SBI4U Ch7 Review

One Gene-One Enzyme Hypothesis

The hypothesis, proposed by Beadle and Tatum, that each gene is unique and codes for the synthesis of a single enzyme

One Gene-One Polypeptide Hypothesis

The hypothesis that each gene is unique and codes for the synthesis of a single polypeptide; the restated version of the one gene-one enzyme hypothesis

Central Dogma

The fundemental principle of molecular genetics, which states that genetic information flows from DNA to RNA to proteins

Transcription

Mechanism by which the information coded in nucleic acids of DNA is copied into the nucleic acids of RNA; something rewritten in the same language

Translation

Mechanism by which the information coded in the nucleic acids of RNA is copied into the amino acids of proteins

Messenger RNA (mRNA)

The end product of the transcription of a gene; mRNA is translated by ribosomes into a protein

Transfer RNA (tRNA)

A carrier molecule that binds to a specfic amino acid and adds the amino acid to the growing polypeptide chain

Ribosomal RNA (rRNA)

an RNA molecule within the ribosome that bonds the correct amino acid to the polypeptide chain

RNA polymerase

an enzyme that reads a DNA strand and creates a complementary strand of RNA

Template strand

the DNA strand that is copied into an mRNA molecule durng gene transcription

Genetic Code

The specific coding relationship between bases and amino acids they specify; the genetic code can be expressed in terms of either RNA or DNA bases

Codon

A group of three base pairs that code for an individual amino acid

Start Codon (Initiator Codon)

The codon that signals the start of a polypeptide chain and initiates translation

What is the one start codon and its corresponding amino acid?

AUG and Methionine

Stop Codon

A codon that signals the end of a polypeptide chain and causes the ribosome to terminate translation

What are the three stop codons?

UAA, UAG, and UGA

Promoter

A nucleotide sequence that lies just before a gene and allows for the binding of RNA polymerase

TATA box

A region of the promoter that enables the binding of RNA polymerase

Coding strand

The DNA strand that is not being copied, but contains the same sequence as the new RNA molecule

Termination sequence

A sequence of bases at the end of a gene that signals the RNA polymerase to stop transcribing

poly(A) tail

A chain of adenine nucleotides that are added to the 3’ end of the pre-mRNA to protect it from enzymes in the cytosol

5’ cap

A sequence of seven Gs that is added to the start of a pre-mRNA molecule; the ribosomes recognize this site and use it as the site of initial attachment

Exon

A sequence of RNA or DNA that codes for part of a gene

Intron

A non-coding sequence of DNA or RNA

Spliceosome

an enzyme-protein complex that removes introns from the mRNA

Small ribonucleoprotein (snRNP)

A protien that binds to introns and signals them for removal

Alternative splicing

A process that produces different mRNAs from pre-mRNA (exons and introns), allowing more than one possible polypeptide to be made from a single gene

anticodon

the complementary sequence of base pairs on a tRNA that corresponds to a codon on an mRNA

Aminoacylation

The process by which a tRNA molecule is bound to its corresponding amino acid

aminoacyl-tRNA

a molecule of transfer RNA bound to its associated amino acid

Reading Frame

A particular system for seperating a base pair sequence into readable codons

polysome

a complex that is formed when multiple ribosomes attach to the same mRNA molecule in order to facilitate rapid translation

Insulin

A hormone produced in the pancreas that lowers the blood glucose level by promoting the uptake of glucose by the body cells

lac operon

a cluster of genes that contains the DNA sequence to regulate the metabolism of lactose

operator

the region in the operon that regulatory factors bind to

repressor protein

a protein that binds to the operartor to repress gene transcription

inducer

a signal molecule that triggers the expression of an operon’s genes

corepressor

signal molecule that binds to a regulatory protein to reduce the expression of an operon’s gene

how do cancer cells work

cancer cells lack tumor suppressor genes and otjher regulators because of mutations

Point mutation

a change in a sungle nucleotide within a gene

substitution

the replacement of one pair in a DNA sequence by another base pair

Insertion

the addition of a base pair (small-scale mutation) or larger coding region (large-scale mutation) to a DNA sequence

Deletion

the removal of a base pair (smal-scale mutation) or larger coding region (large scale mutation) from a DNA sequence

Inversion

Two adjacent bases trading places (small-scale mutation) or the reversal of the sequence of DNA (large-scale mutation)

Single nucleotide polymorphism (SNP)

a difference in the DNA between individuals caused by point mutations

missense mutation

mutation that changes a single amino acid in the coding sequence

nonsense mutation

a mutation that results in a premature codon stop

silent mutation

a mutation that does not alter the resulting sequence of amino acids

frameshift mutation

a shift in the reading frame resulting in multiple missense/nonesense effects

translocation

the movement of entire genes or sequences of DNA from one chromosome to another

spontaneous mutation

mutation that is caused by an error in DNA replication

induced mutation

mutation that is caused by an environmental agent

mutagen

environmental agent that direcrtly alters the DNA within a cell

Mutagen examples

carcinogens, chemicals, radiation