DNA Replication, Transcription, and Translation: Key Concepts for Biology

Prokaryotic DNA Replication

The process of duplicating DNA in prokaryotic cells, typically occurring in the cytoplasm and involving a single circular chromosome.

Eukaryotic DNA Replication

The process of duplicating DNA in eukaryotic cells, which occurs in the nucleus and involves multiple linear chromosomes.

Dispersive Replication

A model of DNA replication where parental DNA strands are broken into pieces and new DNA is synthesized in between.

Conservative Replication

A model of DNA replication where the original DNA molecule remains intact and a completely new copy is made.

Semi-Conservative Replication

The model of DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.

Matthew Meselson and Franklin Stahl

Scientists known for their experiment that provided evidence for the semi-conservative model of DNA replication.

Replication Bubbles

Regions of DNA where the double helix is unwound and replication is actively occurring.

DNA Helicase

An enzyme that unwinds the DNA double helix during replication.

Replication Fork

The Y-shaped region where the DNA is split into two strands for replication.

Leading Strand

The strand of DNA that is synthesized continuously in the same direction as the replication fork.

Lagging Strand

The strand of DNA that is synthesized discontinuously in short segments opposite to the direction of the replication fork.

DNA Ligase

An enzyme that joins Okazaki fragments on the lagging strand by forming phosphodiester bonds.

Primer

A short strand of RNA that provides a starting point for DNA synthesis.

Primase

An enzyme that synthesizes the RNA primer needed for DNA replication.

DNA Polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides complementary to the template strand.

Topoisomerase

An enzyme that alleviates the tension in the DNA helix ahead of the replication fork by cutting and rejoining DNA strands.

Nuclease

An enzyme that cuts DNA or RNA into smaller pieces by hydrolyzing the phosphodiester bonds.

Nucleotide Excision Repair

A DNA repair mechanism that removes damaged nucleotides and replaces them with the correct ones.

Single-Strand Binding Protein

Proteins that bind to single-stranded DNA during replication to prevent it from re-annealing.

Telomeres

The repetitive nucleotide sequences at the ends of eukaryotic chromosomes that protect them from degradation.

Telomerase

An enzyme that extends telomeres, allowing for the complete replication of linear chromosomes.

Francis Crick

A scientist known for co-discovering the structure of DNA and contributing to the understanding of gene expression.

Transcription

The process of synthesizing RNA from a DNA template.

Translation

The process of synthesizing proteins from mRNA, involving ribosomes and tRNA.

What three ways does RNA differ from DNA?

1. RNA contains ribose sugar, while DNA contains deoxyribose. 2. RNA is usually single-stranded, whereas DNA is double-stranded. 3. RNA has uracil (U) instead of thymine (T).

mRNA

Messenger RNA, which carries genetic information from DNA to the ribosome for protein synthesis.

rRNA

Ribosomal RNA, which is a component of ribosomes and plays a crucial role in protein synthesis.

tRNA

Transfer RNA, which transports amino acids to the ribosome during translation.

Transcription Unit

A segment of DNA that is transcribed into RNA.

Promoter

A DNA sequence that initiates transcription of a gene by providing a binding site for RNA polymerase.

Eukaryotic

Organisms whose cells contain a nucleus and other membrane-bound organelles.

Initiation

The first phase of transcription where RNA polymerase binds to the promoter and begins RNA synthesis.

Elongation

The phase of transcription where RNA polymerase adds nucleotides to the growing RNA strand.

Termination

The phase of transcription where RNA polymerase reaches a terminator sequence and releases the newly synthesized RNA.

Transcription Factors

Proteins that help regulate the transcription of genes by assisting RNA polymerase in binding to the promoter.

RNA Modification

The process of altering the primary RNA transcript, including capping, polyadenylation, and splicing.

Introns

Non-coding sequences in a gene that are removed during RNA splicing.

Exons

Coding sequences in a gene that are retained and expressed in the final mRNA.

