Heredity and Variation
Short Questions
1. Why do offspring from sexual reproduction show more variation than asexual reproduction?
- Sexual reproduction combines genes from two parents, creating diverse traits.
2. How does a gene influence a trait like plant height?
- Genes control enzyme efficiency, affecting hormone production for growth.
3. What role does the centromere play in a chromosome?
- It divides the chromosome into arms and aids in cell division.
4. Why is DNA called the “master molecule”?
- It controls cell functions, growth, and reproduction.
5. How does the double helix structure of DNA support its function?
- It allows DNA to store and replicate genetic information accurately.
6. What happens if adenine pairs with cytosine instead of thymine in DNA?
- It causes a mutation, altering the genetic code.
7. Why are homologous chromosomes important in heredity?
- They ensure traits are inherited in pairs from both parents.
8. How does Mendel’s monohybrid cross demonstrate dominance?
- The dominant trait (e.g., tallness) appears in all F1 generation plants.
9. Why did Mendel choose pea plants for his experiments?
- They have clear, contrasting traits and are easy to cross-pollinate.
10. What is the significance of the 3:1 ratio in Mendel’s F2 generation?
- It shows the segregation of dominant and recessive traits.
11. How does a dihybrid cross differ from a monohybrid cross?
- It studies two pairs of contrasting traits, not one.
12. Why is Down syndrome called trisomy 21?
- It results from an extra 21st chromosome, totaling 47 chromosomes.
13. How does sickle-cell anemia affect oxygen transport?
- Sickle-shaped RBCs carry less oxygen due to altered hemoglobin.
14. Why are carriers of sickle-cell anemia not always affected?
- They have one normal and one defective gene, masking symptoms.
15. What is the role of DNA fingerprinting in identifying criminals?
- It matches a person’s unique DNA sequence to crime scene evidence.
16. How do simple and complex tissues differ in plants?
- Simple tissues have one cell type; complex tissues have multiple types.
17. Why is epithelial tissue critical for animal survival?
- It protects organs and regulates substance exchange.
18. How does meristematic tissue contribute to plant growth?
- Its dividing cells increase plant length and girth.
19. Why is xylem considered a complex tissue?
- It contains multiple cell types for water and mineral transport.
20. What makes biotechnology different from traditional breeding?
- It uses genetic engineering and tissue culture for precise trait changes.
21. How does tissue culture ensure disease-free plants?
- It grows plants from virus-free meristem cells in sterile conditions.
22. Why are GM crops resistant to environmental stress?
- Their altered DNA enhances tolerance to drought, heat, or pests.
23. How does agritourism benefit rural communities?
- It generates income through farm visits and produce sales.
24. Why are cocoons boiled in sericulture?
- To kill pupae and loosen silk fibers for extraction.
25. How does animal husbandry support agriculture?
- It provides milk and labor for farming activities.
Long Questions
1. What is the role of DNA in heredity?
- DNA carries genes that store information for traits, passed from parents to offspring. It controls cell functions and ensures traits like height or eye color are inherited.
2. How do chromosomes differ in males and females?
- Females have 44+XX chromosomes, while males have 44+XY. The XX or XY pair determines the sex of the individual.
3. What is the structure of a DNA molecule?
- DNA has a double helix structure, like a twisted ladder, with sugar-phosphate rails and nitrogenous base pairs (A-T, C-G). These bases form genes that control traits.
4. What are the types of RNA and their functions?
- RNA has three types: mRNA carries protein-making instructions, tRNA brings amino acids, and rRNA helps form ribosomes. Together, they help synthesize proteins in cells.
5. What is a monohybrid cross? Give an example.
- A monohybrid cross studies one pair of contrasting traits, like tall (TT) and dwarf (tt) pea plants. It shows a 3:1 phenotypic ratio in the F2 generation.
6. What is Turner syndrome?
- Turner syndrome occurs when a female has only one X chromosome (44+X), leading to sterility. It causes improper growth of reproductive organs.
7. What is sickle-cell anemia and its symptoms?
- Sickle-cell anemia is a genetic disorder where red blood cells become sickle-shaped, reducing oxygen flow. Symptoms include joint pain, fatigue, and low hemoglobin.
8. Why is DNA fingerprinting useful?
- DNA fingerprinting identifies a person’s unique gene sequence, helping trace lineage or identify criminals. It’s widely used in forensic science and paternity tests.
9. What are the types of animal tissues?
- Animal tissues include epithelial (covering), connective (support), muscular (movement), and nervous (signal conduction). Each performs specific functions in the body.
10. What is the role of meristematic tissue in plants?
- Meristematic tissue helps plants grow by dividing actively, found in tips of roots and shoots. It increases plant length and girth.
11. What are the benefits of tissue culture?
- Tissue culture produces many disease-free plantlets quickly, even without seeds. It helps grow rare plants and saves endangered species.
12. What are genetically modified crops? Give an example.
- GM crops have altered DNA for better traits, like pest resistance or nutrition. Example: BT cotton is pest-resistant, reducing pesticide use.
13. How does biotechnology help in agriculture?
- Biotechnology creates high-yielding, stress-resistant crops using genetic engineering and tissue culture. It improves food security and reduces chemical use.
14. What is agritourism and its benefits?
- Agritourism combines farming with tourism, attracting visitors to farms with fruit trees or gardens. It generates income through plant and produce sales.
15. What is sericulture and how is silk produced?
- Sericulture is rearing silkworms to produce silk from their cocoons. Silkworms spin cocoons, which are boiled to loosen silk fibers for weaving.
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