What happens when the opaque-2 mRNA encounters the ribosome? A)The ribosome read

Question

What happens when the opaque-2 mRNA encounters the ribosome?

A)The ribosome reads the mRNA and uses that information to build the opaque-2 protein using amino acids that are available in the cytoplasm

B) The ribosome folds up the mRNA into a specific shape to that it can be transported back to the nucleus.

C) The mRNA is added to the ribosome which makes the ribosome bigger and better able to store nucleotides for the germinating seed

D) The ribosome is an enzyme and chemically converts the nucleotides in the mRNA to amino acids.

Question 2

What will happen if Opaque 2, the zein gene transcription factor is "knocked out" by a mutation and the Opaque 2 protein is not made in the developing endosperm of the seed?

A) Nothing, the seed will still make zein proteins because zein genes are consitutively transcribed

B) The seed will not make as many copies of the zein proteins and instead make other seed storage proteins. This changes the seed structure

C)The seed starts making all starch and no protein becasue zein genes are the only protein encoding genes in endosperm cells

D) The seed starts making zeins in the embryo instead of the endosperm because the opaque 2 transcription factor mutation is only present in the genes of endosperm cells. Cells in other parts of the seed carry the normal (non-mutant) version of the opaque2 gene.

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OPAQUE2 is a transcription factor protein which regulates (turns on) zein genes Endosperm cell opaque2 mRNA. ribosome aque protein Zein mRNAs zein genes forming protein body endoplasmic reticulum chromosome ......so what happens ifopaque2 gene is knocked out (mutated)

Explanation / Answer

Ans. 1. Correct option. A: The ribosome reads the mRNA….. .

mRNA is translated into protein on ribosomes. During the process, amino acids specific to each codon on mRNA are sequentially brought to ribosome and linked by peptide bond producing the protein.

Option B: Incorrect. Ribosome does fold mRNA

Option C. Incorrect: Ribosomes does not store nucleotides

Option C. Incorrect: Ribosome translates mRNA into protein.

Ans. 2.

Given, Opaque 2 is a transcription factor for zein gene

            Opaque 2 gene is knocked out (removed/ eliminated from being expressed or forming protein)

            Opaque 2 is NOT made in developing endosperm of the seed.

Correct option: B. The seed will not make as ………

Mutation leading to non-functional opaque 2 gene leads significant reduction (not 100 % reduction, say X % reduction where, X < 100) in zein gene expression. Reduced zein gene expression caused reduced production of specific proteins leading to change in seed structure.

Option A. Incorrect: Zein gene transcription reduced causing reduced expression.

Option C. Incorrect: There are thousands of proteins being expressed in endosperm cells (and all other cells) other than zein gene.

Option D. Incorrect: Opaque 2 gene is endosperm-specific gene. It is not expressed in embryo.

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