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How Organisms Grow: Cell DivisionChromosomes: threadlike strands of DNA inside a cell’s nucleus
Mitosis - The process of Cell Division5 Phases of Mitosis:
PROPHASE: Gets everything ready to divide● Duplicate DNA● Centrioles get in right
position● Prepare cell for division
Mitosis - The process of Cell Division5 Phases of Mitosis:
PROMETAPHASE: separates duplicated genetic material● Nuclear envelope breaks
down● Mitotic spindle completed● Sister chromatids move
towards center of cell
Mitosis - The process of Cell Division (continued)5 Phases of Mitosis:
METAPHASE: pieces align for division● DNA lines up along central
axis● Centrioles send out tubules
that connect to DNA● DNA condensed into 2
chromosome strands connected with centromere
Mitosis - The process of Cell Division (continued)5 Phases of Mitosis:
ANAPHASE: separation begins● Half of chromosomes go
to one side of cell● Other half go to other
side
Mitosis - The process of Cell Division (continued)5 Phases of Mitosis:
TELOPHASE: division finishes up● Cell membrane closes in
and splits cell into two pieces
● 2 separate cells each with half of original cell’s DNA
Mitosis - The process of Cell Division (continued)CYTOKINESIS: process of cell actually dividing into two cells● Cytoplasm splits● Cell pinches off● Two new cells form
Mitosis - The process of Cell Division (continued)INTERPHASE: normal state of the cell● Known as the “resting
state”● goes about its normal
business until next cell division
Regeneration● Provides organisms with a means of replacing lost or damaged tissues
and organs (through the process of mitosis)
In Humans:
● Heals wounds and replaces damaged tissue
In Plants and Some Animals:
● Can regenerate major body parts● Planaria - a type of freshwater flatworm
that can regenerate most of its body
Asexual Reproduction● The production of new organisms without the joining of male and female
cells (through the process of mitosis)
Two Ways Organisms Reproduce Asexually:
● Fission ○ simple cell division
● Budding○ tiny bud forms on parent cell ○ copy of parent chromosomes enter bud○ when bud is fully grown, it separates from parent cell
Sexual Reproduction● Cells from two parent cells unite to form one cell called a ZYGOTE
○ Contains chromosomes from both female and male○ Human body cells have 46 chromosomes○ Zygote can’t have 92 chromosomes○ Reproductive cells only have 23 chromosomes
● Meiosis ○ the process that reduces the number of chromosomes in reproductive
cells
Stages of Meiosis8 Stages of Meiosis
1. PROPHASE I- The chromosomes condense, and the nuclear membrane breaks down,
crossing-over occurs.
2. METAPHASE I- Pairs of similar chromosomes move to the middle of the cell.
3. ANAPHASE I- Similar chromosomes move to opposite poles of the cell.
4. TELOPHASE I and CYTOKINESIS- Chromosomes gather at the poles of the cell; cytoplasm divides
Stages of Meiosis (continued)8 Stages of Meiosis
5. PROPHASE II- A new spindle forms around the chromosomes
6. METAPHASE II- Chromosomes lines up in the middle
7. ANAPHASE II- Centromeres divide, chromatids move to opposite side of the cell
8. TELOPHASE II and CYTOKINESIS- A nuclear membrane forms around each new set of chromatids, the
cytoplasm divides
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