CIENCIAS ACC

CELL CYCLE

Eukaryotic cells pass through a regular sequence of growth and division, during the life of an organism. Is a repeating sequence of cellular growth and division, during the life of an organism. 

Cells have a system that controls the bases of the cycle, a “red – Green light system” regulated by feedback information from the cell.

The cycle has Checkpoints (inspection points) at which feedback signals from the cell, can trigger the next phase (activate Green light) Is controlled for many proteins.

CELL CYCLE PHASES

The interphase is the first three phases of the cycle. A Cell will enter the last to phases of the cell cycle only if its about to divide.

1. First growth (G1) phase: during the G1 phase, a cell grows rapidly and carries out its routine functions. For most organisms, this phase occupies the major portion of their life. The cells that are not dividing remain in the G1. Some somatic cells, such as most muscle and nerve cells, never divide. If this cells die, the body cannot replace them.

2. Synthesis (S) phase: a cell’s DNA is copied during S. at the end, each chromosome consists of two chromatids attached at the centromere.

3. Second growth (G2) phase: in this phase, preparations are made for the nucleus to divide. Microtubules (hollow protein fibers), are arranged during G2 in preparation for mitosis.

4. Mitosis: is the process in which during the cell division in which the nucleus of a cell is divided into two nuclei. Each nucleus ends up with the same number and kinds of chromosomes as the original cell. Asexual reproduction, or to replace damaged tissues.

Spindle: is the structure that helps more chromosomes during Mitosis. Is made up of both centrioles and microtubule fibers.

Centromere: is the organelle that organizes the assembly of the spindle, and contains two centrioles (in animal cells)

-Prophase: chromosome coil up, are visible, Nuclear envelope dissolves. A spindle forms.

-Metaphase: chromosome move to the center (equator). Spindle fibers link the chromatids of each chromosome to opposite poles.

-Anaphase: centromeres divide. The 2 chromatids are now chromosomes, and move toward opposite poles

-Telophase: nuclear envelope forms at each pole. Chromosomes are now at the opposite poles, uncoil, spindle dissolves. Cytokinesis begins.

5. Cytokinesis: process during cell division in which cytoplasm divides. Sexual reproduction. The membrane 

- In animal cells: the cell in pinched in half by a belt of protein threads.

- In plants: That has a rigid cell wall, the vesicles of Golgi apparatus fuse at the midline of the dividing cell and form a cell plate. 

Mitosis and Cytokinesis produce new cells that are identical to the original cells and allow organisms to grow, replace damaged tissues, and in some organisms reproduce asexually.

Spindle: is the structure that helps more chromosomes during Mitosis. Is made up of both centrioles and microtubule fibers.

Centromere: is the organelle that organizes the assembly of the spindle, and contains two centrioles (in animal cells)

Prophase: chromosome coil up, are visible, Nuclear envelope dissolves. A spindle forma

Metaphase: chromosome move to the center (equator). Spindle fibers link the chromatids of each chromosome to opposite poles.

Cancer is the uncontrolled growth of cells, a disorder of the cell division. If one genes that regulate cell growth and division is mutated, this protein may not function, and the regulation of the cell growth may be interrupt or disrupted.

ïMutation: can inactivate the control proteins overproducing growth – promoting molecules

CELL CYCLE EXPLANATION 

• spindle fiber forms in metaphase
• en anaphase los chromosomes se separan
• for telophase, chromosomes are already in opposite sides.
• SEXUAL CHROMOSOMES: 23 PAIRS. 22: AUTOSOMES. 46. DIPLOID 
• SEXUAL CELLS: HAPLOID CELLS. EGGS AND SPERM. 23 CHROMOSOMES. just your eggs (ovulos) and sperm 
• somatic is any cell in your body that isn't sexual. mitosis. somatic are liver cells, skin cells, tissue cells. 
• sexual cells: meiosis
• autosome is chromosome. somatic is cell. 
• mitosis when damage tissue, growth or cell replacement

interphase: process needed to prepare the cell for mitosis

PHASES OF MITOSIS

1. prophase
2. metaphase
3. anaphase
4. telophase

cytokinesis

CHECKPOINTS ARE THE ONES IN CHARGE OF SUPERVISING THE FUNCTION OF THE CELL DURING THE GROWING PROCESS. IF THIS ONE ISNT APROPIATE, MUTATIONS AND CANCER HAPPEN

