Lecture Notes on DNA, Genome, and Gene Coding

Overview of DNA and Genome

• DNA Packing: DNA is packaged into multiple chromosomes.
• Genome: The total DNA of an organism, represented by its chromosomes.
• Chromosome Types:
  • Sex Chromosomes: Determine biological sex; most organisms have one pair.
  • Autosomes/Somatic Chromosomes: Chromosomes other than sex chromosomes.

Chromosome Count

• Within a species, organisms usually have the same number of chromosomes.
• Chromosome count varies between species (e.g., houseflies have 8, some dog breeds have 78).
• Humans have 46 chromosomes, or 23 pairs.

Karyotype

• Karyotype: A picture of an organism’s chromosomes.
• Displays chromosomes in pairs (22 pairs of autosomes, 1 pair of sex chromosomes).
• Example: XX = female, XY = male in humans.

Genes and DNA Structure

• Chromosomes are highly compacted DNA structures containing genes.
• Genes: Segments of DNA coding for specific proteins.
• Each gene corresponds to instructions for one protein.
• Locus/Loci: Location of a gene on a chromosome; constant within a species.

Analogy - IKEA Instructions

• Genome as a collection of all instructions (like IKEA furniture manuals).
• Chromosomes as volumes of instructions.
• Genes as specific instructions for a piece of furniture.
• Locus as a specific page in a manual.

Coding and Non-Coding DNA

• Not all DNA codes for proteins.
• Prokaryotes: Less DNA, mostly coding for proteins.
• Eukaryotes: More DNA, significant portion non-coding.

Types of Non-Coding DNA

• Introns: Non-coding segments within genes.
• Exons: Non-coding segments outside genes.
• Regulatory DNA: Determines when and where genes are expressed.
• Other types: Fragments, duplicates, pseudogenes.

Summary

• Chromosome holds DNA and multiple genes.
• Genes code for proteins, but not all DNA sequences code for proteins.
• Introns and exons are key concepts in non-coding DNA.
• Understanding the genome involves understanding how these structures interact and function.