Cells and Development: Mitosis

Question 1

What are the two main processes of cell division?

Answer 1

Meiosis: how germ cells produce
Mitosis: for all other cell division

Question 2

What happens in mitosis and what are the four phases?

Answer 2

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

Question 3

What happens in prophase?

Answer 3

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)

Question 4

What happens in metaphase?

Answer 4

In this step, chromosomes are aligned to the middle of cell by spindle fibers that are attached on kinetochores.

Question 5

What happens in anaphase?

Answer 5

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.

Question 6

What happens in telophase?

Answer 6

Termination of mitosis happens. The spindle apparatus disappears, the nuclear membrane reforms around each set of chromosomes and nucleoli reappears.

Question 7

What happens during cytokinesis?

Answer 7

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.

Question 8

What is embryogenesis?

Answer 8

Journey of an egg developing into embryo

Question 9

Where do female germ cell - oocyte and male sperm cell contact with each other?

Answer 9

Secondary oocyte (made from primary oocyte) travels to fallopian tube and that’s where they meet

Question 10

What happens during fertilization?

Answer 10

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.

Question 11

How’s zygote formed?

Answer 11

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)

Question 12

Where does zygote need to move?

Answer 12

Zygote cannot stand still and it has to move from fallopian tube to uterus to implant

Question 13

What’s the process that zygote undergoes while moving to uterus?

Answer 13

It undergoes cleavage i.e. rapid mitotic division

Question 14

What are the three major phases of zygote development?

Answer 14

1. Morula
2. Blastula
3. Gastrula

Question 15

What’s morula?

Answer 15

Here the embryo is small, solid ball of cells (stem cells that are undifferentiated)

Question 16

What’s blastulation?

Answer 16

When cells start migrating to the outside of zygote forming a hollow hall and they release fluid

Question 17

What’s blastula?

Answer 17

When the embryo is done with blastulation step it’s called blastula

Question 18

What are trophoblasts?

Answer 18

These are the outer layer of cells that develop into placenta, chorion, and amniotic sack that surrounds baby as it develops

Question 19

What’s inner cell mass?

Answer 19

The mass that develops into a baby if everything goes well

Question 20

What’s ectopic pregnancy?

Answer 20

When zygote implants somewhere else. Note: Zygote can only survive in uterus

Question 21

What happens during gastrulation?

Answer 21

The inner cell mass of the embryo develops into three primary germ layers that will be precursor for every differentiated cell

Question 22

What does endoderm (inner layer - within) give rise to?

Answer 22

It gives rise to digestive tract including pancreas, liver, lungs, bladder, and distal urinary tract

Question 23

What does ectoderm (outer layer) give rise to?

Answer 23

It forms epidermis, hair, eyes, epithelium of upper respiratory tract (including nose and mouth), and nervous system

Question 24

What does mesoderm (middle layer) give rise to?

Answer 24

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)

Question 25

What stages do cells need to go through in order to accomplish their specialized functions?

Answer 25

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

Question 26

What are totipotent stem cells?

Answer 26

These cells have greatest potency and can differentiate into any cell type

Question 27

What are pluripotent cells?

Answer 27

These stem cells can only differentiate into the cell types of fetus

Question 28

What are multipotent stem cells?

Answer 28

These cells have weak potency and highly specialized i.e. they can only differentiate into cell types within a particular cell lineage

Question 29

What is another factor that plays a role in cell specialization?

Answer 29

Location of cells as it receives signals from other cells for development

Question 30

What’s induction?

Answer 30

Process where presence of one cell influences the development of another cell

Question 31

What are the different types of signals that cells uses to communicate?

Answer 31

1. Autocrine: Act on same cell that secreted the signal
2. Paracrine: Act on cells of local area
3. Juxtacrine: Involve cell directly stimulating the receptors of adjacent cell
4. Endocrine: Secreted into the blood stream i.e. communicating with cells all over the body

Question 32

What’s apoptosis?

Answer 32

Programmed cell death