Basic genetics and patterns of inheritance
Hung N. Winn, Frank A. Chervenak, Roberto Romero in Clinical Maternal-Fetal Medicine Online, 2021
Genes are composed of deoxyribonucleic acid (DNA) and are contained on the chromosomes. Each strand of DNA has a specific sequence of four nucleotides, each containing a different base, adenine, thymine, cytosine, or guanine. Adenine pairs with thymine and cytosine pairs with guanine as two complementary strands of DNA are wound together to form a double helix. Genes have a common basic structure (Fig. 20). First, there are upstream sequences that regulate transcription, known as promoters and enhancers. Then, there is a transcription initiation site, followed by a series of alternating exons and introns. The DNA sequence serves as a template from which messenger RNA (mRNA) is made; this process is known as transcription. As transcription proceeds, a primary mRNA is made from the DNA sequence of the gene, which includes the introns. The intron sequences are then spliced out and the exons are linked together to form the mature mRNA molecule. Thus, the exons are the only portions of the gene that specify the final protein product. The mature mRNA molecule is used to make the protein product by the process of translation. Groups of three nucleotides, called codons, code for specific amino acids. Transfer RNA (tRNA) and ribosomal RNA (rRNA) interact with the mRNA to assemble the amino acids into a polypeptide chain to form the final protein molecule.
Antibiotics: The Need for Innovation
Nathan Keighley in Miraculous Medicines and the Chemistry of Drug Design, 2020
The sequence of bases on the mRNA are organises as discrete triplet codes; three bases code for one amino acid, and different sequences of triplet bases, each called a codon, code for a particular amino acid. For example, GAC codes for the amino acid aspartic acid. The process of translation is not as straightforward as the amino acids lining up along the mRNA strand. A second type of RNA, called transfer-RNA, is involved. The tRNA is a smaller molecule and is responsible for binding free amino acids in the cytoplasm and bringing them to the mRNA template. The tRNA molecules contain an anticodon, which is the opposite sequence to that on the mRNA and is complementary, therefore the tRNA carrying the amino acid can bind to mRNA. Different codons are also present on the mRNA strand to determine where to start and terminate translation into a protein.
General Radiation Biophysics and Biology
George W. Casarett in Radiation Histopathology, 2019
The high radiosensitivity of the DNA and chromosomes, and the potential molecular consequences of their injury, offer a plausible explanation for the severe consequences of absorption of small amounts of radiation energy. The genetic code for the production of all cellular constituents resides in the DNA and the sequence of its bases. The replication of DNA molecules precedes nuclear and cellular division, with DNA acting as its own template and also as a template for the production of messenger RNA which is released to the cytoplasm and directs protein synthesis in ribosomes. Transfer RNA provides the amino acids necessary for the protein synthesis on the basis of the messenger RNA template and, by its interaction with messenger RNA, forms the enzymes and structural proteins for cell function and structure.
Blocking SP/NK1R signaling improves spinal cord hemisection by inhibiting the release of pro-inflammatory cytokines in rabbits
Published in The Journal of Spinal Cord Medicine, 2023
Yuehuan Zheng, Nannan Wang, Zhe Chen, Liqiang Shi, Xiangyang Xu
The normal functioning of the central nervous system (CNS) requires the interaction of multiple cell types, including neurons, glial cells, and non-nerve cells.23 Electron microscopy shows that the nissl body is a ribosome similar to the rough endoplasmic reticulum pool in neurons. Each ribosome is a complex composed of rRNA and proteins that use transfer RNA and amino acids to synthesize proteins from mRNA. In other words, the nissl bodies is a major component of the neuronal protein synthesis mechanism.24 It is reported that the nissl bodies is a large basophilic mass and particle in the neuronal cell body or dendrites. When neurons are damaged, the nissl bodies dissolve and even disappear. During damage recovery, the nissl bodies appear again and reach normal levels. Therefore, nissl bodies can be used as markers of the functional state of neurons.24 In this study, we preliminarily found that the number of nissl bodies increased notably in the spinal cord tissue of the rabbits in the OB group on the 7th day, suggesting that the nissl bodies may be involved in the repair process of SCI.
Ribosomopathies and cancer: pharmacological implications
Published in Expert Review of Clinical Pharmacology, 2022
Gazmend Temaj, Sarmistha Saha, Shpend Dragusha, Valon Ejupi, Brigitta Buttari, Elisabetta Profumo, Lule Beqa, Luciano Saso
Transfer RNA (tRNA) carrying an antisense triplet to decode mRNA and their amino acids are linked to a growing polypeptide chain. The translation process consists of four phases: initiation, elongation, termination, and ribosome recycling [2–6]. Genes responsible for nucleolar organization are present in the short arm of acrocentric chromosomes (chromosomes 13, 14, 15, 21, and 22), the so-called nucleolar organization region (NOR) [7]. Further steps mainly include processing of endo- and exonucleolytic cleavage and modifications, such as pseudouridylation and methylation in rRNAs 18S, 5.8S, and 28S rRNA [8]. RNA Pol III is responsible for the transcription of 5S in the nucleolus, and 5S rRNA genes are organized in clusters of tandem repeat units on chromosome 1 [9]. 5S rRNA is transcribed in the nucleus and remains there before it joins 60S in the form of 5S RNP [10]. Ribosome biosynthesis, including processing three RNA polymerases and activating more than 200 non-ribosomal factors within the nucleolus, requires considerable cellular energy compared to other cellular processes [11,12].
The war against bacteria, from the past to present and beyond
Published in Expert Review of Anti-infective Therapy, 2022
Lucrezia Bottalico, Ioannis Alexandros Charitos, Maria Assunta Potenza, Monica Montagnani, Luigi Santacroce
Mechanism of action – In position 5 of the 2-deoxyptreptamine ring they carry a hydroxyl, while in positions 4 and 6 they bind to amino sugars. The remaining positions of the ring carry free amino groups that bind with high affinity to the A-site on the 16S ribosomal RNA of the bacterial 30S ribosome. Because of this interaction, the antibiotics promote codon misreading on delivery of the aminoacyl transfer RNA and subsequent mistranslation. This results in error prone protein synthesis, incorrect amino acids assembly into a polypeptide and ultimately damage to the membrane and to other components of the bacterial cell. Because of their chemical structure and high surface charge, aminoglycosides are poorly absorbed via the gastrointestinal tract and are, thus, administered via the intravenous or intramuscular route for systemic infections.
Related Knowledge Centers
- Complementary DNA
- Genetic Code
- Molecule
- Nucleotide
- Protein
- Ribosome
- Rna
- Amino Acid
- Messenger Rna
- Rna
- Messenger Rna
- Complementary DNA
- Translation