2.12 Week 5 Nucleus DNA Ribosomes.pdf

Nucleus, DNA and Ribosomes Mrs Cassy Ross Week 5 – Cell Biology SCI1023-N-GJ1-2021 2022 Learning Outcomes • Define the parts and the function of the nucleus • Discuss the dogma of the cell biology (DNA-RNA-Protein) • Identify the parts and the function of the ribosome How does the nucleus contro...

Nucleus, DNA and Ribosomes Mrs Cassy Ross Week 5 – Cell Biology SCI1023-N-GJ1-2021 2022 Learning Outcomes • Define the parts and the function of the nucleus • Discuss the dogma of the cell biology (DNA-RNA-Protein) • Identify the parts and the function of the ribosome How does the nucleus control the cell? • Contains the genetic information of the cell in the form of deoxyribonucleic acid (DNA) or chromosomes and thus, controls cell growth and multiplication • The site of DNA replication (formation of an identical copy of DNA) • Regulates cell metabolism by synthesizing various enzymes • Contains encoded instructions for the synthesis of proteins in DNA Nucleus – Parts of the nucleus Nucleus Parts of the nucleus: Nucleus – the control centre • Every eukaryotic cell has a nucleus • Contains all instructions for the cell • DNA = deoxyribonucleic acid • Universal genetic code (instructions) • DNA molecule – divided into genes Nucleus – DNA - the genetic code Game script - is a code DNA – is a code Graphical display is the output Protein is the output What do we have in common with all of these organisms? 18% DNA 50% 82% 76% Levels of DNA packaging DNA = Deoxyribonucleic acid We have 99% of our DNA in common with all other humans! 2 DNA • DNA stands for deoxyribonucleic acid • This chemical substance is present in the nucleus of all cells in all living organisms • DNA controls all the chemical changes which take place in cells • The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA • The kind of organism which is produced (buttercup,giraffe, herring, human etc) is controlled by DNA DNA molecule • DNA is a very large molecule made up of a long chain of sub-units • The sub-units are called nucleotides • Each nucleotide is made up of i. A 5-carbon sugar called deoxyribose ii. a phosphate group -PO4 and iii. a nitrogen-containing base Nucleotide The sugar, phosphate group and nitrogenous base combine to form a nucleotide. Lots of nucleotides together make up a nucleic acid Phosphate Base Deoxyribose sugar Nucleic acid Nitrogenous bases • • Two heterocyclic rings purines = made up of adenine and guanine Pyrimidine's cytosine and thymine (and uracil but only in RNA!) Pentose Sugar • Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule • Deoxyribose is almost the same but lacks one oxygen atom Phosphate group • Very negatively charged and allows for interaction with DNA histones • Binds to the 5th carbon on the pentose sugar Nucleoside vs Nucleotide Nucleoside is only composed of a nitrogenous base and pentose sugar Nucleotide is composed of nitrogenous base, a pentose sugar and a phosphate group The bases The most common organic bases are: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) PO4 Joined nucleotides A molecule of DNA is formed by millions of nucleotides joined together in a long chain PO4 PO4 PO4 sugar-phosphate + bases backbone PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 Complementarity The bases always pair up in the same way Ø Adenine forms a bond with Thymine Adenine Ø Cytosine bonds with Guanine Cytosine Thymine Guanine 5’ PO4 PO4 2 hydrogen bonds! adenine PO4 thymine PO4 3 hydrogen bonds! cytosine Left side 5’ - 3’ 3’ Right side 5’ - 3’ guanine PO4 PO4 PO4 3’ PO4 5’ Phosphodiester bond Copyright 2002, Pearson Education, Inc. Publishing as Benjamin Cummings. • 5’ is a phosphate group • 3’ is OH group When bound together creates a very strong bond! The paired strands are coiled into a spiral called A DOUBLE HELIX THE DOUBLE HELIX Sugar-phosphate chain Bases Major Groove Minor groove Huntington’s disease • Targets histones in a process called deacetylation – removes the aceytl groups tightening the interaction between histone and DNA. • Inhibits transcription • Particularly important in nerve cells that transcribe nerve growth factors • Leads to destruction of nerve cells Can you draw and label a nucleotide? Can you draw and label a nucleotide? Phosphate Deoxyribose Sugar Nitrogenous base Complete the diagram below by writing the correct letters for the bases that are complimentary to each other A G G T A C C A A G T A T G G C A C Multiple choice questions to practice! https://forms.office.com/Pages/ResponsePage.aspx?id=WxHSQ16ltkad97 AziOz8YJgLck9C2W1KmWFNRVEB5b5UQVRVQ1ZPNTQ5Nk41U0lPQjZ aU1QwS0lIUy4u Replication • Before a cell divides, the DNA strands unwind and separate • Each strand makes a new partner by adding the appropriate nucleotides • The result is that there are now two double-stranded DNA molecules in the nucleus • When the cell divides, each nucleus contains identical DNA • This process is called replication PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 The strands separate PO4 PO4 PO4 PO4 Each strand builds up its partner by adding the appropriate nucleotides PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 Genetic Code • The sequence of bases in DNA forms the Genetic Code • A group of three bases (a triplet) controls the production of a particular amino acid in the cytoplasm of the cell • The different amino acids and the order in which they are joined up determines the sort of protein being produced Genetic code • This is a small, imaginary protein molecule showing how a sequence of 5 different amino acids could determine