DNA: An Introduction to structure and function. DNA by the numbers. Why do we study DNA? Chromosomes and DNA

Transcription

1 DA: An Introduction to structure and function Hopefully a review The structure of DA - your job during the PowerPoint: Make a labeled sketch Label the structure of a nucleotide Know which bases pair up and how they are held together Explain why the structure of the DA molecule is often described as a zipper. Make a sketch of DA replication Explain how DA holds information DA by the numbers A human has 46 chromosomes, a plum tree has 48, a chicken has 78 and an ant has 2 Each human cell has about 2 m of DA The average human has 75 trillion cells The average human has enough DA to go from the earth to the sun more than 400 times DA has a diameter of only m The earth is 150 billion m or 93 million miles from the sun. Why do we study DA? importance to all life on Earth medical benefits such as cures for diseases Genetic Engineering But What does DA do? Where is the DA? Functions of DA Two primary functions - transmit information from one generation to the next -provide blueprint for making proteins the same way every time Two Types of DA nuclear or chromosomal DA (inherited from mother and father) mitochondrial DA (inherited from mother only) hromosomes and DA DA makes up the chromosomes Genes are coded for in different regions of chromosomes More about this soon!! 1

2 DA DA is often called the blueprint of life - Why? In simple terms, DA contains the instructions for making proteins within the cell. The Shape of the Molecule DA is a very long polymer The basic shape is like a twisted ladder double helix The Double Helix Molecule The DA double helix has two strands twisted together eed to look at the structure of one strand ne Strand of DA Backbone is alternating phosphate and deoxyribose, a sugar The teeth are nitrogenous bases phosphate deoxyribose bases ne Strand of DA ucleotides -P Phosphate ne deoxyribose together with its phosphate and base make a nucleotide. Deoxyribose itrogenous base 2

3 The Structure of DA Four nitrogenous bases DA has four different bases: ne strand of DA is a polymer of nucleotides ne strand of DA has many millions of nucleotides ytosine Thymine T Adenine A Guanine G Two Kinds of Bases in DA Pyrimidines are single ring bases Purines are double ring bases Pyrimidines: Thymine and ytosine Thymine and cytosine each have one ring of carbon and nitrogen atoms Purines: Adenine and Guanine Adenine and guanine each have two rings of carbon and nitrogen atoms thymine cytosine Adenine Guanine 3

4 Two Stranded DA DA has two strands that fit together something like a zipper The teeth are the nitrogenous bases but why do they stick together? Hydrogen Bonds The bases attract each other because of hydrogen bonds Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DA Hydrogen Bonds, cont. When making hydrogen bonds, thymine always pairs up with adenine And cytosine always pairs up with guanine Important: Adenine and Thymine always join together A T ytosine and Guanine always join together G Why do we care? How can we use this? DA Replication DA is unwound DA Replication An enzyme called DA Polymerase adds complementary bases to single stranded - A with T - with G 4

5 Practice The whole story A bit more complicated - but cool! omplicated, but K Draw the replication for the sequence of bases: Include a labels of the backbone structure and the hydrogen bonds The structure of DA: Make a labeled sketch Label the structure of a nucleotide Know which bases pair up and how they are held together Explain why the structure of the DA Molecule is often described as a zipper. Make a sketch of DA replication Explain how DA holds information 5