1. Chapter 3 – Part 2– Cell Cycle
Interphase
G1 (gap 1) – metabolic activity and vigorous growth
G0 – cells that cease dividing
S (synthetic) – DNA replication
G2 (gap 2) – preparation for division
Mitotic phase
Mitosis and cytokinesis

2. Interphase – G0
G0 represents not simply the absence of signals for mitosis but an active repression of the genes needed for mitosis.
Cancer cells cannot enter G0 and are destined to repeat the cell cycle indefinitely
Most cells will leave the cell cycle, temporarily. They remain in G1 until properly stimulated to begin dividing again.
Often G0 cells are terminally differentiated: they will never reenter the cell cycle but remain in G1 until they die. (muscle and nerve cells)

3. Interphase – S phase (DNA replication)
_________untwists the double helix and exposes complementary strands
Helicase
Each nucleotide strand serves as a template for building a new ______________ strand
complementary
RNA primers
_____________are added to begin DNA synthesis
DNA polymerase III
__________________continues from the primer and covalently adds complementary __________ to the template
nucleotides
Since DNA polymerase only works in one direction:
5` to 3`
A continuous leading strand is synthesized
A discontinuous lagging strand is synthesized
__________ splices together the short segments of the discontinuous strand
DNA ligase
PLAY

4. Mitosis – Nuclear Division
Essential for body growth and tissue repair
The phases of mitosis are:
Prophase
Anaphase
Metaphase
Telophase
Cytokinesis – division of the cytoplasm
Cleavage furrow formed in late anaphase by contractile ring
Cytoplasm is pinched into two parts after mitosis ends
PLAY

5. Early and Late Prophase
Asters are seen as chromatin condenses into chromosomes
Nucleoli disappear
Centriole pairs separate and the mitotic spindle is formed
PLAY
PLAY

6. Metaphase
Chromosomes cluster at the middle of the cell with their centromeres aligned at the exact center, or equator, of the cell
This arrangement of chromosomes along a plane midway between the poles is called the metaphase plate
PLAY

7. Anaphase Centromeres of the chromosomes split
Motor proteins in kinetochores pull chromosomes toward poles
PLAY

8. Telophase and Cytokinesis
New sets of chromosomes extend into chromatin
New nuclear membrane is formed from the rough ER
Nucleoli reappear
Generally cytokinesis completes cell division
PLAY
PLAY

9. Control of Cell Division
Surface-to-volume ratio of cells
Contact inhibition
Chemical signals such as growth factors and hormones
Cyclins and cyclin-dependent kinases (Cdks) complexes

10. Cell destruction – death
Necrosis "cell homicide" -Inflammation with secondary injury to surrounding normal tissues..
Apoptosis "cell suicide". -No Inflammation or secondary tissue injury

11. Control of Cell Reproduction
Most cells divide an average of about 50 times
Mitotic clock -tips of chromosomes (telomeres) about 12,000 nucleotides
nucleotides lost with each division
When repeats are gone cell quits dividing.
Cell Differentiation - when cells develop different structures and specialized functions.
Stem cell can divide to form a progenitor cell
Click screen to add animated notes.
totipotent – can give rise to any cell type
pluripotent – can give almost any cell type in the body
multipotent – can differentiate into a limited range of cells

12. Loss of Cell Division Control - Cancer
Division to frequent dysplasia neoplasmtumor
benign -->lump in place
malignant - lump extends into surrounding tissue
resembling a crab -->metastasis
Genes that cause cancer
oncogenes activate other genes that increase cell division
tumor suppressor gene – normally regulate mitosis; if inactivated they will not regulate mitosis
Environmental causes?
Cancer treatments are directed at procedures that kill fast dividing cells. What normal cells do they also effect?

13. Protein Synthesis Each triplet specifies coding for an amino acid
DNA serves as master blueprint for protein synthesis
Genes are segments of DNA carrying instructions for a polypeptide chain
Triplets of nucleotide bases form the genetic library
Each triplet specifies coding for an amino acid

14. Transcription
Transfer of information from the sense strand of DNA to RNA
Transcription factor
Loosens histones from DNA in the area to be transcribed
Binds to promoter, a DNA sequence specifying the start site of RNA synthesis
Mediates the binding of RNA polymerase to promoter
DNA triplets are transcribed into mRNA codons by RNA polymerase

15. Translation to Polypetide
Roles of the Three Types of RNA
Form Initiation complex
Messenger RNA (mRNA) carries the genetic information from DNA in the nucleus to the ribosomes in the cytoplasm
Transfer RNAs (tRNAs) bound to amino acids base pair with the codons of mRNA at the ribosome to begin the process of protein synthesis
Ribosomal RNA (rRNA) is a structural component of ribosomes

16. Information Transfer from DNA to RNA
Return

17. Centrioles
Small barrel-shaped organelles located in the centrosome near the nucleus
Pinwheel array of nine triplets of microtubules
Form the bases of cilia and flagella
Organize mitotic spindle during mitosis
kinetochore
Return

18. Back