BIO 1A03 T1M4: Nucleic Acids

Plasmids

Small circular DNA molecules that carry only 1-2 genes (e.g., antibiotic resistance) and can replicate independently of the core genome and transfer from one cell to another

Chromosome

Double stranded DNA molecule

In euk:
- Large linear chromosomes
In prok:
- Smaller circular chromosomes (with some exceptions)
In mito:
- Contain their own smaller chromosome (eg. E. Coli → super coiled into ~100 loops ⇒ form nucleoid - allowing a lot of info to fit in a small nucleoid area)

super coiling 

coiling that occurs IN ADDITION to the coils of a helical DNA structure
⤷ preserves the double helix structure and compacts the DNA into a small space

Genome Map

maps that locate an organism's genome, showing all the genes on a prokaryotic chromosome.

Operon

cluster of genes involved in the metabolism of sugar (lactose)

Lac Gene

Found in the lac operon in E. Coli, it codes for proteins that allow bacteria to metabolize lactose when there is no glucose.

Frederick Griffith's experiment

S-strain bacteria of Strep. ⇒ pathogenic (has a smooth, polysaccharide coating, protecting the bacteria from dying from the body's immune system)

R-strain bacteria of Strep. ⇒ non-pathogenic (rough exterior, no coating)

R-strain + Heat-killed S-strain -
⤷ independently, R-strain and/or Heat-killed strain == mice alive...
⤷ BUT if mixed together, mice died
⤷ The deadly poison from the heat-killed S-strain was passed on to the alive-R-Strain bacteria... becomes a S-strain (essentially) ⇒ kill mice
⤷ Griffth referred to this as the transformation principle: when non-virulent bacteria becomes a virulent one (non-toxic → toxic)

S-strain Bacteria

⇒ pathogenic (has a smooth, polysaccharide coating, protecting the bacteria from dying from the body's immune system)

R-strain Bacteria

non-pathogenic (rough exterior, no coating)

R-strain + Heat-killed S-strain

independently, R-strain and/or Heat-killed strain == mice alive... BUT if mixed together, mice died
⤷ The deadly poison from the heat-killed S-strain was passed on to the alive-R-Strain bacteria... becomes a S-strain (essentially) ⇒ kill mice

transformation principle

when non-virulent bacteria becomes a virulent one (non-toxic → toxic) --  a change in cell behavior resulting from the incorporation of genetic material from outside of the cell

Avery-MacLeod-McCarty experiment

→ purpose: experiment to find which macromolecule was responsible for having the genetic material
- 6 tubes (control, polysaccharides, lipids, RNA, protein, DNA ⇒ with enzymes destroying each macro), each mixed with S strain-heat killed bacteria
- Mixed in the R-strain bacteria
- Injected into the mouse
- All the mice died, except the one injected with DNA (+ DNAse)
- If a blood sample was taken, S-strain bacteria is still found in all the mice (not DNA mouse) → bc of the presence of S-strain, the genetic material that's making the smooth coat is still being transferred (R-strain takes on killed S-strain properties) ≠ genetic material
- If mouse lives & S-strain isn't in the blood... the genetic material is LOST (destroyed) & R-strain bacteria can't pick up information
∴ concluded that DNA is hereditary information responsible for transformation

Rosalin Franklin

used X-ray diffraction to aim X-rays at DNA to create images based on diffraction of atoms in DNA molecule [Photo 51]

Watson and Crick

discovered the double stranded helix structure of DNA after seeing Photo 51 but did not give credit to Franklin or Chargaff

Nitrogenous bases

nitrogen-containing molecules that are essential components of nucleotides and nucleic acids like DNA and RNA

Pyrimidines

single ring structure → cytosine, thymine, uracil

Purines

double-ring structure → adenine, guanine

Phosphodiester bond

bond that joins together to form the backbone of the DNA strand via condensation/dehydration synthesis

⤷ connects the phosphate at the 5' end and the OH at the 3' end

Chargaff's rules

DNA from any cell of all organisms should be a 1:1 ration of purines and Pyrimidines
⤷ held by H-bonds (G≡C, A=T)
⤷ 3 H-bonds btw GC... 2 H-bonds btw AT
⇒ form antiparallel strands...

Antiparallel strands

5' = free phosphate group & 3' = free OH-group
⇒ joins together... forming 2 strands, complementary to each other that's antiparallel
⇒ connected by H-bonds (non-permanent... but a lot of then = strong and stable)

Hydrophobic amino acids

Hydrocarbon (alkyl) chain — like fatty acids; Benzene ring — very phobic

Hydrophilic amino acids

Charged polarized (presence of COOH, NH2); Capable of H-bonding (OH)

Special amino acids (exceptions)

Glycine - has a 'hydrogen' as the R-side group
⇒ Phobic bc of the "CH-H," or CH2 ⇒ phobic, but slightly polar

Proline - cyclic in water, ⇒ composed of CH cyclic
Phobic

Cysteine - has a 'SH' thiol group, behaves like OH
⇒ Philic