DNA & Proteins (SACE) PDF

DNA & Proteins Chromosomes and DNA  SACE Key Ideas – by the end of this chapter you should know… Science Understandings DNA stores and transmits genetic information; it functions in the same way in all living things. DNA is a helical double-stranded molecule. In eukaryotes, DNA is bound to pro...

DNA & Proteins Chromosomes and DNA  SACE Key Ideas – by the end of this chapter you should know… Science Understandings DNA stores and transmits genetic information; it functions in the same way in all living things. DNA is a helical double-stranded molecule. In eukaryotes, DNA is bound to proteins (histones) in linear chromosomes, which are found in the nucleus. DNA is unbound and circular in the cytosol of prokaryotes and in the mitochondria and chloroplasts of eukaryotes. Compare chromosomes in prokaryotes and eukaryotes. Replication of DNA allows for genetic information to be inherited. Base-pairing rules and method of DNA replication are universal. Describe the structural properties of the DNA molecule, including:  nucleotide composition and pairing  the weak bonds between strands of DNA that allow for replication. Explain the importance of complementary base pairing (A–T and C–G). Describe and represent the process of semi-conservative replication of DNA. Types of Cells: There are two basic forms of cells: - Prokaryotes - Eukaryotes Prokaryotes: Prokaryotes (eg bacteria) approx 1µm in size Genetic material is a single circular piece of coiled DNA No true nucleus (no membrane around DNA) DNA is located in a region called the nucleoid. Contain organelles called ribosomes. Do not contain membrane bound organelles Eukaryotes: Genetic material (DNA) is linear (chromosomes) Have a true (membrane bound) nucleus Region between the nucleus and the cell membrane is called the cytoplasm. Suspended in the cytoplasm are membrane bound organelles that have specialised structures and functions. Large size between 10 – 100µm Eukaryotes vs Prokaryotes: Prokaryotic Cell Eukaryotic Cell Bacteria Animals, plants, fungi and protists Small (1 – 10 um diameter) Large (10 – 100 um diameter) No Nucleus, DNA is found in the nucleoid Has Nucleus region. Low level of internal organization High level of internal organisation Organelles not bound by membranes Organelles bound by membranes Single circular chromosomes, consisting of one Multiple linear chromosomes May have extra DNA in the form or a plasmid No extra chromosomal DNA (Mitochondrial DNA and DNA in chloroplasts is double stranded and circular and not bound to proteins – similar to prokaryotic DNA) Usually has peptidoglycan (combination of If present, cell wall is made ups of polysaccharide (cellulose in plants, chitin protein and polysaccharide) cell wall in arthropods and some fungi) A Little Bit of Chemistry! All matter is made up of atoms. Atoms of different kinds can be joined together by chemical bonds to form molecules Energy is required to hold the atoms together, so chemical bonds are a source of energy. Macromolecules have large numbers of atoms - many bonds are needed to hold atoms together. Macromolecules therefore contain large amounts of energy. Organic molecules (contain carbon) 4 major types of organic compounds in cells and organisms Macromolecules are all organic molecules Each macromolecule group (polymer) are as they all contain the atoms carbon, made from different types of monomers hydrogen and oxygen. (subunits): Proteins – Amino acids Remember this:CHONPS! Lipids – Fatty acids and glycerol Carbon Carbohydrates/Polysaccharides – Hydrogen Monosaccharides Oxygen Nucleic Acids – Nucleotides Nitrogen Phosphorus They all play important roles in cells, Sulfur structurally and chemically Nucleic Acids 2 TYPES OF NUCLEIC ACID DNA - deoxyribonucleic acid RNA - ribonucleic acid DNA DNA is found in all living cells DNA is a molecule that stores and transmits – it is universal to all iving information in cells that is necessary to direct cell organisms. processes. It is believed that DNA formed approximately 3.5 The structure of DNA was discovered by James Watson billion years ago when the and Francis Crick. Watson-Crick model of DNA first forms of life arose. structure. Watson Crick Discovery Universal DNA Different species on Earth differ in: The number of chromosomes DNA is universal – but has lots of variation!! found in cells The base sequence of genes found in their DNA This is due to different arrangements of the The length of the DNA molecules building blocks – DNA Nucleotides. and hence the number of bases. Every species on Earth consists of cells that use DNA as its coding system. Organism Number of chromosomes per cell Human 46 Each species has its own set of DNA and different numbers of chromosomes, but it is Bacteria 1 the same chemical bound to proteins called Rock Dove 80 histones to form structures called Pea 14 chromosomes. Simple Algae 16  There are 5 types of nitrogen base DNA Structure A- C- ADENINE CYTOSINE G- GUANINE T- THYMINE DNA - long chain molecules (polymers) made of U- URACIL (RNA only) repeating sub-units called nucleotides. A nucleotide consists of a - sugar molecule (deoxyribose sugar), - a phosphate group and - a nitrogen base. Complementary bases DNA has 4 bases (A, T, G and C) (A & G are purines, C & T are pyrimidines). Evidence for complimentary base pairing is supported by the fact that Adenine Always Binds To Thymine each species has identical amounts Guanine Always Binds To Cytosine of Adenine and Thymine in their DNA, and also identical amounts of This is called COMPLEMENTARY BASE PAIRING Guanine and Cytosine. Complementary bases are held together by weak hydrogen bonds. (i.e the bonds are easily broken) – this creates 2 complementary strands. DNA Structure Each base is attached to a sugar molecule The phosphate of one nucleotide is The structure of DNA is attached to the sugar of the next nucleotide described as a double helix. Two strands with complimentary base pairs, joined by weak hydrogen bonds (representing a ladder like