Ch. 11) The Cell Cycle and Cell Division

what cellular events occur in all organisms?

cell division signals, DNA replication, DNA segregation, cytokinesis

why do cells divide?

to increase body size, to replace worn out or dead cells, repair damaged tissue, and pass on genetic information

what is the difference between haploid and diploid?

refers to the amount of chromosomes in a cells nucleus. Gametes and sperm cells are haploid because they contain one set of chromosomes, 23. Somatic cells are diploid because they contain a full set of chromosomes, 46.

what is the cell cycle?

the phases a cell goes through to produce daughter cells

what are the phases of the cell cycle?

interphase, mitosis, and cytokinesis

what is interphase?

nucleus is in tact. Has 3 phases: G1, S, and G2

what is the G1 phase of interphase?

cell growth to prepare for DNA replication. Chromosomes are chromatids

What is the S phase of interphase?

DNA is copied and sister chromatids come together. Centrosomes are replicated

What is the G2 phase of interphase?

cell does final growth checks and prepares for the cell to divide. Prepares for division by creating structures that can be used for moving the chromatids

what cells trigger the transition from one phase of interphase to the next?

cyclin-dependent kinases (CDKs)

how does a cyclin-dependent kinase function?

Cyclin binds to CDK and exposes its active site, a protein substrate and ATP bind together to produce a phosphorylated protein, the protein then regulates the entire cell cycle.

what cell controls the G1 to S transition?

CDK in the restriction point (R)

what role does the retinoblastoma protein (RB) do in the restriction point?

RB inhibits the cell cycle but when phosphorylated by cyclin-CDK protein, RB becomes inactivated and does not block the cell cycle anymore

what does mitosis produce?

2 identical sets of cells (2 cells with the same amount of DNA)

What are the stages of mitosis?

PPMAT

What is prophase?

chromosomes become visible and are held together by cohesin, spindle fibers form, nuclear envelope disappears and kinetochore (prometaphase)

What is metaphase?

The centrosomes from the spindle fibers pull at the kinetochores of the chromosomes to align the chromosomes at the midline of the cell

What is anaphase?

the spindle fibers pull on the centrosomes and separate them into sister chromatids

What complex separates any leftover cohesin at the centromeres of a cell from metaphase to transition to Anaphase?

anaphase promoting complex (A P C)

What is telophase?

cells move to the spindle poles, chromosomes condense, two nuclear membranes are formed

What is cytokinesis?

the division of the cytoplasm

how does cytokinesis differ for plants and animal cells?

in animal cells- microfilaments of actin and myosin interact to pinch the cell in half

in plant cells- golgi apparatus create vesicles that fuse together to form a cell plate and divide the cell (cell plate maintains a cell wall)

what is sexual reproduction?

fusion of haploid cells to create 4 haploid daughter cells

what is a gamete?

sperm and egg cells, fuse together to make the zygote. Contain only one set of chromosomes and are haploid (n)

fertilization

2 haploid cells fuse together to form a diploid zygote, 2n

what is meiosis?

mitosis 2x, two nuclear divisions but DNA is replicated once. It ensures diploid cells from mitosis become haploid and each cell will contain 23 chromosomes

What is Meiosis I?

duplicated chromosomes line up and cross over in prophase at the chiasmata and creates recombinant chromatids. Random arrangement at metaphase, chromosomes line up in the center of the cell and then are separated. Anaphase, the homologous pairs are separated. Telophase produces 2 haploid cells

What is Meiosis II?

same steps as mitosis, 2 haploid cells are created

how many sperm cells are produced in meiosis?

4 sperm cells

how many egg cells are produced in meiosis?

1 egg, 3 polar cells

what are some errors in meiosis?

nondisjunction = homologous pairs not separating at anaphase I or sister chromatids not separating at meiosis II. Nondisjunction results in aneuoploidy which is a excessive or lack of chromosomes

what is translocation?

a piece of chromosome breaks and attaches to another chromosome

what is polyploidy

organisms with extra sets of chromosomes

necrosis

cell is damaged or starved of oxygen and nutrients

what happens in apoptosis?

cell detaches from neighboring cells, chromatin is digested by enzymes that cut DNA between nucleosomes, the cell forms membrane lobes called blebs that break away from the cell, surrounding cells ingest the cell

what signals initiate apoptosis?

hormones, growth factors, viral infections, toxins, extensive DNA damage. They act through signal transduction pathways which can affect mitochondria and kill the mitochondria and all ATP production.

what is a tumor?

a large mass of cells

what is an oncogene protein?

causes cells to divide uncontrollably

what is a tumor suppressor?

prevent cells from rapidly dividing, inactive in cancer cells

what is P53?

transcription factor in the cell cycle, have mutations in the gene of tumors