Mutations p 307 Mutations are changes in the
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Mutations (p. 307) Mutations are changes in the genetic material. Mutations may be genetic mutations or chromosomal mutations.
Genetic Mutations occur in the “code” on DNA or m. RNA • Mistakes in – copying the DNA : • Inserting the wrong nucleotide • Skipping or adding a base when a new strand is assembled.
There are 2 general types of genetic mutations. 1. Point Mutations • Involve only one or a few nucleotides. • Occur at a single point on the sequence. • Are substitutions. Substitution: THE FAT CAT ATE THE RAT THE TAT CAT ATE THE RAT
2. Frameshift Mutations • Involve the insertion or deletion of a nucleotide • The resulting shift causes every grouping of three bases after the mutation to be different.
Deletion: THE FAT CAT ATE THE RAT THE ATC ATA TET HER AT Insertion: THE FAT CAT ATE THE RAT THE FFA TCA TAT ETH ETA T
Are these a) point mutations or frameshift mutations? b) substitutions, deletions or insertions? 1. THE FAT CTA TER AT 2. THE FAT CAA ATE THE RAT 3. THE EFA TCA TAT ETH ERA T
Gene Mutations • So, gene mutations result from changes in a single gene. • They may be point mutation (substitution) or frameshift mutations (insertions or deletions).
• They may be passed on to the next cellular generation. HOW? • Depending on which gene they effect they may cause no obvious problem or they may be devastating. (What would happen if there was a frameshift mutation in the gene that codes for the production of DNA polymerase? )
Chromosomal mutations (p. 308) • Chromosomal mutations involve changes in the number or structure of chromosomes. • Such mutations may change the locations of genes on a chromosome and may even change the number of copies of some genes available to the organism.
Four types (p. 308): • Deletions – The loss of all or part of a chromosome • Duplications – Extra copies of the chromosome • Inversions – Reversal of the direction of part of the chromosome • Translocations – Part of one chromosome breaks off and attaches to another (ie. 13 to 14)
Chromosomal mutations • http: //www. youtube. com/watch? v=XAGxp 9 j 5 rtc
Chromosomal Disorders • Non-disjunction: when this occurs, abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may result.
Nondisjunction Section 14 -2 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Go to Section:
Examples of Non-Disjunction Disorders • Down’s Syndrome • XXY • Klinefelter’s • Turner’s Syndrome
Gene regulation • For Monday, read pages 309 to 312 in your text.
