Common misconceptions › Class 12 › Biology › Molecular Basis of Inheritance Class 12 Biology · Chapter 5 · NCERT (lebo105)
Molecular Basis of Inheritance: common misconceptions
See the tempting mistake students make in Molecular Basis of Inheritance, why it feels right at first glance, and a worked visual example that shows the right idea.
Worked visual “If your child says…” (8) Teach & practice The tempting mistake & worked visual Does a cell transcribe all its DNA at once? Wrong
A cell must copy its whole genome into RNA whenever it needs a protein.
Why it feels right. Transcription sounds like the genome copying that occurs before cell division.
Right
Transcription makes RNA from selected regions of DNA. DNA replication copies the genome.
Worked example
Transcription
Gene X → RNA for X → Protein X can be made
Replication
DNA across chromosomes → Copies of the DNA
Transcription can copy one selected gene into RNA. Replication copies DNA across the chromosomes. A cell making more of protein X can transcribe the gene for X. During DNA replication, it instead copies the DNA across its chromosomes. If your child says… (8 concept checks in this chapter)
As you work through Molecular Basis of Inheritance , listen for these everyday misunderstandings and use the prompt alongside each one.
If your child says…
“The most tightly packed genes work hardest.”
Ask together Which DNA looks easier to reach: the exposed stretch or the tightly packed region? What’s true Looser packing usually makes genes easier to reach and transcribe. If your child says…
“Protein carried the inherited change.”
Ask together Why did the inherited change survive when proteins were destroyed? What’s true Transformation required DNA, and phage experiments also traced DNA into bacteria while protein coats remained outside. If your child says…
“Both new strands grow in one continuous piece.”
Ask together Can both strands grow towards the opening while adding only at their 3′ ends? What’s true The templates run in opposite directions, but new DNA grows only from five-prime to three-prime. At each fork, this means one new strand must be made in short pieces. If your child says…
“The coding strand is the strand being copied.”
Ask together Which DNA strand has bases complementary to the growing RNA? What’s true Polymerase reads the template, although the resulting RNA resembles the coding strand. If your child says…
“Every base swap shifts all the later triplets.”
Ask together Did replacing UUU with UUC add or remove a position in the message? What’s true Replacing a base preserves the grouping; adding or deleting bases can shift it. If your child says…
“Lactose makes the repressor block the genes more strongly.”
Ask together Can a repressor that loses its grip keep blocking this DNA site? What’s true The inducer weakens the repressor’s grip on the operator. If your child says…
“Useful genome information should be open to everyone.”
Ask together Would you want an insurer reading your health risks without your permission? What’s true Sharing identifiable genome data without consent can expose people to discrimination. If your child says…
“All the child’s DNA bands come from the mother.”
Ask together Which maternal band could explain the child’s 10-repeat variant? What’s true At this chromosome region, the child inherits a variant from each biological parent. Use this chapter three ways Previous chapter Principles of Inheritance and Variation Next chapter Evolution
In the app, your child answers a short check-in with confidence taps, and you see which of these misunderstandings showed up—and which ones are gone.
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