The Cell Cycle

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Today’s Lesson

Is brought to you by the letter C

And the numbers 23 and 46

Important Vocabulary

• Chromatin: Long, tangled strands of DNA found in the cell nucleus during Interphase

• Chromosomes: Structures that carry the genetic material that is copied and passed from generation to generation of cells. Humans have 23 pairs of chromosomes; 46 total chromosomes

• Chromatids: Chromosomes duplicate during S phase and are attached by a centromere. The two copies are called chromatids.

Chromatids & Centromere

Vocab. Continued . . .

• Centromere: Cell structure that joins the two chromatids.

• Homologous Chromosomes: Paired chromosomes with genes for the same traits, structure and function. Humans have 23 Homologous Chromosomes.

• Parent Cell: Original cell in interphase, before division occurs.

• Daughter Cell: Cells produced from parent cell at the end of the cell cycle.

Cell Cycle

• Made up of 3 Phases– Interphase

– Mitosis

– Cytokenesis

Interphase

• Cell spends 90% of its lifetime in interphase

• G1 phase: cell grows

• S phase: DNA (chromosomes) replicate

• G2 phase: cell prepares to divide

Mitosis

• Occurs AFTER interphase is finished

• Consists of 4 phases:– Prophase– Metaphase– Anaphase – Telophase

Prophase

• Early – chromatin coil up and become chromosomes. Each crhomosomes is made up of 2 identical parts called chromatids joined by a centromere

• Mid – nuclear envelope begins to disappear

• Late – nuclear envelope gone and centrioles move towards poles as spindles form.

Metaphase

• Early – centrioles at poles and spindle fibers attach to centromeres of chromosomes

• Mid – chromosomes in the process of lining up along the equator of the cell

• Late – chromosomes lined up along equator of cell.

Anaphase

• Early – Centromeres split apart as spindles bring chromatid pairs towards opposite poles

• Mid – chromatids moving closer to opposite poles

• Late – chromatids at opposite poles

Telophase

• Early – Nuclear envelope begins to form

• Late – 2 distinct daughter cells are formed

Can you guess what my favorite phase is?

Telly – phase!

Cytokenesis

• Cytoplasm divides• IN PLANTS: cell plate forms between cells,

cell membrane forms around each side of cell plate, and cell wall forms around membrane

• IN ANIMALS: cell membrane pinches off between old and new cell, creating 2 separate cells

Let’s count how many daughter cells come from 1 parent cell!

1. . . . 2. . . . . 2 daughter cells!