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2021-05-14

Why does a new DNA strand elongates only in the 5 to 3 direction?

Why does a new DNA strand elongates only in the 5 to 3 direction?

why does a new DNA strand elongates only in the 5′ to 3′ direction? DNA polymerase can only add nucleotides to the free 3′ end.

Does DNA polymerase synthesized from 5 to 3?

New DNA is made by enzymes called DNA polymerases, which require a template and a primer (starter) and synthesize DNA in the 5′ to 3′ direction. During DNA replication, one new strand (the leading strand) is made as a continuous piece.

Is CCA a stop codon?

Three sequences, UAG, UGA, and UAA, known as stop codons, do not code for an amino acid but instead signal the release of the nascent polypeptide from the ribosome….Inverse RNA codon table.

Amino acid Cys, C
Compressed UGY
Amino acid Pro, P
DNA codons CCU, CCC, CCA, CCG
Compressed CCN

Is UAC a stop codon?

The 42mer mRNA analogs containing the canonical stop (UGA, UAA, UAG) or sense (UAC, UGG) codons are indicated.

Are there exceptions to the genetic code?

The genetic code consists of 64 triplets of nucleotides. These triplets are called codons. With three exceptions, each codon encodes for one of the 20 amino acids used in the synthesis of proteins.

Is UAC a start codon?

The AUG start codon signals the ribosome to place in the amino acid methionine because the tRNA that has methionine attached to it has the anticodon sequence UAC. Therefore the tRNA will temporarily bind to the mRNAs sequence. This places the start codon part of the mRNA at a new ribosome position called the ‘P’ site.

Which is stop codon?

There are 3 STOP codons in the genetic code – UAG, UAA, and UGA. These codons are also known as nonsense codons or termination codons as they do not code for an amino acid. The three STOP codons have been named as amber (UAG), opal or umber (UGA) and ochre (UAA).

How are stop codons recognized?

Stop codons are nucleotide triplets in messenger RNA (mRNA) that serve a key role in signaling the end of protein coding sequences (e.g., UAG, UAA, UGA). Premature stop codons are those that occur within the normal coding sequence due to a mutation.

Why is met the start codon?

Methionine is specified by the codon AUG, which is also known as the start codon. Consequently, methionine is the first amino acid to dock in the ribosome during the synthesis of proteins.

Do all proteins start with Met?

Not every protein necessarily starts with methionine, however. Often this first amino acid will be removed in later processing of the protein. A tRNA charged with methionine binds to the translation start signal. When the ribosome reaches a stop codon, no aminoacyl tRNA binds to the empty A site.

What happens if one amino acid is substituted for another in a polypeptide chain?

Explain what happens if even one amino acid is substituted for another in a polypeptide chain. Provide a specific example. A change in gene sequence can lead to a different amino acid being added to a polypeptide chain instead of the normal one. This causes a change in protein structure and function.