Attachment of acetyl groups to histone promotes transcription.
This mechanism is known as histone acetylation and it is a part of gene expression. The lysine residues inside the N-terminal tail from the histone core of the nucleosome are the substrate for enzymes-histone acetyltransferase which transfer an acetyl functional group from another molecule. Acetylation removes the positive charge on the histones and thus decrease the interaction negatively charged phosphate groups of DNA. As a result, chromatin becomes more relaxed structure and transcription is promoted.
Answer:
adenine pairs with Thymine and guanine always pairs with cytosine respectively
Explanation:
In DNA nucleotide subunits, there are four nitrogenous bases:
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
Each of these bases can be divided into two categories: purine bases and pyrimidine bases.
Adenine and guanine are examples of purine bases. This means their structure is a nitrogen-containing six atom ring joined with a nitrogen-containing five atom ring that share two atoms to combine the two rings.
Thymine and cytosine are examples of pyrimidine bases.
Note that RNA replaces thymine with a different pyrimidine base called uracil (U).
The complementary base pairing rule, Chargaff's rule states that DNA base pairs are always adenine with thymine (A-T) and cytosine with guanine (C-G). A purine always pairs with a pyrimidine and vice versa. However, A doesn't pair with C, despite that being a purine and a pyrimidine.
P site, initiation step of translation, the fmet charged tRNA assembles in this site of the ribosome.The small ribosomal subunit, mRNA, initiator tRNA, and large ribosomal subunit come together to form the initiation complex. The P site of the completed ribosome is where the initiator tRNA is located.
When an amino acid, tRNA, and mRNA come together inside the ribosome, translation begins. The process of translation continues as the mRNA passes through the ribosome after it has started. Each codon pairs with a new tRNA anticodon, bringing in new amino acid to lengthen the chain.
At the subunit interface, tRNA molecules bind to the ribosome in a solvent-accessible channel. The big and small subunits each feature three tRNA binding sites known as the aminoacyl site (A site), peptidyl site (P site), and exit site (E site). The expanding polypeptide chain of amino acids is held in place by the tRNA by the P site, also known as the peptidyl site. The new amino acid that will be added to the polypeptide chain is stored in the aminoacyl tRNA, to which the A site (acceptor site) binds.
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