Genetics Section I Quiz

Study Notes

Eukaryotic genetic material is primarily located in the nucleus.
Genetic information is divided into chromosomes rather than existing as a single DNA strand.
DNA is organized into structural units called nucleosomes composed of DNA wrapped around histone proteins.
Approximately 200 base pairs of DNA can wrap around one histone (67 nm DNA per histone).
Nucleosomes coil and supercoil to form solenoid structures, facilitated by linker histones.
Solenoids can be further compacted on a protein scaffold to fit within the nucleus.

Mendel's experiments provided indirect evidence for gene transmission across generations, prompting questions about the chemical basis of heredity in the early 20th century.
Initial beliefs favored proteins as the hereditary material until nucleic acids emerged as potential candidates.
Resistance existed, even into the first half of the 20th century, against the idea that DNA was responsible for heredity.

Used Streptococcus pneumoniae to study virulence in mice.
Identified two strains based on morphological traits:
- Virulent S strain: smooth appearance due to polysaccharide capsule.
- Nonvirulent R strain: rough appearance, lacking a capsule.

Step 1:
- Injection of S strain into a mouse resulted in death.
- Injection of R strain into a mouse allowed for survival.
Step 2:
- Boiling and injecting heat-killed S strain into a mouse led to survival.
- Combining heat-killed S strain with live R strain resulted in death.

Observed that cellular debris from heat-killed S strain could convert the R strain into a virulent form, a process termed transformation.
Transformation refers to the alteration of a genome through external DNA derived from another genotype.

Aimed to identify the specific molecule responsible for the virulence trait observed in Griffith's experiments.
Experimental design involved destroying various chemical categories in extracts of dead S cells to determine which component was essential for transferring virulence to R cells.