Controlling Gene Expression and Epigenetics

Controlling gene expression involves either activating or inhibiting genes. Activation leads to protein production, while inhibition prevents it.

Example: Oestrogen can activate genes by binding to receptors on transcription factors, causing them to enter the nucleus and bind to DNA promoters.

Gene inhibition can be achieved using siRNA (small interfering RNA), which binds to complementary sections on mRNA and prevents translation.

Highlight: Epigenetics refers to heritable changes in gene function without altering the DNA base sequence.

The epigenome, a chemical layer surrounding chromatin (DNA-histone complex), can cause chromatin to become more condensed or loose, affecting gene activation or inactivation.

Vocabulary: Acetylation and methylation are processes that affect the genome by modifying the chromatin structure.

Gene Mutations and Cancer

Gene mutations are changes in the base sequence of DNA. There are two main types:

1. Substitution: Replacing one base with another
2. Insertion/Deletion: Adding or removing a base

Example: A substitution mutation can be silent (no change in amino acid), mis-sense (different amino acid), or non-sense (premature stop codon).

Cancer is the formation of a malignant tumor due to uncontrolled cell division (mitosis). Malignant tumors differ from benign tumors in several ways:

• Rapid growth
• Unspecialized cells
• Ability to spread (metastasis)
• Systemic effects
• Require aggressive treatment (surgery, chemotherapy, radiotherapy)

Highlight: Cell division is normally controlled by two genes: proto-oncogenes and tumor-suppressor genes.

Proto-oncogenes stimulate cell division by producing growth factors and receptor proteins, while tumor-suppressor genes inhibit cell division. Mutations in these genes can lead to cancer development.

Vocabulary: Metastasis is the spread of cancer cells from the primary tumor to other parts of the body.

Epigenetic Regulation of Gene Expression

This page would likely delve deeper into the mechanisms of epigenetic regulation of gene expression. It might discuss various epigenetic mechanisms such as DNA methylation, histone modification, and chromatin remodeling.

Vocabulary: Epigenetic modifications are chemical changes to DNA or associated proteins that can alter gene expression without changing the DNA sequence.

The page could provide examples of epigenetics in humans, such as how environmental factors can influence gene expression and potentially lead to disease. It might also discuss how epigenetic changes can be inherited across generations.

Example: Exposure to certain chemicals during pregnancy can lead to epigenetic changes in the developing fetus, potentially affecting health outcomes later in life.

The page might explore what can affect epigenetic molecules that regulate gene expression, including diet, stress, and environmental toxins. It could also discuss how epigenetic changes can be reversible, opening up possibilities for new therapeutic approaches.

Highlight: Understanding epigenetic regulation is crucial for developing new treatments for diseases like cancer, where abnormal gene expression plays a key role.

What are Stem Cells and How Do They Differentiate?

Stem cells are unspecialized cells with the potential to form different types of cells. They become specialized through a process called differentiation, which involves changes in cell shape, number of organelles, and new content. This occurs by controlling gene expression, where some genes are activated while others are inhibited.

Definition: Differentiation is the process by which stem cells become specialized cells with specific functions.

In animals and humans, stem cells are classified based on their potential:

1. Totipotent: Zygote
2. Pluripotent: Embryonic stem cells
3. Multipotent: Bone marrow stem cells
4. Unipotent: Tissue-specific stem cells

Vocabulary: Induced pluripotent stem cells (iPS cells) are created by turning unipotent body cells into pluripotent cells, similar to embryonic stem cells.

Stem cell therapy in humans has two main uses:

1. Producing tissues or organs for transplant
2. Treating irreversible diseases by injecting stem cells at the site of the disorder

In plants, stem cells are found in the embryo (zygote/embryonic stem cells) and in adult plants (meristem cells in stem, shoot, and root).

Example: Plant stem cells are used in tissue culture (micro propagation) for large-scale production of genetically identical plants.