Cell biology flash cards
Flash cards on cell structure, organelles, plant and animal cells, bacteria, diffusion, osmosis, active transport, mitosis and microscopy for school biology.
Flash card deck21 cardsIntermediateSchool
Genetics and DNA basics flash cards
Flash cards on DNA, genes, chromosomes, alleles, dominant and recessive traits, Punnett squares, meiosis, mutation and sex determination for school genetics.
Free to use, edit, print and study. No account needed: your set stays on this device.
The cards, front and back
- 1Front
What is DNA?
BackDeoxyribonucleic acid, the chemical that carries genetic information. It is a polymer made of two strands twisted into a double helix.
- 2Front
What are the four bases in DNA and how do they pair?
BackAdenine (A), thymine (T), cytosine (C) and guanine (G). A always pairs with T, and C always pairs with G.
- 3Front
What is a gene?
BackA short section of DNA that codes for a particular sequence of amino acids, which makes a specific protein.
- 4Front
What is a chromosome?
BackA long, coiled molecule of DNA, found in the nucleus of eukaryotic cells, carrying many genes.
- 5Front
How many chromosomes are in a normal human body cell?
Back46, arranged in 23 pairs. One chromosome of each pair comes from each parent.
- 6Front
What is a genome?
BackThe entire genetic material of an organism.
- 7Front
What is an allele?
BackA different version of the same gene. For example, a gene for a trait might have one allele for one form and another allele for a different form.
- 8Front
Dominant and recessive alleles
BackA dominant allele shows its effect even when only one copy is present (written with a capital letter, such as B). A recessive allele only shows its effect when two copies are present (lower case, such as b).
- 9Front
Homozygous and heterozygous
BackHomozygous means both alleles are the same (BB or bb). Heterozygous means the two alleles are different (Bb).
- 10Front
Genotype and phenotype
BackThe genotype is the combination of alleles an organism has, such as Bb. The phenotype is the characteristic that shows, such as eye colour, which results from the genotype and sometimes the environment.
- 11Front
Two heterozygous parents (Bb × Bb) are crossed. What are the expected offspring ratios?
BackGenotypes: 1 BB : 2 Bb : 1 bb. Phenotypes: 3 showing the dominant trait to 1 showing the recessive trait, a 3:1 ratio.
- 12Front
What is a Punnett square used for?
BackTo show all the possible combinations of alleles from two parents and work out the probability of each genotype and phenotype in the offspring.
- 13Front
What are gametes?
BackSex cells: sperm and egg cells in animals, pollen and egg cells in plants. In humans they contain 23 chromosomes, one from each pair.
- 14Front
What happens in meiosis?
BackA cell divides twice to make four gametes, each with half the number of chromosomes, and each genetically different from the others.
- 15Front
Compare mitosis and meiosis.
BackMitosis makes two identical body cells with a full set of chromosomes, for growth and repair. Meiosis makes four genetically different gametes with half the chromosomes, for sexual reproduction.
- 16Front
How is sex determined in humans?
BackBy the sex chromosomes. Females usually have XX and males usually have XY. Each egg carries an X, and each sperm carries either an X or a Y.
- 17Front
What is a mutation?
BackA change in the DNA sequence. Most mutations have no effect, some change a protein so it works differently, and a few can be harmful or helpful.
- 18Front
How does DNA code for proteins?
BackA sequence of three bases (a triplet) codes for one amino acid. The order of the triplets sets the order of amino acids, which decides the shape and job of the protein.
- 19Front
Give two differences between DNA and RNA.
BackRNA is usually single-stranded, while DNA is double-stranded. RNA contains the base uracil (U) instead of thymine (T).
- 20Front
What causes variation between individuals?
BackGenetic causes (the alleles inherited from parents, plus mutations) and environmental causes (such as diet, climate and lifestyle). Most characteristics are affected by both.
- 21Front
What is natural selection?
BackIndividuals with variations that suit their environment are more likely to survive and reproduce, so they pass on their alleles. Over many generations this can change a species.
How to use this template
This deck covers the core ideas of genetics: the structure of DNA and base pairing, genes, chromosomes and the genome, alleles, dominant and recessive traits, genotype and phenotype, Punnett squares and ratios, gametes and meiosis, sex determination, mutation, how DNA codes for proteins, DNA compared with RNA, variation and natural selection. It suits GCSE and IGCSE biology, Year 10 and Year 11 science, high school biology and the start of AP or IB genetics. Learn the vocabulary first, because every genetics question depends on it, then use Test mode and spaced repetition to keep the terms sharp. Print it double-sided to use in class.
Tips
- Learn the vocabulary in pairs that are easy to confuse: gene and allele, genotype and phenotype, homozygous and heterozygous, mitosis and meiosis.
- Draw a Punnett square for every cross question, even simple ones. It is quick and examiners often give a mark for it.
- Always say what each letter stands for before you start a cross, for example B is the dominant allele and b is the recessive allele.
- Be clear about ratios, fractions, percentages and probabilities. A 3:1 ratio means three quarters, or 75%, show the dominant trait.
- Remember that a mutation does not have to be harmful. Many have no effect at all.
Make it fit
- Add cards for topics your course includes, such as codominance, sex-linked inheritance, family pedigree charts or genetic engineering.
- Add a worked Punnett square for a specific example your teacher uses, written as a short list on the back.
- Make reverse cards with the definition on the front and the key word on the back.
- Split the deck into DNA and protein synthesis, and inheritance.
Updated October 28, 2026