Genes and DNA

Chapter 6

DNA Fun Facts… Nearly 6 feet of DNA strands are located

in the nucleus of every cell in your body We have over 3 billion base pairs in

our DNA Every person’s DNA is 99.99% similar to

that of another person It is estimated that 98.5% of the

chimpanzee genome is the same as the human genome.

Sec. 1: What does DNA look like? Goals:

List 3 important events that led to understanding the structure of DNA

Describe the basic structure of DNA

Explain how DNA can be copied

Important People in DNA’s discovery…. 1…Erwin Chargaff

2…Rosalind Franklin

3…James Watson and Francis Crick

•Chargaff’s rules!

•She discovered the shape of DNA using X-rays

•Built the 1st model of DNA

Amount of A=T, G=C

DNA Short for “deoxyribonucleic acid” Is a large chemical molecule that

resembles a twisted ladder Contains all the genes that

determine the traits of an organism Found inside every living cell on

Earth

DNA contains the following:

Four Bases (these make the ladder rungs)

A=adenine, T=thymine, G=guanine, C=cytosine

Sugar and Phosphate (make the sides)

( Sides are also called the backbone )

Bases are complementary:

A always pairs with T

G always pairs with C

Therefore….CCTAG complementary to GGATC

Nucleotides They are the subunits of DNA

They contain a sugar, phosphate, and one of the 4 bases:

Genome:

the genome is the entirety of an organism's hereditary information

DNA’s Shape: Double helix

Tap for Brainpop !

When copies are made…

DNA is copied every time a cell divides.

Each new cell gets a copy of all the DNA

Making Copies of DNA: Replicate: this means making

copies

Each base only pairs with one other base: A-T C-G

This means each side of the DNA strand is complementary

Write the complimentary strand:

ATCGTTAGGCT

How copies are made:

During replication, the DNA molecule splits (unzips) down the middle where the bases meet

As the bases on the original molecule are exposed, complementary nucleotides are added to each side of the ladder

“see diagram next slide”

Each half of the molecule is old DNA,

and half is new DNA:

Tap for animation

Nucleotides come from a variety of sources, but primarily from the foods you eat. Animals and plants also have genomes, do not forget. So, when you eat vegetables or any kind of meat or fruit, you're also ingesting that organism's genome. So, your body metabolizes all these things, along with proteins, lipids, carbs, etc. So, the nucleic acids are metabolized and broken down into nucleotide bases. These can then be used to replicate your own genome. Additionally, some of your own cells that die will release their genomes, and the nucleotides in these can be recycled.

Sec. 2: How DNA Works

It is the of nucleotides that creates the

code of life.

One half strand of DNA has a complementary half and the sequence is preserved.

The bases in DNA: The bases read like a book. A, G, T, C form the alphabet of the code. Groups of THREE bases code for a

specific amino acid. Strings of these amino acids make up

proteins.

Each gene is a set of instructions for making a protein.

The big idea:

Gene’s Sequences of A’s, G’s, T’s, and C’s tell the cell what Protein to make.

Proteins: Are everywhere in cells. Act as chemical messengers. Are the reason living things look so

differently from each other.

1.Enzymes are proteins. Enzymes catalyze chemical reactions - helping reactions happen as needed.

2. Proteins are structural elements of organisms.

3. Proteins make up parts such as hair, horns, hooves, nails, ...

4. Proteins are integral parts of membranes, helping to transport materials and acting in cell recognition.

5. The cytoskeleton that gives cells shape and support are made of protein, as well as the spindle fibers, cilia, flagella, centrioles, ...

6. Proteins carry oxygen, give immunity, contract muscles, ..

Genes Make Proteins (which are made up of amino acids): 1. A copy of a portion of DNA is made

and transferred out to the cytoplasm This copy is called mRNA (messenger

RNA) 2. The copy is fed through a ribosome,

three bases at a time 3. Transfer molecules feed the correct

amino acid to the ribosome 4. Amino acids are dropped off and joined

together to make the correct protein

•arginine - arg - R (•asparagine asn - N (gif, interactive) •aspartic acid - asp - D (gif, interactive) •cysteine - cys - C (gif, interactive) •glutamine - gln - Q (gif, interactive) •glutamic acid - glu - E (gif, interactive) •alanine - ala - A (gif, interactive) •glycine - gly - G (gif, interactive) •histidine - his - H (gif, interactive) •isoleucine - ile - I (gif, interactive) •leucine - leu - L (gif, interactive) •lysine - lys - K (gif, interactive) •methionine - met - M (gif, interactive) •phenylalanine - phe - F (gif, interactive) •proline - pro - P (gif, interactive) •serine - ser - S (gif, interactive) •threonine - thr - T (gif, interactive) •tryptophan - trp - W (gif, interactive) •tyrosine - tyr - Y (gif, interactive) •valine - val

Watch the “Gene Scene” !

Genome:

the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA.

Human genome analogy:An analogy to the human genome stored on DNA is that of instructions stored in a library:

•The library would contain 46 books (chromosomes)

•The books range in size from 400 to 3340 pages (genes)

•which is 48 to 250 million letters (A,C,G,T) per book.

•Hence the library contains over six billion letters total;

•The library fits into a cell nucleus the size of a pinpoint;

•A copy of the library (all 46 books) is contained in almost every cell of our body.

Gene therapy and colorblindness video

DNASong

!http:/

/www.youtube.com/watch?

v=FUA6_Ucw3i

4

Changes in Genes: When there is a change in the

order of bases in an organism’s DNA it is called a

Three Types of Changes in Genes:

1. Substitution: Base pair replaced

Ex.

2. Base pair added: Insertion:

Ex.

3. Base pair removed: Deletion

Ex.

Genetic disorder: Sickle Cell Anemia Happens with red blood cells GAA changed to GTA This substitution makes red blood

cells that have a distorted shape:

Mutation can result in:

1. A genetic disorder (possible death)

2. An improvement

3. No change at all

Big Deal?

Cells do make special proteins to detect errors in DNA (DNA police!)

When an error is found, it is usually fixed

(but not always)Correct sequence stolen!

Things that can cause a mutation in DNA

Examples: UV radiation, excess of X-Rays,

asbestos ( see next slide!), chemicals in cigarette smoke

ASBESTOS:

In the ground

Wrapped around a pipe

Why was it used?

From the time that asbestos was discovered in the first century, its properties amazed people. It had the ability to protect from heat, flames, noise and condensation. In fact, early Greeks used it for both lamp wicks and clothing.

By the 1800s, asbestos was considered to be even more of a “miracle mineral” and was used in conjunction with the growth in industry. Using this readily available and inexpensive material in all manners of household construction offered many benefits, with no visible drawbacks, at the time. Asbestos could be used to fill spaces, cover items, mix with liquids or combine with paints. It could keep flames lit, heat in, cold out, sound clear, damp areas dry and cement strong. In fact, by the 1970s it seemed that mankind was still discovering uses for asbestos. It was put into paints, adhesives, clay, crayons, protective wear, metal ware and, of course, appliances. With its adaptability, it seemed to meet countless needs in different ways.

Genetic Engineering Transfer genes from one

organism to another:

Human milk gene in cow Firefly gene in a plant

Genetic Identification:

Identifies unique patterns in an individual’s DNA