http://youtu.be/qoERVSWKmGk

If the DNA of one cell is stretched out, it makes a 7 ft. long string

There are about 5 trillion cells in the human body

If you connected all the DNA together, it would be long enough thatit would take light over 10 hours10 hours to travel its length

This is a whole lot of information

(ruptured bacteria)

The Basics of The Basics of DNADNA

DNA and Heredity…DNA and Heredity…

Rosalind Franklin’s Rosalind Franklin’s research was used research was used in the discovery of in the discovery of DNA structureDNA structure

Francis Crick & Francis Crick & James Watson James Watson developed the first developed the first model of DNAmodel of DNA

Watson & Crick Watson & Crick concluded that all concluded that all living cells contain living cells contain DNADNA

• ProkaryotesGenetic material is a single loop of DNALocated in the cytoplasm

• EukaryotesGenetic material in the form of a chromosomeLocated in the nucleus

Review the Cell…Review the Cell…

• Cells contain the nucleusCells contain the nucleus

• The nucleus is the “brains” The nucleus is the “brains” of the cellof the cell

Chromatin – DNA tightly wrapped around proteins (histones)

Chromatin supercoils to form chromosome

Chromosome visible during mitosis

Review the Cell…Review the Cell…

• Chromosomes are found Chromosomes are found inside the nucleusinside the nucleus

• Chromosomes contain genesChromosomes contain genes

• Genes are made up of DNAGenes are made up of DNA

What is DNA?

• The genetic material The genetic material determines how an determines how an organism develops. organism develops.

• How? The sequence of How? The sequence of nucleotides (nitrogen nucleotides (nitrogen bases)determine the bases)determine the traits of an organism.traits of an organism.

The main functions of The main functions of DNA are to:DNA are to:

1.) Store and 1.) Store and maintain genetic maintain genetic informationinformation

2.) Provides 2.) Provides instructions for making instructions for making organismsorganisms

What does DNA Stand for?What does DNA Stand for?

• DNA is a Double Helix - like a twisted rubber ladder made from three main components (like legos)

• Sides of the ladder are composed of alternating sugarsugar and phosphatephosphate pieces

• Each “rung” of the ladder is made up of two complementary nitrogenous basesnitrogenous bases– A complements T

– C complements G

• DNA is put together in chunks called NUCLEOTIDES– Each nucleotide has a sugar, PO4

3- and base

• A nucleotide is held together with strong molecular bonds

• Oxygens provide the “hooks” necessary to bind to other NTP’s

• We identify where these Oxygens are by labeling the carbons of the deoxyribose sugar

1’

2’3’

4’

5’

(see, no oxygen at 2’…)

• Each of the components of the nucleotide binds to another nucleotide to form a single DNA strand– Since OxygenOxygen easily forms two

strong bonds, the phosphate and sugars both bind most strongly

– The HydrogensHydrogens on the base bind less strongly with an Oxygen or Nitrogen from another base to bind one strand to another

• Finally we have the characteristics of double stranded DNA

• STRONG bonds between the deoxyribose sugars and phosphates

• WEAK bonds between the Hydrogen and Oxygen or Nitrogen (weaker between A and T than C and G)

• Twisting of the two anti-parallel strands to form a double helix

• Heat it up, which bonds break first?...

• We start with some double stranded DNA

• Replication= The copying of DNA prior to the cell undergoing division

• It occurs at multiple sites along the DNA strand simultaneously

• DNA strands are complementary- that is each strand can be used to make the other strand.

• DNA Helicase comes on the scene binds and

• UNWINDSUNWINDS the DNA upstream

• Then UNZIPSThen UNZIPS the hydrogen bonds between the base pairs This site is known as the replication bubble

• DNA single-stranded binding proteins stabilize the single strand structure.

– The sites on DNA where separation and replication occur are called replication forks.

– Replication takes place in both directions until each chromosomes is completely copied. In a 5’→ 3’ direction.