structure) are twisted to form the double helix structure. Allows for ‘unzipping’ which we cover later in replication Structure Of The DNA Molecule (Summary): DNA consists of two strands wrapped around each other to form a double helix. The backbone of each strand consists of alternating sugar and phosphate molecules. Attached to each sugar molecule is one of four bases (A, T, G and C). Each base pairs with its complementary base on the other DNA strand. ACGTCTC pairs with TGCAGAG RNA compared to DNA RNA is single stranded, DNA is double RNA has the bases A, U, G and C RNA has ribose sugar, DNA has deoxyribose sugar Why U in RNA?? One main reason is that uracil production is less engery RNA and DNA are both involved in the consuming than thymine and uracil forms relatively synthesis of proteins. RNA is a weaker bond with adenine while thymine forms a temporary store of genetic information stronger one. Instead of just the two copies we have with DNA, there are thousands of copies of RNA. If one before this is passed on for protein goes bad, this is much less of a big deal. Also, RNA synthesis. doesn't stay around very long. If 40% of the bases of a DNA molecule are thymine, then the DNA molecule also contains: J. 10% adenine. K. 40% cytosine. L. 10% guanine. M. 40% uracil. DNA & Chromosomes Under a microscope, individual chromatin strands cannot be distinguished from each other - it’s a big mess we can barely see! When the cell divides, the chromatin condenses to form thicker, more visible structures called chromosomes. Chromosomes in prokaryotes and eukaryotes Chromosomes in Prokaryotes – bacteria Chromosomes in Eukaryotes – plants, animals, fungi, protists Circular linear No histones Contain histones Located in the cytoplasm Located in the nucleus One per cell Two or more per cell Most have no introns (non-coding DNA) Have introns (non-coding DNA) Centromere-like structures attaches to the cell Centromere attaches to spindle fibres during cell membrane during cell division (binary fission) division  DNA & Chromosomes ▪ DNA molecules are considerably long. ▪ “If you stretched the DNA in one cell all the way out, it would be about 2m long and all the DNA in all your cells put together would be about twice the diameter of the Solar System.” ▪ DNA is inside the nucleus of a eukaryotic cell and is wrapped up with proteins (called histones) to form long-thread like structures called chromatin. ▪ DNA is supercoiled using enzymes so that it takes up less space.  Chromosomes in Humans We call a picture of the complete set of In human cells, there are 23 pairs of chromosomes lined chromosomes (so 46 individual up in ordered pairs chromosomes in total). a karyotype. One pair (called the sex chromosomes) determines the sex of a human. The other 22 pairs are called autosomes and determine a variety of other characteristics. Genetic Diseases in One extra Humans chromosome #21 results in Downs Syndrome: Stunted growth Mental impairment Flat facial profile heart disease 1 in 800 babies One extra sex chromosome results in Klinefelter’s Syndrome: Infertile Incomplete puberty Language and learning problems Decreased mental development Poor motor skills and coordination Errors in our DNA can result in A range of diseases (heart, lung, diabetes, thyroid, cancer, some pretty serious changes. osteoporosis) Genetic Diseases in Humans Errors in our DNA can result in some serious changes. Most often, if an extra chromosome is present anywhere else, the baby will abort in utero. However, errors within genes can produce an enormous array of genetic diseases. Genes Gene – a segment of DNA on a chromosome that contains the complete sequence of bases needed to direct the manufacture of a protein or RNA. Each gene has a specific (fixed) location (Locus) on a particular chromosome. e.g. the gene for cystic fibrosis is found on chromosome 7. Chromosomes are made up of genes Each of the 46 chromosomes (23 pairs) are made up of many genes. Pairs of chromosomes have equivalent genes on them. gene that codes for the protein Keratin (structural component of hair, nails and skin) is found on chromosome 17 gene that codes colour vision in humans is located on the X chromosome mutated gene that results in Cystic Fibrosis is located on Chromosome 7 Summary DNA Chromatin ❖chemical unit of genetic information ❖long thread like structure made up of DNA wrapped up with proteins (histones) Genes ❖present when the cell is not dividing ❖functional units of genetic information ❖Specific DNA sequences ❖determine protein synthesis, physical Chromatids characteristics and inheritance ❖Duplicate copies of chromosomes, only present during cell division (mitosis and Chromosomes meiosis) ❖structural units of genetic information ❖short thick rod structures ❖form just before cell division as Analogy chromatin condenses ❖each chromosome = large DNA Chromatin is like cotton thread, molecule ❖many genes on each chromosome Histones are the cotton reel You will learn more about these later during Cells topic!! Telomeres are repeating chunks ▪ Do not code for genes of code that act as the DNA ▪ Repetitive sequences of DNA equivalent of the plastic or metal aglet capping the end of a Telomeres ▪ Keep ends of chromosomes from shoelace. sticking to each other ▪ Prevent loss of genes https://courses.lumenlearning.com/wm- biology1/chapter/reading-telomeres/  Websites CK-12 Biology https://www.ck12.org/biology/dna/ Khan Academy https://www.khanacademy.org/test-prep/mcat/biomolecules/dna/a/dna-structure-and-function Lumen Learning https://courses.lumenlearning.com/microbiology/chapter/structure-and-function-of-dna/ Videos Bozeman – What are Chromosomes? 5:34 https://www.youtube.com/watch?v=tsVHWbXqum8 Anytime Education – What is DNA 7:55 https://www.youtube.com/watch?v=CfpdlRfaQu4 Anytime Education – DNA, Chromosomes and Genes 13:29 http://www.anytimeeducation.com/negative-feedback/ Amoeba Sisters - DNA, Chromosomes, Genes, and Traits: An Intro to Heredity 8:17 https://www.youtube.com/watch?v=8m6hHRlKwxY