DNA & RNA Composition and Structure PDF

Composition and structure of DNA and RNA by Dr.Ezat Mersal Definitions DNA, definition and history Chemical structure of DNA DNA and RNA differentiation Known the definition and history of DNA Explain the chemical structure of DNA Compare between DNA and...

Composition and structure of DNA and RNA by Dr.Ezat Mersal Definitions DNA, definition and history Chemical structure of DNA DNA and RNA differentiation Known the definition and history of DNA Explain the chemical structure of DNA Compare between DNA and RNA  History of DNA  The history of genetic research began with Gregor Mendel the "Father of Genetics". He had performed an experiment with plants in 1857 that led to increased interest in the study of genetics.  DNA was first observed by a German biochemist named Frederich Miescher in 1869.  James Watson and Francis Crick worked out the three- dimensional structure of DNA, based on work by Rosalind Franklin 1953: Structure of DNA Revealed by Watson &Crick  DNA & RNA ❖Nucleic acids are biopolymers or large biomolecules made up of monomers known as nucleotides. ❖Nucleic acids are: ✓DNA – Deoxyribonucleic acid. ✓RNA – Ribonucleic acid. DNA is a long polymer made from repeating units called nucleotides. ❑ The base pairs that join the two strands are stacked like a spiral staircase in the interior of the molecule. ❑ Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. © 2015 John Wiley & Sons, Inc. All rights reserved. ❑ B form: the B form of DNA, first described by Watson and Crick, is right-handed and contains 10 base pairs per turn. ❑ A form: which is similar to the B form but more compact. ❑ Z form: which is left-handed and has its bases positioned more toward the periphery of the helix. © 2015 John Wiley & Sons, Inc. All rights reserved.  The strands each run from 5' to 3' and run in antiparallel, or opposite, directions from one another.  Ifthe DNA strand was parallel, replication would not be possible. © 2015 John Wiley & Sons, Inc. All rights reserved.  How Chemical Bonds hold DNA together? Covalent bonds- between sugar & phosphates of 2 nucleotides (Phosphodiester bonds) Hydrogen bonds- between complementary nitrogenous bases – Base-Pair Rule (Chargraff’s Rule) Adenine Thymine Guanine Cytosine One side : A T A T C A T G C G G G Other side : ? ? ? ? ? ? ? ? ? ? ? ?  DNA Comprised of genes It founds in non-dividing cell nucleus as chromatin which composed of Protein/DNA complex Chromosomes form during cell division Duplicate to yield a full set in daughter cell The DNA in prokaryotes are smaller in size, circular and present in cytoplasm while the eukaryotic DNA is larger in size, arranged on chromosomes and located in the nucleus of the cell.” © 2015 John Wiley & Sons, Inc. All rights reserved.  DNA vs RNA DNA RNA Site Nucleus Cytoplasm Sugar Deoxyribose Ribose Nucleotides A,T,G and C A,U, G and C Arrangement Double helix Single helix Types One mRNA, tRNA, and rRNA Synthesis By replication By transcription - Storage and transfer of genetic Protein synthesis by Function and hereditary translation characters Principal Types of RNAs Produced in Cells Type of RNA Function mRNAs Messenger RNAs, code for proteins rRNAs Ribosomal RNAs, form the basic structure of the ribosome and catalyze protein synthesis tRNAs Transfer RNAs, central to protein synthesis as adaptors between mRNA and amino acids snRNAs Small nuclear RNAs, function in a variety of nuclear processes, including the splicing of pre-mRNA snoRNAs Small nucleolar RNAs, help to process and chemically modify rRNAs MicroRNAs, regulate gene expression by blocking translation of specific mRNAs and cause their miRNAs degradation Small interfering RNAs, turn off gene expression by directing the degradation of selective mRNAs siRNAs and the establishment of compact chromatin structures piRNAs Piwi-interacting RNAs, bind to piwi proteins and protect the germ line from transposable elements Long noncoding RNAs, many of which serve as scaffolds; they regulate diverse cell processes, including X- lncRNAs chromosome inactivation © 2015 John Wiley & Sons, Inc. All rights reserved. ❑ Denaturation: Alkali or heat causes the strands of DNA to separate but does not break phosphodiester bonds. ❑ Renaturation: If strands of DNA are separated by heat and then the temperature is slowly decreased under the appropriate conditions, base pairs reform, and complementary strands of DNA come back together. ❑ Hybridization: A single strand of DNA or RNA pairs with complementary base sequences on another strand of DNA or RNA. Properties of Mitochondrial DNA: ❑ 1. The mitochondrial genome is a double-stranded circular DNA molecule found within the mitochondrial matrix. ❑ 2. The genetic code for the mitochondria is slightly different than that of genomic DNA. ❑ 3. The genome codes for 13 protein subunits of the electron transport chain, a large and small ribosomal RNA (rRNA), and 22 transfer RNAs (tRNAs). ❑ 4. Mitochondrial DNA is maternally inherited. ❑ (a) Mitochondria from the egg contribute exclusively to the zygote. ❑ (b) The mitochondria autonomously reproduce, and therefore, all the mitochondria are of maternal origin. ❑ 5. Mitochondrial DNA has a high mutation rate ❑ (about 5 to 10 times greater than the nuclear genome). © 2015 John Wiley & Sons, Inc. All rights reserved.  Feng, P., Ding, H., Yang, H., Chen, W., Lin, H., & Chou, K. C. (2017). iRNA- PseColl: identifying the occurrence sites of different RNA modifications by incorporating collective effects of nucleotides into PseKNC. Molecular Therapy-Nucleic Acids, 7, 155-163.  Liu, B., Wu, H., & Chou, K. C. (2017). Pse-in-One 2.0: an improved package of web servers for generating various modes of pseudo components of DNA, RNA, and protein sequences. Natural Science, 9(04), 67.  Recommended reading:  Jorde, Carey, Bamshad and White. Medical Genetics, 3rd edition.  Lippincott’s biochemistry, 6th edition.  Recommended electronic resources: http://www.genome.gov/glossary.cfm http://www.ncbi.nlm.nih.gov/genome/ http://www.ncbi.nlm.nih.gov/omim/  Basic genetics : a human approach / BSCS. Dubuque, IA, Kendall/Hunt Pub. Co., c1999. 147 p. QH431.B305 1999  Genes, ethnicity, and ageing. Edited by Lincoln H. Schmitt, Leonard Freedman, Rayma Pervan. Nedlands, Australia, Centre for Human Biology, University of Western Australia ; Singapore, River Edge, NJ, World Scientific, c1995. 100 p.QH455.G45 1995  Genetic polymorphisms and susceptibility to disease. Edited by M. S. Miller and M. T. Cronin. New York, Taylor & Francis, 2000. 266 p.