Chromosome vs. Gene Mutations

1. Chromosome vs. Gene Mutations Chapter 12: Human Inheritance Patterns Monkemeier 2012

2. Chromosome mutations involve changes in the structure of a chromosome OR the loss or gain of a chromosome. Gene mutations involve a change in the nucleotide –base sequence of a gene on a DNA molecule. Chromosome vs. Gene Mutations Monkemeier 2012

3. Chromosome Mutations • Three types of chromosome mutations that involve the structure of the chromosome are: deletion, insertion, and translocation. • Deletion: is the loss of a piece of a chromosome due to breakage. • Inversion: a chromosomal segment breaks off, flips around backward, and reattaches. • Translocation: a piece of one chromosome breaks off and reattaches to a nonhomologous chromosome. Monkemeier 2012

4. Changes in Chromosome Structure • Deletion: is the loss of a piece of a chromosome due to breakage. Monkemeier 2012

5. Changes in Chromosome Structure • Inversion – a chromosomal segment breaks off, flips around backward and reattaches. Monkemeier 2012

6. Changes in Chromosome Structure • Translocation: a piece of a chromosome breaks off an reattaches to a nonhomologous chromosome. Monkemeier 2012

7. Mutations in Numbers of Chromosomes! • The loss or gain of a chromosome is due to nondisjuction. • Nondisjunction is the failure of homologous chromosomes to separate during meiosis. Monkemeier 2012

8. Gene Mutations • The substitution, addition, or removal of a single nucleotide within a DNA molecule is a point mutation. • The DNA molecule is “read” in groups of three nucleotide bases at a time. • A single point mutation such as an insertion or a deletion will change the “reading frame” of the DNA molecule. Monkemeier 2012

9. Point Mutations • Insertion –the adding of a nucleotide into the DNA sequence. Monkemeier 2012

10. Point Mutation • Deletion- a nucleotide within a gene is lost. Monkemeier 2012

11. Point Mutation - Substitution • Substitution: one nucleotide replaces another. (this is the least harmful of the three point mutations since it does not change the reading frame) Monkemeier 2012

12. Frameshift Mutation Monkemeier 2012 DNA is read in groups of three nucleotides. The three consecutive nucleotides are known as a reading frame. The reading frame can be disrupted by the point mutations known as insertion or deletion. When the reading frame is disrupted, protein synthesis will be affected.

13. Frameshift Mutation Monkemeier 2012

14. Gene Mutations Monkemeier 2012 Gene mutations affect the protein synthesis. Three consecutive nucleotides on a DNA molecule are known as a codon. Genes are composed of many codons. The reading frame for DNA is known as a codon.

15. Thought Question Monkemeier 2012 Differentiate between a chromosomal mutation and a gene mutation. Chromosomal mutations are changes in the structure or the numbers of chromosomes (a gain or loss). Gene mutations involve changes in the nucleotide sequence of the DNA molecule.