1. 3.0 DNA is the inherited material responsible for variation
Objectives:
Describe the relationship among chromosomes, genes, and DNA and their role in storing genetic information
Distinguish between cell division during Asexual reproduction and cell division during Sexual reproduction.
Investigate the transmission of characteristics from parent to offspring, and identify examples of different patterns of inheritance.
Identify examples of dominant and recessive characteristics.
One of most endangered species on earth.
Only left in the world
Needs captive breeding program to have a chance at surviving.
With so few Bengal tigers left how can variation be created?
Scientists and geneticists can analyze their DNA to determine which two tigers should mate and reproduce. By understand DNA and Chromosomes scientists can predict the characteristics the tiger cubs are likely to have.

2. 3.1 DNA – Transmitter of Genetic Code
Canis Familiaris
Understanding how the genetic code is transferred from one generation to the next led to the breeding of purebred dogs and was not intended to promote variation.
However, many different breeds of dogs were developed that had specific, desired characteristics.
Making Canis Familiaris one of the most physically varied species on Earth.

3. 3.1 DNA – deoxyribonucleic acid,
Characteristics are passed on from one generation to another within a species through the genetic code of the parents.
This genetic code is called DNA.
DNA is the “blueprint” that is passed on from the parents to the offspring is found in a molecule of the cell nuclei.
This molecule, deoxyribonucleic acid, (DNA) is the inherited material responsible for variation.
All living organisms contain DNA in their cells.

4. 3.1DNA continued
Oswald Avery, a Canadian Scientist proposed that a large molecule first fount in cells’ nuclei was responsible for storing such information and passing it on. Therefore he proposed that DNA was the material of inheritance.

5. 3.1 DNA and the Genetic Code
DNA was discovered prior to 1944.
All DNA molecules contain exactly the same chemicals, but the way the chemicals combine determines the characteristics of the organism.
James Watson and Francis Crick unraveled the structure of DNA, revealing the key to the multitude combinations of variation that are possible.
The DNA molecule is like a ladder twisted into a spiral (see image). The sides of the ladder are the same in all DNA molecules, but the rungs are what make the variations. Each rung pairs up two of the following chemicals: guanine (G), cystosine (C), adenine (A) and thiamine (T).
The arrangement of these four chemicals creates the code that the cells are able to interpret. This is the genetic code of the organism.

6. 3.1 Chromosomes
DNA contains all the instructions, which create the organism's characteristics.
The multitude of characteristics for each organism means that there is a lot of DNA in any one cell.
This DNA is arranged in the cell in compact packages, called chromosomes.
Every human cell contains 46 chromosomes. In order to have a complete human organism, all 46 of the chromosomes must be present.
Not all organisms have the same number of chromosomes (Dogs have 78, cats have 38).
Every cell of a human contains 23 pairs of chromosomes (23 x 2 = 46).
Not all of the chromosomes from species to species are the same, which accounts for the different characteristics between the species.

7. 3.1 Chromosomes continued
If the DNA from a typical human body cell was stretched out it would be about two metres long, more than times longer than the dell it came from.
To fit such a large amount of DNA into their cells, organisms arrange their DNA into packages.
These packages are called Chromosomes.

8. 3.1 Genes
A single gene is an uninterrupted segment of DNA, which contains the coded instructions for the organism.
Researchers found out that (by working on the fruit fly):
Genes are located in the chromosomes
Each chromosome has numerous gene locations
Genes come in pairs
Both genes in a pair carry DNA instructions for the same thing. Leg length in the fruit fly is an example.
In the fruit fly, the two leg-length genes occupy matching locations on the two chromosomes.
DNA code may not be exactly the same in both locations

9. 3.1 David Vetter “bubble boy”
David Vetter lived for 12 years inside a plastic bubble.
He had Severe Combined Immune Deficiency (SCID), a genetic disorder that made his body incapable of fighting disease.
The gene for SCID is found on the X Chromosome.

10. 3.1 Alleles Homework Assignment Check and Reflect page 45
Offspring inherit genes from both parents.
The genes exist in an array of possible forms that differ as to their exact DNA sequence.
These variations in forms are called alleles.
The ultimate combination of the chromosome pair is what makes the variation possible - combining the different variations of different characteristics to create a unique variation.
Homework Assignment
Check and Reflect page 45
Questions 1 – 4, 6, 7, 8
Due next class

11. 3.2 Cell Division Mitosis #1 Cell Division and Asexual Reproduction
Asexual reproduction involves only one parent and
does not use specialized sex cells.
Offspring are genetically identical to the parent.
In single celled organisms, binary fission enables the
parent cell to split its contents equally between the two
new cells.
1st - parent cell duplicates its DNA first then divides.
Duplicated DNA lines up at center of the cell.
Cell begins to split down the middle taking half of the DNA with it.
Two cells are created with equal amounts of DNA to its parent cell.
In multi-cellular organisms the process that produces two new cells with the same number of chromosomes is called Mitosis (growth and cellular repair).
MiToSis = produces Two new cells with the Same number of Chromosomes.
Mitosis

12. 3.2 Cell Division Mitosis vs Meiosis
#2 Cell Division and Sexual Reproduction in Plants and Animals
Sexual reproduction uses specialized cells (gamates) usually among 2 parents.
The offspring have genetically different characteristics,
The specialized sex cells (gametes) unite to form a zygote, which develops into the new organism.
If the gametes or sex cells contained the same amount of DNA as every other cell, then the Zygote would have twice the amount of DNA it needs, So…… the body must somehow create special cell with half the number of Chromosomes.
Meiosis is cell division that produces 4 cells each with half the DNA.
When the male and female gametes unite, the Zygote has a complete set of DNA. .
Meiosis = 4 sex cells each having half the number of chromosomes.
Mitosis vs Meiosis

13. Meiosis – When cells in our bodies divide in such a way that the amount of DNA in the cell is cut in half.  Why do we do this?  To make reproductive cells - gametes.  If one forms a cell (or gamete) with only half the normal amount of DNA, and then combines that cell with someone else's gamete through fertilization, the result will be a new individual with an entirely new combination of DNA. MeioSiS = Meiosis Makes Specialized “Sells”
Copy, divide, divide again
46 chromosomes
46 chromosomes
23 chromosomes
23 chromosomes
Zygote
46 chromosomes

14. Assignment:
Read all of pages 46 – 48 including the “infobit” and the “Research” columns
Complete the Check and Reflect Questions 1-7