KnowSoda
ScienceBiology
Genetics & DNA: fun facts and quiz
The essentials in 7 ideas, with fun facts, an illustrated story and a quiz to see how much you know.
The essentials
DNA
DNA is a long molecule that stores the instructions for building and running a living thing. It’s shaped like a twisted ladder: a double helix.
Key fact
Stretched out, the DNA in one of your cells is about 2 metres long.
Genes
A gene is a stretch of DNA that holds the recipe for something, often a protein. Humans have roughly 20,000 protein-coding genes.
Key fact
Any two people share about 99.9% of their DNA.
DNA & Inheritance
You inherit half your DNA from each parent. That’s why you might have your mother’s eyes and your father’s hair.
Key fact
Identical twins share almost exactly the same DNA.
Chromosomes
DNA is packed into chromosomes. Most human cells have 46, in 23 pairs. One pair helps decide biological sex, usually XX or XY.
Key fact
Dogs have 78 chromosomes.
Dominant & Recessive
Genes come in versions called alleles. A dominant one shows up even with just one copy; a recessive one only shows with two copies.
Key fact
Gregor Mendel found these rules breeding pea plants in the 1860s.
Mutations
A mutation is a change in DNA. Most do nothing, some cause disease, and a few help. Mutations are the raw material of evolution.
Key fact
Each of us carries dozens of new mutations our parents didn’t have.
The Human Genome
The Human Genome Project, finished in 2003, read nearly all 3 billion letters of human DNA. Today a genome can be read in about a day.
Key fact
The first genome took 13 years and about 3 billion dollars.
Fun facts
Rosalind Franklin’s X-ray images were key to working out DNA’s shape in 1953.
A tiny water flea has more genes than you: about 30,000.
Siblings share about half their DNA on average, but the exact share varies, roughly from 40% to 60%.
Birds flip the mammal pattern: in birds, it’s the females that carry two different sex chromosomes.
Mendel’s work was ignored for about 35 years, until scientists rediscovered it in 1900.
Blue eyes may trace back to a single mutation in one person who lived 6,000 to 10,000 years ago.
Only about 1 to 2% of human DNA holds the instructions for making proteins.
Story: A Race Declared a Draw
A Race Declared a Draw
1990s. Two teams race to read the human genome: a public project of labs around the world, and a company led by Craig Venter.
The public team puts its results online every day, free, so nobody can lock up our DNA with patents.
In June 2000, the rivals announce a first draft together at the White House, and call it a tie.
True or false?
Tap your answer to see if you got it, and why.
-
Question 1 of 10
DNA is shaped like a double helix.
Show the answer
True. Two strands twisted around each other.
-
Question 2 of 10
Genes are sections of DNA.
Show the answer
True. Recipes for making proteins.
-
Question 3 of 10
DNA carries information passed from parents to children.
Show the answer
True. Half from each parent.
-
Question 4 of 10
Most human cells have 46 chromosomes.
Show the answer
True. In 23 pairs.
-
Question 5 of 10
A recessive trait needs two copies of the allele to show.
Show the answer
True. One from each parent.
-
Question 6 of 10
Some mutations have no effect at all.
Show the answer
True. Most are harmless.
-
Question 7 of 10
The Human Genome Project was completed in 2003.
Show the answer
True. After 13 years of work.
-
Question 8 of 10
Only humans have DNA.
Show the answer
False. Every known living thing uses DNA.
-
Question 9 of 10
Every person’s DNA is completely different from everyone else’s.
Show the answer
False. We share about 99.9% of it.
-
Question 10 of 10
Children inherit all of their DNA from just one parent.
Show the answer
False. Half comes from each parent.
Keep going in the app
KnowSoda learns what you know and brings back what you’re about to forget. Genetics & DNA has 6 more ideas at the Advanced and Expert levels.
Sources
- National Human Genome Research Institute — Genetics glossary and Human Genome Project
- Nature Education (Scitable) — DNA, genes, chromosomes, Mendel
- King’s College London — Rosalind Franklin
- Encyclopaedia Britannica — heredity, mutation
- The Nobel Prize — Chemistry 2020 (CRISPR); Physiology or Medicine 2022 (Pääbo)
- U.S. Food and Drug Administration — First gene therapies for sickle cell disease (2023)
