Bio Exam set 2

The first stage of a biological process, such as transcription or translation. During transcription, RNA polymerase binds to DNA and begins making RNA. During translation, the ribosome assembles on mRNA and starts protein synthesis.

Initiation

A type of mutation where one or more nucleotides are added into a DNA sequence. Insertions can change how proteins are made and may cause frameshift mutations.

Insertion

A membrane receptor that opens or closes a channel when a signaling molecule binds to it, allowing ions like Na⁺ or Ca²⁺ to move across the membrane.

Ion channel receptor

A hormone produced by the pancreas that lowers blood glucose levels by helping cells absorb glucose from the bloodstream.

Insulin

A series of protein kinases that activate one another by phosphorylation, amplifying a cellular signal. Common in cell signaling pathways.

Kinase Cascade

A signaling molecule that binds specifically to a receptor to trigger a cellular response. Examples include hormones and neurotransmitters.

Ligand

A mutation in which one DNA base change causes a different amino acid to be inserted into a protein. This may alter protein function.

Missense Mutation

A species widely studied to understand biological processes because it is easy to grow and genetically analyze. Examples include mice, fruit flies, and yeast.

Model organsim

Identical twins formed when a single fertilized egg splits into two embryos. They share nearly identical genetic material.

Monozygotic twins

A mutation that changes a codon into a stop codon, causing protein synthesis to end early and often producing a shortened protein.

Nonsense mutation

A membrane-bound organelle in eukaryotic cells that contains DNA and controls gene expression and cell activities.

Nucleus

A cluster of genes in prokaryotes controlled together under one promoter, allowing coordinated gene expression.

operon

The “peptidyl site” of the ribosome where the tRNA carrying the growing polypeptide chain is held during translation.

P-site

An enzyme that removes phosphate groups from proteins or other molecules, often turning signaling pathways off.

Phosphatase

A long chain of adenine nucleotides added to the 3’ end of eukaryotic mRNA that helps stabilize the mRNA and assists in translation.

Poly (A) Tail

A DNA sequence where RNA polymerase and transcription factors bind to begin transcription of a gene.

Promoter

A protein that receives and responds to signaling molecules, allowing cells to detect changes in their environment.

Receptor

A membrane receptor that activates itself and other proteins by adding phosphate groups to tyrosine amino acids after ligand binding.

Receptor tyrosine kinase

A trait or allele that is expressed only when an individual has two copies of the allele.

Recessive

Segments of DNA that control when, where, and how much a gene is expressed, such as promoters and enhancers.

Regulatory regions

A molecule inside the cell that passes along signals from receptors to target molecules during signal transduction.

Relay molecule

Regulatory proteins that bind to DNA and block transcription of genes.

Repressors

A cellular structure made of RNA and proteins that carries out translation by assembling amino acids into proteins.

Ribosome

The process in eukaryotes where introns are removed from pre-mRNA and exons are joined together to form mature mRNA.

RNA Splicing

A mutation that occurs naturally due to errors in DNA replication or chemical changes in DNA, without exposure to mutagens.

Spontaneous mutation

An intracellular receptor that binds steroid hormones and often acts as a transcription factor to regulate gene expression.

Steroid hormone receptor

The final stage of transcription or translation where synthesis stops and the completed RNA or protein is released.

Termination

Proteins that bind to specific DNA sequences and help regulate the transcription of genes.

Transcription factors