CENTRIOLES DIVIDE THE CELL DURING MITOSIS

MEIOSIS

• scrambles forms of genes
• HOMOLOGOUS CHROMOSOMES: one from mother, one from father
• MEIOSIS 1: separates homologous chromosomes:
• interphase: chromosomes replicate. identically sister chromatids attached to centromeres
• prophase 1: crucial. chromatids align with homologous. CROSSING OVER CAN OCCUR (exchange of segments during synapsis)

in meiosis there is no DNA replication (NO INTERPHASE)

MEIOSIS

make 4 genetically different cells

23 SINGLE CHROMOSOMES EACH

1 EGG

POLAR BODY. USELESS EXCEPT IN PLANTS

PMAT X2

the structures:

chromosomes (2 of each, mom and dad homologues)

 centrosome: centrioles

MEIOSIS 1

interphase: 

nuclei with 2 pairs of chromosomes

duplicate centrosomes

organize chromosomes

copy DNA

prophase1: synapsis: organization: mom and dad coming together (cross over) 4 CHROMATIDS. variation. combine

methaphase1: independent orientation. order chromosomes. variation

2 raised to the # of pairs

spindle attach to centromere of each chromosomes (IND ASSORTMENT)

anaphase: pulls apart

telophase: forming nuclei

cytokinesis: divide cell

MEIOSIS 2

PORPHASE 2

chromosomes line againe

no crossing over

METHAPHASE 2

spindle attaches

ANAPHASE 2

chromosomes separated

TELOPHASE 2

divides in 4 cells (different)

fertilize as sperm and process again (organism to divide)

differences between mitosis and meiosis

1. meiosis forms tetras in prophase 1, mitosis just duplicates chromosomes

2. meiosis does 2 divisions

3. synapsis occurs in meiosis

4. 4 daughter cells in meiosis

REPLICATION, TRANSCRIPTION, TRANSLATION

REPLICATION

DNA replicates in the nucleus. In the phase of mitosis called interphase specifically in S.

Gene: Particular sequence of DNA that can be translated into a protein.

DNA polymerase: add nucleotides to make 2 new strands.

TRANSCRIPTION: happens in the nucleus

Takes information of DNA to RNA.

GEN= DNA -> protein -> trait

Protein: amino acid + amino acid = protein (enzymes, albumin, muscle protein)

Amino acid: subunit of the proteins

Nitrogenous base: A-T-C-G/U (RNA)

Gene code: particular sequence of nitrogenous bases, that are going to carry our genetic information.

Ribosome: organelle in charge of making the proteins. Protein factory.

Info is in DNA but I have to rewrite information in RNA

3 differences 

1. DNA 2 strands. RNA 1 strands

2. Bases: DNA= A-T-C-G. RNA= A-U-C-G.

3.sugar: DNA deoxyribose. RNA ribose, ribose contains one more sugar.

RNA polymerase: is an enzyme that adds and links complementary RNA nucleotides during transcription. produces only 1 strand.

In RNA T is replaced by U.

mRNA: messenger RNA. Carries the sequence out of the nucleus

RIBOSOMES (PROTEIN FACTORY)

MITOCHONDRIA (ENERGY)

TRANSLATION: Happens in the cytoplasm.

the message that you have in RNA is finally being translated to the protein. Produces proteins from the RNA.

Codons: groups of 3 nitrogenous bases that is giving me the info to know what amino acid I am going to need to put in this place to make my protein. 3 letters than can be translated into amino acids.

tRNA: brings the amino acids. Assistant of mRNA.

rRNA: the RNA that s making the ribosome.

mRNA: carrying the message. 

anticodon: I have a signal and someone has opposite signal to match with mine.