Bio Chapter 11
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A change in genotype caused when cells take up foreign genetic material.
Alfred Hershy and Marth Chase performed an experiement that settled the controversy.
Viruses are composed of DNA surrounded by a protective protein coat. Bacteriophage- a virus that infects bacteria.
Structure of DNA
Double Helix found by Watson and Crick that lit up with radioactive material.
The subunits that make up DNA
3 Parts of DNA
Phosphate group, a 5-carbon sugar, and a nitrogen containing base
Sugar Molecule from which DNA gets its full name, deoxyribonucleic acid
Nitrogent base of DNA may be
Adenine, guanine (Purines: two rings of carbon and Nitrogen atoms) thymine, and cytosin (Pyrimidines: single ring of carbon and nitrogen atoms)
- equaled the amount of thymine (AT)
- equaled the amount of cytosine (GC)
Complementary base pairs
Sequence of bases on strand determins the sequences of N bases on the other strand of DNA
The process of making a copy of DNA, which occurs during the (s) phase of the cell cycle.
Step one of DNA Replication
The double helix needs to unwind before replication can begin. Accomplished by enzymes called DNA helicases which open the double helix by breaking the hydrogen bonds between two strands.
Step two of DNA replication
Additional protenis prevent the strands from assuming their double-helical shape. Replication forks are areas where the double helix separates. Enzymes known as DNA polymerases add nucleotides to the exposed nitrogen bases according to the baseparing rules forming two double helixes.
Third Step of DNA Replication
The process of step two continues until all of the DNA has been copied and the ploymerases are signaled to detach. Nucleotide sequences are identical in the two DNA molecules.
Checking for errors in DNA replication
Dna polymerases are important in "proofreading" the nuleoties - can backtrack. Errors in DNA replication about one error per 1 billion nucleotides.
How can a mutation occur
Mistakes during replication, chemical changes (smoke) or by radiation e.t.c
Mutations in Germ-Line Tissue:
Mutations that occur between germ-line cells are the ones that get passed on from one generation to the next. This also explains diversity we see in Evolution.
Mutations in Somatic Tissues
This type of mutation can occur only when there are new allele that replace the old one.
Altering the Sequence of DNA
This type of mutation in which the changes in the nucleotide sequence affects the message itself. For example, Point mutation in which only one nucleotied in a sequence is changed. Also a phenomenon called Frame-shift mutation in which insertion or deletion of nucleotides affects the orginal gene sequence.
DNA replications occurs from
5 prime to 3 prime
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