Genetics for 2ry Level Students

Genetics for 2ry Level Students

• This course covers the identification, function, and variation of genetic material.
• Part one focuses on identifying and organizing genetic material.
• Part two explores the function of genetic material.
• Part three examines phenotyping and variation in genetic material.

Part One: Identification and Organization of Genetic Material

• Requirements of genetic material:

  • Contain biologically useful information in a stable form.
  • Be able to reproduce and transmit information faithfully.
  • Be able to express itself.
  • Be capable of variation (mutations and recombination).

• DNA and RNA structure: Covered in the course.

• Relating DNA structure to genetic requirements: Covered in the course.

• Evidences in prokaryotes and eukaryotes: Covered in the course.

Part Two: Function of Genetic Material

• Molecular genetics: Studying biochemical and molecular mechanisms by which hereditary information is stored in DNA and transmitted to proteins. Includes PCR sequencing.

• Population genetics: Examining factors that determine the genetic composition of populations, including genetic changes that isolate new species.

Part Three: Phenotyping and Variation in Genetic Material

• DNA replication: DNA replication is semi-conservative. Each strand acts as a template for new strand synthesis.

• Prokaryotes Experiment: Bacteria were grown in a medium containing a heavy isotope of nitrogen, then transferred to a light isotope medium. DNA was extracted at various times and analyzed. This demonstrated semi-conservative replication.

• Eukaryotes Experiment: Eukaryotic chromosome structure was observed. An image (Figure 4) of this was included in the material, potentially for visual study.

• DNA translation: The third requirement of genetic material, translating DNA nucleotide sequences into amino acid sequences during protein synthesis. Genes control the synthesis of single polypeptide chains.

• DNA variation: Variation occurs through mutation and recombination. Mutation is a change in the DNA base sequence, affecting genetic information and newly synthesized proteins. Recombination involves genetic exchange between homologous chromosomes during meiosis.

DNA Structure

• DNA and RNA are made of nucleotides.
• Each nucleotide consists of a phosphate group, a sugar, and a nitrogenous base.
• DNA's sugar is deoxyribose; RNA's is ribose.
• DNA has four bases: Adenine, Guanine, Cytosine, and Thymine.
• RNA has four bases: Adenine, Guanine, Cytosine, and Uracil.

RNA Classes

• Informational RNA (mRNA):

  • Messenger RNA carries genetic information from DNA to ribosomes for protein synthesis.
  • mRNA is an intermediate in decoding genes into polypeptide chains.

• Functional RNA (rRNA and tRNA):

  • rRNA combines with proteins to form ribosomes (protein synthesis machinery).
  • tRNA carries amino acids to mRNA during protein synthesis.

• Functional RNA specific to eukaryotes:

  • Small nuclear RNA (snRNA) participates in splicing (modifying) pre-mRNA into mRNA.
  • Spliceosomes are ribonucleoprotein particles formed from snRNA and proteins.
  • Small cytoplasmic RNA (scRNA) controls protein traffic in eukaryotic cells.

• microRNAs and small interfering RNAs:

  • They are small non-coding RNAs that regulate gene expression through RNA interference.
  • MicroRNAs silence mRNA by:
    • Cleaving mRNA into pieces.
    • Shortening the poly A tail, destabilizing mRNA.
    • Decreasing mRNA translation efficiency.
  • siRNAs resemble miRNAs but derive from longer double-stranded RNA.

Relating DNA Structure to Genetic Requirements

• DNA as a coded molecule: DNA's information content is in the sequence of its bases. Different species have different genetic information.
• Chargaff's experiment: Equal amounts of purines and pyrimidines were found in DNA, leading to the rule A+G = T+C. This base-pairing ratio (A/T, G/C) is constant within a species.