1. What is Mendelian inheritance?
Answer: Mendelian inheritance refers to the principles of inheritance proposed by Gregor Mendel, which include the laws of segregation and independent assortment governing the inheritance of traits from parents to offspring.
2. Explain incomplete dominance and provide an example.
Answer: In incomplete dominance, neither allele is completely dominant over the other, resulting in a blended phenotype in heterozygotes. An example is the inheritance of flower color in snapdragons, where red and white alleles produce pink flowers in heterozygotes.
3. Describe co-dominance and give an example.
Answer: Co-dominance occurs when both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows traits of both alleles simultaneously. An example is the ABO blood group system, where individuals with AB blood type express both A and B antigens.
4. What are multiple alleles, and how do they influence inheritance?
Answer: Multiple alleles refer to the existence of more than two alleles for a particular gene in a population. They increase genetic diversity and can result in various phenotypic expressions, as seen in the inheritance of blood groups with ABO alleles.
5. Explain the inheritance of blood groups and mention the alleles involved.
Answer: The inheritance of blood groups involves multiple alleles (IA, IB, i) that determine the ABO blood type system in humans. IA and IB are co-dominant, while i is recessive. Different combinations of these alleles determine the blood type.
6. Define pleiotropy and provide an example.
Answer: Pleiotropy occurs when a single gene influences multiple, seemingly unrelated phenotypic traits. An example is sickle cell anemia, where a mutation in the hemoglobin gene affects multiple organs and systems in the body.
7. Explain polygenic inheritance with an elementary idea.
Answer: Polygenic inheritance involves the additive effects of multiple genes on a single phenotypic trait. An example is human skin color, which is controlled by the cumulative effects of several genes.
8. What is the chromosome theory of inheritance?
Answer: The chromosome theory of inheritance states that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for Mendelian patterns of inheritance.
9. Differentiate between chromosomes and genes.
Answer: Chromosomes are thread-like structures composed of DNA and proteins found in the nucleus of cells, while genes are segments of DNA that code for specific proteins or RNA molecules and are located on chromosomes.
10. Explain sex determination in humans, birds, and honeybees.
Answer: In humans, sex determination is based on the presence of sex chromosomes (XX for females, XY for males). In birds, it is also chromosomal (ZW for females, ZZ for males), while in honeybees, it is determined by the number of chromosome sets (diploid females, haploid males).
11. What is linkage and how does it relate to crossing over?
Answer: Linkage refers to the tendency of genes located on the same chromosome to be inherited together. Crossing over, the exchange of genetic material between homologous chromosomes during meiosis, can break the linkage between genes.
12. Explain sex-linked inheritance with examples.
Answer: Sex-linked inheritance refers to the inheritance of traits controlled by genes located on the sex chromosomes. Examples include hemophilia and color blindness, which are more commonly expressed in males due to their inheritance on the X chromosome.
13. Name some Mendelian disorders in humans and briefly describe one of them.
Answer: Mendelian disorders in humans include Thalassemia, Huntington’s disease, and cystic fibrosis. Thalassemia is an inherited blood disorder characterized by abnormal hemoglobin production, leading to anemia and other complications.
14. What are chromosomal disorders in humans? Provide examples.
Answer: Chromosomal disorders result from abnormalities in chromosome number or structure. Examples include Down syndrome (trisomy 21), Turner syndrome (monosomy X), and Klinefelter syndrome (XXY).
15. Explain the search for genetic material and DNA as genetic material.
Answer: The search for genetic material involved experiments by scientists like Griffith, Avery, MacLeod, McCarty, and Hershey-Chase, which established DNA as the genetic material based on its role in transformation and viral replication.
16. Describe the structure of DNA and RNA.
Answer: DNA (deoxyribonucleic acid) is a double-stranded helical molecule composed of nucleotides, while RNA (ribonucleic acid) is usually single-stranded and contains ribose sugar instead of deoxyribose. Both molecules have nitrogenous bases adenine, guanine, and cytosine, while DNA has thymine and RNA has uracil.
17. Explain DNA replication.
Answer: DNA replication is the process by which DNA makes a copy of itself during cell division. It occurs in the S phase of the cell cycle and involves the unwinding of the DNA double helix, formation of replication forks, and synthesis of complementary strands by DNA polymerase.
18. Define central dogma and explain transcription and translation.
Answer: The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein. Transcription is the synthesis of RNA from a DNA template, while translation is the synthesis of protein from an RNA template.
19. Discuss gene expression and regulation, mentioning the Lac Operon.
Answer: Gene expression refers to the process by which information from a gene is used to synthesize a functional gene product (protein or RNA). Regulation of gene expression ensures that genes are turned on or off at the right time. The Lac Operon in bacteria is a classic example of gene regulation, where the expression of genes involved in lactose metabolism is controlled by lactose availability.
20. What is the genome, and what was the significance of the Human Genome Project?
Answer: The genome is the complete set of an organism’s genetic material, including all of its genes. The Human Genome Project was a landmark scientific endeavor that mapped and sequenced the entire human genome, providing valuable insights into human biology, evolution, and disease. DNA fingerprinting and protein biosynthesis are methods and processes used to identify individuals and synthesize proteins, respectively.