Human insulin molecule is composed ofone α-chain having 21 amino acids andone β-chain having 30 amino acids. How many functional insulin genes occur in adult humans?
One
Understanding Functional Insulin Genes in Humans
The question asks about the number of functional genes that encode for insulin in adult humans. Insulin is a crucial hormone involved in regulating blood sugar levels.
As the question mentions, the mature human insulin molecule is composed of two polypeptide chains:
- An α-chain consisting of 21 amino acids.
- A β-chain consisting of 30 amino acids.
These two chains are linked together by disulfide bonds in the mature protein.
How is Insulin Produced from a Gene?
Despite having two chains, the insulin molecule in humans is encoded by a single functional gene. This gene is located on the short arm of chromosome 11 (specifically at locus 11p15.5).
The process from gene to mature insulin involves several steps:
- The insulin gene is transcribed into messenger RNA (mRNA).
- The mRNA is translated into a precursor protein called preproinsulin. This is a single polypeptide chain that includes a signal peptide, the B chain, the C-peptide, and the A chain (in that order).
- The signal peptide is cleaved off as the protein enters the endoplasmic reticulum, resulting in proinsulin. Proinsulin is a single folded chain with disulfide bonds forming between regions that will become the A and B chains.
- Proinsulin is transported to the Golgi apparatus and then to secretory vesicles.
- Within the secretory vesicles, the C-peptide is cleaved out by enzymes (proteases). This leaves the mature insulin molecule, which consists of the A and B chains linked by disulfide bonds. The C-peptide is also released into the bloodstream.
Therefore, even though the final hormone has two chains, they originate from a single polypeptide precursor molecule encoded by one functional gene.
Number of Functional Insulin Genes
In adult humans, there is typically only one functional gene encoding insulin (the INS gene on chromosome 11). While pseudogenes or gene variations might exist in the genome, only this one gene is actively transcribed and translated to produce functional insulin.
Based on the understanding of human genetics and insulin synthesis, the number of functional insulin genes in adult humans is one.
Revision Table: Key Facts About Human Insulin Gene
| Feature | Description |
|---|---|
| Number of Functional Genes | One (1) |
| Gene Name | INS |
| Chromosome Location | Chromosome 11 (11p15.5) |
| Encoded Product (Initial) | Preproinsulin (single polypeptide) |
| Mature Insulin Structure | α-chain (21 amino acids) + β-chain (30 amino acids), linked by disulfide bonds |
Additional Information: Insulin Processing
The cleavage of proinsulin into mature insulin and C-peptide is an essential step for insulin activation. The C-peptide is often measured clinically as an indicator of endogenous insulin production because it is released in equimolar amounts with insulin. This detailed processing highlights how a single gene can give rise to a mature protein with complex structure.
Similar Questions
Which one of the following proteins gives lustrous shiny appearance to silk fibre?
Blue Baby Syndrome is caused by the contamination of
Pearl is a hard object produced within the soft tissues of a mollusk. Which one of the following is the main constituent of pearl?
Two wires are made having same length and area of cross-section A. Wire 1 is made of copper and wire 2 is made of aluminium. It is given that the electrical conductivity of copper is more than that of aluminium. In this context, which one of the following statements is correct?
A ray of light is incident on a plane mirror at an angle of 40° with respect to a surface normal. When it gets reflected from the mirror it undergoes a deviation of
Infrared, visible and ultraviolet radiations /light have different properties. Which one of the following statements related to these radiations/lights is not correct?
After using for some time, big transformers get heated up. This is due to the fact that
1. Current produces heat in transformers
2. Hysteresis loss occurs in transformers
3. Liquid used for cooling gets heated
Select the correct answer using the code given below.A person is standing on a frictionless horizontal ground. How can he move by a certain distance on this ground?
How many hydrogen atoms are contained in 1.50 g of glucose (C 6H 12 06 )?
Which of the following radioactive substances enters/enter the human body through food chain and causes/cause many physiological disorders?
Important Questions from Miscellaneous
Read the given figure and find the region representing persons who are educated and employed but not confirmed in job.
The magazine in which Mahatma Gandhi mentioned what he wanted the Constitution to do is:
Which gas shields the surface of the earth from ultraviolet radiation from the sun?
Which event is marked as an Intangible Cultural Heritage of Humanity by UNESCO?
Who has been conferred with the rank of the Commander of the Order of the British Empire in 2018?
