290 likes | 428 Views
From DNA to Proteins. Section 2.3 BC Science Probe 9 Pages 42-47. DNA Structure. A DNA molecule looks kind of like a twisted ladder. DNA Structure. A DNA molecule is made up of 2 strands of smaller molecules called nucleotides. DNA Structure. A nucleotide is composed of: A sugar molecule
E N D
From DNA to Proteins Section 2.3 BC Science Probe 9 Pages 42-47
DNA Structure • A DNA molecule looks kind of like a twisted ladder.
DNA Structure • A DNA molecule is made up of 2 strands of smaller molecules called nucleotides
DNA Structure • A nucleotide is composed of: • A sugar molecule • A phosphate molecule • A nitrogenous base molecule
DNA Structure • The sides of the ladder are made of the sugar and phosphates. • The rungs are the nitrogenous bases.
DNA Structure • There are 4 nitrogenous bases: • Adenine (A) • Thymine (T) • Cytosine (C) • Guanine (G)
DNA Structure • Adenine always pairs with thymine. • Cytosine always pairs with guanine.
DNA Structure • DNA replicates itself before cell division. • The molecule splits and new bases join up with the bases on the parent strand. • The new strands are called daughter strands.
The Genetic Code • DNA has a 4-letter code. • The 4 letters are A, T, G & C for the 4 nitrogenous bases in the nucleotides.
The Genetic Code • These bases combine to form 3-letter words. • Each 3-letter word codes for one of the 20 different amino acids. • Amino acids are what proteins are made of. • Different combinations of amino acids make different proteins. • Proteins determine the characteristics of organisms.
The Genetic Code • So all of the 3-letter words put together in a cell’s DNA form the instructions for all of the body’s cells to follow!
DNA to Genes • Your DNA (or anything else’s) is organized into genes. • A gene is a short section of DNA that contains the instructions to make a specific protein. • These instructions are determined by the order of the bases.
DNA to Genes • All of an organism’s genes (all of its DNA) is called the genome. • The human genome is contained in 23 pairs of chromosomes.
Genes to Proteins • The making of proteins is called protein synthesis. • The code for the protein comes from the DNA. • Protein synthesis takes several steps:
Genes to Proteins • 1. mRNA is made from DNA. • RNA is ribonucleic acid, a single stranded molecule similar to DNA.
Genes to Proteins • 2. mRNA is transferred from the nucleus (the region that stores DNA) to the ribosomes (the site where protein synthesis occurs). This brings the mRNA to somewhere useful.
Genes to Proteins • 3. Ribosomes match up each set of nucleotides in the mRNA to a matching tRNA, starting at the "AUG" (ATG, the start sequence). The matching tRNA is carrying the amino acid for that specific sequence.
Genes to Proteins • 4. The amino acid on the tRNA is added on to the growing polypeptide (protein) chain.
Genes to Proteins • Eventually, the ribosomes hit a point in the RNA that codes for "STOP". This completes the synthesis of the protein.
Genes to Proteins • Proteins have many functions: • Enzymes • Hormones • Insulin • Hemoglobin • Fibrinogen • Keratin • Collagen
Genes and Variation • Genes are responsible for all of the characteristics that make up a species. • Different species have different genes. (Ex. tree vs. human)
Genes and Variation • All members of the same species have the same number and types of genes. • There are variations among genes. • Ex. The genes for eye colour can code for blue eyes, brown eyes or green eyes.
Genes and Variation • Different versions of genes produce different variations or traits. • Some are controlled by only one gene. • Some are controlled by a combination of genes.