Bio 107 topic 5 Flashcards
What properties must genetic material possess?
- store information
- replicate
- change over time
Gregor Mendel
- first to describe heredity
- transmission of traits from one generation to the next
- did the dyed flower experiment
What transmits traits?
chromosomes (DNA + protein)
Frederick Griffith
wanted to a if a trait can be passed between bacterial cells so he conducted an experiment with mice infected by different strains of Streptococcus pneumonia
- smooth cells= pathogenic (kill)
- rough cells= non pathogenic (don’t kill)
- A substance is being passed from dead S cells to live R cells, which “transforms” them into S cells
Thomas Hunt Morgan
conducted an experiment where he bred drosophila fruit flies, looking for mutations to determine how they were inherited. Found traits are associated with chromosomes
Why did most scientists think the heritable material was protein and not DNA?
- protein is more complex
- nucleic acids too uniform
- DNA is too simple
- Didn’t think bacteria and humans would share the same genetic material
How did they discover it was DNA that was the hereditary material?
modified Griffith’s experiment
- Took samples of heat-killed S cells and removed specific components using enzymes
- Mixed each sample with live R cells, and observed the ability to infect mice
- Transformation cannot occur unless DNA is present, therefore DNA must be the hereditary material
Bacteriophage
- virus that infects bacteria
- composed of a protein coat and DNA
What does bacteriophage do to a bacteria cell?
- makes new DNA and protein
- packages into new viruses
- cells burst and release virus particles
Radioactive Isotope
- an unstable form of an element that emits detectable energy
- can be used to lab organic molecules
What is DNA?
a polymer of nucleotides connected by phosphodiester bonds
- deoxyribose
- nitrogenous base (4)
- phosphate
What purine and pyrimidine go together?
A + T
G + C
Rosalind Franklin
found the shape of DNA from x-ray crystallography
What did x-ray crystallography say about DNA
- regularity and cross=helix
- proposed a double helical structure
Watson and Crick
interpreted Franklins data and made the structure of DNA
- DNA is a helix made up of two nucleotide strands (double helix)
- helix has a fixed width of 2 nm
- two strands run antiparallel
- sugar and phosphate face out, nitrogenous bases face in
- strands held together by H-bonds
How many bonds between the complementary base pairs?
A+T=2
G+C=3
How does DNA fit the requirements of the hereditary molecule?
Storage of information
- Information encoded in the order of the bases
- Next class: triplet code (3 bases=1 amino acid)
Capable of replication
- Complementary base pairing rules allows a strand of DNA to be copied
Ability to change over time
- Many known mechanisms for changes in sequence (mutation
