The Genome Allows for Genetic Diversity within Species
Definition
Genome
The genome is the complete set of genetic instructions that determines the structure, function, and traits of an organism.
- The genome is the instruction manual for building and maintaining an organism, written in the four DNA bases A, T, C, and G.
- It includes:
- Coding DNA: Sequences that encode proteins.
- Non-coding DNA: Sequences that regulate gene expression or have other functions.
- Think of the genome as a comprehensive instruction manual where:
- Chapters = Chromosomes, long strands of DNA wrapped around proteins.
- Sentences = Genes, specific sequences coding for proteins.
- Spaces = Non-coding regions, essential for timing and regulation.
Unity Within a Species
- All members of a species share the same set of genes arranged in the same order on their chromosomes.
- This shared structure ensures that organisms can reproduce successfully, allowing homologous chromosomes to pair, align and cross over correctly during meiosis.
All humans have the hemoglobin gene on chromosome 11, regardless of which allele version they inherit.
TipUnderstand that if the chromosomes don't pair correctly, sexual reproduction would fail.
Genetic Diversity within a Species
While genomes are largely uniform within a species, small variations exist, creating individual uniqueness.
Single-Nucleotide Polymorphisms (SNPs)
Definition
Single-Nucleotide Polymorphism (SNP)
SNPs are single base-pair changes in the DNA sequence.
- The most common source of variation is the single-nucleotide polymorphism (SNP).
- SNPs occur roughly once every 650,000 base pairs in humans, resulting in 4,000-5,000 SNPs per individual.
Eye color
- A single SNP might alter one base in this gene, resulting in blue eyes instead of brown.
- This demonstrates how small genetic changes can lead to visible differences within a species.
Why Are SNPs Important?
- Trait Variation: SNPs contribute to differences in height, fur color, or disease resistance.
- Evolutionary Insights: They act as markers to trace inheritance patterns and evolutionary relationships.
- Individual Uniqueness: SNPs drive the subtle variations that differentiate individuals within a population.
- Keep in mind that most SNPs are neutral.
- They don’t affect an organism’s traits or survival.
- However, some SNPs can have significant impacts, such as increasing the risk of certain diseases or providing resistance to infections.
Unity and Diversity Across Species
- Within species: Humans share approximately 99.9% of their DNA with each other. This explains why all humans belong to the same species and can reproduce together.
- Between species: Humans share approximately 99% of their DNA with chimpanzees, reflecting evolutionary relatedness.
- SNPs and other variations account for the 0.1% difference between individual humans, explaining why people look and behave differently despite being the same species.
Lactose tolerance in adults is caused by SNPs in regulatory regions of the LCT gene.
Note- Even identical twins, who begin life with the same genome, accumulate genetic differences over time due to mutations and environmental influences.
- This highlights the dynamic nature of genetic diversity.
- Why do all members of a species share the same gene order on chromosomes?
- How does shared genome structure support successful meiosis?
- What is a single-nucleotide polymorphism (SNP)?
- What percentage of DNA do humans share with each other?
- How do SNPs contribute to trait variation?
- Why is genetic diversity important for a species?
