NEET Biology · Flashcards
This deck has 20 flashcards on Genetics & Evolution for NEET Biology, from NCERT Class 12. It covers the NCERT chapters Principles of Inheritance and Variation, Molecular Basis of Inheritance and Evolution.
Heredity, Molecular Basis of Inheritance, and Evolution (Class 12 Biology) with key concepts, formulas, and visual aids.
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Card 1 of 20
Define Incomplete Dominance and give an example.
Hint: Think: Blending of traits (like red + white = pink).
Answer
A genetic situation where one allele does not completely dominate another, resulting in a new, blended phenotype in the heterozygote. Example: Flower colour in Snapdragon (Antirrhinum majus) where Red (RR) x White (rr) gives Pink (Rr).
Card 2 of 20
What is the genetic basis of the ABO blood group system in humans?
Hint: Multiple alleles exist in a population, but an individual only has two.
Answer
It is an example of Multiple Alleles and Co-dominance. The gene 'I' has three alleles: IA, IB, and i. IA and IB are co-dominant (expressing both A and B antigens), while 'i' is recessive (producing no antigen).
Card 3 of 20
Differentiate between Pleiotropy and Polygenic Inheritance with examples.
Hint: Pleio = many (effects), Poly = many (genes).
Answer
Pleiotropy: A single gene controls multiple phenotypic traits (e.g., Phenylketonuria, which causes mental retardation and reduction in hair/skin pigmentation). Polygenic Inheritance: Multiple genes control a single phenotypic trait, often showing a gradient (e.g., Human skin colour, human height).
Card 4 of 20
Explain the sex determination mechanism in Honey Bees.
Hint: Males have a grandfather but no father.
Answer
It is a haplo-diploid sex determination system. Females (queens and workers) are diploid (32 chromosomes) and develop from fertilized eggs. Males (drones) are haploid (16 chromosomes) and develop parthenogenetically from unfertilized eggs.
Card 5 of 20
Who proposed the Chromosomal Theory of Inheritance, and what does it state?
Hint: Sutton and Boveri noticed chromosomes parallel gene behavior.
Answer
Proposed by Walter Sutton and Theodor Boveri. It states that chromosomes are the vehicles of genetic heredity. The pairing and separation of a pair of chromosomes during meiosis lead to the segregation of a pair of factors (genes) they carry.
Card 6 of 20
Briefly describe the chromosomal configurations for Down's, Klinefelter's, and Turner's syndromes.
Hint: Trisomy vs Monosomy.
Answer
Down's syndrome: Trisomy of chromosome 21 (47, XX or 47, XY). Klinefelter's syndrome: Extra X chromosome in males (47, XXY). Turner's syndrome: Absence of one X chromosome in females (45, XO).
Card 7 of 20
What was the Hershey-Chase experiment, and what did it prove?
Hint: DNA has P, Protein has S.
Answer
Alfred Hershey and Martha Chase used bacteriophages labeled with radioactive Phosphorus (32P, labels DNA) and radioactive Sulfur (35S, labels protein). It proved unequivocally that DNA is the genetic material that enters the bacteria, not protein.
Card 8 of 20
Describe the structure of a Nucleosome.
Hint: Beads on a string.
Answer
The basic repeating structural unit of chromatin. It consists of about 200 base pairs of negatively charged DNA wrapped around a positively charged histone octamer (composed of two molecules each of H2A, H2B, H3, and H4).
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