Cell Cycle & Division

Prophase

1. Centromeres start to go to opposite sides of the cell 2. Chromatin condenses into chromosomes 3. Spindle fibers form 4. Nuclear membrane breaks down 5. Motor proteins on spindle fibers begin to move chromosomes to the center of the cell

Metaphase

1. Chromosomes line up at the middle (equator) of the cell 2. Spindle fibers are attached to the centromere 3. No nuclear membrane

How many copies of DNA are in each chromosome?

2 copies: the two sister chromatids are identical parts of ONE of the 46 chromosomes in the body.

At what point are all of the cells of a human adult stem cells?

By the time someone is a baby (and even an itty-bitty fetus) their cells are all adunt stem cells (no longer embryonic).

What is the difference between normal cells and cancer cells in terms of communication?

Cancer cells don't interact with other cells as normal cells do. Cancer cells do not respond to signals from neighboring cells that "tell" them to stop growing, while normal cells do.

Why can't a cell be too big? Why are cells limited in size?

Cells can't transport materials quickly enough if a cell is too big. Also, if the surface area to volume ratio gets wonky, the regulation of nutrients and other regulations for functions gets messed up, possibly killing the cell.

What is chromatin?

Chromatin is composed of a cell's DNA, mixed with protein (histones), and they are loosely laid around in nucleus. Remember that chromatin is NOT just composed of DNA, but is held together by proteins!

Which stem cells grow faster, adult stem cells or embryonic stem cells?

Embryonic stem cells grow faster than adult stem cells

What are embryonic stem cells?

Embryonic stem cells, under proper conditions, can differentiate to form all specialized cells in the human body (but cannot form into an entire fetus due to the lack of an umbilical cord and other essential supportive tissues). They can be isolated and grown in special conditions in the laboratory.

What is the difference between normal cells and cancer cells, in terms of growth factors?

Growth factors are regulatory molecules that stimulate cell and tissue function through influencing cell differentiation by changing their biochemical activity and cellular growth and regulating their rate of proliferation (division). Cancer cells have less growth factors than normal cells.

Why is genetic variation important for an organism? (Why are asexual organisms at risk?)

If the environment suddenly changes, or a new factor of survival is now in place, or a fatal mutation occurs, the organisms that asexually reproduce cannot adapt to the environment due to the lack of the ability to naturally select and combine important traits.

Longest part of the cell cycle

Interphase

What are the three parts of the cell cycle?

Interphase (growth, DNA copying) Mitosis (division of nucleus) Cytokinesis (division of cytoplasm & organelles)

Chromosomes align in the center of the cell

Metaphase

Multipotent, Pluripotent, Todipotent

Multipotent stem cells can give rise to many, but a limited number of, cells in the body Pluripotent stem cells can differentiate into all cell types except for extra embryonic tissue Todipotent stem cells can differentiate to an unlimited number of cells in the body

Is DNA always in the form of an X-shaped chromosome?

No, the DNA only coils up like that for the cell division part of the cell cycle. X-shaped chromosomes are basically made up of coiled chromatin.

What is the difference between normal cells and cancer cells in terms of growth?

Normal cells stop reproducing once enough cells are present; cancer cells reproduce uncontrollably, even when there are enough cells. Cancerous cells also have too many growth factors (chemicals that tell cells to grow and divide).

Chromatin condenses into chromosomes

Prophase

Nuclear envelope breaks down

Prophase

What are the four phases of cell division (mitosis)?

Prophase Metaphase Anaphase Telophase Remember PMAT!

What can scientists do with donated blastocysts?

Scientists can remove cells (identical stem cells) from the inner mass of the blastocyst and then place them in a laboratory dish to grow more embryonic stem cells.

What do scientists want to use stem cells for?

Scientists want to use stem cells to treat diseases such as diabetes, heart disease, spinal cord issues, and more.

Some tissues in the body have higher mitotic indexes than others because some parts of the body need to replicate their cells more. What are some tissues that might have higher mitotic indexes?

Skin cells, muscle cells, intestinal lining and stomach cells, and some others, have naturally higher mitotic indexes due to the need of more replication.

Daughter chromosomes arrive at the poles

Telophase

Do some different types of cells divide at different rates?

Yes. For example: Red blood cells replace every 4 months. Skin cells replace every 2 weeks. Intestines replace every 16 years.

All cells in a cell line are genetically ____________.

identical

Out of the 4 egg cells produced after meiosis, what number of these eggs can be fertilized?

1

What is the process of meiosis?

1. A diploid (46 chromosome) cell goes through interphase and replicates all of its DNA (each chromosome now has a sister chromatid) 2. The homologous pairs of chromosomes find each other and "cross over" and exchange DNA 3. The homologous pairs line up in tetrads (2-file line) and split down the middle of the two lines 4. There are now 2 cells, with 23 DUPLICATED chromosomes. 5. These chromosomes line up and split apart, now forming 4 genetically different haploid cells.

