AP biology- Unit 7, Cell cycle, Mitosis and Mieosis

Why do cells divide?

1. Cell size is limited, so cells cannot get too big

2. Development form a fertalized egg

3. Growth/repair

What phases are in the cell cycle?

Interphase, Mitosis, and Cytokensis

What happens in interphase? (Specific parts)

- Growth 1- new organelles form.

-Synthesis- Chromosomes are copied, and Chromatids form.

- Growth 2- More cell growth, annd prep for mitosis, MTOC forms.

Explain the structure of chromosomes

-Chromosomes are made up of DNA.

-The messy form of DNA is called Chromatin, which condensed into chromsomes.

-Each Chromsome has 2 idential chromatids.

- Each pair of chromatids is attached at the centrometer.

What are kintetchochore? and what does it do

Each pair of chromatids is attached at the center by a centromere, and the kintochore protein froms on the centrome and splits it up duting mitosis by attaching to the microtubles which shortern to pull apart chromosomes.

What are microtubles, and the types and what do they do?

Microtubles form miotic spindles which help pull the chromosomes apart. The microtubles attached pull apart chromosomes, and the non attached microtubles lengthen and stretch the cell to help with seperation.

What is MTOC?

Structure responsible for kinetochore microtubules. There are 2 of them on opposite poles of the cell. They form in the miotic spindle.

What happens in Prophase?

In prophase, the longest phase of mitosis, the MTOC seperate and go to opposite poles.

-Chromatin condenses into chromosomes.

- Spindle Micrtoubles forms in the MTOC

The nuclear envelople disolves/breaks down.

What happens in metaphase?

In metaphase, chromosomes line up across the center of the cell.

-Spindle Microtubles connect the kintochore to the centromere of each chromosome to the poles of the spindle.

What happens in Anaphase?

In anaphase, the sister chromatids are pulled apart into chromosomes.

-The chromosomes move until they separate into 2 groups.

What happens in telophase?

Chromosmes gather at opposite sides and loose their shapes. A new nuclear envelope forms aroud each group of chromosomes.

What happens in cytokensis?

The cytoplasm pinches in half, and each daughter cell has an identical set of duplicate chromosomes. In animals, a ring of microfilaments pinches to split. In plants, cell plate forms and divides the cell in 2.

Why are checkpoints used in the cell cycle?

to regulate the progressions through the cell cycle and growth. These checkpoints can result in growth and division, stopping and entering g0, and Aborting and going into apoptosis.

What does the G1 checkpoint do? what happens if it passes the checkpoint or doesnt?

- Is the cell large enough to divide?

-Does the cell have enough nutrients to supply daughter cells?

-Is there damage to the DNA?

-If passes, then s phase occurs.

If fails, then move to G0 or Apoptosis.

What does the G2 checkpoint do? what happens if it passes the checkpoint or doesnt?

- Has the DNA replicated?

-Is there significant damage to the DNA?

-If passed, then moves to M phase,

-If fails then apoptosis occurs.

What does the M checkpoint do? what happens if it passes the checkpoint or doesnt?

-Are all of the chromosomes attached properly to the mitoic spindle?

-If passed then cytokenisis happens.

-If fails, then apoptosis happens.

what are cyclins? What do they do (activate)?

Regulatory proteins that control the progress of the cell cycle. They activate the cyclin-dependent kinase (CDK).

What do cyclin dependent kinease do (CDK)?

Control the cells proccesses (decide when/if they move to next phase)by phosphorylation. When a cyclin and CDK bind, the CDK becomes activated, and binds to the target protein and phosphorylates it. This target protein will then trigger an event in the cell (ex:move to next phase), and the cyclin is then broken down, and the CDK is reused, but becomes inactive when not binded to cyclin.

What happens with cyclins in cancer?

The cyclins are always on, allowing the next phase to start and not regulating the cells, and ignoring checkpoints.

What is density dependent inhibiton?

Where crowded cells stop dividing.(Cancer cells ignore this and divde anyways)

What is a transformation?

The process where a healthy cell becomes cancerous.

what is a tumor and what are the types?

A tumor is a mass of abnormal cells that replicate uncontrolably.

-Benign tumors- Abnormal cells that stay in one place.

-Malignant- Abnormal cells that spread and change.

what is apoptois?

programmed cell death

What are tummor suppressors?

Genes that block the cell cycle from progressing, and prevent the formation of cancerous tumors.

What is tumor protein P53?

at G1, and blocks progression when the DNA is damaged. Transcription is triggered.

What are oncogens?

Genes that cause cancer becausen of mutation.

What are stem cells?

