Unit 5: Cell Cycle Mitosis/Meiosis

Cell Divison

The continuity of life is based on the reproduction of cells

why do cells divide

Reproduce

Renewal

Repair

Replacement

Make new cells

cell cycle

the entire life of the cell, including growing and reproducing.

How is chromatin formed

chromatin is formed by wrapping DNA around proteins called histones

DNA

our genetic material, our genes

Genes

specific sections or parts of our DNA

Chromatin

DNA and proteins

chromosomes

thread-like structures in the nucleus that are made of chromatin

genome

all of our DNA, all DNA in an organism

What does each duplicated chromosome have

two sister chromatids that are identical

Centromere

where the duplicated sister chromatids attach to form a chromosome

interphase

90% of the cell's life, during which growth, protein synthesis, and chromosome duplication occurs. Has 3 sub-phases

G1 phase

"first gap" the cell grows

G0

stopping point for some cells that don't divide

S phase ( synthesis phase )

"synthesis" chromosomes duplicate

G2 Phase

"second gap" cell grows more and prepares for division

What happens during the mitotic phase ?

the cell divides , subphases include mitosis and cytokinesis

mitosis

when the nucleus divides

cytokinesis

when the cytoplasm and the rest of the cell divides

Mitotic Spindle

a structure made of microtubules and proteins that controls chromosome movement during mitosis

where is the mitotic spindle made?

centrosome ( organelle)

Asters

short microtubules that extend out from the centrosome

Kinetochores

are where the asters attach to chromosomes

What happens in prophase - mitosis

Chromatin condenses & can be seen in microscope

The nuclear membrane breaks up

Microtubles begin to get into place around the chromosomes

What happens in Metaphase - mitosis

Chromosomes line up in the middle of the cell (metaphase plate)

what happens in anaphase - mitosis

Sister chromatids pull apart and begin to move to opposite sides of the cell

what happens during telophase - mitosis

Two new nuclei begin to form

New nuclear membranes begin to form

What happens in cytokinesis - mitosis

The cytoplasm of the parent cells divide to form 2 new daughter cells

cleavage furrow

In animals, a cleavage furrow forms to pinch the cell in two

cell plate

made of vesicles that are filled of cellulose and forms between two new cells to create a new cell wall

Binary fusion

Prokaryotes (bacteria and Archaea) reproduce by binary fission, meaning "division in half."

Origin on replication

Bacteria have one chromosome, which is a big circle, which reproduces starting at the origin of replication.

cell cycle control system

The cell cycle is driven by molecular signals present in the cytoplasm, called the

G1 checkpoint

"restriction point" if the cell is told to stop it goes to G0 non-dividing phase (like muscle and nerve cells)

Kinases

enzymes that activate or deactivate proteins of the cell cycle

cyclins

are proteins that must be attached to kinases to be active; they are cyclin dependent kinases (Cdks)

MPF

"maturation-promotion factor" triggers G2

density-dependent inhibition

cells are over-crowded so they can not continue growing

anchorage dependence/ dependent

the cells must be attached to something to grow

Cancer cells are neither..

density dependent or anchorage dependent

What do cancer cells invade ?

other tissues

Transformation

when a normal cell becomes cancerous

Bengin tumor

Cells in the mass that remain together and do not spread from the area of local growth

metastasizes

cancer moves to other tissue

malignant tumors

invade surrounding tissues and can metastasize

Radiation

damages cancer cell DNA

chemotherapy

toxic drugs interfere with the cell cycle of rapidly dividing cancer cells

surgery

physically cut out the cancer cells

Stem cells

Unspecialized cells that can become many different cells (differentiate)

what do stem cells become in early development

In early development, they become every tissue in the body

what can stem cells be used to help cure

Could be used to grow healthy tissues to cure:

Diabetes, Parkinson's, Alzheimer's, heart disease,e

genetics

the scientific study of heredity and hereditary variation.

Heredity

is the transmission of traits from one generation to the next.

variation

how offspring differ from their parents and siblings

Genes

segments of DNA. Copies of genes (with some differences due to crossing over) are passed from parents to children.

gametes

sex cells, eggs and sperm, that carry genes from one generation to the next.

fertilization

Process in sexual reproduction in which male and female reproductive cells join to form a zygote

zygote

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

embryo

the developing human organism from about 2 weeks after fertilization through the second month

fetus

In humans, the term for the developing organism between the embryonic stage and birth.

newborn

birth to 1 month

karyotype

a picture of all 23 pairs of chromosomes (duplicated to be 46) arranged in order from 1 🡪 23.

homologous chromosomes

are pairs; one from Mom and one from Dad

autosomes

non sex chromosomes we have 22 pairs

sex chromosomes

chromosomes that determine our gender we have one pair of these

Diploid cell characteristics

Diploid Cells:

2n

46 chromosomes

Somatic cells (body cells)

2 sets of chromosomes

2n = 46

Skin, nerve, muscle...all body cells

Zygotes

Haploid cell characteristics

Haploid Cells:

n

23 chromosomes

Gametes only

Egg and sperm

1 set of unduplicated chromosomes

n=23

Sex cells

Meiosis

cell division that reduces the number of sets of chromosomes from two to one, creating gametes (eggs and sperm).

It ONLY happens in the ovaries and testes.

Gametes have ..

half has many chromosomes

Interphase - meiosis

Chromosomes replicate during S phase and are two genetically identical sister chromatids.

Prophase 1 - meiosis

90% of meiosis

Chromosomes condense

Crossing over occurs: DNA in non-sister chromatids mix and match; resulting in genetic variation of offspring

corssing over

Pieces of DNA swap, happens in prophase one

tetrad

all 4 chromatids ( 2 homologous chromosomes paired together)

Chiasma

Each tetrad has at least one site of chiasma, where crossing over occurs.

metaphase 1 - meiosis

Tetrads line up on the metaphase plate

anaphase 1- meiosis

The chromosomes begin to move to the poles.

Sister chromatids remain attached!

Telophase I and Cytokinesis - meiosis

2 new cells form.

Each chromosome is still composed of two sister chromatids.

Prophase 2 meiosis

A new spindle apparatus forms, and the 2 new cells get ready to divide again.

metaphase 2 meiosis

Chromosomes line up on the metaphase plate.

anaphase 2 meiosis

sister chromatids pull apart

Telophase II and Cytokinesis meiosis

Nuclei form, 4 new haploid daughter cells are formed.

Each of the 4 daughter cells are genetically different.

Male results of meiosis

All 4 daughter cells become sperm

Happens after puberty

Female results of meiosis

Only 1 of the 4 daughter cells become the egg

Other cells become polar bodies which support the egg

Happens before a girl is born

Mitosis

Cells divide once

No crossing over

Two daughter cells made

Daughter cells are identical to each other and parents

Daughter cells are 2n

Occurs in somatic cells

Meiosis

Cells divide twice

Crossing over (prophase I)

Four daughter cells made

Daughter cells are all different from each other and parents

Daughter cells are n

Occurs in ovaries/testes

Makes gametes

recombinant chromosomes

A chromosome created when crossing over combines the DNA from two parents into a single chromosome.

What does crossing over power

Powers natural selection/evolution: all individuals are different and the most fit survive to reproduce

Makes species more "hardy," if bad things happen, at least some will have adaptations that help them survive.

random fertilization