The nucleotide sequence in mrna is determined by

General
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the nucleotide sequence in mrna is determined by

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The nucleotide sequence in mRNA is determined by

Answer:
The nucleotide sequence in messenger RNA (mRNA) is determined by the sequence of nucleotides in the DNA template strand during the process of transcription. Transcription is a fundamental step in the flow of genetic information in cells, where the genetic code stored in DNA is converted into a complementary RNA sequence, which can then be decoded to synthesize proteins.

1. DNA Structure and the Central Dogma of Molecular Biology:

  • DNA (deoxyribonucleic acid) is a double-stranded helix composed of four types of nucleotides, which are identified by their nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).
  • According to the central dogma of molecular biology, the flow of genetic information can be summarized as DNA → RNA → Protein. This signifies that the information in DNA is transcribed into RNA, which is then translated into proteins.

2. Transcription Process:

  • Transcription is the process where the genetic information in a DNA sequence is copied into a complementary RNA sequence by the enzyme RNA polymerase.
  • The process begins at a specific sequence on the DNA called the promoter. RNA polymerase binds to the promoter and unwinds the DNA strands.
  • One of the DNA strands, called the template strand (or antisense strand), serves as a template for the RNA synthesis. The RNA polymerase reads the nucleotide sequence of the template strand in a 3’ to 5’ direction and synthesizes a complementary mRNA strand in a 5’ to 3’ direction.

3. Base Pairing Rules:

  • The nucleotide sequence in the mRNA is complementary to the DNA template strand. The base pairing rules during transcription are similar to those in DNA replication but with a crucial difference: in RNA, uracil (U) is used instead of thymine (T).

  • The base pairing rules are:

    • Adenine (A) in DNA pairs with Uracil (U) in RNA.
    • Thymine (T) in DNA pairs with Adenine (A) in RNA.
    • Cytosine (C) pairs with Guanine (G), and vice versa.

    For example, if the DNA template strand has the sequence:
    5’ - AGCTACG - 3’,
    the complementary mRNA sequence would be:
    3’ - UCGAUGC - 5’.

4. The Resulting mRNA Sequence:

  • The nucleotide sequence in mRNA is complementary to the DNA template strand and identical (with uracil replacing thymine) to the coding (or sense) strand of DNA.
  • This mRNA sequence carries the coding instructions to the ribosomes, where translation occurs, resulting in the synthesis of a specific protein encoded by the mRNA.

Final Answer:
The nucleotide sequence in mRNA is determined by the sequence of nucleotides in the DNA template strand through the process of transcription, where RNA polymerase synthesizes a complementary RNA strand based on the base pairing rules.