4- Nucleic acids (DNA & RNA)الاحماض النووية

Watson and Crick discovered the double helix الحلزون المزدوج In April 1953, James Watson and Francis Crick shook the scientific world with an elegant double-helical model for the structure of deoxyribonucleic acid or DNA. In April 1953, James Watson and Francis Crick shook the scientific world with an elegant double-helical model النموزج الحلزونى المزدوج for the structure of deoxyribonucleic acid or DNA. Watson and Crick began to work on a model of DNA with two strands, the double helix. Watson and Crick began to work on a model of DNA with two strands, the double helix الحلزونى المزدوج.

A gene is a small region in the DNA الجينات هي اجزاء صغيرة من الحمض النووي. Nucleic acids store تخزنand transmitتنقل hereditary information. Nucleic acids store تخزنand transmitتنقل hereditary information المعلومات الوراثية. There are two types of nucleic acids: There are two types of nucleic acids: 1)- ribonucleic acid (RNA); 1)- ribonucleic acid (RNA); 2)- deoxyribonucleic acid (DNA). 2)- deoxyribonucleic acid (DNA). Organisms inherit DNA from their parents الاباء. Organisms inherit تتوارث DNA from their parents الاباء. – Each DNA molecule is very long and usually consists of hundreds to thousands of genes. – When a cell divides, its DNA is copied ينسخand passed to the next generation of cells. – When a cell divides تنقسم, its DNA is copied ينسخand passed to the next generation of cells.

Nucleic acids are polymers سلسلة عديدة of monomers وحدات احادية called nucleotides. تسمي النيوكليتيدات Nucleic acids are polymers سلسلة عديدة of monomers وحدات احادية called nucleotides. تسمي النيوكليتيدات Each nucleotide consists of three parts: a nitrogen base قاعدة نيتروجينية, a pentose sugar سكر خماسي, and a phosphate group. مجموعة فوسفات Each nucleotide consists of three parts: a nitrogen base قاعدة نيتروجينية, a pentose sugar سكر خماسي, and a phosphate group. مجموعة فوسفات The nitrogen bases (rings حلقاتof carbon and nitrogen) come in two types: Purines and Pyrimidines. The nitrogen bases (rings حلقاتof carbon and nitrogen) come in two types: Purines and Pyrimidines. The pentose sugar السكر الخماسيjoined to the nitrogen base is riboseسكر ريبوز in nucleotides of RNA and deoxyribose ريبوز منزوع الاكسجين in DNA. The pentose sugar السكر الخماسيjoined to the nitrogen base is riboseسكر ريبوز in nucleotides of RNA and deoxyribose ريبوز منزوع الاكسجين in DNA. The only difference الفارق between the sugars is the lack نقص of an oxygen atom on carbon 2 in deoxyribose. The only difference الفارق between the sugars is the lack نقص of an oxygen atom on carbon 2 in deoxyribose. The nucleic acid strand is a polymer of nucleotides سلسلة من النيوكليتيدات

Structures of nucleic acids (DNA & RNA) o H H H H H CH 2 o P o o o Sugar-phosphate backbone Base o P o o o o H H H H H CH 2 Base DNA nucleotide نيوكليوتيدة Bases Thymine (T) Adenine (A) Cytosin e (C) Guanine (G) Purine Pyrimidine Deoxyribose Phosphate group

Fig. 16.3, Page 290 The PO 4 group of one nucleotide is attachedترتبط to the sugar of the next nucleotide in line فى صف مستقيم.The PO 4 group of one nucleotide is attachedترتبط to the sugar of the next nucleotide in line فى صف مستقيم. The result is a “backbone” of alternating تبادل phosphates and sugars, from which the bases starts.The result is a “backbone” of alternating تبادل phosphates and sugars, from which the bases starts.

Nitrogenous bases القواعد النيتروجينية Sugar-phosphate backbones Thymine (T) Adenine (A) Cytosine (C) Guanine (G) Purine Pyrimidines Hydrogen bonds Nitrogenous bases Uracil (U)

An RNA molecule is single polynucleotide chain (single strand). An RNA molecule is single polynucleotide chain (single strand). DNA molecules have two polynucleotide strands (double strand) that spiral around to form a double helix حلزون مزدوج. DNA molecules have two polynucleotide strands (double strand) that spiral around تدور حلزونيا to form a double helix حلزون مزدوج.

ribonucleic acid ( RNA) a)- Messenger RNA (mRNA)الرسول carries information for protein synthesis يحمل المعلومات المسؤلة عن تخليق البروتين a)- Messenger RNA (mRNA)الرسول carries information for protein synthesis يحمل المعلومات المسؤلة عن تخليق البروتينMessenger RNA (mRNA)Messenger RNA (mRNA) b)- Ribosomal RNA (rRNA) الريبوسوميis the construction siteموقع تخليق where the protein is made. b)- Ribosomal RNA (rRNA) الريبوسوميis the construction siteموقع تخليق where the protein is made.Ribosomal RNA (rRNA)Ribosomal RNA (rRNA) c)- Transfer RNA (tRNA) delivers يحمل the amino acid to at protein synthesis عند تخليق البروتين. c)- Transfer RNA (tRNA) delivers يحمل the amino acid to at protein synthesis عند تخليق البروتين.Transfer RNA (tRNA)Transfer RNA (tRNA)

DNA RNA o H H H H H CH 2 Deoxyribose sugar ( O on C2 is missed ) o OH H H H H CH 2 Ribose sugar (no missed O) R ibo- N ucleic- A cid D eoxiribo- N ucleic- A cid Single stranded nucleic acid Double stranded nucleic acid Bases: A, G, C, T Bases: A, G, C, U

Repeated Sugar - Phosphate Sugar–Phosphate-BaseSugar–Phosphate-Base PolynucleotidePolynucleotide DNA backbone One nucleotide DNA Molecule DNA Double stranded RNA single stranded TCGATAG AGTCTAC UUmRNA DNA