Halloran Honors Bio - 11 Protein Synthesis, Gene Expression & Mutations

genome

all the genetic material in an organism's cells

DNA

nucleic acid molecule shaped as a double helix; capable of replicating and determining the inherited structure of a cell's proteins

nucleotide

the subunit of DNA; composed of phosphate, deoxyribose sugar, and a nitrogenous base (A, G, C, or T)

RNA

a type of nucleic acid consisting of ribonucleotides; usually single-stranded; functions in protein synthesis and as the genome of some viruses

ribonucleotide

the subunit of RNA; composed of phosphate, ribose sugar and a nitrogenous base (A, G, C, or U)

chromosome

a single piece of supercoiled DNA with associated organizational proteins; found in the nucleus of eukaryotic cells; contains genes that encode traits

chromatin

a loose, more dispersed form of DNA, existing as a mass of very long, thin fibers; state of the DNA when the cell is not dividing

gene

a section of DNA that codes for how to make a certain protein

protein

biomolecule that consists of CHONS; subunits are amino acids; constructed using the information found in genes

trait

an observable, genetically determined characteristic of an organism

transcription

the process in which the genetic code sequence in DNA is copied to mRNA; occurs in the nucleus of eukaryotic cells

translation

the process in which the genetic information coded in mRNA is read by a ribosome and directs the formation of a specific protein; occurs in the cytoplasm

mRNA

messenger RNA; synthesized from DNA, attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein

rRNA

ribosomal RNA; a globular form of RNA that is combined with proteins to form a ribosome

tRNA

transfer RNA; molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA

RNA polymerase

enzyme that matches a complementary ribonucleotide to the DNA template strand then seals it onto the growing mRNA strand using dehydration synthesis

transcription initiation

transcription factors align RNA polymerase

transcription elongation

RNA polymerase uses code on the template strand of the DNA to build a strand of mRNA

transcription termination

RNA polymerase stops building mRNA when it reaches the terminator sequence on the DNA

promoter

DNA sequence found just before the start of a gene where transcription factors bind to help guide RNA polymerase into place

terminator

DNA sequence found at the end of the gene that triggers RNA polymerase to stop transcription

complementary base pairing

the alignment of hydrogen bonding between particular pyrimidines and purines (Adenine & Thymine; Guanine & Cytosine)

template strand

the side of the DNA used to create mRNA during transcription; read 3' - 5'; also known as the sense strand

sense strand

the side of the DNA used to create mRNA during transcription; read 3' - 5'; also known as the template strand

nontemplate strand

the side of the DNA temporarily held aside during transcription (not used); runs 5' - 3'; also known as the antisense strand

antisense strand

the side of the DNA temporarily held aside during transcription (not used); runs 5' - 3'; also known as the nontemplate strand

splicing

eukaryotic mRNA editing in which introns are removed from the pre-mRNA and exons are ligated together; splicing of pre-mRNA can be different in different tissues

introns

noncoding sections within a eukaryotic gene that are cut out of the mRNA

exons

the coding regions of a eukaryotic gene that are kept and spliced together during mRNA editing

ligase

the enzyme that connects two fragments of nucleic acid to make a single fragment; connects mRNA exons during editing

mRNA cap

a short sequence of modified nucleotides added to the 5' end of the mRNA molecule

poly A tail

the modified end of mRNA in which 50-250 adenine nucleotides are added to the 3' end

triplet

sequence of three nucleotide bases on DNA

codon

sequence of three ribonucleotide bases on mRNA

anticodon

sequence of three ribonucleotide bases on tRNA

ribosome

cell organelle constructed by the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of two subunits composed of rRNA and protein molecules

small ribosomal subunit

binds on first during translation

large ribosomal subunit

binds onto the small ribosomal subunit once the first tRNA molecule has bound to the start codon

A site

accepts the new incoming tRNA

P site

the amino acid chain from the tRNA at this site is peptide bonded to the incoming amino acid at the A site

E site

where empty tRNAs from the P site are shifted to exit the ribosome

amino acids

the monomers of proteins

polypeptide chain

a linear chain of amino acids

peptide bonds

the bonds that join amino acids

AUG

start codon; codes for methionine

methionine

the first amino acid in most proteins; called for by the start codon AUG

stop codon

codes for a releasing factor which triggers the ribosome to stop translation, detach from the mRNA and release the polypeptide chain

operon

a group of genes whose transcription is controlled by a promoter and operator

operator

the DNA sequence prior to a group of genes where the repressor can bind to prevent transcription

repressor

a protein that can bind to the operator and prevent the trancription of the genes

inducer

a specific small molecule that inactivates the repressor in an operon

transcription factors

a regulatory protein that binds to DNA and affects transcription of specific genes

TATA box

a DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex

TATA binding protein

finds and binds to the TATA box, the DNA sequence that signals the start of transcription, and then distorts the DNA helix so other transcription factors can join in

enhancers

a DNA sequence that recognizes certain transcription factors that can stimulate transcription of nearby genes

histones

proteins that assist in DNA coiling in eukaryotes; DNA helix is wrapped around a group of 8 histones to form a nucleosome

proteome

the set of proteins expressed by an organism's cells

mutation

a change in a cell's DNA sequence

point mutation

mutation in which one nucleotide base is exchanged for another; also known as a substitution mutation

silent mutation

a base substitution which results in the same amino acid being encoded

missense mutation

a base substitution which results in a different amino acid being coded for

nonsense mutation

a base substitution in which the new codon codes for stop; often results in the polypeptide chain ending too early

frameshift mutations

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide; may change every amino acid that follows the point of the mutation

addition

mutation that inserts an additional nucleotide into the gene; results in a frameshift

deletion

mutation that deletes a nucleotide from the gene; results in a frameshift

mutagen

any external, environmental agent that induces mutations

allele

different coding versions of a gene; create the variants for a trait

sickling hemoglobin

variant form of hemoglobin produced from a single point mutation in the hemoglobin gene

somatic cell

any body cell other than a reproductive cell

germ cell

a cell that develops into a reproductive cell

homeotic gene

genes that determine which parts of the body form what body parts

syndactyly

a genetic mutation that results in the fusion of digits

polydactyly

a genetic mutation that results in the formation of additional digits