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MCAT Bio: Genes

Terms

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Define:
1. Mutation
a. Gene vs. Chromosomal
b. Somatic vs. germ cell
c. spontaneous vs. induced
1. Mutation is alteration in the genome not as a result of of recombination.
a. Gene mutation: Only one gene is changed, Chromosome: structure of chromosome is modified.
b. Somatic: occurs in body cell, is not passed down through generations. Germ cell mutation is.
c. Spontaneous: occurs due to random natural processes. Induced occurs due to mutagens.
1. Define: Point Mutation
2. Different types of Pt. mutations
1. Mutation that changes a single base pair
2. i. Base pair-substitution mutation
ii. Insertion/deletion
Define b.p. substitution mutation and give different types.
Mutation in which one b.p. is replaced by the other.
i. Transition mutation: involving switch of base pairs from A-T to C-G (or vice versa)
2. Transversion: Reversal of same b.p.
Mis-sense vs. non-sense mutations
1. Mis-sense mutation is a b.p. mutation that occurs in the amino acid coding sequence.
i. Silent mutation: causes no change in amino acid sequence.
ii. Neutral mutation: causes no change in protein fxn.
2. Non-sense mutation: If either substitution or addn/deletion causes creation of stop codon. Translation of protein stopped entirely.
Define: Addition and Deletion Mutations and list the two types.
Mutations caused by insertion or deletion of a b.p.
Frameshift mutations: if add/del occurs in non-multiples of 3, genetic sequence will be shifted since bp are read in groups of 3. Often results in non-functional proteins
Non-frameshift mutations: add/del occurs in multiples of 3. May result in partially or even completely functional proteins.
Chromosomal mutations:
Duplication vs. deletion
Aneuploidy vs. polyploidy
Deletion occurs when portion of chromosome breaks off or is lost during recomb. or crossing over.
Duplication occurs when a DNA fragment breaks free and incorporates into the homologous chromosome.
Aneuploidy: deletion/duplication occurs for one chromosome.
Polyploidy: occurs for multiple chromosomes.
1. Translocation vs. inverstion.
2. Describe process by which above occurs.
1. Translocation: Process by which one chromosome is inserted into another chromosome.
Inversion: same as translocation but orientation is inverted.
2. Process: Occurs via DNA segments called transposons which excise themselves from a chromosome and reinsert themselves into another. Transposons are usually flanked by identical nucleotide sequences which allows inversion. Note: transposon may either excise and move or copy itself and stay.
1. Define wild type
2. Forward vs. backward mutations.
1. Original state (prior to mutations)
2. Forward mutation: mutates further away from wild type.
Backward: regression to wild type.
1. Define cancer
2. Oncogenes
1. Cancer is unrestrainted and uncontrolled growth of cells. Cells usually divide 20-50 times before dying.
2. Oncogenes are genes that cause cancer. They mutate from proto-oncogenes which govern normal growth in humans. Causes of these mutations are called carcinogens
Describe different phases of cell life cycle.
First growth phase G1
Synthesis S
Second Growth Phase G2
Mitosis/Meiosis M
Cytokinesis C
G1, S and G2 are called interphase.

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