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.
Following statements describe the characteristics of the enzyme Restriction endonuclease. Identify the
incorrect statement.
AI-generated explanation. Check against your textbook.
Explanation:
The incorrect statement is option 1. Restriction endonucleases cut both strands of DNA at specific sites, producing double-stranded breaks (blunt or with sticky ends). They recognize specific palindromic sequences and cut within those sites, breaking the sugar-phosphate backbone on both strands. Options 2, 3, and 4 correctly describe these features as per NCERT biology.
🧠 Did You Know?
Restriction enzymes are essential tools in genetic engineering and cloning, enabling precise cutting and joining of DNA fragments.
💡 NCERT Memory Line:
Restriction endonucleases recognize palindromic DNA sequences and make double-stranded cuts at specific sites.