The Beginning of mRNA Is Not Translated
Interestingly, not all regions of an mRNA molecule correspond to particular amino acids. In particular, there is an area near the 5' end of the molecule that is known as the untranslated region (UTR) or leader sequence. This portion of mRNA is located between the first nucleotide that is transcribed and the start codon (AUG) of the coding region, and it does not affect the sequence of amino acids in a protein (Figure 3).
So, what is the purpose of the UTR? It turns out that the leader sequence is important because it contains a ribosome-binding site. In bacteria, this site is known as the Shine-Dalgarno box (AGGAGG), after scientists John Shine and Lynn Dalgarno, who first characterized it. A similar site in vertebrates was characterized by Marilyn Kozak and is thus known as the Kozak box. In bacterial mRNA, the 5' UTR is normally short; in human mRNA, the median length of the 5' UTR is about 170 nucleotides. If the leader is long, it may contain regulatory sequences, including binding sites for proteins, that can affect the stability of the mRNA or the efficiency of its translation.
Answer:
Penicillin binds and inhibits bacterial enzyme DD-transpeptidase.
Explanation:
Penicillin is made up of 4 rings of β-lactam and acts by binding to DD-transpeptidase of bacteria. The DD-transpeptidase facilitates the cross-linking of the peptidoglycan cell wall of bacteria. This leads to malformation of the protective cell wall of the bacteria and causes it to lyze and die.
The answer is the epididymis. It is a contracted, tightly-coiled tube linking back of the testicles to the deferent duct (vas deferens). The epididymis contains three parts and these are the head, body, and tail. The head of the epididymis is positioned on larger pole of testis. It stocks sperm for maturation.
Vertebrates have a bilateral symmetry due to which their entire body is divided into right and left halves while the invertebrates either have radial symmetry or the bilateral symmetry. Therefore, option D is correct.
The other basic differences between the vertebrates and the invertebrates are that vertebrates have a spinal cord and a backbone while invertebrates lack them, vertebrates have well developed brain, lungs or gills in respiratory system and closed circulatory system.
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