– There are two replicating strands the leading strand and the lagging strand. The leading strand moves in a forward motion. The lagging strand move in a backwards motion.

• Extra: The lagging strand is made up of Okazaki fragments which replicate short pieces of DNA at a time.

• DNA polymerase joins individual nucleotides to produce a DNA molecule, which is a polymer.

• Complementary BasesComplementary Bases begin adding into both sides of the ds DNA

• A binds with T, C binds with G (no other possibility because of the shape of the bases!)

• The final job of the Polymerase is to ProofreadProofread the sequence of nucleotides after they are added (back on the 5’ end) and to clip out any that are incorrectly paired nucleotides.

• Extra Primase is an enzyme that helps start DNA replication in an Okazaki fragment.

• Extra DNA ligase removes the gaps that are in place due mainly to the use of primase in the lagging strand.

• Finally you have 2 identical copies identical copies of double stranded DNA

– The original strand serves as a templatetemplate for the new strand

– The resulting DNA molecules are made up of one parent parent (original) strand and one daughter daughter (new) strand

YouTube - DNA Replication 45 seconds

YouTube - BioRap (DNA Replication and Protein Synthesis with a Beat)

http://youtu.be/qoERVSWKmGk

Review Review QuestionsQuestions

Which of the following determines the traits of an organism?

A cell nucleus

B chromosomes

C DNA

D eggs

Which of the following determines Which of the following determines the traits of an organism?the traits of an organism?

A is incorrect because the nucleus

does not determine traits but contains information that does.

B is also incorrect because chromosomes do not determine traits but contain information that does.

Which of the following determines Which of the following determines the traits of an organism?the traits of an organism?

C is correctcorrect because DNA is the genetic information, found in the nucleus, that determines the traits of an organism.

D is incorrect because eggs are a cell that contain genetic material that will be used to determine traits, but does not determine an organism's traits itself.

DNA molecules separate into single strands, which are then used to construct two identical strands of DNA. This process ensures that the —

A cytoplasm is in equilibrium

B mitochondria are genetically identical to the chloroplasts

C parent cells use little ATP

D daughter cells are genetically identical to the parent cells

DNA molecules separate into single strands, DNA molecules separate into single strands, which are then used to construct two which are then used to construct two identical strands of DNA. This process identical strands of DNA. This process ensures that the —ensures that the —

A is incorrect because cytoplasm is not part of DNA molecules; rather, cytoplasm is the fluid-like substance that fills a cell.

B is incorrect because mitochondria are not identical to chloroplasts; further, animal cells do not have chloroplasts, but do replicate DNA.

C is incorrect because ATP is a high energy molecule needed to provide energy for normal cellular function and is not part of DNA.

D is correctcorrect because by producing identical strands of DNA, it ensures that the daughter cells are genetically identical to the parent cell.

DNA molecules separate into single strands, DNA molecules separate into single strands, which are then used to construct two which are then used to construct two identical strands of DNA. This process identical strands of DNA. This process ensures that the —ensures that the —

The nucleus is the part of the cell that

A provides structure and support.

B supplies energy to the other organelles.

C changes sunlight into carbohydrates.

D contains genetic information about the organism.

The nucleus is the The nucleus is the part of the cell that part of the cell that

A is incorrect because structure and support is provided by cell membranes and cell walls.

B is incorrect because mitochondria are the parts of the cell that provide energy.

The nucleus is the The nucleus is the part of the cell that part of the cell that

C is incorrect because chloroplasts are the organelles that carry on photosynthesis.

D is correctcorrect because the nucleus contains chromosomes that are made up of genes that contain DNA which is the genetic information about an organism.

Which of the following is not a part of DNA?

A adenine

B citric acid

C deoxyribose

D phosphate

Which of the following is not a part of Which of the following is not a part of DNA?DNA?

A is incorrect because adenine is one of the bases that make up DNA.

B is correctcorrect because citric acid is not part of DNA.

C is incorrect because deoxyribose is sugar which is part of DNA

D is incorrect because phosphate is a part of DNA.