Cell Cycle, Cell Growth, Death & Differentiation

Question 1

What is Binary Fission?

Answer 1

The splitting of one parent cell into two genetically
identical daughter cells.

Question 2

In what organisms does Binary Fission occur?

Answer 2

Occurs in prokaryote microbes such as bacteria

Question 3

What are the stages of Binary Fission?

Answer 3

1. Replication: of circular DNA
2. Attachment: of the two circular DNA molecules to the poles of the plasma membrane.
3. Lengthening: of the cell
4. Division: into two cells by constriction across the middle of the cell.

Question 4

What is the purpose of Cell Replication in Multicellular organisms?

Answer 4

– Restoring the nucleus-to-cytoplasm ratio
– Growth and development
– Maintenance and repair

Question 5

What is the purpose of Cell Replication in Unicellular organisms?

Answer 5

– Is a simple form of reproduction that’s creates a new genetically identical individual.

Question 6

What are the 3 steps of the cell cycle in Eukaryotes?

Answer 6

STEP 1: Replication of DNA of parent cell – INTERPHASE
STEP 2: Organisation & separation of chromosomes to opposing poles in parent cell and two new nuclei - MITOSIS
STEP 3: Division of parent into 2 daughter cells - CYTOKINESIS

Question 7

What is the G1 Stage?

Answer 7

Cell undergoes growth. Mitochondria/Chloroplast divide. Protein needed for DNA replication is produced

Question 8

What is the S Stage?

Answer 8

DNA Replication occurs.

Question 9

What is the G2 Stage?

Answer 9

Cell continues to grow. Protein for microtubules of the spindles is produced.

Question 10

Prophase?

Answer 10

Chromosomes condense (shorter & thicker)
spindles form
nuclear membrane breaks down.

Question 11

Mataphase?

Answer 11

Double stranded chromosomes line up at the equator of the cell

Question 12

Anaphase?

Answer 12

Sister chromatids separate and are pulled to opposite ends of the spindle by contracting spindle fibres

Question 13

Telophase?

Answer 13

Nuclear membrane forms around each group of single stranded chromosomes and they gradually decondense.

Question 14

Cytokenisis?

Answer 14

The mitochondria and chloroplast (plants) surround each of the two new nuclei.
Animal cells: A bridge of cytoplasm between the two nuclei narrows and the plasma membrane pinches in to separate the nuclei. Two new cells are formed. Called
cleavage
Plant cells: A cell plate forms between the two groups of chromosomes and develops into a new cell wall. Two new cells are formed. Called Cell plate

Question 15

What are Checkpoints?

Answer 15

Checkpoints detect errors in the replication of genetic
material to produce two genetically identical daughter cells. If an error is found at a checkpoint the cell cycle is either aborted or delayed to correct the error.

Question 16

G1 Checkpoint?

Answer 16

The parental DNA is checked for damage or
incomplete. If an error is detected the cell may be targeted for self destruction or it may enter G0 (non dividing stage)

Question 17

Protein P53

Answer 17

The protein p53 checks the DNA at this stage. It is referred to as a tumour suppressing protein.

Question 18

G2 Checkpoint?

Answer 18

The replicated daughter DNA is checked for errors.

Question 19

M Checkpoint?

Answer 19

The sister chromatids are checked to ensure they are
attached to the correct microtubules of the spindle.
This ensures they are pulled to opposite poles of the
spindle. If an error is detected the process is delayed
until it is fixed

Question 20

What is Apoptosis?

Answer 20

Programmed cell death is a genetically controlled and highly regulated process of cell self-destruction.
The signal pathway of apoptosis brings about the planned death of various cells including:
– Cells at the end of their natural life (such as gut lining cells)
– Cells infected with a virus
– Excessive cells

Question 21

An intrinsic (internal) signal within the cell - Apoptosis?

Answer 21

The mitochondrial pathway;
– The intrinsic pathway is used when cells come under stress, such as through infection or damage. When cells are damaged during the cell cycle and the damage cannot be repaired, they undergo apoptosis via the intrinsic pathway.

Question 22

An extrinsic (external) signal, where the signal is from a source external to the cell- Apoptosis?

Answer 22

The death receptor pathway;
– One way this may be generated is by a signal from the immune system.

Question 23

What is Necrosis?

Answer 23

Necrosis is unplanned cell death such as that occurring when cells suffer trauma and die prematurely.

Question 24

What can happen with Overproduction of cells?

Answer 24

When more cells are produced than those lost
- Psoriasis
- Cancers

Question 25

What can happen with Mutations?

Answer 25

In the genes that control the regulation. This means that the checkpoints are overridden: No error detection
or correction occurs.

Question 26

What is Cell Differentiation?

Answer 26

Is the process by which cells become specialised for a specific function.

Question 27

What are Stem Cells?

Answer 27

Are undifferentiated or unspecialised cells that have the ability to differentiate into organ - or tissue - specific cells with specialised functions.

Question 28

What are Totipotent Stem Cells?

Answer 28

Give rise to all cell types.
i.e. Fertilised egg and embryonic cells of a two, four or
eight-cell embryo

Question 29

What are Pluripotent Stem Cells?

Answer 29

Can differentiate into many cell types.
i.e. Embryonic stem cells from the inner cell mass of the
embryonic blastocyst.

Question 30

What are Multipotent Stem Cells?

Answer 30

Have the ability to differentiate into a closely related family of cells.
i.e. A multipotent blood stem cell can develop into a red blood cell, a white blood cell or platelets

Question 31

What are Oligopotent Stem Cells?

Answer 31

Have the ability to differentiate into a few cell types
i.e. Adult (somatic) lymphoid or myeloid stem cells.

Question 32

What are Unipotent Stem Cells?

Answer 32

Produce only cells of their own type.
i.e. Adult (somatic) muscle stem cells.

Question 33

Obtaining Stem Cells - Embryonic stem cells (ESCs)?

Answer 33

May be obtained from the inner cell mass of an early embryo at a stage known as a blastocyst
– Taking these cells from the inner mass of a blastocyst destroys an embryo and this procedure has raised ethical issues

Question 34

Obtaining Stem Cells - Parthenotes?

Answer 34

Are another potential source of embryonic stem cells.
– These are derived from unfertilised human eggs that
are artificially stimulated to begin development.

Question 35

Obtaining Stem Cells - Adult stem cells (more accurately called somatic stem cells)?

Answer 35

Can be obtained from various sources throughout the body such as bone marrow, skin, the liver, the brain, adipose tissue and blood.
– In addition, another source of stem cells is cord blood that can be harvested from the umbilical cord of a baby after birth.
– Are multipotent.

Question 36

Obtaining Stem Cells - Induced pluripotent stem cells
(iPSCs)?

Answer 36

– Some specialised adult somatic (skin) cells could be genetically reprogrammed to return to an undifferentiated embryonic state.
– The creation of iPSCs does not involve the ethical issues related to the embryo deaths that necessarily accompany embryonic cell stem cells derived from blastocysts.

Question 37

STEM CELLS IN MEDICINE?

Answer 37

Regenerative medicine is still at the experimental stage but it raises promises for the treatment of degenerative conditions; (such as Parkinson’s disease and type 1 diabetes) and severe trauma injuries (spinal cord injuries)

Therapeutic cloning is the creation; through the technique of somatic nuclear transfer; of an embryo for the purpose of obtaining stem cells from that embryo.