Cells and Development: Mitosis Flashcards
What are the two main processes of cell division?
Meiosis: how germ cells produce
Mitosis: for all other cell division
What happens in mitosis and what are the four phases?
A single cell is divided into two genetically identical daughter cells
1. Prophase: Preparation
2. Metaphase: Bringing chromosomes to the middle
3. Anaphase: Action
4. Telophase: Termination
>. Cytokineses - cleavage
What happens in prophase?
In this phase, three structures; chromosomes (that divide into chromatids earlier), centriole (which organizes spindle apparatus), and spindle apparatus (which enables the separation of chromosomes) undergo preparation in order for cell to divide.
Towards the end, nuclear membrane dissolves, nucleoli disappear, and centrioles separate onto the opposite sides of the cell and begin to form spindle apparatus that attaches directly to chromosomes via kinetochores (protein structure on chromosome)
What happens in metaphase?
In this step, chromosomes are aligned to the middle of cell by spindle fibers that are attached on kinetochores.
What happens in anaphase?
The centromere split allowing the identical sister chromatids to separate. The fibers get shorten and sister chromatids are pulled towards the opposite poles of cell.
What happens in telophase?
Termination of mitosis happens. The spindle apparatus disappears, the nuclear membrane reforms around each set of chromosomes and nucleoli reappears.
What happens during cytokinesis?
This is a cleavage step. This process separates the cytoplasm and organelles. A contractile actin-myosin pinches one cell into two daughter cells with same identical information.
What is embryogenesis?
Journey of an egg developing into embryo
Where do female germ cell - oocyte and male sperm cell contact with each other?
Secondary oocyte (made from primary oocyte) travels to fallopian tube and that’s where they meet
What happens during fertilization?
Sperm cell penetrates onto the oocyte and fuses it’s nucleus inside the cell. Note: a release of calcium ions from oocyte prevents any other sperm from entering into the cell. Only one sperm can enter. Both sperm and oocyte - each contain half of genetic information.
Ca+ ions also allows secondary oocyte to undergo second meiotic division to form a mature egg cell called ovum.
How’s zygote formed?
Ovum merges with sperm nucleus and forms a zygote. It’s possible to form two zygotes if two cells come and get in contact with two different sperm cells (which turn into twins)
Where does zygote need to move?
Zygote cannot stand still and it has to move from fallopian tube to uterus to implant
What’s the process that zygote undergoes while moving to uterus?
It undergoes cleavage i.e. rapid mitotic division
What are the three major phases of zygote development?
- Morula
- Blastula
- Gastrula
What’s morula?
Here the embryo is small, solid ball of cells (stem cells that are undifferentiated)
What’s blastulation?
When cells start migrating to the outside of zygote forming a hollow hall and they release fluid
What’s blastula?
When the embryo is done with blastulation step it’s called blastula
What are trophoblasts?
These are the outer layer of cells that develop into placenta, chorion, and amniotic sack that surrounds baby as it develops
What’s inner cell mass?
The mass that develops into a baby if everything goes well
What’s ectopic pregnancy?
When zygote implants somewhere else. Note: Zygote can only survive in uterus
What happens during gastrulation?
The inner cell mass of the embryo develops into three primary germ layers that will be precursor for every differentiated cell
What does endoderm (inner layer - within) give rise to?
It gives rise to digestive tract including pancreas, liver, lungs, bladder, and distal urinary tract
What does ectoderm (outer layer) give rise to?
It forms epidermis, hair, eyes, epithelium of upper respiratory tract (including nose and mouth), and nervous system
What does mesoderm (middle layer) give rise to?
It develops into musculoskeletal system (which helps to move around and move fluids through the body), lymphatic system (lymph nodes), circulatory system (heart) and genitourinary system (kidneys)
What stages do cells need to go through in order to accomplish their specialized functions?
Stages of cell specialization:
1. Specification: cells know what they want to be but they aren’t committed yet so they can be anything
2. Determination: Now cell is irreversibly committed to particular function and cell lineage.
3. Differentiation: Cell undergoes changes to become a determined cell
What are totipotent stem cells?
These cells have greatest potency and can differentiate into any cell type
What are pluripotent cells?
These stem cells can only differentiate into the cell types of fetus
What are multipotent stem cells?
These cells have weak potency and highly specialized i.e. they can only differentiate into cell types within a particular cell lineage
What is another factor that plays a role in cell specialization?
Location of cells as it receives signals from other cells for development
What’s induction?
Process where presence of one cell influences the development of another cell
What are the different types of signals that cells uses to communicate?
- Autocrine: Act on same cell that secreted the signal
- Paracrine: Act on cells of local area
- Juxtacrine: Involve cell directly stimulating the receptors of adjacent cell
- Endocrine: Secreted into the blood stream i.e. communicating with cells all over the body
What’s apoptosis?
Programmed cell death
