1. Structure of DNA & Replication
(6a) Identify components of DNA and describe how information for specifying traits of an organism is carried in the DNA.
(6b) Recognize that components that make up the genetic code are common to all organisms.

2. DNA Deoxyribonucleic Acid Where is it found? ALL CELLS HAVE DNA
Nucleus of Eukaryotic Cells
Cytoplasm of Prokaryotic Cells
What does it do?
Contains genes that code for traits.
Controls cells activities

3. Structure of DNA Shape of DNA referred to as Double Helix Made up of:
Hydrogen Bonds
Shape of DNA referred to as Double Helix
Made up of:
Sugar-Phosphate Backbone
Nitrogen bases
connected by hydrogen bonds
Sugar-Phosphate Backbone
Nitrogen Bases

4. Monomer of DNA - Nucleotide
DNA is made of repeating nucleotides:
Nucleotides consist of 3 parts:
Sugar (Deoxyribose)
Phosphate
Nitrogen Bases
Sugar
Deoxyribose
phosphate
Nitrogen Base
4types

5. Circle each nucleotide in your diagram. How many nucleotides are shown?

6. Nitrogen Bases & Pairing Rules
In DNA, there are 4 possible nitrogen bases.
1 . 2. 3. 4.
Adenine
Guanine
Cytosine
Thymine
Adenine and Thymine always pair together
Guanine and Cytosine always pair together

7. Importance of Nitrogen Bases
Nitrogen bases = the genetic code
Sequence of nitrogenous bases determines the characteristics or traits of an organism.
The more similar two organisms are, the more similar their order of nucleotides or nitrogenous bases will be.
DNA -> Gene -> Protein -> Trait

8. DNA Replication Replication = making copies of DNA
When a new cell is created (through mitosis), DNA must be created to control the new cell.
One original parent DNA molecule is copied to create two identical daughter DNA molecules.
Parent DNA
Daughter
DNA

9. STEPS OF DNA REPLICATION
Double helix unwinds
STEP 2:
Parent strands separate or “unzip”
STEP 3:
Parent strands serve as templates for building new strands of DNA
STEP 4:
End result is 2 identical molecules of DNA

10. Mitosis & Meiosis
(5a) Describe the stages of the cell cycle including DNA replication and mitosis and the importance of the cell cycle to the growth of organisms.
(6g) Recognize the significance of meiosis to sexual reproduction.

11. Somatic Cells (Body cells)
Types of Cells
Somatic Cells (Body cells)
Gametes
(Sex cells)
All cells other than sex cells
Made by mitosis
Contain 2 copies of each chromosomes (homologous chromosomes)
diploid cells = # 2n
Ex. Humans =46 chromosomes
Egg and sperm cells
Made by meiosis
Contain 1 copy of each chromosome
Haploid = # 1n
Ex. Humans: =23 chromosomes

12. Steps of Mitosis – for growth and repair
Growth & DNA Replication occurs
Chromosomes condense
Chromosomes line up in middle of cell
Chromosomes pull apart
(And Cytokinesis) Cell and chromosomes divide into two separate cells

13. Disadvantages of Mitosis
Mitosis produces specialized cells (ex. Liver, heart, and nerve cells)
Controlled by gene regulation – genes turned on and off in different cells to produce different shapes, structures, and functions.
Cancer – unregulated growth of cells leading to tumors in the body.
Disadvantages of Mitosis

14. Steps of Meiosis – to produce sex cells

15. Meiosis – 2 Rounds of Division
Interphase I: DNA Replication
Prophase I: Chromosomes form TETRAD, crossing-over occurs
Metaphase I: Tetrads line up in middle
Anaphase I: Tetrads pull apart
Telophase I: 2 daughter cells produced
****NO DNA REPLICATION*****
Prophase II: 2 daughter cells prepare to divide
Metaphase II: chromosomes line up
Anaphase II: chromosomes split
Telophase & Cytokinesis: 4 genetically different daughter cells produced

16. Advantages of Sexual Reproduction
Produces GENETIC VARIATION
Offspring genetically different from each other and parents – may provide better chances of survival!
Mutations can arise in sex cells – leading to gene or chromosomal mutations.
Ex. Down’s syndrome (trisomy 21)
Disadvantages of Sexual Reproduction

17. Comparison of Mitosis & Meiosis
Produces somatic cells
For growth and repair
1 round of division
2 genetically identical cells produced
Can lead to cancer
Meiosis:
Produces gametes
For sexual reproduction
2 rounds of division
4 genetically different cells produced
Can lead to genetic abnormalities