DNA & Gene Expression - Edexcel International AS Biology

Flashcards covering key concepts in DNA replication, gene expression, and protein synthesis.

Semi-Conservative Replication

A method of DNA replication where one strand of the original DNA is conserved in each new DNA molecule.

Mitosis

A type of cell division that produces two daughter cells with the same genetic material as the parent cell.

Helicase

An enzyme that unwinds the DNA double helix by breaking hydrogen bonds between base pairs.

DNA Polymerase

An enzyme that synthesizes new DNA strands by catalyzing condensation reactions between nucleotides.

Nucleoside Triphosphates

Activated nucleotides with three phosphate groups, essential for DNA replication.

Phosphodiester Bonds

Covalent bonds that link the sugar-phosphate backbone of nucleotides in DNA.

Leading Strand

The DNA strand that is synthesized continuously in the 5’ to 3’ direction.

Lagging Strand

The DNA strand that is synthesized discontinuously in short segments called Okazaki fragments.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand during DNA replication.

DNA Ligase

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

Meselson-Stahl Experiment

An experiment that demonstrated DNA replication is semi-conservative using isotopes of nitrogen.

Triplet Code

A sequence of three nucleotide bases in DNA that codes for a specific amino acid.

Amino Acids

The building blocks of proteins, determined by the sequence of nucleotide bases in genes.

Non-Overlapping Code

Property of the genetic code where each base is read only once and does not overlap with adjacent codons.

Degenerate Code

The characteristic of the genetic code where multiple codons can encode the same amino acid.

Universal Code

The concept that the genetic code is largely the same across different organisms.

Transcription

The process of copying a segment of DNA into mRNA.

Translation

The process where mRNA is decoded to synthesize proteins.

mRNA

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

tRNA

Transfer RNA that brings the appropriate amino acids to the ribosome during translation.

Anticodon

A region on tRNA that is complementary to a codon on mRNA.

Start Codon

The first codon of a messenger RNA (mRNA) transcript that is translated by a ribosome; usually AUG.

Stop Codon

Codons in mRNA that signal the termination of translation.

Ribosome

The molecular machine that facilitates the translation of mRNA into a polypeptide.

Condensation Reaction

A chemical reaction where two molecules combine to form a larger molecule, releasing a small molecule such as water.

Gene

A sequence of nucleotides in DNA that encodes a specific polypeptide or protein.

Template Strand

The DNA strand used as a guide for synthesizing complementary RNA during transcription.

Coding Strand

The strand of DNA that has the same sequence as the mRNA except for the presence of uracil instead of thymine.

Nuclear Envelope

The double membrane surrounding the nucleus, through which mRNA exits to the cytoplasm.

Cytoplasm

The fluid inside a cell, excluding the nucleus, where translation occurs.

Primary Structure

The unique sequence of amino acids in a protein that determines its shape and function.

Transcribed Strand

The DNA strand that is used as a template to create mRNA.

Genetic Engineering

The manipulation of an organism's genes using biotechnology.

Base Pairing

The specific pairing of nitrogenous bases (A with T, G with C) in DNA or RNA.

Hydrogen Bonds

Weak chemical bonds that form between base pairs, stabilizing the DNA double helix.

DNA Double Helix

The structure formed by two strands of DNA wound around each other.

Gene Expression

The process by which the information encoded in a gene is used to synthesize a functional gene product.

RNA Polymerase

An enzyme that transcribes DNA into RNA by synthesizing complementary RNA strands.

Activated Nucleotides

Nucleotides that are ready to be incorporated into a growing nucleic acid chain during replication.

Genetic Continuity

The preservation of genetic information from one generation of cells to the next.

Hydrogen Bonding

The attraction between polar molecules; a crucial interaction in the stability of DNA and RNA.

Centrifugation

A method used to separate mixtures based on density by spinning them at high speed.

Nucleotide Bases

The nitrogenous components of nucleotides that form the genetic code; include adenine, thymine, guanine, cytosine.

Transcription Factors

Proteins that bind to specific DNA sequences to regulate the transcription of genetic information.

Gene Regulation

The control of the timing and rate of gene expression.