Biology Unit 3- central dogma

proteins

serve in transport, storage, or membranes, or they may be toxin or enzymes

enzymes

act as catalysts in biochemical reactions

hormones

chemical-signaling molecules

Central Dogma

DNA -> (Transcription) RNA -> (Translation) Protein

Transcription

the process of creating a complementary messenger RNA (mRNA) copy from a segment of DNA

Translation

the process where ribosomes use the genetic information in messenger RNA (mRNA) to synthesize proteins

intron

a non-coding segment of DNA or a primary RNA transcript that is removed during the splicing process

exon

a segment of DNA or RNA that codes for a protein or a part of a protein

DNA features

double-stranded, deoxyribonucleotides, (A,T,C,G)

RNA features

single-stranded, ribonuclotides, (A,U,G,C)

Messenger RNA (mRNA)

a single-stranded molecule that carries genetic information from DNA in the cell's nucleus to ribosomes in the cytoplasm to be translated in proteins

Ribosomal RNA (rRNA)

serves as the structural and catalytic core of ribosomes

Transfer RNA (tRNA)

acts as an adaptor in protein synthesis by carrying specific amino acids to the ribosome and matching them to the correct cocoons on the mRNA sequence

Micro RNA (miRNA)

RNA molecules that regulate gene expression by binding to messenger RNA and inhibiting protein production

3 steps of transcription

initiation, elongation, termination

Transcription initiation

RNA polymerase binds to a specific DNA sequence called the promoter to begin the process of creating an RNA copy of a gene

Steps of Transcription Initiation

1.) binding to the promotor 2.) DNA unwinding 3.) Template strand selection 4.) mRNA synthesis

transcription factors

proteins that control the rate of gene transcription by binding to specific DNA sequences, RNA polymerase I, II, & III

RNA polymerase II

responsible for transcribing the overwhelming amount of eukaryotic genes

RNA polymerase I

found in the nucleus that synthesis rRNA

RNA polymerase III

transcribes a variety of structural RNAs

enhancers and silencers

DNA sequences that regulate gene expression by controlling the rate of transcription

Stages of Eukaryotic Transcription

Initiation, Elongation, Termination

Transcription Initiation

the enzyme RNA polymerase binds to a specific DNA sequence called a promotor to begin the process of creating an RNA copy of a gene

Transcription elongation

the stage of gene expression where the RNA strand is extended by adding new nucleotides

Transcription Termination

the RNA polymerase detaches from the DNA, releasing the newly synthesized RNA transcript

Spliceosomes

the RNA-protein complex that is responsible for intron-exon splicing in eukaryotes

Steps of mRNA processing

capping, splicing, polyadenylation

Start Codon

AUG

direction transcription & translation occurs

5' to 3' direction

Degeneracy

cellular mechanism to reduce the negative impact of random mutations

Ribosome

a complex macromolecule composed of structural and catalytic rRNA

Polypeptide chain

long, linear sequence of amino acids linked together by peptide bonds

A site (Aminoacyl site)

entry point for new tRNA molecules that carry an amino acid

P site (Peptidyl site)

holds the tRNA that is attached to the growing polypeptide chain. A peptide bond forms between the amino acid in the A site and the polypeptide chain in the P site, and the chain is transferred to the tRNA in the A site

E site (Exit site)

After the polypeptide chain has been transferred to the new tRNA, the now-uncharged tRNA moves to the E site

Point mutation

mutations that affect a single base pair

Substitution Mutation

one base is replaced by another

Silent Mutations

Point mutations that are not detectable in the final product

Nonsense mutation

point mutation that generates a stop codon

Missense mutations

results in the replacement of one amino acid by another, which may alter the function of the protein

Insertion

addition of a base

Deletion

removal of a base

Gene expression

the process of turning on a gene to produce RNA and protein

Repressor

prevent transcription of a gene in response to an external stimulus

Activators

increase the transcription of a gene

lac operon

turns off under normal conditions (high glucose)

turns on when glucose is absent and lactose is present

trp operon

when tryptophan is present = repressor binds to operator, blocking synthesis

absence of tryptophan = repressor dissociates from operator, synthesis proceeds

gel electrophoresis

The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.

Reproductive cloning

method scientists use to clone or identically copy an entire multicellular organism

Parthenogenesis

an embryo grows and develops without egg fertilization

Genetic recombination

exchanging DNA between homologous chromosome pairs

Cytogenetic mapping

uses information from microscopic analysis of stained chromosome sections

Radiation hybrid mapping

uses radiation, such as x-rays, to break the DNA into fragments

Sequence mapping

DNA sequencing technology that allowed for creating detailed physical maps with distances measured in terms of the number of base pairs

methylation

tightly packed (gene silencer)

acetylation

loosely packed

Top strand

coding strand

Bottom strand

template strand

Nondisjunction

the failure of homologous chromosomes or sister chromatids to separate properly during cell division

Anticodon

the opposite of the codon (ex. AUG = UAC)

DNA microarray

a set of DNA sequences representing the entire set of genes of an organism, arranged in a grid pattern for use in genetic testing.