A gene locus has two alleles A, a. If the frequency
of dominant allele A is 0.4 then what will be the
frequency of homozygous dominant, heterozygous
and homozygous recessive individuals in the
population?
AI-generated explanation. Check against your textbook.
Explanation:
In population genetics under Hardy–Weinberg, if the dominant allele A has frequency p and recessive allele a has frequency q, then p + q = 1. Given p = 0.4, q = 0.6. Genotype frequencies are: AA = p^2 = 0.16, Aa = 2pq = 2 × 0.4 × 0.6 = 0.48, aa = q^2 = 0.36. So the distribution is 0.16 (AA); 0.48 (Aa); 0.36 (aa).
🧠 Did You Know?
The Hardy–Weinberg principle predicts genotype frequencies from allele frequencies in large, randomly mating populations with no evolution.
💡 NCERT Memory Line:
In a trait governed by a single gene with two alleles, genotype frequencies are p^2, 2pq, q^2 for AA, Aa, aa respectively, where p is frequency of A and q of a.
What map unit (Centimorgan) is adopted in the
construction of genetic maps?
AI-generated explanation. Check against your textbook.
Explanation:
In NCERT, one map unit is a centimorgan, which corresponds to a 1% recombination frequency between two genes on a chromosome. So, the distance between two genes is measured by the percentage of offspring showing recombination. A 1% recombination means a 1 cM distance. The correct option is 4: 1% cross over.
🧠 Did You Know?
Recombination frequency cannot exceed 50% for genes that are linked; 50% or more indicates genes behave as if on different chromosomes (independent assortment).
💡 NCERT Memory Line:
A centimorgan (cM) is the unit of map distance; 1 cM equals 1% recombination between two genes.
AI-generated explanation. Check against your textbook.
Explanation:
Option 2 is incorrect. In domesticated birds (fowls), the sex of the offspring is determined by the egg (the female gamete), which can carry either Z or W. The sperm always carries only a Z chromosome. Thus, sex is determined by the type of egg, not the sperm, according to NCERT biology.
🧠 Did You Know?
In birds, females are the hens (ZW) and males are the cocks (ZZ). The egg determines whether the offspring will be male (ZZ) or female (ZW).
💡 NCERT Memory Line:
In birds, sex determination is by the egg and the W chromosome in eggs decides female offspring, while the sperm contributes only Z.
Under which of the following conditions will there
be no change in the reading frame of following
mRNA?
5'AACAGCGGUGCUAUU3'
AI-generated explanation. Check against your textbook.
Explanation:
The reading frame is set by codons of three bases. The given mRNA has codons: AAC | AGC | GGU | GCU | AUU. Deleting an entire codon (GGU at positions 7–9) removes 3 bases, preserving the frame. Hence, no shift occurs with option 1.
🧠 Did You Know?
Inserting or deleting any number of bases not divisible by three shifts the reading frame (frameshift), changing all downstream codons and potentially altering the protein.
💡 NCERT Memory Line:
A reading frame is read in consecutive triplets; indels not in multiples of three cause frameshifts and alter the amino acid sequence.
In a plant, black seed color (BB/Bb) is dominant over white seed color (bb). In order to find out the genotype of the black seed plant, with which of the following genotype will you cross it?
Explanation: NCERT Page no.70 (Topic-5.1 MENDEL'S LAWS OF INHERITANCE)
Which one of the following can be explained on the basis of Mendel's Law of Dominance?
A. Out of one pair of factors one is dominant and the other is recessive.
B. Alleles do not show any expression and both the characters appear as such in F2 generation.
C. Factors occur in pairs in normal diploid plants.
D. The discrete unit controlling a particular character is called factor.
E. The expression of only one of the parental characters is found in a monohybrid cross.
Choose the correct answer from the options given below:
Explanation: NCERT Page No.59,(Topic-4.2.1 Law of Dominance)