Polygenic Inheritance 🌈

Some traits don’t fit neatly into “either–or” boxes. Instead of just purple vs. white flowers or tall vs. short people, we see a smooth spread of possibilities—think of all the different human heights you notice every day. These smoothly varying traits are usually polygenic, meaning they’re guided by three or more genes working together. :contentReference[oaicite:0]{index=0}

What makes a trait polygenic?

• 🌟 Many genes, many alleles: Each gene involved typically has two alleles (dominant and recessive). The more genes, the bigger the “mix-and-match” possibilities. :contentReference[oaicite:1]{index=1}
• ➕ Add-up effect: Every allele’s influence is additive. Your final look (phenotype) is the sum of all those little pushes. :contentReference[oaicite:2]{index=2}
• 🌤️ Environment matters: Polygenic traits often shift with nutrition, sunlight, altitude, and more. Genes set the range; the environment fine-tunes the outcome. :contentReference[oaicite:3]{index=3}

Classic example: Human skin colour 🖐️

Imagine three genes—A, B, and C—each with a dominant form (dark-skin booster) and a recessive form (light-skin reducer).

The shades between these extremes arise because every dominant allele adds a “dash of pigment,” while each recessive allele withholds it. :contentReference[oaicite:4]{index=4}

Visualising the gradient 📈

If you graphed every possible skin-tone genotype, you’d see a neat bell-shaped curve—lots of people with intermediate shades and fewer at the extremes. That smooth distribution is a hallmark of polygenic inheritance. :contentReference[oaicite:5]{index=5}

Important Concepts for NEET 📌

1. Polygenic traits show continuous variation rather than discrete categories.
2. Each dominant allele contributes additively to the phenotype; recessive alleles withhold that contribution.
3. Environment + Genes together shape the final look—essential for understanding real-world phenotypes.
4. The bell-curve distribution of phenotypes helps distinguish polygenic inheritance from single-gene Mendelian patterns.

Keep these ideas handy, and you’ll breeze through questions on quantitative traits! 🎯