Unspecialized cells that can become specialized under certain conditions.

What is cell potency?

The ability of stem cells to become specialized. more potency means more ability.

What are cellular defferentiations?

The process where dividing cells loose their stem cell abilty and become specialized.

What does meiosis result in?

The transmission of chromosomes from one generation to the next. It is the cell division that produces Gamates.

what are gamates?

sex cells (sperm and egg)

What happens to gamates during fertalization?

The male gamete fuses with the female gamate to produce a zygote with two sets of chromosomes.

What happens when an organism is able to reproduce?

The ovaries and testees produce haploid gamatees.

What is the formation of gamates called?

Gamaetogenesis

What is a gene?

A heritable unit of information found on the DNA.

What is an allele?

A specific form of a gene (ex- eye color)

What is a geneome?

A complete set of genetic information in an organism or cell.

What are homologous chromosomes?

Maternal and paternal pair chromosomes that a organism inhabits from their parents.

Why are homologus pairs seperated into gametes before reproduction?

to prevent chromosome doubling.

What is a diploid?

nuclei with pairs of Homologous chromosomes are diplod. They have 2 gene copies (alleles) for each trait. (a cell with 46 chromosomes)

What is a Haploid?

Nuclei with only one set of chromosomes. They have one allele

for each trait. ( 26 chromosomes)

What happens to haploids and diploids during reproduction?

Dioploids become haploids.

What happens in the interphase of meiosis?

DNA is replicated, and DNA supercoils into chromosomes with 2 sister chromatids.

How many rounds of cell division happen in meiosis?

2

What happens in Meiosis 1? (General)

Reduction divison- seperates the chromosmes of a homologus pair. Each gamete cell will have half a chromosome from each Homologous pair. This seperates the alleles for every gene. M1 will result in 2 haploid daughter cells with replicated chromosomes.

What happens in Meiosis 2? (General)

Seperation of sister chromatids. After m1, the gametic cells each have one pair of chromatids. The seperation of them produces gametic variation because the genes crossover.

What happens in Prophase 1(MEIOSIS)?

-The homologus pairs will pair up and spindle tubes will grow from each pole to the equator(like mitosis).

- The nonsister chromatids will then crossover, and exchange DNA segments/alleles.

-The nuclear envelope condenses, and chromatins become chromosomes.

-Each pair of homologous chromosomes will form a group of 4 called a tetrad.

Whats a tetrad?

group of 4 homologus chromosomes (2 pairs).

What is chiasmata?

X-shaped crossovers

Why is crossing over important?

Because it allows for the. non-sister chromatids to exchange DNA segments/alleles.

What happens in Metaphase 1(MEIOSIS)?

- The homologus pairs of chromosomes will line up in the center.

-The spindle microtubles attach to each chromosome in each pair

What happens in Anaphase 1(MEIOSIS)?

The homologous pairs are pulled to opposite poles of the cell. Each chromosome still has 2 chromatids.

What happens in Telophase and Cytokenisis 1(MEIOSIS)?

-2 nuclear membranes from and the cell seperates into two.

Do the two cells created in Telophase and cytokenisis 1 have the same chromosomes and alleles?

NO

What happens in Prophase 2(MEIOSIS)?

-The cell has divided, forming two haploid cells.

-New Spindle microtubles grow.

What happens in Metaphase 2 (MEIOSIS)?

-The chromosomes line up in the center.

-Because of crossing over, theres no longer sister chromatids of each chromosomes arent genetically the same.

What happens in Anaphase 2(MEIOSIS)?

-The sister chromatids seperate and move to opposite poles.

What happens in Telophase & cytokenisis 2(MEIOSIS)?

-Haploid cells are in the end of mieosis.

-This ends up with 4 cells.

What are the three determaining factors of genetic variation?

1.Independent assortment of chromosomes.

2.Crossing over (P1).

3.Random fertilization- Each sperm has different DNA.

What causes Non-disjunction?

-Chromosomes not seperating properly

What Karyogram?

Placenta or aminotic fluid is used to get the DNA of the baby, and line up chromosomes to check the gender, and chromosome count to make sure no chromosome related dissorders are present.

What chromosomes do females and males have?

-Females- two x chromosomes

-Males- one x one y

What is down syndromes second name, and why does it happen?

-Trisomy 21.

-Happenes when theres an extra chromosome in 21.

Why does turner syndrome happen?

-One less chromosome 23.

Why does kinefelter syndrome happen?

-One or two extra sex chromosomes.( XXY,XXXY)

-Is MALE.

Why does Metfemale syndrome happen?

-Extra female sex chromosome. XXX