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Nucleus

Nucleus. General features of nuclei A-Major components 1-nuclear envelope 2-Nuclear Sap 3-one to several nucleoli 4-Nuclear chromatins. B-nuclear function. 1-In heredity(store house for gentic information) 2-Cell division(nucleus regulates the processes of cell division

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Nucleus

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  1. Nucleus • General features of nuclei • A-Major components • 1-nuclear envelope • 2-Nuclear Sap • 3-one to several nucleoli • 4-Nuclear chromatins

  2. B-nuclear function • 1-In heredity(store house for gentic information) • 2-Cell division(nucleus regulates the processes of cell division • 3-Controlling all cellular function

  3. C-Nuclear Morphology • 1-Nuclear size: small,medium,large • 2-Number per cell: one nuclus,two nuclei (liver cells,superficial cells of transitional epithelium)&many nuclei (osteoclast cells of bone&skeletal muscle cells • 3-shape : round,oval,flattened,rod-shaped,kidney shape,segmented • Nuclear location:basal,central or eccentric

  4. Nuclear Structures

  5. Structures of nucleus • Four components • 1-nuclear envelope • 2-nuclear sap • 3-nucleolus • 4-Nuclear chromatin

  6. 1-Nuclear envelope • Dark basophilic membrane which surrounds the nucleus • LM: appears as single dark membrane • a-Inner fibrillar membrane(rich in chromatin fibers • b-outer granular membrane(rich in ribosomes) • c-nuclear pores(formed nuclear membrane complex which is formed of peripheral spoks&cenral plug this plug diaphragm which regulate the passage of protein from cytoplasm to enter the nucleus

  7. High mag TEM of a nucleolus Pars fibrosa/granulosa (dense black) and fibrillar center (arrow)

  8. 2-Nuclear Sap • It is acolloidal clear solution, • it is formed of nucleoproteins,enzymes,phosphors,potassium&calcium • Two type of nuclei • 1- open face nucleus: large amount of nuclear sap present in liver cells • 2- condensed nucleus: less amount of nuclear sap(lymphocyte) • Function of nuclear sap • 1- provide amedium in which ribonucleic acid(Ri,t&m RNA) • 2-Move towards the nuclear pores

  9. 3-nucleolus: • basophilic mass formed of RNA&DNA • The nucleolus may enlarge in size in protein • forming cells in rapidly growing cancer cells • LM: dark basophilic mass • Function of the nucleolus • It forms rRNA&mRNA

  10. 4-Chromatin material • basophilic particles&chromosomes are formed during cell division • Structures: are formed mainly of nucleoprotein which is formed of DNA nound to basic protein called histones • Stain:basophilic due to presence of DNA • LM: basophilic granules

  11. There are two type of chromatin • 1-Euchromatin(active chromatin • 2-Heterochromatin(In active)

  12. 1-Euchromatin: • Invisible by LM • Very lightly with basic stain • Most active chromatin • Control protein synthesis

  13. 2-Heterochromatin: • inactive chromatin • Visible by LM as cours granules • Appears as masses of nucleoprotein called nucleosomes • Stain dark with basic stain • They do not dirct any protein synthesis

  14. Function of chromatin • 1-guides protein synthesis inside the cell • 2-stores the genetic information of the individuals • 3-DNA chromatin material====rRNA,mRNA,tRNA are formed

  15. TEM of interphase nuclei and a mitotic cell with condensed chromosomes (arrow)

  16. Nuclear pores (arrows) Nuclear pores(en face)

  17. Colorized TEM of nuclear pores (blue) en face

  18. Nucleic Acid • They are the bases of life, • control the cellular functions • Two Types of nucleic acid: DNA&RNA

  19. 1-DNA= Deoxy-ribonucleic acid • DNA molecules are present in the nuclear chromatin,chromosomes&mitochondria • DNA represent the hereditary substances or genes • DNA molecules consists of two chins forming double helix • There are 4 types of nitrogenous bases in DNA molecules

  20. 1-Adenine(A) ,2-Thymine (T),3-Guanine(G),4-cystosine (C) • DNA carries&stores the genetic,information of ech cell • DNA transfers the genetic information by the following 2 processes • a-replication of DNA to form more DNA • b-transcription of DNA to form 3 types of RNA

  21. 2-RNA= Ribonucleic Acid • The same structure to DNA but with some differences • DNA: present in nucleus,mitochondria of cytoplasm • DNA present in the nucleus&cytoplasm • DNA: takes blue colour========= • RNA: takes red colour=========Methyl-green-pyronin stain

  22. 1-Ribosomal RNA=r-RNA • They are formed in the nucleolus from loops of DNA • Move to the cytoplasma&are known as ribosomes • Present free in cytoplasm • Function: they are the sites for protein synthesis

  23. 2-Messenger RNA=mRNA • Information codes for proteine synthesis are present on DNA • DNA---------------mRNA======which control the processes of protein synthesis • mRNA can direct the synthesis of many identical protein signal which indicate where to begin and where to end translation

  24. 3-Transfer RNA=tRNA • t-RNA are formed inside the nucleus from DNA has two arms • a-tRNa==attched to amino acid • ==called anticodon

  25. DNA is used to produce mRNATranscription

  26. Steps of protein Synthesis in the cell • 1-DNA molecule: specific types of protein which share information of hormones&enzymes • 2-DNA: have ability to from copies of DNA by replication of DNA • 3-DNA :can manufacture three kinds of RNA

  27. a-r-RNA=protein factories • b-m-RNA=code carries • c-t-RNA=Amino acid transfers

  28. 4-m-RNA molecule in the cytoplasm&association with • a-ribosomes(read the secret messages which are present on the mRNA • b-three t-RNA molecules(wanted amino acids from the cytoplasm • c-three amino acids

  29. 5-amino acid by tRNA====mRNA&correct aligment • 6-amino acids to form apolypeptide • 7-release polypeptide&dissociation of ribosomes from messenger RNA====newly synthesized protein

  30. Ribosomes -composed of rRNA (ribosomal RNA) & protein -may be dispersed randomly throughout the cytoplasm or attached to surface of rough endoplasmic reticulum -often linked together in chains called polyribosomes or polysomes -Primary function to produce proteins

  31. TRANSLATION mRNA then moves from the nucleus into the cytoplasm & is used to produce a protein

  32. The life cycle of the cell • Changes which occur in the cell during division(mitosis)&during rest(Interphase) • The cell cycle==mitotic part(two doughter cell) • ==Interphase part (resting condition before starting another cell division

  33. Subdivide into 3 three stages • 1-G-1 stage(Gap one stage)presynthesis): 46-s-Chromosomes • 2-S.2 stage(DNA synthesis)replication of DNA molecules have 46 identical paris of chromatids(92 chromatids • 3-G2(post DNA duplication): have 46 D-chromosomes

  34. Types of cells in relation to their cell renewal • Three types of cells in the body • 1-Non-renewing cells • Cells cannt divide== nerve cells they are not replaced • 2-continously renewing cells • These cells unable to divide:replaced by doughter cells arising from mother cells called stem cells of the same family

  35. Stem cells • a-unipotential stem cell: one type of the cells ex. Testicular cells • b-multipotential stem cells: bone marrow cells produce different type of cells • 3-potential-renewble cells • Ex.of these cells are:liver cells&endocrine cells • Nuclear changes during cell necrosis • 1-pyknosis:nucleus becomes smaller&deeply stained • 2-karyorrhexis:nucleus breks into small fragments • Karyolisis:the nucleus dissolves&disappears

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