Genetics Test

GENETICS STUDY GUIDE

I. Genetics Basics

• Definition: Study of how genes/traits are passed down generations.

II. DNA (Deoxyribonucleic Acid)

• Structure:

  • Double-stranded, double helix, found in nucleus, makes up chromosomes.

  • Genes: Portions of DNA coding for traits.

  • Nucleotide Parts:

    • Nitrogenous bases:

      • Adenine (A) ↔ Thymine (T)

      • Cytosine (C) ↔ Guanine (G)

    • Sugar: Deoxyribose

    • Phosphate group

• Replication:

  • Exact duplication before cell division.

  • Enzymes: Helicase (unzips), DNA Polymerase (adds nucleotides).

III. RNA (Ribonucleic Acid)

• Structure: Single-stranded.

• Types:

  • mRNA: Carries DNA message to ribosome.

  • tRNA: Brings amino acids to ribosome.

  • rRNA: Makes ribosomes.

• Nitrogenous bases:

  • Adenine (A) ↔ Uracil (U)

  • Cytosine (C) ↔ Guanine (G)

IV. Processes

• Transcription: DNA → mRNA (Uracil replaces Thymine).

  • Enzyme: RNA Polymerase.

  • Example:

    • DNA: T-A-G-C

    • mRNA: A-U-C-G

• Translation:

  • Ribosome reads mRNA.

  • tRNA brings amino acids.

  • Codons (3 nucleotides) → Amino acids.

  • Example:

    • DNA: T-A-G

    • mRNA: A-U-C

    • Amino acid: Iso

VI. Mutations

• Types:

  • Gene Mutations:

    • Deletion: Nucleotide missing.

    • Insertion: Nucleotide added.

    • Inversion: Segment reattaches incorrectly.

    • Translocation: Segment attaches to different chromosome.

  • Chromosomal Mutation: Change in chromosome number (e.g., Trisomy 21 - Down Syndrome).

VII. Mendelian Genetics

• Key Terms:

  • Phenotype: Physical traits.

  • Genotype: Genetic makeup (AA, Aa, aa).

  • Alleles: One from each parent.

  • Dominant allele always expressed if present.

• Punnett Square: Predicts genotype/phenotype probabilities.

Good luck on your test! 🚀