Codon

A sequence of three nucleotides in mRNA that specifies a particular amino acid.

Stop Codons (3)

Codons that signal the termination of protein synthesis: UAA, UAG, UGA.

Start Codon

The codon (AUG) that signals the beginning of translation and codes for the amino acid methionine.

Reading Frame

The way nucleotides in mRNA are grouped into codons for translation.

Anticodon

A sequence of three nucleotides in tRNA that is complementary to a codon in mRNA.

Ribosome

A cellular structure that facilitates the translation of mRNA into proteins.

P site

The peptidyl site on the ribosome where the tRNA carrying the growing polypeptide chain is located.

A site

The aminoacyl site on the ribosome where new tRNA carrying an amino acid arrives during translation.

E site

The exit site on the ribosome where tRNA, having donated its amino acid, exits the ribosome.

Codon Recognition

The process by which the tRNA anticodon pairs with the mRNA codon during translation.

Peptide Bond Formation

The chemical bond formed between amino acids during protein synthesis.

Translocation

The process during translation where the ribosome moves along the mRNA, shifting the tRNA from the A site to the P site.

Gene Expression

The process by which information from a gene is used to synthesize functional gene products, typically proteins.

Gene Regulation

The mechanisms that control the expression of genes, determining when and how much of a gene product is made.

Gene Specialization

The process by which different genes are expressed in different cell types, leading to specialized functions.

Mutations

Changes in the DNA sequence that can affect gene function and lead to variations in traits.

Gene Mutation

A permanent alteration in the DNA sequence of a gene.

Point Mutation

A mutation that involves a change in a single nucleotide in the DNA sequence.

Silent Mutation

A mutation that does not change the amino acid sequence of a protein.

Missense Mutation

A mutation that results in a different amino acid being incorporated into a protein.

Nonsense Mutation

A mutation that creates a premature stop codon in the protein-coding sequence.

Frameshift Mutation

A mutation caused by insertions or deletions that shift the reading frame of the genetic message.

Impact on Phenotype with Gene Mutations

Gene mutations can lead to changes in phenotype, potentially resulting in diseases or altered traits.

Chromosomal Mutations

Alterations in the structure or number of chromosomes, which can affect multiple genes.

Gene Translocation

A chromosomal mutation where a segment of DNA is moved from one location to another within the genome.

Gene Duplication

A mutation that results in the duplication of a segment of DNA, leading to multiple copies of a gene.

Impact on Phenotype with Cell Type

The effect of mutations can vary depending on the cell type and its specific functions.

Spontaneous Mutations

Mutations that occur naturally without external influence, often due to errors in DNA replication.

Mutagens

Agents that increase the rate of mutations, such as chemicals or radiation.

Carcinogens

Substances that are known to cause cancer by inducing mutations in DNA.

Genetic Engineering

The manipulation of an organism's DNA to achieve desired traits or outcomes.

Restriction Maps

Diagrams that show the locations of restriction enzyme cut sites within a DNA molecule.

Restriction Sites

Specific sequences of DNA where restriction enzymes cut the DNA.

DNA Fingerprinting

A technique used to identify individuals based on unique patterns in their DNA.

Recombinant DNA Technology

A method for combining DNA from different sources to create new genetic combinations.

Clone

An organism or cell produced asexually from one ancestor to which they are genetically identical.

Transgenic Organisms

Organisms that have been genetically modified to contain genes from other species.

Gene Knockout

A genetic technique in which a specific gene is made inoperative, allowing researchers to study its function.

Concerns of Genetic Engineering

Ethical, environmental, and health-related issues arising from the manipulation of genetic material.

Human Genome Project

An international scientific research project aimed at mapping and understanding all the genes of the human species.

Genetic Screening

The process of testing individuals for specific genetic conditions or predispositions.

Gene Therapy

A technique that uses genes to treat or prevent disease by inserting, altering, or removing genes within an individual's cells.