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1. DNA. DNA. DNA stands for deoxyribose nucleic acid Present in the nucleus of all cells in all living organisms DNA controls all the chemical changes within the body which take place in individual cells DNA controls the kind of cell that is formed, (muscle, blood, nerve etc)
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DNA • DNA stands for deoxyribose nucleic acid • Present in the nucleus of all cells in all living organisms • DNA controls all the chemical changes within the body which take place in individual cells • DNA controls the kind of cell that is formed, (muscle, blood, nerve etc) • DNA also controls what kind of organism is produced (dog, cat, human, pine tree)
What is DNA? • A large molecule made of units called nucleotides • Each nucleotide is made of: • A sugar (deoxyribose) • A phosphate • A nitrogen base
One Nucleotide • Each nucleotide has one of four bases • Adenine (A) • Thymine (T) • Cytosine (C) • Guanine (G) • All nucleotides have a phosphate and a sugar but the bases can change
Adenine (A) Thymine (T) The Nitrogen Bases • Adenine and Thymine bases are always paired together (see how the ends fit like a puzzle)
Cytosine (C) (G) Guanine The Nitrogen Bases • Cytosine and Guanine bases are always paired together (see how the ends fit like a puzzle)
A DNA Molecule • A molecule of DNA is formed by millions of nucleotides joined together in a long chain
A DNA Molecule • DNA consists of a coiled double strand of nucleotides (called a double helix) • Sugar phosphate chains are on the outside and the nitrogen bases are on the inside joined together by chemical bonds
DNA Replication • Before a cell divides, the DNA strands unwind and separate • Each strand makes a new strand of DNA by adding the appropriate nucleotides that match the ones in the strand (makes it’s other puzzle piece)
DNA Replication • So that when the cell divides, each nucleus contains identical DNA • And this process is called replication
The strands separate 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 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 Each strand builds up its partner by adding the appropriate nucleotides
Genetic Codes • The special programming in DNA are actually codes. • Each code in DNA is made up of 3 consecutive bases (3 in a row) called a codon. • Each codon is in charge of making a particular amino acid and a group of amino acids is called a protein.
Genetic Code • There are 20 different amino acids that can be made • The different amino acids and the order in which they are joined up determines the sort of protein being produced • We know that proteins make up most of the structure of cells and tissues
Amino Acids and Proteins • The sequence of codons are important to form a protein with a specific structure and function • The sequence is also written as: CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA - Ala Val Gly Gly Arg Pro Leu Gly Ala Val Gly Gly Arg Pro Leu Gly
DNA and Genes • Each sequence of codons that form a certain protein is the “gene” for that protein. • Ex. Lets say this is the sequence for of codons to form Protein A. It would be called Gene A. CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA - Gly Ala Val Gly Arg Pro Leu Gly