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DNA

DNA. The common thread of life. Dr. J.J.Timmel. What are the functions of DNA?. There are two main functions of DNA It is the molecule of heredity. It contains the information needed to construct proteins. What is heredity?.

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DNA

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  1. DNA • The common thread of life. Dr. J.J.Timmel

  2. What are the functions of DNA? • There are two main functions of DNA • It is the molecule of heredity. • It contains the information needed to construct proteins.

  3. What is heredity? • Heredity is the term used to explain the transfer of genetic information from one generation to the next. • You inherited half of your DNA (your genes) from Mom, and the other half from Dad. • DNA is the molecule that allows this to happen.

  4. Structure of DNA • As you surely remember the basic building blocks of DNA are nucleotides. • Here we see the phosphate group and 5-Carbon Sugar.

  5. The third part of a nucleotide is the nitrogen base. There are two types of nitrogen bases: Purines: A and G which have a double ring structure. Pyrimidines: T and C which have a single ring. Nitrogen bases.

  6. Genes to Proteins. • Your DNA is housed in the nucleus of every cell in your body. • Most of the time, the DNA is in long twisted strands called Chromatin. Very thin, and cannot be seen using a regular compound light microscope. • The Chromatin condenses to form Chromosomes prior to cell division. These can be seen.

  7. Genes to proteins cont. • These strands of chromatin are made up of many genes. A gene can be hundreds or thousands of nucleotides long. (The entire human genome consists of 3 BILLION nucleotides). • Each gene is a series of nucleotides which contains the information to make a protein. • 1 gene = 1 protein.

  8. The genetic code • Genetists (Scientists who study genetics) were interested in determining how information in your genes was used to create proteins. • They knew that there were 20 different amino acids and that there were 4 types of nucleotide.

  9. Cracking the code. • Since there were twenty amino acids and only 4 nucleotide types, they knew that the genetic code had to consist of more than one nucleotide. 41= 4 Ex. The nucleotide Adenine by itself does not code of the amino acid Threonine.

  10. Cracking the code (cont.) • By applying the same logic, they realized that the genetic code could not consist of two nucleotides either. 42=16 Adenine and Cytosine together does not code for the amino acid Threonine.

  11. Cracking the code • Expanding on the theme, they realized that sequences of 3 nucleotides would give more than enough combinations to code for all 20 amino acids. 43=64 Adenine, Cytosine and Guanine DO code for the amino acid Threonine. They call these 3-nucleotide sequences CODONS. We will be using the actual genetic code later in this unit.

  12. The Genetic Code Lets take a look. DNA genetic code

  13. DNA Replication • Prior to cell division (mitosis or meiosis) the cell must make another copy of, or replicate it’s DNA. • The DNA molecule basically unzips itself by breaking the hydrogen bonds holding the two strands of nucleotides together. • Each strand then forms a second strand by using free nucleotides which are found in the nucleus. • DNA replication simple • DNA replication complex

  14. DNA and RNA • Both are nucleic acids, and are very similar to each other. • There are some differences. DNA RNA Sugar: Deoxyribose Ribose Strands: 2 1 Nitrogen Base: Thymine Uracil Location Nucleus Nucleus & Cytoplasm

  15. RNA transcription • While DNA contains an entire library’s worth of information, it is a big, big molecule. • It is so big, it cannot fit through the pores of the nuclear membrane. • To get the information needed to make proteins to the ribosomes, the DNA needs some help.

  16. Enter the messenger • In order to get the information stored in a gene to the ribosome, messenger RNA (mRNA) is transcripted. • First, the DNA will partially unzip itself to expose one gene’s worth of code. • An enzyme called RNA polymerase then copies a strand of RNA based on the template strand of the DNA.

  17. mRNA transcription • RNA transcription simple • RNA transcription complex

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