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Lecture 16

BIOL 1201 Lecture Notes - Lecture 16: Metaphase, Phenotype, ChromosomePremium


Department
Biological Sciences
Course Code
BIOL 1201
Professor
Moroney, James
Lecture
16

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BIOL 1201-Lecture 16- Genetics and Cell Division
Mutations
Increases genetic variability
o May be neutral, negative and rarely – positive
Two general classes:
o Substitution of a base or bases = point mutation
o Insertion or deletion of bases= frame shift mutation
Consequences of a point mutation
o Silent – the change in DNA sequence does not cause a change in the amino acid
sequence.
Many proteins have multiple codons that code for it. If the DNA changes but it still codes
for the same protein as before.
o Missense – the change the DNA sequence also leads to a change in the amino acid
sequence.
Still don’t know whether it is good or bad, or it might not change anything
o Nonsense – The DNA change leads to a stop codon = premature termination
Consequences of a frameshift mutation
o A frameshift mutation is caused by an insert of one or more bases or a deletion of one
or more bases.
o It almost always leads to the disrupting of the protein because every amino acid after
the insertion/deletion will be different from the normal protein.
o Very serious
o Fig. 17.24
Sickle-cell hemoglobin: not all negative. Can fight against malaria.
CONTROL OF GENE EXPRESSION
Almost all cells have all the possessed DNA by an organism
Only 3-5% of the genes in a cell are expressed at one time
GENETIC CODE
Inheritance and genes
o Phenotype, traits, alleles
Genes and enzymes
o Development is produced by metabolic pathways
o Metabolic pathways are a series of enzymatic steps
o Hypothesis – genes code for enzymes
Beadle and Tatum – classic studies of the relationship between genes and enzymes
o Synthesis of the amino acid arginine
o Studied bread mold aspergillus that required arginine for growth
o Phenotype changed because one enzyme was missing
o Concluded that one gene coded for one enzyme; “one gene-one enzyme hypothesis”
Cell Cycle
Diploid cell: two copies
● Reproduction
Growth and development
● Repair
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