1. Introduction to Genetic Continuity

3. Cell Division Asexual Reproduction Sexual Reproduction
The production of offspring from a single parent
Offspring inherit the genes of that parent only
Reproduction without sexual intercourse
Sexual Reproduction
The production of offspring from the union of 2 sex cells, one different from each parent
Genetic make-up of offspring is different from that of either parent
Reproduction with sexual intercourse

4. Cell Division Fertilization Possible advantages of reproducing:
the union of male and female sex cells (egg & sperm)
Possible advantages of reproducing:
Asexually?
Sexually?

5. Cell Theory Recap All living things are made up of 1 or more cells.
Cells come from pre-existing cells by cell division.

6. Principles of Cell Division
Early studies show that a single cell makes two cells by an equal split of nuclear contents in a process call Mitosis
Cytokinesis refers to the equal split of cytoplasm and the organelles contained within it
Parent Cell is the cell that divides
Daughter or Sister Cells are the 2 cells that result from the division (they are genderless)

7. Principles of Cell Division
A cells genetic information is contained in the DNA (deoxyribonucleic acid) molecules in the nucleus
The DNA molecules are found in structures called chromosomes
A human body cell contains 46 chromosomes
To prepare for mitosis the cell makes a duplicate copy of each DNA molecule
this causes each chromosome to be doubled
Replication & separation of duplicate chromosomes ensure that the daughter cells are genetically identical to each other and the parent cell
Replication ensures future cell divisions because each daughter cell is a potential parent cell for the next generation

8. Principles of Cell Division
How many chromosomes result after the cell division?
All body cells have the same genetic information because all cells in the body are made from the same fertilized egg
Muscle, brain, and heart all contain the same chromosomes
Not all cells in the body have the same shape or perform the same functions
Why do different cells do different jobs? How do specialized cells know which genes to use?
The million dollar question…

9. Investigation Break Comparing SA’s of small and large cells
Work in partners, but each record your own work
You need 8 sugar cubes & 1 ruler
Record your data & answer questions on next slide
You have 15-minutes

10. Ponder away…
Measure the SA of 8 individual cubes, then the SA of 8 cubes stacked together
If the cubes were cells, which would have the larger SA?
Describe the SA-Volume relationship
Why is this useful to a cell?

11. Answers
The total SA of the cube would be half the total SA of the eight individual cubes.
The smaller cells would have a larger total SA.
The ratio of cell surface area to volume would be greater for smaller cells than for larger ones.
Active cells need a maximum SA to quickly allow nutrients to diffuse in and waste to diffuse out.

12. The Cell Cycle Sequence of events from one cell division to another
Cycle doesn’t pause after each phase, it is a continuous process
Nuclear division makes up only a small part of the cell cycle
Interphase makes up the larger remaining portion of the cell cycle

13. Interphase Chromatin Centromere Sister Chromatids
Genetic material during interphase
Tangled fibrous complex of DNA and protein with a eukaryotic nucleus
Centromere
The structure that holds the chromatids together
Sister Chromatids
Chromosome and its duplicate attached to one another by a centromere
The pair remain attached until separated during mitosis

15. Prophase Early Prophase Late Prophase Chromosomes continue to condense
Chromosomes condense becoming
shorter and thicker
Centrioles move to opposite poles of cell
Spindle fibers start to form
Centrioles are small protein bodies that are found
in the cytoplasm of animal cells
Spindle fibers are protein structures that guide chromosomes during cell division
Late Prophase
Chromosomes continue to condense
Centrioles assemble and spindle fibers attach to centromeres of chromosomes
Nuclear membrane starts to dissolve

16. Metaphase Chromosomes line up at the equatorial plate
Nuclear membrane completely dissolves

17. Anaphase
Centromeres divide forming chromosomes (before they were chromatids)
Move to opposite poles of cells
Identical set of chromosomes moves to each pole

18. Telophase Chromosomes lengthen again Spindle fibers disappear
Nuclear membrane forms around chromosomes
Human have 46 unique chromosomes in each new nucleus

19. Cytokinesis
Cytoplasm starts to divide once chromosomes are at opposite poles of cell
In animal cells, a furrow pinches off the cell into 2 parts
In plant cells, a cell plate forms between the two chromatin masses. It eventually develops into a cell wall.