What Are Chromosomes and Genes?
Chromosomes are thread-like structures made of DNA that carry genetic information. Genes are specific sections of DNA within chromosomes that code for particular proteins and traits, passed from parents to offspring through reproduction.
A chromosome is a package of DNA wrapped around proteins; a gene is a segment of DNA on a chromosome that codes for a specific trait. Together, they form the basis of heredity.
- 1↓DNA (double helix)The molecule containing genetic code, made of 4 bases (A, T, G, C).
- 2↓Histone proteinsDNA wraps around histone proteins to form nucleosomes.
- 3↓ChromatinNucleosomes condense into a thread-like structure.
- 4↓ChromosomeFurther coiled chromatin, visible during cell division.
- 5Gene locationA specific DNA segment on the chromosome coding for one trait.
Step-by-step worked examples
A human has 46 chromosomes. How many are inherited from each parent?
Humans inherit 23 from mother (egg) and 23 from father (sperm). Total: 46 chromosomes (23 pairs).
What does the gene for eye color code?
It codes for a protein that produces eye pigment. Different alleles produce brown, blue, or green eyes.
How many genes are on a human chromosome?
Chromosome 1 has ~2,000 genes. Smaller chromosomes have fewer (e.g., chromosome 21 has ~300 genes). Total: ~20,000–25,000 genes in the human genome.
Flashcards
Quick quiz
Q1.A gene codes for…
Q2.Chromosomes are made of…
Q3.How many chromosomes come from your mother?
Q4.Which is smaller — chromosome or gene?
The full card deck, worked steps and AI-tutor support for “What Are Chromosomes and Genes?” are in Notek — study by hand before your exam.
Common mistakes
Chromosome and gene are the same thing. — Correct: A chromosome is a large structure; a gene is a small segment of it.
All genes code for visible traits like eye color. — Correct: Genes code for proteins controlling traits, metabolism, immunity, etc.
You inherit 46 genes total from parents. — Correct: You inherit ~20,000–25,000 genes (from both parents combined).
Genes are always 'turned on' in every cell. — Correct: Gene expression is selective — different cells activate different genes.
FAQ
What is the difference between a chromosome and a gene?
A chromosome is a large structure of coiled DNA; a gene is a small segment of DNA on a chromosome coding for one protein.
How many genes do humans have?
Approximately 20,000–25,000 genes across all 46 chromosomes.
What is an allele?
An allele is a variant form of a gene. For example, 'brown eye' and 'blue eye' are two alleles of the eye-color gene.
Do you inherit all your mother's genes?
No — you inherit ~half your genes from mother and ~half from father (23 chromosomes from each parent).