Cytokinesis

1. Cell membranes pinch off, now there are two cells 2. FOR PLANT: Cell plate (new cell wall) forms 3. Cytokinesis only occurs once the nucleus forms back again

Telophase

1. Nuclear membrane starts to reform 2. Chromosomes start to uncoil 3. FOR PLANT: Cell plate (wall) begins to form back 4. Cleavage furrow forms and starts to pinch off the cell

Anaphase

1. Sister chromatids separate to opposite sides of the cell 2. Still no nuclear membrane! 3. Motor proteins on spindle fibers "walk" chromatids to opposite sides of the cell

If a cell is larger than normal, what needs to happen?

A cell that is larger needs to have a unique shape to increase the surface area. Since volume increases faster than surface area, a special shape to allow more surface area is needed. Examples of this are red blood cells (flattened), and nerve cells (have long pieces).

What are the parts of a chromosome?

A chromosome is made of two genetically identical sister chromatids (DNA duplicates to two sister chromatids during synthesis) that are connected by a centromere. Telomeres are the tips of the chromatids. During cell division, the chromosomes are moved around by motor proteins on the spindle fibers connected to the centromeres, and are pulled apart that way during anaphase during mitosis.

What are adult stem cells?

Adult stem cells can differentiate, but only to a limited number of tissue types. Some fetal or adult tissues (such as umbilical cord, blood, bone marrow, muscle, and brain) contain adult stem cells that produce cells to replace ones that are lost through normal wear and tear, injury, or disease, but again are limited to most types of division and differentiation.

What happens if you receive an extra chromosome or are missing a chromosome?

An extra or missing chromosome makes it so that protein, nutrient, and various other bodily regulations are off, potentially killing the organism.

What is the difference between normal cells and cancer cells in terms of the cell cycle?

Cancer cells do not regulate their cell cycle as easily as normal cells: sometimes cancer cells end up smaller or more uneven in size because of rapid cell division. They also end up "immature," meaning they do not grow fully. Meanwhile, normal cells divide and replicate normally.

Cell is cleaved into two new daughter cells

Cytokinesis

What is the name to describe eukaryotes dividing, and what is the name to describe prokaryotes dividing?

Eukaryotes go through MITOSIS to divide, prokaryotes go through BINARY FISSION to divide. Prokaryotes have a singular, circular chromosome, and no nucleus. Eukaryotes, meanwhile, need to evenly divide their chromosomes and DNA.

What is In Vitro fertilization?

In vitro fertilization (IVF) offers infertile couples a chance to have a child who is biologically related to them. With IVF, a man's sperm and a woman's eggs are combined in a laboratory dish where a zygote forms. Then the zygote begins to divide by mitosis, and a blastocyst is formed. A blastocyst is a four to five day old embryo made of about 100 cells that each contain DNA from both of the parents. For assisted reproduction, between two and four of the blastocyts may be transferred to the woman's uterus (womb) to implant and hopefully develop into a baby. Extra ("left-over") embryos may be stored for future use or may be donated for use in embryonic stem cell research.

What are stem cells? (What are the three properties?)

Stem cells are cells that have three properties: 1. They are unspecialized, meaning they do not have any tissue-specific structures that allow them to perform specialized functions (they can't pump blood through the body or carry impulses like nerve cells). 2. They are capable of dividing and self-renewing continually. Specialized cells like muscle cells, blood cells, or nerve cells normally do not divide. Stem cells can self-renew by dividing many times to produce millions of stem cells. 3. They can differentiate into specialized cells. Even though stem cells have the same information, they can "turn on" certain genes to transform (differentiate) into any specialized cell they want.

Are chromosomes easily visible in the cell during interphase?

Technically, the DNA of the cell is

Which tissue would have a higher mitotic index, normal cells or cancer cells? (Mitotic index is the ratio of dividing cells to the total number of cells in the tissue.)

The cancerous cells would have a higher mitotic index, as they divide more rapidly, causing the dividing ratio of the cell cycle to be higher.

growth factor

To make stem cells differentiate into specialized types of cells, scientists place them in environments that contain signal molecules called growth factors. These growth factors include proteins and other molecules that turn on, or turn off, the expression of specific genes that lead to specific cell structures and functions.

haploid (N)

a cell with 23 chromosomes

diploid (2N)

a cell with 46 chromosomes

zygote

a fertilized egg cell

cell line

a group of cells grown under special conditions in a laboratory

fertilization

a process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote

meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores

Amoebas and other single-celled organisms are genetically identical due to ____________________.

asexual reproduction

Cells __________; one cell doesn't just keep growing and growing

divide

Asexual cell division results in genetically ___________ cells.

identical

gametes

sex cells (egg cells for women and sperm cells for men)

mitosis

the process in cell division by which the nucleus divides, typically consisting of four stages, prophase, metaphase, anaphase, and telophase, and normally resulting in two new nuclei, each of which contains a complete copy of the parental chromosomes

differentiation

when unspecialized stem cells give rise to specialized cells