7th Grade Genetics Quiz
Questions: 16 · 10 minutes
1. Which statement best defines a mutation?
A change in the DNA sequence
The visible expression of a dominant allele
The passing of an unchanged trait from parent to offspring
The separation of allele pairs when sex cells form
2. Which statement correctly relates genes, DNA, and chromosomes?
DNA is made of genes, but neither is associated with chromosomes.
Genes are made of chromosomes that leave the cell nucleus.
Genes are segments of DNA located on chromosomes.
Chromosomes are small sections found inside individual genes.
3. Two genetically identical plants receive different amounts of light and grow to different heights. What is the best conclusion?
Height cannot be influenced by genes.
The taller plant must have gained a dominant height allele.
Genetically identical organisms must always develop identical phenotypes.
Environmental conditions can influence phenotype even when genotype is the same.
4. What is a gene?
A cell produced during reproduction
An observable characteristic, such as flower color
One complete set of an organism's chromosomes
A segment of DNA that carries information related to a characteristic or function
5. What is an important role of meiosis in sexual reproduction?
It produces identical body cells for growth.
It produces sex cells with half the usual number of chromosomes.
It doubles the chromosome number in every body cell.
It guarantees that all offspring have identical alleles.
6. In a simple Mendelian model, T is dominant for tall plants and t is recessive for short plants. What percentage of offspring from Tt × tt is expected to be short?
75%
0%
25%
50%
7. Why does a typical egg or sperm cell carry only one allele for a particular gene?
One allele is removed after fertilization.
The dominant allele destroys the recessive allele.
Paired alleles separate when sex cells form during meiosis.
Organisms create new alleles only when reproduction begins.
8. In a simple dominant-recessive model, a plant displays the recessive wrinkled-seed trait. Which allele combination must it have?
Two dominant alleles
One dominant allele and one recessive allele
Either two dominant alleles or a mixed allele pair
Two recessive alleles
9. Which characteristic is most directly determined by inherited genetic information?
ABO blood type
A suntan developed during summer
Stronger muscles after regular exercise
A scar left by an injury
10. In a simple recessive-inheritance model, two parents do not show a recessive trait, but their child does. Which explanation best fits the evidence?
The child received two dominant alleles.
Only one parent contributed an allele for the trait.
Both parents were likely heterozygous carriers of the recessive allele.
The recessive allele became dominant in the child.
11. A rabbit has black fur. The words “black fur” describe the rabbit's:
Allele
Genotype
Phenotype
Chromosome pair
12. For a cross between two heterozygous animals, Bb × Bb, what is the probability of an offspring with genotype bb?
50%
25%
75%
100%
13. Purple flowers (P) are dominant to white flowers (p). If a plant with two dominant alleles is crossed with a plant with two recessive alleles, what are the expected offspring?
Half would have two dominant alleles and half would have two recessive alleles, producing equal numbers of purple and white flowers.
Every offspring would have one dominant and one recessive allele and would produce purple flowers.
Every offspring would inherit two dominant alleles and would produce purple flowers.
Every offspring would have one dominant and one recessive allele and would produce white flowers.
14. A pea plant has the genotype Tt. How should this genotype be described?
Homozygous dominant
Heterozygous
Homozygous recessive
Recessive phenotype only
15. Tallness is dominant to shortness. A tall plant of unknown genotype is crossed with a short plant, and some offspring are short. What is the tall parent's genotype?
It has one dominant tallness allele and one recessive shortness allele.
It has two dominant tallness alleles.
It has two recessive shortness alleles.
It has no alleles related to plant height.
16. Two siblings have the same biological parents but differ in several inherited traits. What best explains this difference?
Each sibling can inherit a different combination of parental alleles.
The parents' genes permanently change after each child is born.
Each sibling receives all dominant alleles from one parent.
Only the older sibling inherits chromosomes from both parents.