DNA carries genetic instructions in the nucleus of every cell, organised into chromosomes. A gene is a section of DNA coding for a specific trait, and alleles are different versions of the same gene (like one for brown eyes, one for blue). Offspring inherit one allele from each parent for each gene — a dominant allele will show its trait even with only one copy, while a recessive allele only shows if both copies are recessive.
Example
If brown eyes (B) is dominant and blue eyes (b) is recessive, a child with one B allele and one b allele (Bb) will have brown eyes — the recessive blue-eye trait only appears if a child inherits b from both parents (bb).
Key terms
Gene:
A section of DNA coding for a specific trait.
Allele:
A different version of the same gene.
Dominant / recessive:
A dominant allele shows with one copy; a recessive allele needs two copies to show.
Questions
1. DNA carries:
Genetic instructions
Only water
No information at all
Only sugar
2. A gene is:
A section of DNA coding for a trait
A type of cell only
A whole organism
A type of chromosome shape
3. An allele is:
A different version of the same gene
A whole chromosome
A type of cell
A type of protein only
4. Offspring inherit alleles from:
Both parents, one from each
Only one parent
Neither parent
Random strangers
5. A dominant allele shows its trait:
Even with only one copy
Only with two copies
Never
Only in plants
6. A recessive allele shows its trait:
Only if both copies are recessive
With just one copy
Never, under any circumstance
Only in animals
7. DNA is found in the:
Nucleus of cells
Outside of cells only
Nowhere in the body
Only in blood
8. If brown eyes (B) is dominant and blue (b) is recessive, a Bb genotype would result in:
Brown eyes
Blue eyes
No eye colour at all
A mix of colours in every case
9. For blue eyes (recessive) to appear, a child needs:
Two recessive alleles (bb)
Just one recessive allele
Two dominant alleles
No alleles at all
10. A chromosome is best described as:
A structure organising DNA
A single gene only
A type of cell membrane
A protein with no DNA
11. Two parents who are both Bb (brown eyes) could have a child with which genotype?
bb (blue eyes)
Only BB, never anything else
Only Bb, never anything else
No possible offspring
12. A trait controlled by a single gene with clear dominant/recessive alleles is called:
A simple Mendelian trait
An impossible trait
A trait with no genetic basis
A trait only affected by environment
13. Why might two brown-eyed parents (both Bb) have a blue-eyed child?
Each parent can pass on their recessive allele, and the child could inherit two recessive alleles
This is genetically impossible
Blue eyes always skip a generation exactly once
Eye colour has no connection to genetics
14. A genotype refers to:
The genetic makeup (alleles) an organism has
Only the physical appearance of a trait
A type of chromosome shape only
A type of cell division
15. A phenotype refers to:
The observable physical trait resulting from a genotype
The genetic code itself, not the trait shown
A type of chromosome only
A random, unrelated concept
16. A Punnett square is a tool used to:
Predict the possible genotypes of offspring from a genetic cross
Measure a person's height
Replace the need for any genetic information
Only apply to plants, never animals
17. Two parents, one BB (brown) and one bb (blue), would most likely have children with:
All Bb genotype, showing brown eyes
Only bb genotype children
Only BB genotype children
No possible offspring
18. Why can two organisms with the same phenotype (observable trait) sometimes have different genotypes?
A dominant trait can result from either one or two dominant alleles (e.g. BB or Bb)
Phenotype and genotype are always identical concepts
This scenario is genetically impossible
Recessive traits always produce different phenotypes from dominant ones
19. Some traits, like height, are influenced by multiple genes and environmental factors. This makes them:
More complex than simple single-gene, dominant/recessive traits
Identical in complexity to eye colour inheritance
Impossible to be influenced by genetics at all
Entirely determined by one single gene
20. Why is understanding heredity important in fields like medicine, beyond just predicting physical traits?
Some genetic conditions can be inherited, and understanding patterns helps with diagnosis and genetic counselling
Heredity has no connection to health or medical conditions
Only physical traits like eye colour are ever inherited
Medicine has no practical use for genetic information
21. Why might a family tree (pedigree) showing several generations be a useful tool in genetics?
It can help trace how a trait or condition has been inherited across a family over time
Family trees have no connection to genetic inheritance patterns
Only a single generation is ever relevant to genetics
Pedigrees are used exclusively for historical records, not genetics
Answer key (parent copy)
1. Genetic instructions
2. A section of DNA coding for a trait
3. A different version of the same gene
4. Both parents, one from each
5. Even with only one copy
6. Only if both copies are recessive
7. Nucleus of cells
8. Brown eyes
9. Two recessive alleles (bb)
10. A structure organising DNA
11. bb (blue eyes)
12. A simple Mendelian trait
13. Each parent can pass on their recessive allele, and the child could inherit two recessive alleles
14. The genetic makeup (alleles) an organism has
15. The observable physical trait resulting from a genotype
16. Predict the possible genotypes of offspring from a genetic cross
17. All Bb genotype, showing brown eyes
18. A dominant trait can result from either one or two dominant alleles (e.g. BB or Bb)
19. More complex than simple single-gene, dominant/recessive traits
20. Some genetic conditions can be inherited, and understanding patterns helps with diagnosis and genetic counselling
21. It can help trace how a trait or condition has been inherited across a family over time