THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN

• Both ___1___and transfer _______are used.

1. mRNA 2. RNA (tRNA)

Translation involves switching from the ___1____ "language" to the ___2_____"language."

1. nucleotide 2. amino acid

__codons are possible. • Some amino acids have more than one possible codon.

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• facilitate the export of the mRNA from the nucleus, • protect the mRNA from degradation by cellular enzymes, and • help ribosomes bind to the mRNA. • The ________ themselves are not translated into protein.

A cap and tail of extra nucleotides are added to the ends of the mRNA to:

codes for methionine • also signals the start of transcription (start codon).

AUG

• Transcription rewrites the _________ using the same nucleotide "language."

DNA code into RNA,

1. The anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome. 2. The polypeptide separates from the tRNA in the P site and attaches by a new peptide bond to the amino acid carried by the tRNA in the A site. 3. The P site tRNA (now lacking an amino acid) leaves the ribosome, and the ribosome translocates (moves) the remaining tRNA (which has the growing polypeptide) from the A site to the P site.

Each addition occurs in a three-step elongation process.

ribosomal RNAs and proteins.

Each subunit is composed

adds amino acids to the polypeptide chain until a stop codon terminates translation

Elongation

• the ribosome reaches a stop codon • Stop codons are UAA, UAG, UGA • the completed polypeptide is freed from the last tRNA, and • the ribosome splits back into its separate subunits.

Elongation continues until the termination stage of translation, when:

_____ undergoes processing before leaving the nucleus.

Eukaryotic mRNA

(expressed sequences)

Exons =

establishes where translation will begin.

Initiation

• mRNA • a tRNA bearing the first amino acid • the two subunits of a ribosome.

Initiation brings together

1. An mRNA molecule binds to a small ribosomal subunit, and a special initiator tRNA binds to mRNA at the start codon. • The start codon reads AUG and codes for methionine. • The first tRNA has the anticodon UAC. 2. A large ribosomal subunit joins the small subunit, allowing the ribosome to function. • The first tRNA occupies the P site, which will hold the growing polypeptide. • The A site is available to receive the next amino-acid-bearing tRNA.

Initiation occurs in two steps.

(intervening sequences)

Introns =

• encodes amino acid sequences • conveys genetic messages from DNA to the translation machinery of the cell.

Messenger RNA (mRNA)

amino acids are added one by one to the first amino acid.

Once initiation is complete

_______ the links between genotype and phenotype.

Proteins are?

• The genetic instructions for the amino acid sequence of a polypeptide chain are written in ______ of nonoverlapping three-base "words" called codons.

RNA as a series

_____ removes introns (intervening sequences) and joins exons (expressed sequences) to produce a continuous coding sequence.

RNA splicing

come together during translation. • Have binding sites for mRNA and tRNAs. • The _________ of bacteria and eukaryotes are very similar in function. • However, the differences are medically significant. • Certain antibiotic drugs can inactivate bacterial ________ while leaving eukaryotic ribosomes unaffected. These drugs are used to combat bacterial infections.

Ribosomal subunits

build polypeptides

Ribosomes

•_______ the functioning of mRNA and tRNA and, ultimately, the synthesis of polypeptides.

Ribosomes coordinate

small and large.

Ribosomes have two subunits:

____ codons correspond to amino acids. signal

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from DNA in the nucleus to RNA, and then RNA in the cytoplasm to protein.

The molecular chain of command is:

______ specify one amino acid.

Three nucleotides

1. initiation, 2. elongation 3. termination

Transcription of a gene occurs in three main steps:

the synthesis of RNA under the direction of DNA.

Transcription:

________ function as an, interpreter converting the genetic message of mRNA into the language of proteins.

Transfer RNA (tRNA) molecules

• picking up the appropriate amino acid • using a special triplet of bases, the anticodon, to recognize the appropriate codons in the mRNA.

Transfer RNA molecules perform this interpreter task by:

______ occurs on the surface of the ribosome.

Translation

1. initiation 2. elongation 3. termination

Translation can be divided into the same three phases as transcription:

the synthesis of proteins under the direction of RNA.

Translation:

many eukaryotic genescode for a set of polypeptides (rather than just one) by a process called _________.

alternative splicing.

• Each _____ is specified by a codon.

amino acid

7. Genetic information written in ______ is translated into amino acid sequences

codons

DNA specifies traits by __________

dictating protein synthesis:

as the newly formed RNA strand grows

elongation

nearly universal, in that the ______ is shared by organisms from the simplest bacteria to the most complex plants and animals.

genetic code

• The one gene-one enzyme hypothesis was expanded to _________.

include all proteins.

involving the attachment of RNA polymerase to the promoter and the start of RNA synthesis

initiation

Genes provide the ______ for making specific proteins.

instructions

Eukaryotic RNA is processed before leaving the nucleus as _________.

mRNA

• Even this description is not entirely accurate, in that the ______ transcribed from some genes is not translated but nonetheless has important functions.

mRNA

Protein construction requires a conversion of a _______ to an amino acid sequence.

nucleotide sequence

The genetic code is the amino acid translations of each of the _________.

nucleotide triplets.

The sequence of _______ provides a code for constructing a protein.

nucleotides in DNA

• The initial ______ hypothesis was based on studies of inherited metabolic diseases.

one gene-one enzyme

Genes control _________ through the expression of proteins

phenotypic traits

• Most recently, the one gene-one _______ hypothesis recognizes that some proteins are composed of multiple _________.

polypeptide

The genetic code is _____ with more than one codon for some amino acids • unambiguous, in that any codon for one amino acid does not code for any other amino acid

redundant,

• Eukaryotic mRNA has introns, interrupting sequences that ________, the coding regions.

separate exons

• A group of three _____ is called an anticodon

tRNA bases

when RNA polymerase reaches the terminator DNA and the polymerase molecule detaches from the newly made RNA strand and the gene.

termination

The flow of information from gene to protein is based on a ______.

triplet code.

the end of translation.

• Three "stop" codons UAA, UAG, UGA