Module 6 Flashcards
Genetic material must:
- Contain information
- Be transmissible
- Be replicable
- Allow for variation
Griffith’s Experiments
Exposed mice to Smooth (encapsulated) and Rough strains of S. pneumoniae, discovered that inoculation with live Smooth bacteria killed mice and dead Smooth bacteria with live Rough also killed them (theory of transformation)
Avery, MacLeod, and McCarty Experiments
Retried Griffith’s experiments, treated Smooth DNA with DNase and discovered there was no growth
Nucleic Acid Structure (4 levels)
- Nucleotide order
- Linear structure
- Double-helix
- 3D folding
Components of Nucleotides
- Phosphate group
- Pentose sugar (ribose/deoxyribose)
- Nitrogenous base (A, T, C, G, and U)
Pyrimidines (C, T, U) have ____ carbon-nitrogen ring while purines (G, A) have ____
one, two
Nucleotides are connected in a DNA strand via a ____ moving in the ____ direction
sugar-phosphate backbone, 5’-3’
Pauling
Proposed alpha helix structure
Franklin
Performed X-ray diffraction, suggested helical structure of DNA, 10 base pairs (bp) per turn, and that there was more than 1 strand
Chargaff
Suggested that quantities of A and T, and C and G were similar, and that the four nucleotides were coupled
DNA Strand Characteristics
- Two strands twisted together, bound by H bonds between nitrogenous bases
- Deoxyribose pentose sugar
- 10 bps per turns
- Strands run anti-parallel
- Helix is right handed
- Asymmetrical grooves (major/minor)
RNA Strand Characteristics
- Single stranded
- Ribose pentose sugar
- U instead of T
- May include bulge, internal, multi-branched, and stem loops
Bacterial Chromosome Organization
Single, double-stranded DNA circular chromosome residing in nucleoid structure
Nucleoid
Non-membranous structure containing bacterial chromosome
Bacterial DNA Supercoiling
Formation of additional coiling due to twisting, occurs in under (via DNA gyrase) and overwinding (via DNA Topoisomerase I) cases
____ may occur due to negative supercoiling
Strand separation
Eukaryote Chromosome Organization
One or more sets of linear chromosomes, each made up of a single DNA molecule, residing within the membrane-bound nucleus with multiple characteristic sequences
3 types of eukaryotic DNA sequences include:
- Origins of replication
- Centromeres
- Telomeres
Eukaryotes have more DNA than bacteria because:
Of the accumulation of repetitive sequences, more complex processes
Two ways which transposable elements can move:
- Simple transposition (TE moves directly to target site)
- Retrotransposition (TE moves via RNA intermediate)
Simple Transposition
TEs flanked by inverted repeats that contain transposase and catalyze the transposition event
Retrotransposition
Utilizes reverse transcriptase to encode retrotransposons into RNA and then endonuclease/integrase to be added back to DNA
Smaller/simpler species often have ____ TEs in their genome relative to the total number of genes
fewer
Nucleosome
Compacted DNA wrapped around octamer of histone proteins, verified by Noll by digesting DNA and identifying cuts at linker DNA portions using gel electrophoresis to establish “beads on a string” model
30nm Fiber
Folds nucleosomes into loop domains using CCCTC binding factor
Chromosome Territory
When chromosomes are not condensed, they tend to stay together within the nucleus regardless
Heterochromatin
Tightly compacted regions, generally transcriptionally inactive, loop domains compact DNA
Euchromatin
Less condensed, transcriptionally active, 30nm fibers
Condensin
Multiprotein complex that works to condense chromosomes during metaphase
