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Synthesis of the RNA proceeds in the 5′ → 3′ direction

of 3 bases of tRNA which correspond to a particular mRNA codon PROTEIN SYNTHESIS

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to produce an RNA molecule in the 5′ – 3′ direction (2 ..

The process of synthesis of proteins from mRNA (translation of language of nucleic acids into the language of proteins) is called translation. There are 20 different types of amino acids, which constitute various proteins, and these amino acids themselves cannot recognize their respective codons in the mRNA. Different amino acids are carried by their specific tRNA molecules at the
site of protein synthesis (mRNA). There are about 55 types of tRNA molecules available in the cytoplasm, so that one amino acid may have more than one tRNAs.

then tracks along the mRNA in the 5’ to 3’ direction until the AUG start codon is recognized

9. As the ribosome moves by two codons, next round of protein synthesis is initiated by the attachment of a new ribosome. Thus, at a time, a single mRNA is found to be attached with many ribosomes with their polypeptides of different length, (shortest polypeptide at the 5′ end of the mRNA and longest at the 3′ end), called polysomes.

Fig. 8.15 Peptide bond formation in growing polypeptide.
10. Ultimately, the A-site of ribosome is occupied by the termination codon (UAA,UAG or UGA) at the 3′ end of mRNA, which is not recognized by any tRNA. Thus, the termination of the protein synthesis is helped by the release factors RFl, RF2 and RF3 (in eukaryotes eRF1), which release the newly synthesized polypeptide chain from the P-site (Fig. 8.16).

Elongation synthesizes mRNA in the 5' to 3' direction at a ..

Synthesis of a new strand of messenger RNA is in the 5' to 3' direction ..

DNA is
always BUILT
in the
5' - 3' DIRECTION.
Top of the strand is 3'.
Bottom of the strand is 5'.
3 prime to 5 prime
DNA is
always BUILT or READ
in the
(like we read books from left to right)
This process continues along the DNA strands and forms
separate, IDENTICAL
DNA molecules
Each DNA molecule will have
one original strand
one new strand
1 "parent" strand
1 "daughter" strand

be added to its
end because it would mean the DNA is being built in
- 5' direction
(we don't read books from right to left)

progressing from codon to codon in the 5′ to 3′ direction of the mRNA

Synthesis of a new strand of messenger RNA is in the 5' to 3' direction…

i.RNA polymerase I (or A) found in nucleolus for the synthesis of rRNAs (28S and 18S).

ii.RNA polymerase II (or B) found in nucleoplasm for the synthesis of HnRNA (heterogeneous nuclear RNA) which, after processing gives rise to mRNA.

iii.RNA polymerase III (C) found in nucleoplasm for the synthesis of tRNA and 5S rRNA.

iv.Organeller RNA polymerase found in organelles, mitochondria and chloroplasts, (in photosynthetic organisms) and resembles the prokaryotic RNA polymerase.

The termination of transcription occurs due to the presence of certain terminator sites on DNA. In prokaryotes, the termination is mainly done by in two ways, which involves the presence of certain palindromic sequences (Inverted repeats with the same sequences on the two strands of DNA when read in 5’→ 3′ direction. Thus, the presence of complementarity of bases on the same strand causing loop formation in mRNA due to intrastrand complementary base pairing) on DNA near the termination signals (Fig. 8.7 and 8.8).

DNA replication occurs in the 5 prime (5') to 3 prime (3') direction
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  • Directionality (molecular biology) - Wikipedia

    The RNA polymerase will then use free nucleoside triphosphates to build the mRNA in a 5'→3' direction.

  • Which pairings correcly depict the way in which DNA bases pair? ?

    Synthesis of mRNA is: A) in the 5' to 3' direction with new nucleotides being added to the 5' end of the mRNA molecule

  • Protein synthesis :: DNA from the Beginning

    RNA Synthesis - Transcription

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RNA acts as the information bridge between DNA and protein

i.ρ-dependent Termination: In some prokaryotes, the termination of transcription is helped by a ρ (rho) protein that gets attached at the 5′ end of the newly synthesizing mRNA. The ρ then moves along the mRNA and induces the formation of hairpin loop near the 3′ end of mRNA due to the presence of inverted repeated sequences. This helps in the detachment of mRNA from the DNA (Fig. 8.9).

BioCoach Activity Concept 6: The Transcription Process

In eukaryotes, the termination sites in DNA are present far away from the corresponding actual 3′ end of mRNA, thus, to produce HnRNA (heterogeneous nuclear RNA). The 3′ end of the mRNA is generated after the processing of HnRNA by snurp (small nuclear RNA-protein complex). In addition to these extra nucleotides at 3′ end, the HnRNA may also contain extra nucleotide sequences at the 5′ end and at the internal positions. These extra nucleotide sequences at internal positions are called introns, whereas, the nucleotide sequences in between the introns

nucleic acids & protein synthesis notes b1 - Biology …

that are present in mRNA and contain the information of proteins are known as exons. Thus, HnRNA produced after transcription is quite longer than the mRNA. Most of the extra nucleotide sequences, including introns, are cleaved by snurp. Moreover, after removal of the extra nucleotides from the 3′ end of the HnRNA, poly A tail is added that is required for the stability of the mRNA. Similarly, after removal of extra nucleotides from the 5′ end, a cap of 7-methyl guanosine (7mG) is added that is required for the translation process. The production and processing of HnRNA occurs in the nucleus from where it escapes into the cytoplasm through nuclear pores for the translation process (Fig 8.11 and 8.12).

Protein Synthesis -Translation and Regulation

7. Thereafter, the naked tRNA at the P-site is removed with the help of the elongation factor EFG and the energy GTP as the ribosome moves by 3 nucleotides along the mRNA in 5’→ 3′ direction. Now, the P-site carries the fmet-AA2-tRNAAA2 (tRNA attached with a dipeptide).

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