Biology: Genetic Variation and Reproduction

Genetic Variation and Survival

• Genetic variation is crucial for the survival of species on Earth as it allows populations to adapt to changing conditions and prevents extinction.

Types of Reproduction

• Asexual reproduction requires only one individual to produce offspring and is often seen in simple organisms like bacteria and protists.
• Advantages of asexual reproduction include rapid reproduction, no need to find a mate, and no need to care for offspring.
• Disadvantages of asexual reproduction include no genetic diversity, inability to adapt to changing conditions easily, and proneness to extinction.
• Sexual reproduction requires two individuals to produce offspring and provides genetic diversity, reducing the chance of extinction.
• Advantages of sexual reproduction include genetic diversity and reduced extinction risk.
• Disadvantages of sexual reproduction include energy expenditure to find a mate, slower reproduction rate, and uncertainty of reproduction.

Meiosis

• Meiosis produces haploid gametes (egg and sperm in humans) through Interphase, Meiosis I, and Meiosis II.
• Meiosis I produces two haploid cells with attached sister chromatids.
• Meiosis II produces four haploid cells.
• Only cells in human ovaries and testes undergo meiosis.
• Meiosis for sperm production is called spermatogenesis, while meiosis for egg production is called oogenesis.
• Oogenesis produces only one large egg cell.

Meiosis and Genetic Diversity

• Meiosis causes genetic diversity in two ways: independent assortment and crossing over.
• Independent assortment allows for random alignment of homologous pairs during Meiosis I, resulting in many variations.
• Crossing over involves the exchange of parts between homologous pairs, allowing for an infinite number of new combinations.

Meiosis and Mutations

• A mutation is a change in genetic material that can occur during meiosis and be passed on to offspring.
• Mutations can occur at the chromosome or gene level.
• Nondisjunction is a type of chromosome mutation where chromosomes fail to separate during Meiosis, resulting in egg or sperm with incorrect chromosome numbers.
• Nondisjunction can lead to genetic syndromes depending on the affected chromosome.
• Mutations can also occur in the DNA code at the gene level, which will be discussed further in the next unit.