Biology Year 12 on Genetics and Diseases (Grade A+)
Summary:
Mutation is a fundamental process of introducing new alleles into populations, serving as the foundation for genetic variation and evolution. Arising from changes in DNA sequences, mutations can be benign, harmful, or advantageous. They may emerge from errors during cell division, exposure to radiation like x-rays or gamma rays, certain chemicals like benzene, or biological agents such as viruses. While some mutations only impact individual organisms, others, occurring in reproductive cells, can be passed down to subsequent generations, contributing to evolutionary change. Notably, while only 1.5% of human DNA actively codes for proteins, both coding and non-coding regions play crucial roles in determining the function and regulation of genes. Genetic variation, essential for a species’ adaptability and survival, is further enriched through mechanisms like crossing over during meiosis and the randomness of fertilization in sexual reproduction.
Excerpt:
Biology Year 12 on Genetics and Diseases
Module 6: Genetic change
Inquiry question: How does mutation introduce new alleles into a population?
Mutation
➢ Explain how a range of mutagens operates:
Mutations:
- Mutations: Change in the sequence of nucleotides of DNA.
- It can affect whole chromosomes or individual genes. The changes produce variations among organisms that may be harmful, neutral or beneficial.
- Gene mutation: produces new alleles of genes in species and generates new genetic variation. When a gene mutation confers a phenotypic advantage, individuals with the new allele will be at a selective advantage, and natural selection may result in an increased frequency of the allele and the phenotype produced by the mutation.
- Most mutations are due to ransom errors in cell division.
- Induced mutations: caused by environmental agents (mutagens).
- Somatic mutations: changes in DNA sequences that occur in body cells. Only affect that particular individual.
- Gametic mutations: occur in reproductive cells, which gave rise to gametes. These can be passed on to future generations.
How Mutagens Operate?
- Electromagnetic radiation:
- Emitted by electrically charged particles.
- Able to interact with and ionise atoms that they encounter in the body.
- Examples: gamma rays, x-rays and higher energy ultraviolet light.
- High energy states of these radiations mean they can disrupt the hydrogen bonds between nitrogenous bases and phosphodiester bonds, causing chromosomal abnormalities.
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