1. Gene Mutations

2. Target #17- I can describe a gene mutation Gene mutation: a permanent heritable change in the sequence of bases in DNA – Effect can cause a range of consequences from no effect to complete protein synthesis inactivity – Can occur on somatic cells and on sex cells

3. Target #18- I can explain the three causes of gene mutation Three causes of gene mutation – Errors in replication Rare source of mutation DNA polymerase is responsible for proof-reading the new strand against the old strand Usually mismatched pairs are replaced with the correct nucleotide Occurs 1 in every 1 billion nucleotides – Mutagens Environmental influences – Radiation, certain organic chemicals Rate of mutation is usually low because DNA repair enzymes constantly monitor and repair damages

4. – Transposons Specific DNA sequences that have the ability to move to different genes – Can either increase or decrease the expression of the affected gene Nicknamed “jumping genes” Example – Indian corn has both white and red/black kernels » Caused by a transposon interrupting the expression of the gene for black kernel pigment

5. Target #19- I can describe point mutations Point Mutation – Occurs in one or more nucleotides – Includes the substitution, insertion or deletion of nucleotides Can alter the type of amino acid being produced, which may result in the wrong protein being synthesized – Generally occurs during DNA replication

6. Target #20- I can state what occurs during a substitution mutation Substitutions – One base is changed to a different base – Usually affect no more than a single amino acid May have no effect at all Example – If a mutation changed one codon of mRNA from CCC to CCA, the codon would still code for the same amino acid (Proline) – If a change occurs in the first base of the codon CCC, like to ACC, then the amino acid would be different.

7. Target #21- I can state how frameshift mutations affect protein activity Insertions & Deletions – Point mutations in which one base is added or subtracted from the DNA sequence – Also known as frameshift mutations Result in a shift of the reading frame of the genetic message Can result in the changing of the whole protein – Results in a change in, or loss of, the protein’s function

8. Target #22- I can summarize why genetic mutations may be harmful A harmful change caused by genetic mutations may result in the growth of cancer cells – Development of cancer involves a series of accumulating mutations that can be different for each type of cancer Several genes are involved with the suppression of tumor formation, but when mutated cause cancer – Proto-oncogenes and tumor-suppressor genes When those genes are mutated, they do not transcribe/translate cell cycle regulating proteins correctly – Results in the cell cycle not being controlled, and/or apoptosis is not occurring – Characteristics of Cancer Cells Genetically unstable Do not correctly regulate the cell cycle Escape the signals for cell death

9. Target #23- I can summarize why genetic mutations may be beneficial Some genetic mutations have beneficial effects – Results in the production of proteins with new or altered functions that can be useful to organisms in different or changing environments Example: mutations have helped many insects resist chemical pesticides – Also results in organisms who are more successful at surviving and producing offspring The source of all changes in organisms over time via evolution start with genetic mutations