MICRO 9

Prokaryotic Genome

Made up of plasmids and chromosomal DNA.

Gene

A small region of the chromosome that has the information to make a specific protein responsible for a specific trait.

Chromosome in Prokaryotes

Usually a single, circular strand of DNA.

Chromosome in Eukaryotes

Usually multiple, linear strands of DNA.

DNA Packaging in Prokaryotes

Involves supercoiling due to gyrase.

DNA Packaging in Eukaryotes

Involves DNA wrapped around histones.

DNA Nucleotide

Made up of deoxyribose, one phosphate, and one of these nitrogenous bases: adenine, guanine, cytosine, thymine.

Characteristics of DNA

Double helical shape, sugar-phosphate backbone, strands held together by hydrogen bonds, double stranded molecule.

Product of DNA Replication

Two identical DNA molecules.

Replication Location in Bacteria

Occurs in the nucleoid region.

Semiconservative Process

Each new DNA molecule contains one original strand and one new strand.

DNA Polymerase

Adds nucleotides to the RNA primer, growing the new DNA strand.

Helicase

Breaks the hydrogen bonds, separating the two DNA strands.

DNA Ligase

Joins the fragments of DNA together to make a continuous molecule.

Primase

Lays the first nucleotides to start the new DNA strand.

Basic Order of DNA Replication

The two DNA strands are separated, an RNA primer is formed, nucleotides are added to the RNA primer, and all fragments are joined to form a continuous molecule.

Okazaki Fragments

DNA fragments made discontinuously on the lagging strand that are joined together by ligase.

Gene Expression Starting Point

Begins with DNA and makes a protein.

RNA Nucleotide

One nitrogenous base (adenine, guanine, cytosine, uracil), one phosphate, ribose.

Characteristics of RNA

Sugar-phosphate backbone and single stranded molecule.

Steps of Gene Expression

Transcription: DNA transfers information to mRNA; Translation: mRNA is used to make a protein.

Transcription Location in Bacteria

Occurs in the nucleoid region.

RNA polymerase.

Enzyme for adding nucleotides to mRNA

mRNA.

Product of Transcription

Translation Location in Bacteria

Occurs in the cytoplasm on the ribosome.

RNA's Role in Translation

mRNA carries information, tRNA brings amino acids, rRNA makes up the ribosome machinery.

mRNA Codon

A set of three nucleotides in mRNA that codes for a specific amino acid during protein synthesis.

Genetic Code

The relationship between codon on mRNA and the amino acid added to the protein.

Universal Genetic Code

All life uses the same codon-to-amino acid relationship.

Polyribosomal Complex

A single piece of mRNA used simultaneously with many ribosomes.

Mutation

Any change in the sequence or structure of DNA.

Proofreading

A repair mechanism where DNA polymerase checks for mistakes and repairs them.

Excision Repair

A mechanism that fixes DNA damaged by mutagens.

Chemical Mutagens

Substances that cause mutations, such as nitrous acid and ethidium bromide.

Physical Mutagens

Radiation like X-rays and UV light that cause mutations.

Induced Mutations Definition

Changes in DNA due to exposure to physical or chemical mutagens.

Mechanisms of Genetic Diversity in Bacteria

Conjugation, transformation, transduction, and transposons.

Conjugation

Plasmid DNA is transferred between bacteria via a sex pilus.

Transformation

A bacterium takes up DNA from a dead bacterium.

Transduction

A virus introduces bacterial DNA into a bacterium.

Transposon

'Jumping genes' that move within the genome.

Watson & Crick

Determined the 3D model of DNA.

Rosalind Franklin

Determined DNA was a double helix via X-ray diffraction.

Frederick Griffith

Discovered transformation in bacteria.

Barbara McClintock

Discovered transposons.

Chromosome

Single molecule of DNA found in the nucleoid region of bacterial cells.

Gene

A small region of the chromosome that has the information to make a specific protein responsible for a specific trait.

Plasmids

Small circular pieces of DNA found in the cytoplasm that give the bacterial cell an advantage.

Leading Strand

The strand of DNA that is synthesized continuously during DNA replication in the 5' to 3' direction, serving as a template for complementary base pairing.

Lagging Strand

The strand of DNA that is synthesized discontinuously in short fragments (Okazaki fragments) during DNA replication, occurring in the 5' to 3' direction away from the replication fork.

tRNA

A type of RNA that helps decode messenger RNA (mRNA) sequences into proteins by bringing the appropriate amino acids to the ribosome during protein synthesis.