DNA AND ITS STRUCTURE

DNA is located inside the nucleus

DNA is stored in chromosomes, and chromosomes are found in the nucleus

Female and Male Sex Chromsomes

A karyotype is a picture of all the chromosomes in a cell. Humans have 22 pairs of chromosomes and two sex chromosomes

What is DNA? DNA Heredity material for life Known as Deoxyribonucleic Acid Double helix Molecule

What makes DNA so exciting is that it shows how living organisms store information in biological molecules The structure of DNA is nicely suited for this task The structural backbone creates a simple, consistent chain upon which many, many bases can be laid out in an orderly sequence

DNA Your DNA contains a set of instructions for building a human. It is responsible for all inherited characteristics. It directs all the cell’s activities These instructions are inscribed in the structure of the DNA molecule through a genetic code

DNA shows us how living organisms can pass down information to their offspring For example, it tells us how a child can be born with “his mother’s eyes” or “his father’s nose” DNA is compact, yet complex enough to carry all the information needed to guide the development of an entire organism

But there is so much information that needs to be stored about us. How is DNA able to provide enough information for a living organism? The simple answer is that DNA molecules are very, very long Did you know a simple bacteria, E. Coli is 4 million nucleotides sequences long! This corresponds to the information storage capacity of an 8 MB hard drive! Lots of information for a tiny bacteria!

Genes carry information about making all the proteins required by all organisms Interesting, DNA makes proteins, and it is also containing them as well…

Francis Crick and James Watson The first scientists to discover the shape DNA

DNA- a double helix molecule made up of four nucleotide bases, phosphate, and the sugar, deoxyribose

The human genome is approximately 3 billion nucleotides long! The information storage capacity of a 3GB hard drive! We can think of DNA as a “genetic database” for living organisms …okay, let’s move on

DNA is made of a long sequence of smaller units strung together. There are four basic types of unit: Adenine, thymine, guanine, and cytosine

The Nitrogen Bases These bases make up the “rungs” of the ladder: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) DNA is made up of a long sequence of these units strung together.

The capital letters represent the bases: Adenine= A Thymine= T Guanine= G Cytosine= C

Know that adenine only pairs up with thymine and cytosine only pairs with guanine in the DNA molecule

Pairing of the Nucleotide Bases Adenine always pairs with thymine Guanine always pairs with cytosine

The back bone of DNA Made up of phosphate and a sugar called deoxyribose

A codon is a group of three base pairs that code for a specfic amino acid

DNA Replication Base pairs are complementary to each other because each base only bonds with the other base pair CCGA will bond to the sequence GGCT

DNA Replication

STEP 1 First, in replication, a DNA molecule is split down the middle (figure 5) The bases on each side of the molecule are used as a pattern for a new strand As new bases on the original molecule are exposed, complementary nucleotides are added Proteins help to unwind, copy, and rewind the DNA molecule

Half of each of the molecules is old DNA and half is new DNA

Mutations A change in the nucleotide- base sequence of DNA Caused by random errors in the copying of DNA Also, can be caused by things in the environment A physical or chemical agent that causes a mutation is called a mutagen

Do Mutations Matter? Changes in DNA can cause an improved trait, no change, or a harmful trait If the mutation does not change the protein that the gene makes then there will be no change to the trait Can you think of a mutation that could benefit an organism?

A mutagen might have caused this frog to develop six legs

Known Harmful Mutagens

2. What is a mutation? Is a mutation always harmful? The change in the nucleotide- base sequence of DNA. No they are not always harmful- sometimes beneficial, other times no change *Does a mutation always produce a change in the individual? Explain. No, only if it changes a protein that a gene codes for will there be a change in a trait

What is the human genome project? A project designed by the U.S. department of Energy and National Institute of Health to: Identify all the approximately 30,000 genes in human DNA Determine the sequence of the 3 billion chemical base pairs (nucleotides) Store the information in databases improve tools for data analysis Transfer data to private sector Address ethical issues stemming from the project’s findings

DNA Extracted From Strawberries

What are some practical benefits to learning about DNA? Knowledge of the variations of DNA among individuals can help diagnose, treat and someday prevent thousands of disorders that affect us Useful in crime solving cases and paternity suits Help us understand the natural capabilities of our non- human friends- that can be applied in solving challenges in agriculture, health care, energy production, etc

Questions for guess who? That’s right…for you!

Questions 1.Which two scientists are well known for discovering the structure of the DNA molecule? Francis Crick and James Watson

3.The nitrogen base pairing pattern is key to understanding how______occurs. DNA replication

DNA replication ensures that each daughter cell will have____________. All of the genetic information it needs to carry out its activities

4.DNA replication begins when_____________________________ __________________________. the two sides of the DNA molecule unwind and separate, like a zipper unzipping.

6.The molecule separates between the__________on each rung. paired nitrogen bases

Place the steps of DNA replication in order 1. The nitrogen bases that are floating in the nucleus pair up with the bases on each half of the DNA molecule 2.The two sides of the ladder unwind and separate, like a zipper unzipping 3.The new bases are attached 4.The order of the bases in each new DNA molecule will match the order of the old DNA

2, 1, 3, 4

Warm-up If this was a sequence of nitrogen bases in a DNA strand, what would its matching strand look like? A T G C G A T C T A C G C T A G

Warm Up 1. List three facts about DNA (book pages 57-59).

DNA is shaped like a twisted ladder. This shape is known as a double helix. The two sides of the DNA ladder are made up of molecules of sugar, called deoxyribose, alternating with molecules called phosphates The rungs of the ladder are made of nitrogen bases