Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

29. Heredity

Overview of Human Genetics

Anatomy & Physiology

29. Heredity

Overview of Human Genetics

Previous problemNext problem

Problem 8

Textbook Question

If an allele must be present on both the maternal and paternal chromosomes to affect the phenotype, the allele is said to be
(a) Dominant
(b) Recessive
(c) Complementary
(d) Heterozygous

Verified step by step guidance

Understand the question: The problem is asking about the type of allele that must be present on both the maternal and paternal chromosomes to affect the phenotype. This is a fundamental concept in genetics.

Review the definitions of the terms provided in the options: (a) Dominant - an allele that expresses its phenotype even if only one copy is present. (b) Recessive - an allele that requires two copies (one from each parent) to express its phenotype. (c) Complementary - refers to genes that work together to produce a phenotype, not directly related to single alleles. (d) Heterozygous - refers to having two different alleles for a gene.

Focus on the key phrase in the question: 'must be present on both the maternal and paternal chromosomes.' This indicates that the allele's effect on the phenotype requires two copies, one from each parent.

Match the key phrase to the correct term: Based on the definitions, the term that matches this requirement is 'Recessive,' as recessive alleles only express their phenotype when two copies are present.

Conclude the reasoning: The correct answer is (b) Recessive, as it aligns with the condition described in the question. Dominant alleles do not require two copies, complementary refers to gene interaction, and heterozygous describes allele variation, not expression requirements.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Dominant Allele

A dominant allele is one that can express its trait in the phenotype even when only one copy is present. This means that if an individual has at least one dominant allele, the associated trait will be visible, overshadowing any recessive alleles.

Recessive Allele

A recessive allele requires two copies, one from each parent, to manifest its trait in the phenotype. If an individual has only one recessive allele, the dominant allele will mask its effect, making the recessive trait unobservable.

Homozygous vs. Heterozygous

Homozygous refers to having two identical alleles for a particular gene, while heterozygous means having two different alleles. For a recessive trait to be expressed, an individual must be homozygous recessive, possessing two copies of the recessive allele.

Watch next

Master Dominant vs. Recessive Alleles with a bite sized video explanation from Bruce Bryan

Start learning