Mitosis and Meoisis Flashcards
P. A. Levene
(1919) Discovered that:
- DNA is made up of nucleotides (phosphate group, deoxyribose, and nitrogenous base) that are linked in a string
- Nitrogenous bases are purines: double ringed (Adenine and Guanine) and pyrimidines: single ringed (Thymine and Cytosine)
- The bases are held together by hydrogen bonds
Erwin Chargaff
(1940s) Discovered that in any species, the amount of A and T were the same and the amount of C and G were the same
(**)Hershey and Chase
(1952)
- Marked protein coat with bacteriophage (viruses that attack bacteria) with radioactive sulfur (S-35) and the DNA with radioactive phosphorus (P-32)
- Found that protein coat remained outside the bacterial cell and the DNA moved into the cell, directing it to make new bacteriophages
(Before this scientists thought proteins carried the genetic information but know they know it is in the DNA)
Franklin and Wilkins
(1952)
- Used X-rays to photograph molecules
- Research indicated that DNA was like a coil with a constant diameter of 2nm (1 mm = 1 000 000 nm)
Watson and Crick
(1953)
- Made scale models of DNA
- Proposed that DNA is like a spiral staircase with two twisted strands, the sides (“handrails”) were alternating deoxyribose and phosphate molecules and the “rungs” are joined by hydrogen bonds
- Called this the DOUBLE HELIX
- Determined that A is always with T and C is always with G (confirming Chargaff)
What are histones?
Histones are special proteins that DNA is coiled with to form chromosomes
DNA + histones = chromosomes
What are genes and what do they do?
Genes are specific sequences of DNA on a chromosome
They determine the production of proteins that will determine the traits of an individual
Do nucleotides differ in organisms?
No, the DNA of all organisms is made up of the same type of nucleotides
What determines different organisms since nucleotides are the same?
- The sequence of A’s and T’s, C’s and G’s
- The number of chromosomes
- Different proteins
What is a genome?
A complete set of DNA sequence
What determines our genetic information?
The order of A, T, C, and G
How many chromosomes do humans have?
46
What are autosomes?
Chromosomes that are not sex chromosomes
Which pair are the sex chromosomes?
23rd pair
Are sex chromosomes homologous?
The female sex chromosomes are XX so they ARE homologous
The male sex chromosomes are XY so they are NOT homologous