Biology MCQs
Topic Notes: Biology
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
31
What is the chromosomal configuration of the hybrids resulting from a cross between Nicotiana tabacum and Nicotiana sylvestris?
Answer:
12 trivalents and 12 univalents
Nicotiana tabacum is an allotetraploid (2n=48) derived from N. sylvestris (n=12) and N. tomentosiformis (n=12). When crossed with N. sylvestris, the hybrid receives a full set of chromosomes from the parent, leading to complex pairing behavior during meiosis. The resulting hybrid exhibits specific chromosomal associations, including trivalents and univalents, reflecting the genomic homology and structural differences between the parental sets.
32
Which geneticist is credited with observing the phenomenon of crossing over in the fruit fly, Drosophila melanogaster?
Answer:
Thomas Hunt
Thomas Hunt Morgan, often referred to as Thomas Hunt, conducted pioneering research on Drosophila melanogaster. His work provided the experimental evidence for the chromosomal theory of inheritance, including the discovery of genetic linkage and the process of crossing over during meiosis.
33
What term refers to the specific physical location or position of a gene on a chromosome?
Answer:
loci
In genetics, a locus (plural: loci) is the specific, fixed position on a chromosome where a particular gene or genetic marker is located. Each chromosome carries many genes in sequence, and the mapping of these loci is fundamental to understanding inheritance patterns, genetic linkage, and the organization of the genome within an organism.
34
In genetics, what is the specific physical location of a gene on a chromosome called?
Answer:
chromosomes
A locus (plural: loci) refers to the specific, fixed position or location of a gene or a genetic marker on a chromosome. Each chromosome carries many genes, and the locus identifies the precise site where a particular gene resides within the DNA sequence of that chromosome.
35
How many distinct traits of Drosophila melanogaster did Thomas Hunt Morgan investigate in his genetic studies?
Answer:
85
Thomas Hunt Morgan utilized Drosophila melanogaster as a model organism to study inheritance patterns. His extensive research program involved identifying and mapping numerous mutations, eventually documenting approximately 85 distinct traits. This work was instrumental in establishing the chromosomal theory of inheritance and demonstrating that genes are located on specific chromosomes.
36
In what year was the phenomenon of genetic crossing over first documented?
Answer:
1911
The first recorded instance of crossing over was documented by Thomas Hunt Morgan in 1911. This discovery was pivotal in the field of genetics, as it provided evidence for the physical exchange of genetic material between homologous chromosomes during meiosis, thereby explaining the recombination of linked genes.