DNA Structure for Exam 3 Flashcards
Watson and Crick proposed what?
Proposed structure of DNA as a double helix
What is Chargaff’s proposal?
Base composition saying the following:
- Amount of A is proportional to T
- Amount of C is proportional to G
- Note: Percent of C+G and A+T are not equal to one another
What is important about X-ray diffraction? Who studied it?
- Studied by Rosalind Franklin
- Gave the understanding that DNA had a helical structure
In the Watson and Crick model, what were the 3 proposals of DNA
- Double helix
- Two antiparallel strands connected by base pairing
- Stacked nitrogenous based
What does it mean to be Semi-conservative
- Storage of genetic information in sequence of bases
- Mutations or genetic changes that could result in alteration of bases
Watson-Crick DNA model of B-DNA
- Seen under aqueous, low salt conditions aka Nucleus conditions
- Gives 10 bases per turn
- The “normal” form
Compare how A-DNA is diff. to B-DNA
- Slightly more compact than B-DNA
- Prevalent under high salt or dehydration conditions
True/False: C-DNA, D-DNA, E-DNA, and P-DNA are right-handed folds and LESS compact than B-DNA
TRUE
Explain the structure of RNA
- Sugar ribose replaces deoxyribose of DNA
- Nitrogenous base uracil replaces thymine of DNA
- Most are single-stranded with animal viruses w/ double stranded helices as the exception
What are the 3 classes of cellular RNAs (function during gene expression)
- Messenger RNA
- Ribosomal RNA
- Transfer RNA
Define rRNAs
Structural components of
ribosomes for protein synthesis
Define mRNAs
- Template for protein synthesis
- Carry genetic information from
gene to ribosome
Define tRNAs
Carry amino acids for protein
synthesis
16S sequencing is used for what type of identification? What about 18S sequencing?
Prokaryotes: 16S
Eukaryotes: 18S
Define Telomerase RNA and RNA primers
Involved in DNA replication at chromosome ends
Define SnRNA: Small nuclear RNA
- Process mRNAs
- Involved in spliceosome
Define Antisense RNA, microRNA, and siRNA
Involved in gene regulation
Nucleic acids absorb UV light strongly at what wavelengths? And why?
Absorb UV light strongly at 254nm–260nm due to interaction between UV light and ring systems of the bases UV light used in localization, isolation, and characterization
260 nm = what?
280 nm = what?
260 nm = Nucleic acids (DNA and RNA)
280 nm = Proteins
T/F: DNA can denature due to heat or stress?
TRUE! duh ‘o’
Explain Hyperchromic shift?
- Increase in UV absorption of heated DNA in solution
- Denaturation used to determine melting temperature (Tm)
- Graph of absorption vs temperature gives melting profile of DNA
Explain Molecular hybridization
- Denaturation and renaturation of nucleic acids are the basis for
molecular hybridization - Example: Single strands of nucleic acids combine duplex structures, yet are not from same source
- If DNA is isolated from two distinct sources, double- stranded hybrids
will form
Explain Fluorescent in situ hybridization (FISH)
- Uses fluorescent probes to monitor hybridization
- Mitotic cells fixed to slides and subjected to hybridization
- ssDNA is added and hybridization is monitored
- Probes are nucleic acids that will hybridize only with specific chromosomal areas
Define Probes
nucleic acids that will hybridize
only with specific chromosomal areas
Explain Nucleic acid electrophoresis
- Separates DNA and RNA fragments by size
- Smaller fragments migrate through gel at faster rate than large fragments
- Agarose gel
- Porous matrix restricts migration of larger molecules more than it
restricts smaller ones
