Segregation

Definition

Segregation is the process during meiosis where alleles for a gene separate from each other so that each gamete receives only one allele for each gene. This fundamental principle underlies the inheritance patterns described by the chromosomal theory, where chromosomes segregate during cell division, ensuring that offspring inherit a mix of traits from both parents. Segregation also plays a key role in genetic linkage, as it affects how alleles are passed on together when genes are located on the same chromosome.

5 Must Know Facts For Your Next Test

1. Segregation occurs during meiosis I, specifically in anaphase I when homologous chromosomes are pulled apart.
2. The concept of segregation was first clearly articulated by Gregor Mendel, who observed this phenomenon in pea plants and laid the groundwork for modern genetics.
3. In diploid organisms, each individual carries two alleles for each gene, one inherited from each parent, and segregation ensures these alleles are distributed into gametes.
4. When genes are linked on the same chromosome, they do not assort independently; however, segregation still ensures that alleles can be recombined through crossing over.
5. Errors in segregation can lead to aneuploidy, where gametes have an abnormal number of chromosomes, potentially resulting in genetic disorders.

Review Questions

• How does segregation contribute to genetic variation in offspring?
  • Segregation is vital for genetic variation because it ensures that each gamete contains only one allele from each gene pair. When gametes combine during fertilization, the resulting offspring inherit a unique combination of alleles from both parents. This mixing of genetic material contributes to the diversity observed in populations and is a fundamental aspect of evolution.
• In what way does the chromosomal theory of inheritance support Mendel's principles of segregation and independent assortment?
  • The chromosomal theory of inheritance supports Mendel's principles by establishing that genes are located on chromosomes and behave according to specific patterns during meiosis. Segregation relates directly to how alleles for a gene separate during meiosis, while independent assortment refers to how different genes independently separate from one another. Together, these principles explain how traits are inherited and contribute to genetic diversity.
• Evaluate the implications of improper segregation during meiosis on genetic health and diversity within a population.
  • Improper segregation during meiosis can lead to conditions such as aneuploidy, where cells have an abnormal number of chromosomes. This can result in genetic disorders like Down syndrome or Turner syndrome, which can severely impact individual health. Additionally, if segregation errors occur frequently within a population, it could diminish genetic diversity by propagating harmful alleles or reducing reproductive success, ultimately affecting the population's ability to adapt to environmental changes.

Related terms

meiosis:

A specialized form of cell division that reduces the chromosome number by half, creating four haploid gametes from one diploid cell.

allele: Different forms of a gene that can exist at a specific locus on a chromosome, responsible for variations in traits.

chromosomal theory of inheritance: The theory stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis explains inheritance patterns.