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Chromosomes, Genes, and Mutations
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What are chromosomes? Chromosomes are packages of tightly-coiled (condensed) DNA Each chromosome is tightly coiled around proteins called histones
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What are chromosomes? Each human has 23 sets (pairs) of chromosomes, or 46 total chromosomes
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What are genes? A molecular unit of heredity
The name for sections of DNA (and therefore RNA) that code for a specific protein (which has a specific function in the organism)
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What are genes? Since genes are bands/sections of DNA, that means genes are also bands/sections of chromosomes
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How are genes inherited?
Each person has two copies of each gene – one on each chromosome You inherit one chromosome from your mom, and one chromosome from your dad More on meiosis later…
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How are genes mutated? Genes can be mutated when the DNA is mutated or when the chromosomes are mutated There are two types of DNA (gene) mutations: Point Mutations: a change in a single base pair Frameshift Mutations: a single base is added or deleted from DNA Chromosomes can be mutated as well (long segments of DNA)…
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What are examples of chromosomal mutations?
Deletions: part of the chromosome is left out
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What are examples of chromosomal mutations?
Inversions: part breaks out and reinserts itself backwards
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What are examples of chromosomal mutations?
Translocations: part breaks off and is added into a different chromosome
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What are examples of chromosomal mutations?
Non-Disjunction: failure of homologous chromosomes to separate properly during meiosis
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What causes chromosomal mutations?
Problems that occur during meiosis
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What causes chromosomal mutations?
Environmental agents (x-rays, UV light, radioactivity)
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What are the results of chromosomal mutations?
If it occurs in gametes (sex) cells: Can cause birth defects, miscarriage, or no change Few are passed on to next generation because zygote usually dies If it occurs in somatic (body) cells: Can lead to cancer Can have no change
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