GENETICS & GENE THERAPY – ONE-PAGE REVIEW SHEET

Codons

● A codon = 3 bases on mRNA

● Codes for 1 amino acid

● Start: AUG (Methionine)

● Stop: UAA, UAG, UGA

Types of Mutations & Effects on Protein

Insertions

● In-Frame: +3 bases → adds amino acids → usually mild

● Out-of-Frame (Frameshift): not multiple of 3 → changes everything after → severe

Deletions

● In-Frame: −3 bases → loses amino acids → may still work

● Out-of-Frame (Frameshift): not multiple of 3 → major protein change → severe

Substitutions (Point Mutations)

● Missense: wrong amino acid → altered protein

● Nonsense: early STOP → shortened, usually nonfunctional protein

DNA Sequencing Gels

● Read BOTTOM → TOP

● Lanes labeled A, T, C, G

● Read smallest fragments first

● Produces the new DNA strand (5’ → 3’)

Gene Therapy

● Treatment that adds, fixes, or replaces a faulty gene

● Used for genetic disorders, cancer, and immune diseases

Vector (Biotechnology)

● A carrier that delivers genes into cells

● Examples: viruses, plasmids, liposomes

In Vivo and Ex Vivo

● In Vivo: Gene added directly into patient

● Ex Vivo: Cells removed → gene added in lab → cells returned

Good Candidates for Gene Therapy

✔ Monogenic (1 gene disorder)

✔ Exact gene is known

✔ Target cells accessible

✔ Improvement after correction

✔ Safe delivery method

✔ Long-term gene expression

Dangers of Gene Therapy

⚠ Extreme immune response

⚠ Wrong gene modified

⚠ Insertional mutagenesis (can cause cancer)

⚠ Unintended long-term effects

Steps to Make a Recombinant Viral Vector

1. Obtain pure viral vector DNA

2. Cut viral DNA with restriction enzyme

3. Obtain pure human DNA

4. Cut out human gene with same enzyme

5. Insert gene using sticky ends

6. Use ligase to seal DNA

Using the Genetic Code Chart

1. Start with mRNA codon

2. Match 1st base (left) → 2nd base (top) → 3rd base (right)

3. Find the amino acid

Interpreting Graphs

● X-axis = independent variable

● Y-axis = dependent variable

● Look for: ○ Trends ○ Comparisons ○ Cause-and-effect