Unit 13: DNA Structure and Replication Flashcards
What are the four main classes of macromolecules in a cell?
- Carbohydrates (sugars)
- Lipids (fats)
- Proteins
- Nucleic acids- DNA and RNA
By the 1920s, we knew that _____ controlled
heritable traits, that genes were on
__________, and ________ divided equally at cell division.
By the 1920s, we knew that genes controlled
heritable traits, that genes were on chromosomes, and chromosomes divided equally at cell division
In the 1920s, it was also known that _________ contain
_______ and ___.
In the 1920s, it was also known that chromosomes contain
protein and DNA.
What was Frederick Griffith working on in 1928?
1928 Frederick Griffith is working with the bacteria that caused pneumonia.
What are the two strains of pneumococcus (bacteria that causes pneumonia)?
- S or smooth strain
- R or rough strain
What is the S or smooth strain?
Causes pneumonia in mice (virulent).
What is the R or rough strain?
Does not cause pneumonia in mice (nonvirulent).
Which of these strains is a mutant strain?
R is a mutant strain of
Pneumococcus that does not cause disease because it lacks the ‘capsule’ that protects it from the mouse immune system.
What was the conclusion of Griffith’s experiement?
The R strain became deadly after mixing with heat-killed S strain, proving that genetic instructions from the S strain were passed to the R strain.
Continuing Griffith’s work, what did Avery, Macleod, and McCarty use to transform the genetic instructions for the S strain to the R strain?
In Avery’s experiment, they used protease and DNase to figure out what caused the R strain bacteria to transform into the S strain (the harmful one).
What was did protease do in the S and R strains in Avery’s experiment?
Protease broke down proteins, but the bacteria still transformed into the harmful strain because DNA was the real “transforming principle.” (Mouse still died).
What did DNase do in Avery’s experiment?
DNase broke down DNA, and without DNA, the transformation didn’t happen — meaning DNA was the key to making the bacteria harmful. (Mouse lived).
What bacterium were used in the Hershey-Chase experiment of 1952?
Many early experiments in molecular biology were done with phage and the bacterium Escherichia coli or E. coli
What did Hershey and Chase know before beginning their experiment?
- Nucleic acids (DNA, RNA) contains phosphorus, but not sulfur.
- Most proteins contain sulfur, but bacterial proteins don’t have phosphorus.
In the Hershey and Chase experiment, they used ___________ ____ to track whether ____ or ________ was the genetic material.
In the Hershey and Chase experiment, they used radioactive labels to track whether DNA or protein was the genetic material.
What did Hershey and Chase discover was the difference between DNA and protein when these macromolecules entered bacteria cell walls?
They found that only the radioactive DNA (labeled with ^32P, a radioactive form of phosphorus) entered the bacterial cell and was passed on to new viruses. The protein (labeled with ^35S, a radioactive form of sulfur) stayed outside in the empty protein coat and wasn’t passed on.
What was the conclusion between DNA versus protein in the Hershey and Chase experiement?
This proved that DNA, not protein, is the genetic material that carries genetic information.
What did the X-ray of Rosalind Franklin show?
Her X ray crystallography studies indicated that DNA was a repeating structure.
What did Watson and Crick publish in 1953?
They published a model for the structure of DNA (they used Franklin’s X-ray without her permission).
Watson and Crick’s model for the structure of DNA (1953) showed that two __________ strands of DNA wrap
around each other in a ______-handed ________
helix that resembles a twisted ladder.
Watson and Crick’s model for the structure of DNA (1953) showed that two polynucleotide strands of DNA wrap
around each other in a right-handed double
helix that resembles a twisted ladder
Watson and Crick’s model for the structure of DNA (1953) showed that the two strands of DNA are in an ________ polarity - ________.
Watson and Crick’s model for the structure of DNA (1953) showed that the two strands of DNA are in an opposite polarity - antiparallel.
Watson and Crick’s model for the structure of DNA (1953) showed that the the ‘______’ (or rails of the ladder) consists of a _____-_________ ‘______’ which carries no information.
Watson and Crick’s model for the structure of DNA (1953) showed that the the ‘outside’ (or rails of the ladder) consists of a sugar-phosphate ‘backbone’ which carries no information.
Watson and Crick’s model for the structure of DNA (1953) showed that the the ‘_____’ (or rungs of the ladder) consists of _______ ____ organized as flat ‘_____’.
_ pairs only with _, _ pairs only with _.
Watson and Crick’s model for the structure of DNA (1953) showed that the the ‘inside’ (or rungs of the ladder) consists of paired bases organized as flat ‘steps’.
A pairs only with T, G pairs only with C
The ___ strands are held together by weak
_________ ____ between the bases.
The two strands are held together by weak
hydrogen bonds between the bases.
