WAEC SSCE Biology
Study notes for Chromosomes: The basis of heredity Reference should be made to dominant and — part of the WAEC SSCE Biology syllabus. 2 learning objectives with explanations and exam tips.
Chromosomes are thread-like structures found in the nucleus of cells that carry your genes. Think of them as instruction manuals for building your body. Humans have 46 chromosomes arranged in 23 pairs. Each chromosome contains DNA, which holds genetic information passed from parents to children.
When we talk about dominant traits, we mean characteristics that show up easily in offspring. For example, in Nigerian families, dark skin is dominant over light skin, so most children inherit darker complexions. Your genes sit on chromosomes in pairs, and sometimes one gene overpowers the other—that's dominance in action.
The structure of a chromosome includes the centromere (the pinched middle part) and two arms extending outward. During cell division, chromosomes condense and become visible under a microscope, which is why scientists can study them.
Chromosomes are thread-like structures in our cells that carry genes, which are the instructions for our traits. Think of them as instruction manuals that parents pass to their children. When your parents had you, they each gave you chromosomes containing their genes—this is how traits like skin colour, height, and even how your ears look get transmitted from one generation to the next.
Some traits are dominant, meaning they show up easily and override other traits. For example, in Nigeria, many families show dark skin dominance because the gene for dark skin is dominant over lighter skin genes. When a parent passes on a dominant gene for a trait, that trait usually appears in the child.
Understanding how chromosomes transmit these traits helps explain why children resemble their parents. During reproduction, chromosomes separate and recombine, creating new combinations of traits in offspring while maintaining the family's genetic pattern.