the shape and identity of the molecule Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly Val- Cyst-Ala-Ala-Ser-Gly • Each amino acid (Serine, Cysteine, Valine, Glycine and Alanine) is coded for by a particular triplet of bases Coding Cytosine For example: Adenine Codes for Valine Thymine Cytosine (C) Guanine (G) Adenine (A) Codes for Alanine Triplet code • A sequence of three nucleotides on a DNA or RNA molecule codes for a specific amino acid in protein synthesis • Each triplet codes for a specific amino acid CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA Ala Val Gly Gly Arg Pro Leu Gly • The amino acids are joined together in the correct sequence to make part of a protein Ala Val Gly Gly Arg Pro Leu Gly DNA and enzymes • Proteins build the cell structures • Proteins also make enzymes • DNA controls which enzymes are made and the enzymes determine what reactions take place • The structures and reactions in the cell determine what sort of a cell it is and what its function is • DNA exerts its control through the enzymes Chromosomes • Chromosomes are made of DNA and contain genes • In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure • In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46 The 22 autosomes are numbered by size. The other two chromosomes, X and Y, are the sex chromosomes What is a gene? • Basic unit of inheritance • Sequenced of nucleotides • Every person has two copies of each gene, one inherited from each parent. • Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people Gene • A sequence of triplets in the DNA molecule may code for a complete protein • Such a sequence forms a gene • There may be a thousand or more bases in one gene Do you know how many genes contain a human cell? And other cell types? https://gerardofurtado.com/gs/genes.html Genes, DNA and Chromosomes explained YouTube Question 1 Which of the following are components of nucleotides? (a) deoxyribose (b) amino acids (c) phosphate (d) enzymes (e) organic bases Question 2 Which of the following represent a correct pairing of bases? (a) adenine with thymine (b) adenine with guanine (c) thymine with adenine (d) guanine with cytosine (e) thymine with thymine Question 3 DNA molecules are formed from (a) organic bases (b) amino acids (c) deoxyribose (d) nucleotides Question 4 Which of the following are organic bases? (a) Valine (b) Guanine (c) Thymine (d) Serine Question 5 Replication of DNA occurs (a) During cell division (b) before cell division (c) at any time Question 6 A nucleotide triplet codes for: (a) a protein (b) an amino acid (c) an enzyme (d) an organic base What is the ‘Central Dogma’ of Biology? Converted into functional protein product Information DNA Protein Flow of information in cells DNA mRNA Protein How does the nucleus control the cell? Fatemeh’s lecture will cover this 1957 DNA mRNA Protein central dogma in cell biology….. Gene Eye colour is due to protein pigment Gene expression DNA How does the nucleus control the cell? Fatemeh’s lecture will cover this DNA NUCLEUS mRNA transcription translation Cytoplasm Protein central dogma in cell biology….. How does the nucleus control the cell? RNA polymerase transcription DNA NUCLEUS mRNA RNA polymerase decodes the instructions Leaving the nucleus: nuclear export DNA stays in the nucleus Nuclear pore complex mRNA is made in the nucleus and is exported to the cytosol mRNA mRNA is exported through the nuclear pore complex (NPC) Electron micrograph Nucleus structure and nucleo pores https://www.youtube.com/watch?v=lAcY7D3-zS8 This video shows the central dogma in cell biology. How DNA gets to RNA and to protein are concepts that you will revise later in the module with Fatemeh! By now, just have a look of the complexity of processes inside the nucleus, DNA location, how goodies get out from the nucleus to the cytosplasm and proteins are made. Check your understanding….. What happens to the mRNA in the cytosol? mRNA is decoded by a molecular machine called the Ribosome 10 million ribosomes on average in a mammalian cell! Ribosomes are the machines in the factory 60S The job of the ribosome is to make protein 40S Translation The job of the ribosome is to make protein Cytosol ribosome mRNA Nucleus The job of the ribosome is to make protein Cytosol AA6 AA1 AA4 AA3 ribosome AA5 AA2 Amino acids in cytosol mRNA Nucleus The job of the ribosome is to make protein Cytosol AA6 AA1 AA4 AA3 ribosome AA5 AA2 AA1 Amino acids in cytosol mRNA Nucleus The job of the ribosome is to make protein Cytosol AA6 AA4 AA3 ribosome AA1 AA5 AA2 Amino acids in cytosol mRNA Nucleus The job of the ribosome is to make protein AA6 AA4 AA5 ribosome AA1 AA2 AA3 Amino acids in cytosol mRNA Nucleus The job of the ribosome is to make protein AA6 Cytosol AA5 ribosome AA1 AA2 AA3 AA4 Amino acids in cytosol mRNA Nucleus The job of the ribosome is to make protein AA6 Cytosol ribosome AA1 AA2 AA3 AA4 AA5 Amino acids in cytosol mRNA Nucleus The job of the ribosome is to make protein Cytosol ribosome AA1 AA2 AA3 AA4 AA5 mRNA Nucleus AA6 Protein (polypeptide) made on the ribosome Proteins are the tools/products of the cell Ribosomes Recap! Location of Ribosomes determines the location of the proteins Free floating Ribosomes Synthesise proteins to be used within the cell Membrane Bound Ribosomes Synthesise proteins to be used outside the cell Nucleopores Nucleolus Test yourself…. Multiple choice questions to practice! https://forms.office.com/Pages/ResponsePage.aspx?id=W xHSQ16ltkad97AziOz8YHPKVJ7iwLlEi3zi7EZn_8pUODIy V1NVUjhGOFlJSUVUMzJZSkozMkw0Vy4u Any questions? [email protected] Thank you! Thank you