* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download DNA, RNA, and Central Dogma
RNA silencing wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Maurice Wilkins wikipedia , lookup
List of types of proteins wikipedia , lookup
Community fingerprinting wikipedia , lookup
Messenger RNA wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Molecular cloning wikipedia , lookup
Non-coding RNA wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
DNA supercoil wikipedia , lookup
Gene expression wikipedia , lookup
Non-coding DNA wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Epitranscriptome wikipedia , lookup
Molecular evolution wikipedia , lookup
Biochemistry wikipedia , lookup
Point mutation wikipedia , lookup
Expanded genetic code wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Genetic code wikipedia , lookup
DNA and RNA I. DNA Structure Double Helix In the early 1950s, American James Watson and Britain Francis Crick determined that DNA is in the shape of a double helix. Rosalind Franklin’s and Maurice Wilkins’s photographs and crystals led to Watson and Cricks DNA models. A. DNA Nucleotides A nucleotide is two long chains or strands of repeating subunits. Is made of three parts: A five-carbon sugar (deoxyribose) A phosphate group (P bonded to 4 O) A nitrogenous base (made up of N and C) B. The Bonds of DNA Covalent Bonds hold the sugar of one nucleotide to the phosphate group of the next nucleotide to form the chains. Hydrogen bonds join the bases on one strand of DNA to the bases on the other strand. Usually 2 or 3 bonds. C. The Nitrogenous Bases Purines (double ring) Adenine (A) Guanine (G) Pyrimidines (single ring) Cytosine (C) Thymine (T) D. Complementary Bases Base-pairing rules Each pairing contains one purine and one pyrimidine Guanine with Cytosine (G-C) Adenine with Thymine (A-T) The order of nitrogenous bases on a chain of DNA is its base sequence. II. DNA Replication The process by which DNA is copied in a cell before a cell divides by mitosis, meiosis, or binary fission. Mutations occur at a very low frequency (about one in every billion paired nucleotides). Some mutations cause disease such as cancer. Figure 10-10 in Modern Biology © 2006 Notice the direction of the synthesis Steps of DNA Replication (Semi-Conservative Replication) 1. Helicase separates the DNA strands resulting in a replication fork. DNA is unzipped. 2. Complementary nucleotides are added to each of the original DNA strands. Gaps are joined together by DNA ligase. 3. Two DNA molecules, each made up of one new strand and one old strand, identical to the original DNA molecule result. III. Protein Synthesis Ribonucleic acid, RNA, plays a role in protein synthesis. Central Concept DNA RNA protein A. RNA Structure & Function Differences in RNA than in DNA Sugar ribose instead of deoxyribose Nitrogenous base uracil instead thymine Single stranded instead of double stranded Shorter than DNA Types of RNA Messenger RNA (mRNA) – carries instructions from a gene to make a protein Ribosomal RNA (rRNA) – part of the structure of ribosomes Transfer RNA (tRNA) – transfer amino acids to the ribosomes to make a protein B. Transcription The process by which the genetic instructions in a specific gene are transcribed into an RNA molecule. Takes place in the nucleus of eukaryotic cells and in the DNA-containing region in the cytoplasm of prokaryotic cells. Figure 12-14 of Prentice Hall Biology RNA Editing After the RNA is produced, it must be edited before it can be used. Introns are removed and exons are spliced together before the RNA leaves the nucleus. C. The Genetic Code The term for the rules that relate how a sequence of nitrogenous bases in nucleotides corresponds to a particular amino acid. Three adjacent nucleotides (“letters”) in mRNA specify an amino acid (“word”) Three adjacent nucleotides are called a codon and encodes for an amino acid or signifies a start or stop signal. No codon encodes more than one amino acid. The are 64 possible codons and amino acids are can be specified by more than one codon. A start codon is a specific sequence of nucleotides in mRNA that indicates where translation should begin. AUG. Three stop codons are specific sequences of nucleotides in mRNA that indicates where translation should end. Figure 12-17 D. Translation Decoding of the genetic instructions to form a polypeptide Takes place on the surface of the ribosome Protein structure Made of one or more polypeptides Polypeptides are chains of amino acids linked by peptide bonds. Only 20 different amino acids The amino acids sequence determines how the polypeptides will twist and fold into the protein. The shape of the protein is critical to its function. Translation Figure 12-18 Beginning at the start codon, tRNA carrying an amino acid pairs its anticodons pair up with the complementary codon on the mRNA. This continues as an assembly line linking the amino acids and breaking bonds between the tRNA and the amino acids. The linked amino acids form an polypeptide until a stop codon is reached. E. The Human Genome A genome is the complete genetic content. Biologists have now decoded the order of the 3.2 billion base pairs in the 23 human chromosomes. Bioinformatics compares different DNA sequences to try to determine what information the DNA codon encodes. DNA Nitrogen Base – the Gene – Short Segment of double helix “rung on the ladder” Deoxyribose – “sugar side of the ladder” Nucleotide – composed of 3 parts floating free in the cytoplasm DNA – the double helix End of Chapter 10 Notes