Biology: DNA Structure & Gene Function

nucleic acid

DNA and RNA

transcription

DNA acts as a template for the synthesis of RNA

RNA processing

Modification of RNA transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' (mG cap) and 3' ends (poly A tail); only in eukaryotes

translation

the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm

RNA polymerase

An enzyme that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

antisense strand

DNA strand acting as template for transcription

sense strand

strand that has the same base sequence as the mRNA

rRNA

RNA that is combined with special protein that makes up a ribosome

ribosome

Cytoplasmic organelles at which proteins are synthesized during translation

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

DNA triplet

complimentary to mRNA codon; found in DNA

codon

A specific sequence of three adjacent bases on a strand of mRNA that provides genetic code information for a particular amino acid.

anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

AUG

start codon

methionine

first amino acid in most proteins

UGA, UAG, UAA

stop codons

nucleolus

A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes

TATA box

A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex.

promoter

A specific nucleotide sequence in DNA (TAC) that binds RNA polymerase and indicates where to start transcribing RNA.

transcription factors

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

TTATTT

The terminator sequence for transcription

primary mRNA

eukaryotic RNA before it has been processed.

mG cap

added to the 5' end of mRNA during RNA processing; prevents destruction of the mRNA

poly A tail

The modified end of the 3' end of an mRNA molecule consisting of the addition of some 1000 to 250 adenine nucleotides.

RNA splicing

process by which the introns are removed from RNA transcripts and the remaining exons are joined together

introns

A segment of a gene situated between exons that is removed before translation of messenger RNA and does not function in coding for protein synthesis.

exons

A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.

spliceosome

A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.

charged tRNA

a transfer RNA molecule to which the appropriate amino acid has been attached to the acceptor stem

A site

site in the ribosome that holds the tRNA carrying the next amino acid to be added to the polypeptide chain.

P site

site in the ribosome where peptide bonds are formed between amino acids on a growing polypeptide chain

E site

site in the ribosome where uncharged tRNAs leave the ribosome.

frame shift

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

operon

A segment of DNA containing adjacent genes including structural genes and an operator gene and a regulatory gene

inducible gene

Genes whose expression is turned on by the presence of some substance. Regulate catabolic pathways.

repressible gene

A gene that is regulated by a corepressor or inhibitor, which are small effector molecules that cause transcription to decrease.

lac operon

a gene system whose operator gene and three structural genes control lactose metabolism in E. coli

trp operon

Group of genes that are used or transcripted together that codes for the components for production of tryptophan

virus

ultramicroscopic particles that contain nucleic acids, proteins, and sometimes lipids

capsid

Outer protein coat of a virus

lytic infection

Process in which a virus enters a cell, makes a copy of itself, and causes the cell to burst.

lysogenic infection

process by which a virus embeds its DNA into the DNA of the host cell and is replicated along with the host cell's DNA

retrovirus

An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer

reverse transcriptase

An enzyme encoded by certain viruses that uses RNA as a template for DNA synthesis.

duplication

Change in chromosome structure in which a particular segment is present more than once in the same chromosome

translocation

Change to a chromosome in which a fragment of one chromosome attaches to another part of a chromosome

inversion

a kind of mutation in which the order of the genes in a section of a chromosome is reversed

missense

A point mutation in which a codon that specifies an amino acid is mutated into a codon that specifies a different amino acid.

nonsense

Name the type of mutation where the new codon specifies for a stop codon

silent

A type of mutation where there is no change in the resulting polypeptide.

beta

galactosidase

permease

a protein that aids in the movement of lactose across the cell membrane

regulatory gene

A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.

promoter region

1st region of a gene, turns gene on and off, informs the gene when protein synthesis must begin

operator region

Binds repressors and inducers (start and stop transcription). Located between the promoter region and the start site.

tryptophan synthetase

enzyme encoded by the trp genes; made up of 5 different proteins

miRNA

functions in RNA interference and post

antiparallel

The opposite arrangement of the sugar

siRNA

use in degrading mRNA

chaperone proteins

Assist in folding other proteins into secondary and tertiary structure

germline mutation

mutation that occur in gametes (sperm & egg); passed onto next generation

somatic mutation

a mutation that occurs in a body cell; not passed onto next generation

vaccine

A weakened or inactive version of a pathogen that stimulates the body's production of antibodies which can aid in destroying the pathogen

viroid

An infectious particle that consists solely of a strand of RNA and is capable of causing disease in plants

prion

Any of various infectious proteins that are abnormal forms of normal cellular proteins, that proliferate by inducing the normal protein to convert to the abnormal form; causing mad cow disease, kuru, and CJD