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DNA Deoxyribonucleic Acid The blueprint of the cell Building Blocks of Life Recap: • Quarks and Leptons which make up • Atoms which make up • Molecules – DNA and RNA Bases are Molecules – 3 bases make a Codons, each codon codes for a specific Amino Acid – Amino Acids link to form proteins Quarks and Leptons • Proton: 2 up quarks + 1 down quark – +2/3 +2/3 -1/3 = +3/3 or +1 charge • Neutron: 2 down quarks + 1 up quark – -1/3 -1/3 + 2/3 = 0/3 = 0 charge • Electron: 1 electron lepton, -1 charge Atom - 3 types of subatomic particles - Each element has a specific number of protons Artistic representation of DNA Base Molecules Key is C = Carbon atom N = Nitrogen O = Oxygen H = Hydrogen Base Pairing Artistic representation of DNA molecules (Adenine, Guanine, Cytosine, Thymine) • milkywaytoquarks Historical Background • In 1952, Rosalind Franklin used an x-ray method to photograph DNA molecules James Watson and Francis Crick used Rosalind’s photographs to figure out the doublehelical structure of DNA in 1953 Structure of DNA DNA is shaped like a twisted ladder. This shape is called a double helix. • The sides of the helix are made of sugars and phosphates • The “rungs” are paired chemical structures called “bases” DNA has four bases 1: Adenine 2: Thymine 3: Guanine 4:Cytosine Adenine always bonds with Thymine, and Guanine always bonds with Cytosine. The bases fit together like puzzle pieces Imagine you have a piece of DNA, and you cut it down the middle. You would be left with two strands. If we have one strand or side of a DNA sequence, we can tell what the other side is. It works just like a code. If you had this half, you would look at the bases (T stands for Thymine, A for Adenine, C for Cytosine, and G for Guanine), and then think of which bases pair with them. • Thymine bonds with Adenine, Adenine with Thymine, Cytosine with Guanine, etc… Each section of DNA on a chromosome is called a gene. (p 130) Each gene directs the making of a specific protein. Genes are responsible for what you look like, for example, it determines your eye and hair color, and how tall you are, what shape your nose is, etc… Groups of three bases are called codons. Each codon stands for an amino acid. Amino acids make up proteins, which are necessary for building and repairing body tissues. 3 bases = codon each codon is the instructions for an amino acid • Primary Structure: order of amino acids • Tertiary Structure: 3-D structure of protein (the way the amino acids roll up together, like a wad of string) RNA • Before protein synthesis can take place, a “messenger” must first carry the genetic code from the DNA inside the nucleus into the cytoplasm. This genetic messenger is called RNA, which stands for ribonucleic acid. RNA is a lot like DNA, but is has one strand instead of two. It also has a different base, called Uracil, in the place of the base Thymine. There are several types of RNA • Messenger RNA (mRNA) – copies the coded message from the DNA in the nucleus, and carries the message to the ribosome in the cytoplasm. • Transfer RNA (tRNA) carries amino acids to the ribosome and adds them to the growing protein. Replication Process during the Replication Process DNA’s double helix unzips into 2 strands. Each strand’s bases are paired with new complimentary bases forming 2 identical strands of DNA, each half old and half new. transcription Sometimes mistakes are made during replication, for example, an base might be substituted for a wrong base. Or part of the strand might be duplicated or deleted. • These mistakes are called mutations. Mutations are unimportant or bad, causing children or animal babies to be born with extra fingers, albinism, problems with sight, deformities of the heart, cleft palate, muscular dystrophy, color blindness, etc… Review of DNA and transcription 1. Refer to page 133. Raise your hand if you think that the strand on the top is RNA. Raise your hand if it is DNA. DNA CCT-GAT-TAC 2. What are the complimentary bases? GGA-CTA-ATG 3. What happens if there is a mistake made when the DNA is copied? mutation 4. What are the rungs on the DNA ladder called? Bases What are some differences between DNA and RNA? DNA has two strands and the base Thymine RNA has one strand and the base Uracil Sections of DNA on the chromosome responsible for different physical characteristics are called … Genes (not to be confused with jeans) How many bases in a codon? • Three Extra Material • DNA video Bill Nye