Genetics and Inheritance – Cracking the Code of Who We Are

Admin
Jul 26
2 min read

Let’s be honest — Genetics can feel like a puzzle with too many pieces. Dominant vs recessive, genotypes, phenotypes, ratios, crosses… it’s a lot!

But here’s the truth: once you understand the basics, genetics becomes one of the most logical, powerful, and even beautiful parts of Life Sciences.

Because at its heart, it’s the science of you — how you became who you are.

Let me walk with you through this important topic — one step at a time.

🧠 What Is Genetics?

Genetics is the study of how traits are passed from parents to offspring through genes. It explains:

Why some people have brown eyes and others blue 👁️
Why some traits skip generations
How conditions like albinism or blood type are inherited

📘 Key Concepts to Remember

🧬 1. Genes and Alleles

A gene is a unit of inheritance (like the gene for eye colour)
An allele is a version of a gene (e.g., brown vs blue eyes)
You inherit two alleles for each trait — one from each parent

🧬 2. Dominant and Recessive Alleles

Dominant: Always shows if present (written with a capital letter, e.g., B)
Recessive: Only shows if two copies are present (lowercase, e.g., b)
Example:
- BB and Bb = brown eyes (dominant)
- bb = blue eyes (recessive)

🧬 3. Genotype vs Phenotype

Genotype: The combination of alleles (e.g., Bb)
Phenotype: The physical trait you can see (e.g., brown eyes)

🧬 4. Homozygous vs Heterozygous

Homozygous = both alleles are the same (BB or bb)
Heterozygous = different alleles (Bb)

🧪 Punnett Squares: Your Best Friend in Exams

Punnett Squares help predict the outcomes of genetic crosses.

Example:Parents: Bb × BbPossible offspring:

25% BB
50% Bb
25% bb

Phenotype ratio = 3 brown : 1 blue

You’ll use Punnett Squares to answer questions about:

Monohybrid crosses (one trait)
Dihybrid crosses (two traits)
Sex-linked inheritance (like haemophilia)
Blood types (IA, IB, i)

🧬 Sex-Linked Inheritance (Special Case)

Traits like colour blindness and haemophilia are carried on the X chromosome.

Males (XY) are more likely to inherit them because they only get one X
Females (XX) can be carriers without showing the trait

📝 Genetics Exam Tips:

✅ Always use correct lettering (capital for dominant, small for recessive)

✅ Know how to complete and label Punnett Squares

✅ Memorise phenotype and genotype definitions

✅ Understand how to calculate ratios and percentages

✅ Practise sex-linked and blood group crosses

✅ Read every question carefully — they test understanding, not just memory

💬 A Word of Encouragement

Genetics isn’t just about marks — it’s about understanding life at the deepest level.

And just like DNA, your effort today shapes your results tomorrow.

So don’t give up.

Try one cross. Then another.

Then check your answers.And if you fall short? Try again.

That’s how learning works — trial, error, and growth.

I see your progress. And I’m proud of you.