has 4n+2 (where n is any integer) pi * electrons (Huckel’s Rule)
Watson-Crick Model of DNA Structure
Two strands of DNA are antiparallel, sugar-phosphate backbone is on outside of helix with nitrogenous bases on inside
Chargaff’s Rules
in double-stranded DNA, purines = pyrimidines
%A = %T %G = %C
B-DNA
turn every 3.4 nm and contains about 10 bases within that span, major and minor grooves can be identified between interlocking strands
Z-DNA
left-handed helix that has a turn every 4.6 nm and contains about 12 bases within each turn, high GC content or high salt concentration may contribute to its formation
Chromatin
a DNA wound histone (small basic protein)
Nucleosome
two copies of each histone protein, H2A, H2B, H3, and H4 form a histone core and about 200 base pairs of DNA are wrapped around this protein complex
Heterochromatin
small percentage of the chromatin remains compacted during interphase, appears dark under light microscopy, it is transcriptionally silent
Euchromatin
dispersed chromatin, appears light under light microscopy, contains genetically active DNA
Centromere
a region of DNA found in center of chromosomes, sites of constriction, form indentations, allows two sister chromatids to remain connected at centromere until microtubules separate the chromatids during anaphase
Helicase
unwinds DNA, generates two single-stranded template strands ahead of the polymerase
Single-stranded DNA-binding Proteins
bind to unraveled strand, prevent both reassociation of the DNA strands and the degradation of DNA by nucleases
DNA Polymerases
they read the DNA template, or parental strand, and synthesize the new daughter strand
Leading Strand
in each replication fork is the strand that is copied in a continuous fashion, in the same direction as the advancing replication fork
Mismatch Repair
cell machinery in G2 phase of cell cycle, these enzymes detect and remove errors introduced in replication that were missed during the S phase of the cell cycle
Base Excision Repair
affected base is recognize and removed by a glycosylase enzyme, leaves behind an AP site
Apurinic/Apyrimidinic (AP) Site
abasic site, recognized by an AP endonuclease that removes the damaged sequence from DNA
