Section 5.3 DNA & Genetics Chapter Introduction How are traits passed from parents to offspring? Chromatin- DNA in the nucleus loose strands Chromosome- When DNA gets organized before cell division Gene- specific location on a chromosome and codes for a specific trait Rosland Franklin and Maurice Wilkins X Rays help develop model DNA The structure of DNA was first described by Watson and Crick in 1953. Double Helix Genome- the entire sequence of DNA in an organism the human genome has approximately 3 billion chemical base pairs Traits- characteristics example eye color, height- 1
Genome- the whole set of genes for an organism A map of the human genome was completed in 2004. It included sequences for 20,000 100,000 genes. DNA is the information molecule. De-oxy-ribo Nucleic Acid DNA is the information molecule. DNA stores information necessary for a cell to function, grow and divide The info stored in DNA allows a cell to make specific proteins DNA Molecule: A double-helix, twisted ladder Made up of smaller unit called nucleotides Outside made up of sugar- de-oxyribose and phosphate molecules Inside- nitrogen bases are the subunits that make up each of the rung of the ladder There are 4 different nitrogen bases: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) All Tigers Can Growl The Structure of DNA (cont.) A nucleotide is a molecule made of a nitrogen base, a sugar, and a phosphate group. Sugar-phosphate groups form the sides of the DNA ladder. 2
Replication DNA is copied before a cell divides Strands of DNA separate Nucleotides match up base by base C matches G A matches T Replication is the process of copying a DNA molecule to make another DNA molecule. Proteins & Amino Acids Proteins make cell structures and control chemical reactions in living organisms Proteins are large molecules made of amino acids There are 20 different amino acids in our bodies Combinations of these 20 amino acids make up thousands of different proteins DNA & the Genetic Code A gene is the entire sequence of the bases that codes for all the amino acids in a protein The 4 bases - A,T,G,C - are used to code for the 20 amino acids Codon: genetic code is in triplets: 3 nucleotide bases code for 1 amino acid Proteins and Amino Acids 3
RNA Ribonucleicacid Carries information from DNA to build amino acids and proteins Single stranded Outside: Ribose (sugar) and phosphate Contains four Nitrogen bases: Adenine (A) Uracil (U) Cytosine (C) Guanine (G) RNA Three types mrna- messenger RNA: copies and carries the genes code from DNA and brings to ribosome rrna- ribosomal RNA: makes up part of ribosome trna- transfer RNA: brings amino acids to ribosomes to make proteins RNA Transcription- transfers information from DNA to make a strand of RNA Translation- translates nucleotides- reads code to make proteins and amino acids Transcription the process of making RNA from DNA is the first step in making a protein. The process of making a protein from RNA is called translation. 4
Mutations -a change in the genetic make up of an organism Caused by errors in copying DNA( enzymes) Environmental radiation, x-rays, toxinschemicals Mutations can cause no effect, minor changes or great changes Mutations A change in the nucleotide sequence of a gene is called a mutation. mutation from Latin mutare, means to change Mutations (cont.) The 46 human chromosomes contain between 20,000 and 25,000 genes that are copied during replication. Mutations can be triggered by exposure to X-rays, ultraviolet light, radioactive materials, and some kinds of chemicals. There are several types of mutations. Three types of mutations are substitution, insertion, and deletion. In a deletion mutation, one or more nitrogen base is left out of the DNA sequence. In an insertion mutation, one or more nitrogen bases is added to the DNA. In a substitution mutation, one nitrogen base is replaced by a different nitrogen base. Mutations (cont.) The effects of a mutation depend on where in the DNA sequence the mutation happens and the type of mutation. Some mutations in human DNA cause genetic disorders. 5
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