DNA Deoxyribonucleic Acid THE master molecule of life!

DNA DNA is often called the blueprint of life. Why would we refer to this molecules as a blueprint? Why is DNA called the blueprint of life?

DNA Contains instructions for building an organism like these are instructions for building the batmobile. It shows all needed parts and how they fit together.

The DNA in the nucleus gives instructions on how to build proteins The DNA in the nucleus gives instructions on how to build proteins. Proteins are how traits (such as eye, skin, and hair color) are expressed.

Individual Components of DNA/RNA Nucleotides Phosphates Deoxyriboses Nitrogenous Bases:A,T,G,C Histones Hydrogen Bonds Make up Genes RNA Nucelotides Phosphates Riboses Nitrogenous Bases:A,U,G,C Is DNA’s message

To get lots of DNA into a small space… We wrap up the DNA- Allow DNA to coil around histones so that the coils are even and safe from breaking!

Click on picture to watch video. Stop after histones (1:40).

Organization of the DNA Hydrogen Phosphates Sugars Nucleotides DNA Genes Histones Chromosomes From smallest to largest sized structures

? Review monomers versus polymers – what do those words mean? Which of the previous items are monomers and which are polymers?

Checkpoint What is the monomer for DNA? What are the 3 components of that monomer?

Checkpoint What is the monomer for DNA? What are the 3 components of that monomer?

Genes are a series of nucleotides or a segment/section of DNA There are many genes on a chromosome. Humans have 23 homologous chromosomes. (22 pairs are autosomal, 1 pair is sex) Chromosomes are in the nucleus of 2 types of cells: Somatic cells are non-sex cells and are diploid. (Example skin cells) Gametic cells are sex cells and are haploid. (Example sperm or egg)

Using root words to figure this out, what do haploid and diploid mean? Think – pair - share Using root words to figure this out, what do haploid and diploid mean?

More review…Look at the picture showing DNA and answer the following: What organelle is the DNA coming from? What other organelles have DNA in eukaryotic cells? What is an example of a gene shown? What makes up genes? Is DNA a polymer or monomer?

The Shape of the Molecule DNA is a very long polymer. What type of organic compound is this? What functional group would you find on nucleic acids like DNA or RNA? The basic shape is like a twisted ladder or zipper. This is called a double helix.

The Double Helix Molecule The DNA double helix has two strands twisted together. The nucleotides on each strand are held together with covalent bonds The strands are held together by hydrogen bonds We will take apart the DNA molecule to see how it is put together. First, we will look at one strand.

Label your DNA coloring

Complementary Bases Review the possible DNA base pairs and how they bind together in the DNA. Also, review the actual names of the 4 nitrogenous base pairs found in DNA.

Compare DNA and RNA by creating a venn diagram Compare DNA and RNA by creating a venn diagram. Include all of the following traits: Both nucleic acids Both have phosphate in their back bone DNA has a deoxyribose sugar in the backbone RNA has a ribose sugar in the backbone Uses the bases A,T,C,G and U Single stranded Double stranded Can be found outside the nucleus Both are polymers

Think about this: When would you need to make a copy of DNA? Would the copy of DNA need to be identical or slightly different from the original? In what organelles would you find DNA or RNA? How will enzymes be involved in copying DNA? In making RNA?

Stop here for now! You’ll be told when to continue on to DNA replication! Thanks!

DNA Replication

Check for understanding before DNA replication What does “to replicate” mean? When would a cell want to replicate its DNA? What does it mean if something ends in –ase? What are the two types of bonds in DNA and which is the easier to break? What is meant by the term complementary? What does it mean that DNA is a “double helix”?

Goal……

Predict some things about the process of replication….. When will do this process? What has to happen to DNA in order to copy? What should we end with after replication? Think about the product of the replication.

Some basics about the chemistry of DNA The ends of each strand of DNA’s sugar-phosphate backbone, is polar.(What does that mean?) The sugar side is slightly positive (OH) (aka 3’) The phosphate side is slightly negative (P) (aka 5’) Enzymes all build new strands in a 5 (-) to 3’ (+) direction when they work! That means they move along the original strand from 3’ to 5’

Possible ways to get from original (parental DNA) to a newly synthesized molecule of DNA….. Conservative Dispersive Semiconservative

DNA replication Determined by Meselson and Stahl Steps to make more DNA (an exact copy) Unwind double helix and break the H bonds (helicase) Stabilize open strands (use the spooling proteins called histones) Copy DNA by adding complementary nucleotides (DNA polymerase) Check for errors (ligase and polymerase) Connect fragments on the lagging strand (ligase)

Semi-conservative replication Each DNA molecule will consist of an old and a new strand of DNA. This means each parental or original strand of DNA can act as a template to copy. However, based on those back bone charges and the mandatory direction of DNA polymerase, we have a leading and lagging strand during replication.

Charges and Copy Issues Charges on DNA strands and charges on the enzymes copying the DNA cause a “leading” and “lagging” strand during replication. These terms are used to describe the template strand (one being copied) of DNA. Replication enzymes move along the template (original DNA) from 3’ – 5’. While building the new strand from the 5’ – 3’ So the parental strand (template/original) of DNA that starts with the 3’ side is called the “leading strand”. The one that starts with a 5’ is called the “lagging strand”.

Click on pictures for links to video