Chapter 3: Cellular Regeneration and Regulation

embryo

An early stage of development in multicellular organisms following fertilization and before becoming a fetus

conception

the process when a sperm cell fertilized an egg cell to begin the development of an organism

foetus

the unborn offspring of a mammal more than 8 weeks after conception

Gestation period

The time between fertilization and birth during which the embryo and fetus develop in the uterus.

Zygote

A single cell formed by the fertilization of an egg by a sperm, containing a complete set of genetic material

Uterus

A muscular organ in female mammals where the embryo implants and develops during pregnancy.

Morula

An early stage of embryonic development where the zygote has divided into a solid ball of cells

Blastocyst

Structure of a hollow ball of cells that forms a few days after fertilization. Inside are the inner cell mass which will develop into the embryo. The blastocyst attaches to the uterine wall to continue development.

Gastrulation

A process during embryonic development in which the blastocyst reorganizes into three germ layers: ectoderm, mesoderm, and endoderm.

Embryonic germ layers

The three primary layers of cells (ectoderm, mesoderm, and endoderm) formed during gastrulation, which give rise to all tissues and organs.

Ectoderm

The outermost germ layer that forms the nervous system, skin, and sensory organs.

Mesoderm

The middle germ layer that develops into muscles, bones, the circulatory system, and internal structures.

Endoderm

The innermost germ layer that forms the digestive system, lungs, and other internal organs.

Critical periods

Specific time frames during development when an organism is particularly sensitive to environmental influences.

Stem cell

Cell that can divide and develop into specialised cell types.

Embryonic stem cell

Type of stem cell taken from the early embryo that can differentiate into any cell type

Deoxyribonucleic acid (DNA)

The molecule that carries genetic information in cells

Nucleotide

The basic structural unit of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.

Purine

A type of nitrogenous base found in DNA and RNA, including adenine (A) and guanine (G).

Pyrimidine

A type of nitrogenous base found in DNA and RNA, including cytosine (C), thymine (T), and uracil (U) in RNA.

Complementary base pairing

The specific hydrogen bonding of nucleotide bases in DNA (A-T and G-C) and RNA (A-U and G-C).

DNA packaging/structure

DNA molecules are wrapped around 8 histones (special type of protein), which is called the nucleosome, then many nucleosomes forms the chromatins and then many chromatins make up the chromosomes, which are found inside the nucleus

Chromatin

The complex of DNA and proteins in the nucleus that condenses to form chromosomes during cell division

Nucleosome

The fundamental unit of chromatin structure, consisting of DNA wrapped around 8 histone proteins.

Chromosomes

Thread-like structures made of condensed DNA that carry genetic information and found inside the nucleus

Mitosis

A type of cell division that produces two genetically identical daughter cells for growth, repair damaged cells and replace dead cells.

Binary fission

A form of asexual reproduction in prokaryotes where a single cell divides into two identical daughter cells.

chromatid

One of two identical halves of a replicated chromosome.

Centromere

The middle region of a chromosome that links sister chromatids and where spindle fibers attach during mitosis.

G0 phase

A resting phase where cells do not divide but carry out normal functions.

G1 phase

The first growth phase of interphase where the cell grows and prepares for DNA replication.

S phase

DNA replication occurs, doubling the genetic material.

G2 phase

The second growth phase where the cell prepares for mitosis by producing proteins and organelles.

M Phase

The stage of the cell cycle where mitosis and cytokinesis occur.

Sister chromatids

The replicates of the chromosomes (two of them combine)

Diploid

A cell containing two sets of chromosomes (one from each parent).

Full set of chromosomes (46 in humans) 

The symbol '2n' refers to being diploid. Body cells are diploid.

Haploid

is used to describe sex cells/gametes (23) to function. Symbol ‘n’ refers to being a haploid.

Homologous Chromosomes

Pairs of chromosomes, one from each parent, that have the same genes but may have different alleles.

Interphase

The phase of the cell cycle where the cell grows, performs normal functions, and replicates DNA in preparation for division.

Prophase

replicated chromosomes and chromatids become visible and spindle fibers start to form from the centrosomes, and chromatin begins to condense into chromosomes.

In between prophase + metaphase (last on prophase)

The nuclear membrane begins to break down, microtubules continue to extend and attach to the centromere of chromosomes.

Metaphase

replicated chromosomes line up along the equator

Anaphase

The stage of mitosis where sister chromatids are pulled apart toward opposite poles of the cell.

Telophase

The final stage of mitosis is when the nuclear membrane forms around two new nuclei, each number the same as the parent cell. Spindle microtubules begin to retract, and chromosomes begin to decondense back into chromatin, slowly entering cytokinesis.

Cytokinesis

The final step in cell division where the cell splits into two new daughter cells.

Cell plate

A structure formed in plant cells during cytokinesis that develops into a new cell wall.

G1 Check point

Checks for

• Cell size

• Nutrients

• Growth factors

• DNA damage

• Organelles have double

G2 Check point

Checks for

• DNA damage

• DNA replication completeness

M Check point

A checkpoint in mitosis ensuring proper chromosome alignment and attachment to spindle fibers for division at the metaphase plate

Fail discovered in the check points?

• Repair damage (attempt)

• Cell goes through programmed cell death (Apoptosis)

what is Apoptosis

A programmed cell death process that removes damaged or unnecessary cells.

what triggers apoptosis (a receptor-mediated response) by?

internal or external signalling molecules

Major steps of Apoptosis:

1. Cell strinkage (cytoskeleton break down)

2. Breakdown of oganelles + nucleus

3. Blebbing of plasma membrane

4. Formation of apoptosis bodies

5. Phagocytosis of apoplotic bodies

Two pathways for apoptosis:

Extrinsic and Intrinstic

where does intrinsic occur?

mitochondria → released from → cytochrome

where does extrinsic occur

death receptor

what does extrinsic pathway activate

Extrinsic pathway can activate apoptosis on its own and activate the intrinsic pathway.

what does the intrinsic pathway activate?

This pathway acts independently, but can also be activated by the extrinsic pathway in some situations

Caspase

a special enzyme that helps break down a cell during apoptosis. They are already present as inactive precursors within the cell

cancer formation occurs via check points

errors at checkpoints can cause cancer or the inability to form death receptor proteins.

Necrosis

Uncontrolled cell death caused by external factors such as injury or infection.

Phagocytic cell

A type of immune cell that protects the cell as it eats and digests germs, dead cells, and debris.

Benign

A harmless tumor that does not spread.

Malignant

A dangerous tumor that can invade other parts of the body (cancerous).

Culture

The process of growing cells in a controlled laboratory environment.

Metastasis

The spread of cancer cells from the original tumor to other parts of the body.

Angiogenesis

The formation of new blood vessels, often stimulated by tumors to supply oxygen and nutrients.

Spindle microtubules

They attach to centromeres and help separate chromatids into daughter cells during cell division.

centrosome

spindle fibers start to form