AP Bio: Cell Division and Cell Communication

Unicellular organisms: reproduction

Multicellular: development, growth, and repair

Why do cells divide?

Binary Fission

division of cells in a prokaryote

Mitosis

Division of the nucleus for eukaryotes

Interphase and Mitosis

What does the cell cycle include?

Interphase

Prep stage for cell division; happens 90% of the time

Mitosis phase

combines mitosis and cytokinesis; when the cell separates; 10% of the time

G1, S, and G2

What are the components of interphase?

G1

cell growth

S

Synthesis of DNA where it is duplicated and replicated

Need the same DNA in the new cell

Why does DNA duplicate?

G2

Cell growth/prep for division

Chromatin

uncondensed DNA that spreads out; can’t see separate chromosomes

PMAT (Prophase, Metaphase, Anaphase, Telophase)

Whats a good acronym for mitosis?

Prophase

1. already duplicated DNA condenses into 2 sister chromosomes

2. centrosomes move to the opposite sides of the cell and sprout microtubules

3. nuclear envelop disintegrates

Centromere

waist of chromosome where sister chromatids are closely attached

sister chromatids

identical copies

Metaphase

m = middle

1. protein kinetochore “anchor” forms at the centromere of each chromosome

2. microtubules from the mitotic spindle attach to the kinetochore

3. spindle fibers move chromosomes to the middle of the cells (to metaphase plate)

   1. Some don’t attach

kinetochore

complex proteins associated with the centromere of a chromosome during cell division to which the microtubules of the spindle attach

Anaphase

1. Sister chromatids separate and move along microtubules toward opposite sides of the cell

   1. sister hromatids turn into daughter chromatids

   2. microtubules shorten when they connect to the kinetochore

Telophase

1. nuclear envelop reforms

2. chromosomes unwind and go back into chromatic form

Cytokinesis

Animal Cells

• contracting ring of proteins squeezes the cytoplasm and creates 2 cells

Plant Cells

• vesicles form together to make a cell plate, which becomes the cell membrane and cell wall

contractile ring protein

squeezes the cytoplasm in half and creates to cells

G₁,G₂, and M

What are the three checkpoints in a cell

checkpoints

checks to make sure everything is fine in the cell process

if everything is okay the cell can proceed

if something is wrong they stop the cell and transport it to G₀

G₁

checks if the cell is big enough and has enough nutrients

• most important checkpoint

• passes failed cells to G₀

G₀

period where the cell doesn’t divide or prepare to divide

• also serves as a resting place b/c of lack of nutrients

G₂

makes sure that the cell is big enough and DNA is replicated properly

M checkpoint

checks for internal controls

• crucial for correct cell division

• internal controls show that there are external controls

external controls

signals that control cell growth and reproduction

density-dependent inhibition and anchorage dependence

What are the types of external controls/growth factors?

density-dependent inhibition

if there are too many crowded cells it will signal to stop dividing

• signals are dependent on amount of other cells

growth factors

proteins released by certain cells that stimulate cells to divide

anchorage dependence

cells need to be on a surface in order to divide

• cell division stops/pauses

• damage repair system is activated

  • self destruct system is activated

What happens when there is a problem with the DNA or cell found at a checkpoint?

yes, it can just go back and repair itself

Can a cell repair itself if it has moderate damage?

cells undergo apoptosis

What happens to a cell if there is severe damage?

apoptosis

programmed cell death

cancer

unregulated cell division

• requires 6-9 different mutations in oncogenes and tumor suppressor genes

• doesn’t exhibit growth factors

• genes that code for accelerator or brake proteins has a mutation that makes the protein function incorrectly

• cell zooms though the checkpoints without stoping and ignoring signals that say to slow down

How does cancer appear?

oncogenes and tumor suppressor genes

Where do mutations typically appear?

proto-oncogene

protein that tells cells to divide moreo

oncogene

mutated proto-oncogene that causes cells to divide out of control

• accelerator

• loses a function

• binds to more receptors and growth factors

tumor suppressor genes

encode proteins involved in suppressing cell division

• if mutated it doesn’t tell cells to stop dividing

benign tumor

abnormal cells that stay at the original site

• won’t grow or become dangerous

malignant tumor

invaded surrounding tissues

• has potential to keep growing and spreading

• stage 1-3

metastasis

malignant cells have spread from the original site to the other organs/body parts

• secondary tumor presents

• stage 4

• surgery

• radiation

• chemotherapy

• gene therapy

Types of cancer treatments

Asexual reproduction

• 1 parent

• offspring identical to parent

• mitosis/binary fission

  • pros: don’t have to find another mate which takes energy and resources

Sexual reproduction

• 2 parents

• offspring NOT identical to parent

• meiosis

• pros: creates genetic diversity

46 chromosomes and 23 pairs

How many chromosomes and pairs do humans have?

Males have an XY

Females have XX

How do you tell a male from a female in chromosomes?

you have 3 copies of chromosome 21

What happens if you have down syndrome?

no sperm and egg is not made by mitosis.

you would end up have 92 chromosomes

Is sperm and egg made by mitosis?

zygote

egg fertilized by sperm

23 chromosomes

How many chromosomes are in an egg or sperm

meiosis

• production of gametes

• chromosome number decreases

• diploid→haploid

  • 46→23

  • 2n→n

diploid

a full set of chromosomes

somatic cells

body cells that don’t include gametes

haploid

one set of chromosomes

gametes

egg/sperm cells

fertilization

chromosome number is restores

• haploid → diploid

  • n → 2n

homologous chromosomes

same genes but different alleles

• not identical

• have same genes

• two different copies of chromosomes

• one from each parent

• code for same inherited information

sister chromatid

two identical copies formed by the replication of a single chromosome

• made during s phase so they have to be identical

Interphase→Prophase 1→Metaphase 1→Anaphase 1→Telophase 1→Cytokinesis 1→Interkinesis→Prophase 2→Metaphase 2→Anaphase 2→Telophase 2

What are the steps of Meiosis

2 cell divisions

How many cell divisions does meiosis have?

Prophase 1

• DNA is already doubled

• homologous chromosomes get together to form a tetrad

  • crossing over/recombination

crossing over

homologous pairs swap pieces of chromosomes at the inner chromatids at the tips at random

• increases genetic diversity

• DNA breaks and re-attaches

Metaphase 1

tetrads line up in the middle of the cell in pairs

• the side that each chromosome lines up is random

  • same amount of chromosomes as mitosis

independent assortment

which side each chromosome lines up at random

• increases genetic diversity

Anaphase 1

• homologous chromosomes are pulled apart

• still have a full set of chromosomes

Telophase 1

• mitosis spindles go away

• nuclear membrane reforms

Cytokinesis 1

• cytoplasm divides to form two daughter cells

interkinesis

resting stage that certain cells go to between meiosis 1 and 2

meiosis 2

separation of sister chromatids

• retain same number of chromsomes

• basically mitosis

• chromatids are no longer sisters becuase of recombination and random assortment

• 1n→1n

Crossing over, independent assortment, and random fertilization

What are the 3 ways genetic variation is introduced?

4 daughter cells

By the end of meiosis how many daughter cells should you have?