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is the molecule that carries hereditary information.
information is in discrete units called genes
Where are genes located.
genes are segments of DNA located on chromosomes.
What are chromosomes composed of?
DNA and proteins.
what type of experiments showed that DNA was the hereditary material?
Who worked with bacteria that caused pneumonia in the 1920s
What are the two strands of Pneumoncooccus:
- R- did not cause pneumonia in mice\
- S- did cause pneumonia
what killed S-strain and living R-strain?
Some substance from dead S strain had transformed the R strain
Who showed DNA was the transforming material?
Avery, MacLeod, McCarty
What are the 4 kinds of necleotide?
- 1. Bases: adenine (A) Guanine (g) cytosine (C) Thymine (T)
- A=T; C=G
Each necleotide is composed of three parts....
- phosphate group
- deoxyribose (sugar)
- N-containing base
In 1952 who showed that helix was double and had a uniform diameter of about 2nm?? How was it revealed?
Helical structure was revealed by X ray diffraction.
Discovered by Maurice Wilkins and Rosalind Franklin.
The sugar-phosphate backbone forms the double helix. Discovered by...
Discovered by James Watson and Francis Crick by deduced the structure of DNA.
the N-containing bases pair up to form rungs' one from each sugar-phosphate backbone.
bases are hydrogen-bonded. A-T and G-C
The backbones are
antiparallel. Each strand is directional with a free sugar on one end and a phosphate on other. The directions of the two strands are oppposite, tehy run head to tail.
Information depends on the....
sequence of the necleotides NOT their number.
The small number of nucleotides (4) made many scientists skeptical that DNA was the hereditary molecule.
genetic information occurs in...
codons. Triplets ofbases. With 4 distinct bases, there are 64 possible combinations, which means that they can code for the 20 amino acids, start, stop and a number of other functions.
DNA replication is necessary for cell division and requires...
several enzymes: DNA helicase, DNA polymerase and DNA ligase.
Replication is semiconservative.
How many mistakes does DNA polymerase make?
roughly 1 mistake per 10,000 base pairs= good.
error rate reduced to
1 mistake per billion base pairs by proofreading enzymes. THese enzymes use the complementary DNA strand as a template to repair damage. THey excise (cut out) the mismatch and replace it with correct bases.
Other sources of errors in DNA
- Spontaneous chemical degradation
- Ultraviolet radiation
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