University:
Sam Houston State University
Course:
BIOL 1406 | General Biology I
Academic year:

2020
Views:

88

Pages:

12
Author:

StellarStrategist

The paired strands are coiled into a spiral called A DOUBLE HELIX THE DOUBLE HELIX bases sugar-phosphate chain A DIY model of part of a DNA molecule 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 doublestranded DNA molecules in the nucleus So that when the cell divides, each nucleus contains identical DNA This process is called replication PO4 PO4 The strands separate 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 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 1 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 2 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-Cyst-Ser-Ala-Ser-Cyst-Gly Val 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 For example Cytosine Adenine Codes for Valine Codes for Alanine Thymine Cytosine (C) Guanine (G) Adenine (A) Triplet code This is known as the triplet code 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 The proteins build the cell structures They also make enzymes The 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 So DNA exerts its control through the enzymes Genes 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