Chapters 10 and 11 - DNA: The Chemical Nature of the Gene and Chromosome Structure Flashcards
(37 cards)
What are the functions of genetic material?
- Must replicate, control growth and development of organism, and allow organism to adapt to changes in environment
What experiment proved that DNA is the genetic material? How?
- Griffith’s experiment
- A substance in the heat-killed virulent bacteria genetically transformed type IIR bacteria into live, virulent type IIIS bacteria
- Bacterial transformation (DNA sensitive process)
Describe the Avery-MacLeod-McCarty experiment.
- Find chemical nature of transforming substance
- Treat samples of transformed bacteria with enzymes (RNase, protease, and DNase)
- Add treated samples to non-virulent bacteria
- Cultures treated with protease or RNase contained transformed bacteria, but the culture treated with DNase does not
- Only DNase destroyed transforming substance, it is DNA
What substance - RNA or protein - carries the genetic material in tobacco mosiac virus?
- Degrade both types of TMV to yield RNA and coat proteins
- Mix 2 types of protein to create hybrid viruses (red coat and blue RNA, vice versa)
- Infect tobacco with hybrids
- Type of RNA in hybrid parent determines RNA and protein of progeny
- RNA is genetic material of TMV
What are nucleic acids composed of?
Nucleotides
What does every nucleotide have?
- Nitrogen-containing base (Adenine, Thymine, Guanine, Cytosine, Uracil)
- Pentose sugar (deoxyribose, ribose)
- Phosphate (phosphodiester bond)
What is the difference between deoxyribose and ribose sugars?
- Ribose has -OH on 2’ carbon where Deoxyribose has -H
What are the purines?
- Larger; double rings
- Adenine, Guanine
What are the pyrimidines?
- Smaller, single rings
- Cytosine, Thymine, Uracil
What type of bonds are nucleotides joined by?
- Phosphodiester
- Links C-3 of one sugar to C-5 of another
- Same bond in RNA
How was the structure of DNA deciphered? By who?
- Erwin Chargaff
- Determined precise base composition of different types of DNA
- A + G = T + C
OR - Purines = pyrimidines
What did William Astbury discover?
- X-ray diffraction analysis showed that DNA is a polymer of stacked bases
What did Rosalind Franklin and Maurice Wilkins find?
- DNA is a helix
- Photograph 51
What is the Watson-Crick Model?
Background: - %A = %T - %G = %C - Helical structure - Bases stack like coins over each other Assumptions: - DNA is double helix - 2 strands were anti-parallel - Sugars form phosphate backbone - Bases held together by H bonds
How many H bonds are between T and A?
2
How many H bonds are between C and G?
3
What is the width of a DNA molecule (phosphate to phosphate on other strand)?
2 nm
How many base pairs are there per turn of the helix?
10
What is the distance between base pairs in DNA?
0.34 nm
What is the major groove of a DNA molecule?
Space farthest from tight turn
What is the minor groove in DNA?
Tight turn
How does DNA become super-coiled?
- Relaxed, nicked, circular DNA is rotated 360 degrees
- One 360 degree left-handed rotation
- Can return to circular if you cut one strand, and do a 360 degree right-handed rotation
How many times must E. coli DNA be condensed? How big is E. coli DNA and cell?
- Condensed more than 1000 times and folded into a chromosome
- Monoploid
- DNA = 1.5 mm circle
- Cell = 2 micrometer x 1 micrometer
How is bacterial chromosome formed? What are the sizes of each stage?
- DNA is folded and supercoiled with help of RNA and proteins
- Circular unfolded = 350 micrometers
- 40-50 loops = 30 micrometers
- Supercoiled/folded = 2 micrometers
