Genetics

Study of heredity and variation in living organisms.

Genes and DNAMendelian InheritanceGenetic Variation and Mutation
Chromosomes and Cell DivisionGenetic EngineeringNon-Mendelian Inheritance
Personalized MedicineGenetic Testing in FamiliesGenetically Modified Foods
Making Genetics Fun with FlashcardsBreaking Down Big Ideas with Diagrams
Genes and DNAMendelian Inheritanc...Genetic Variation an...Chromosomes and Cell...Genetic EngineeringNon-Mendelian Inheri...Personalized Medicin...Genetic Testing in F...Genetically Modified...Making Genetics Fun ...Breaking Down Big Id...
Advanced Topics

Chromosomes and Cell Division

What Are Chromosomes?

Chromosomes are long, thread-like structures made of DNA and proteins. They’re found in the nucleus of every cell and carry all of your genetic information.

Humans have 23 pairs of chromosomes (46 in total)—one set from each parent. Each chromosome contains hundreds or thousands of genes.

How Do Cells Divide?

There are two main ways cells divide:

  • Mitosis: Cells make exact copies of themselves for growth and repair. Both new cells have the same number of chromosomes as the original.
  • Meiosis: Special cells divide to produce eggs or sperm, each with half the usual number of chromosomes (23 in humans). When egg and sperm unite, the full set is restored.

Importance of Accurate Division

Mistakes in cell division can cause genetic disorders. For example, having an extra copy of chromosome 21 results in Down syndrome.

Chromosomes and Inheritance

Chromosomes determine your biological sex: typically, XX for females and XY for males.

Examples

  • Skin cells divide by mitosis to heal a cut.

  • Meiosis creates sperm and eggs with half the number of chromosomes, which combine to form a new individual.

In a Nutshell

Chromosomes are DNA bundles that divide during cell reproduction, ensuring genetic information is passed on correctly.

Key Terms

Chromosome
A structure in cells that contains DNA and many genes.
Mitosis
Cell division resulting in two identical cells.
Meiosis
Cell division that creates reproductive cells with half the usual number of chromosomes.
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Genetic Engineering