AP Biology Control of Eukaryotic Genes

AP Biology The BIG Questions… How are genes turned on & off in eukaryotes? How do cells with the same genes differentiate to perform completely different, specialized functions?

AP Biology The BIG Review Carrying information in DNA  DNA codes for one amino acid in sets of three (codon)  Amino acids link to form polypeptides  Genes code for polypeptides that control:  The expression of traits (how we look)  The function of the cell  Other genes

AP Biology Epigenetics What causes cells with the same DNA to differentiate? There are chemical reactions which activate and deactivate parts of the genome. Epigenetics is the study of these chemical reactions and the factors that influence them.

AP Biology Epigenome A genome is the complete set of DNA. Epi means "above". The epigenome consists of chemical compounds that mark the genome. The marks tell the DNA what to do, where to do it and when to do it. Can be passed on from cell to cell as cells divide, and from one generation to the next.

AP Biology Changes to the Epigenome Development (during growth) Environmental chemicals Drugs and medicines Aging Diet

Gene – segment of DNA that codes for a specific gene product Gene product – functional protein or RNA molecule Gene expression – using the information in a gene to produce a gene product Gene Expression

All cells within an organism contain the same DNA sequence Only a small portion of genes are expressed in a given cell – Expressed continuously – Expressed only when needed – Many genes are never expressed Regulation in Gene Expression

Cells have the ability to regulate: – Timing of gene expression (turn genes on and off) – Amount of gene product produced Regulation in Gene Expression

Four major stages: – Transcription – RNA processing – RNA transport – Protein translation Regulation occurs at all four stages Process of Gene Expression Gene Primary transcript mRNA Protein

Transcription – synthesis of an mRNA transcript from a gene Regulated by: – Structural DNA changes – Transcription factors – Environmental factors Regulation of Transcription Gene Primary transcript

Transcription factors – proteins that bind to specific DNA sequences to promote or suppress gene expression Can bind to promoter, and start or stop RNA polymerase from binding. Transcription Factors

Internal factors – Cells release signaling proteins that change gene expression External factors – Temperature – Oxygen Environmental Factors

RNA processing – modification of initial mRNA transcript to remove sections not needed. Regulated by: – Splicing – removing sections – Binding and degrading mRNA Regulation of RNA Processing Primary transcript mRNA

RNA transport – export of mature mRNA from nucleus to cytoplasm in eukaryotes Regulated by: – Proteins that limit the amount of mRNA exiting the nucleus Regulation of RNA Transport mRNA

Protein translation – synthesis of a protein from mature mRNA transcript Regulated by: – mRNA structure and proteins that affect translation starting – Environmental factors Example: temperature Regulation of Protein Translation Protein

Protein structure can be changed by the chemicals processing them. Protein folding may be changed and protein will be inactive. Protein Modification

Learning Objectives Describe the process of gene expression Recognize factors that regulate gene expression Regulation of Gene Expression Gene Primary transcript mRNA Protein

Cellular Differentiation Stem Cells | Differentiation Process

Cellular Differentiation Learning Objectives Describe cellular differentiation Identify the roles of DNA, RNA, and environmental factors in the cellular differentiation process

Stem cell – a biological cell that can divide and differentiate into specialized cell types – Includes both embryonic and adult stem cells Cellular differentiation – the process of converting a stem cell into a specialized cell Stem Cells

Differentiation occurs during – Development – Growth – Repair Differentiation Process

Proteins control cell differentiation – Direct structural changes – Direct the cell to begin specialized functions Differentiation of an individual cell depends on the involvement of DNA, RNA, and the environment Differentiation Process

DNA can only be used when it is uncoiled The segments of DNA that are uncoiled determine how the cell will differentiate Role of DNA

RNA controls differentiation during and after transcription – Removes pieces of mRNA during processing, altering the protein produced – Binds and destroy mRNA strands, stopping protein production Role of RNA

Environmental factors can trigger the cell to modify gene expression Internal factors – Specialized cells send out signaling proteins that bind receptors on stem cells External factors – Temperature – Oxygen Role of Environmental Factors

Tissue regeneration research is attempting to alter the differentiation of stem cells – Embryonic stem cells Only in developing embryos – Adult stem cells Remain undifferentiated in adults Using Stem Cells for Tissue Regeneration

Scientists attempt to initiate cell differentiation using – Biochemical signaling agents – Varying environmental conditions – Embryonic genes in adult stem cells Using Stem Cells for Tissue Regeneration

Cellular Differentiation Learning Objectives Describe cellular differentiation Identify the roles of DNA, RNA, and environmental factors in the cellular differentiation process