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Genetics and Heredity: Practice Questions with Answers

Curriculum: Genetics And HeredityGrades: 8–10Questions: 12Mode: Practice

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1. What is a gene?

  1. A chemical that speeds up digestion
  2. A type of cell found only in muscles
  3. A segment of DNA that contains instructions for a trait
  4. The physical appearance of an organism
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Answer: C. A segment of DNA that contains instructions for a trait
A gene is a specific segment of DNA that carries the instructions for building a particular trait, such as eye color.

2. What does DNA stand for?

  1. Dual Nuclear Assembly
  2. Deoxyribonucleic acid
  3. Double Nitrogen Atom
  4. Diploid Natural Allele
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Answer: B. Deoxyribonucleic acid
DNA stands for deoxyribonucleic acid, the molecule that stores genetic instructions in nearly all living things.

3. What is an allele?

  1. A muscle fiber found in the body
  2. A different version of a gene
  3. A cell that has no nucleus
  4. The outer covering of a chromosome
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Answer: B. A different version of a gene
An allele is one of two or more alternative forms of a gene, such as the allele for brown eyes versus the allele for blue eyes.

4. In genetics, what does dominant mean?

  1. A trait that only appears in males
  2. A trait that skips every other generation
  3. An allele whose effect shows up even when paired with a different allele
  4. An allele whose effect is masked when paired with another allele
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Answer: C. An allele whose effect shows up even when paired with a different allele
A dominant allele produces its trait whenever it is present, even if paired with a different, recessive, allele.

5. What is the difference between genotype and phenotype?

  1. Genotype is the observable trait; phenotype is the genetic makeup
  2. Genotype is the genetic makeup; phenotype is the observable trait
  3. They both mean the same thing
  4. Genotype applies to plants; phenotype applies to animals
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Answer: B. Genotype is the genetic makeup; phenotype is the observable trait
Genotype refers to the actual genetic makeup, the alleles an organism carries, while phenotype refers to the physical or observable expression of those genes.

6. Who is often called the father of genetics for his work with pea plants?

  1. Louis Pasteur
  2. Gregor Mendel
  3. Charles Darwin
  4. Isaac Newton
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Answer: B. Gregor Mendel
Gregor Mendel, an Austrian monk, carried out careful breeding experiments with pea plants in the 1800s that revealed the basic rules of inheritance.

7. Why did Gregor Mendel choose pea plants for his experiments?

  1. Pea plants have clear, easy-to-track traits and reproduce quickly
  2. Pea plants cannot reproduce at all
  3. Pea plants are the only plants that pass on traits
  4. Pea plants have no genes
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Answer: A. Pea plants have clear, easy-to-track traits and reproduce quickly
Pea plants show clear-cut traits, like tall versus short or green versus yellow seeds, and grow through many generations quickly, making patterns of inheritance easy to observe.

8. What does it mean if an organism is homozygous for a gene?

  1. It has two different alleles for that gene
  2. It has three alleles for that gene
  3. It has no alleles for that gene
  4. It has two identical alleles for that gene
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Answer: D. It has two identical alleles for that gene
Homozygous means an organism carries two copies of the same allele for a given gene, such as two dominant alleles or two recessive alleles.

9. What does it mean if an organism is heterozygous for a gene?

  1. It has two identical dominant alleles
  2. It has two identical recessive alleles
  3. It has no working copies of the gene
  4. It has one dominant and one recessive allele
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Answer: D. It has one dominant and one recessive allele
Heterozygous means an organism has two different alleles for a gene, typically one dominant and one recessive.

10. What is heredity?

  1. The study of weather patterns
  2. The process of cell division only
  3. The passing of traits from parents to offspring
  4. The process of an organism growing larger
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Answer: C. The passing of traits from parents to offspring
Heredity is the biological process by which traits are passed from parents to their offspring through genes.

11. Where in a cell are most genes located?

  1. In the general cytoplasm
  2. On chromosomes inside the nucleus
  3. In the cell membrane
  4. In the mitochondria only
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Answer: B. On chromosomes inside the nucleus
Most genes are arranged along chromosomes, thread-like structures made of tightly coiled DNA found inside the cell's nucleus.

12. In humans, which pair of chromosomes determines biological sex?

  1. Chromosome pair 1
  2. The 23rd pair (X and Y)
  3. Chromosome pair 10
  4. All chromosome pairs equally
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Answer: B. The 23rd pair (X and Y)
Humans have 23 pairs of chromosomes, and the 23rd pair, made up of X and Y chromosomes, determines biological sex.
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