How Proteins Are Made

Why is there more opportunity for gene regulation in eukaryotic cells than in prokaryotic cells?

A nuclear membrane separates transcription from translation in eukaryotes.

The mRNA codon for starting transcription is

AUG

What are enhancers?

An enhancer is a sequence of DNA that influences transcription but is located thousands of nucleotide bases away from the promoter.

codons, genetic code

Codons are sequences of three nucleotides in an mRNA molecule that correspond to particular amino acids. The genetic code is the amino acids and "stop" and "start" signals coded for by mRNA codons.

Why have no operons been found in eukaryotic cells?

Gene expression is more complex in eukaryotes, and genes with related functions are often scattered on different chromosomes.

The operon that controls the metabolism of lactose is called the ___________

Iac operon

What are introns and exons?

Introns are long segments of nucleotides in eukaryotic genes that have no coding information. Exons are the portions of a eukaryotic gene that are translated into proteins.

What might be the evolutionary advantage of genes being interrupted by introns?

Introns might add evolutionary flexibility because each exon encodes a different part of the protein and cells can shuffle exons between genes, which makes new genes.

RNA polymerase adds complementary [DNA / RNA] nucleotides as it "reads" the gene.

RNA

RNA, messenger RNA

RNA is a type of nucleic acid. Messenger RNA is a form of RNA that carries the instructions for making a protein from a gene to the site of translation.

Transcription begins when [RNA / RNA polymerase] binds to the gene's promoter.

RNA polymerase

What happens to mRNA that includes introns?

The mRNA that contains introns becomes smaller when enzymes cut out the introns and "stitch" the exons back together.

10. What determines where on the DNA molecule transcription begins and where it ends?

Transcription begins at a gene's promoter, a specific sequence of DNA that acts as a "start" signal for a gene that is to be transcribed. Transcription ends at a sequence of bases that acts as a "stop" signal.

What are two differences between transcription and DNA replication?

Transcription makes RNA molecules, and DNA replication makes copies of DNA molecules. Also, in DNA replication, both strands of DNA are used as templates. In transcription, only one strand is used as a template.

ribonucleic acid (RNA)

a model made of linked nucleotides

uracil

a nitrogen base used in RNA instead of the base thymine found in DNA

When can gene regulation occur in eukaryotic cells?

before, during, and after transcription and after mRNA leaves the nucleus or after the protein is functional

17. If a mutation causes a sequence of nucleotides to change from ACGAGA to ACGGA, the mutation is called a(n) [insertion / deletion] mutation.

delection

To break down lactose, Escherichia coli need three different ___________ ,each of which is coded for by a different gene.

enzymes

Mutations can only be passed on to offspring if they occur in [gametes / body cells].

gametes

If a mutation causes a sequence of nucleotides to change from ACGAGA to ACGAGGA, he mutation is called a(n) [insertion / deletion] mutation.

insertion

In eukaryotes, transcription takes place in the [nucleus / cytoplasm].

nucleus

The piece of DNA that overlaps the promoter site and serves as the on-off switch is called a(n) ___________

operator

The group of genes that codes for enzymes involved in the same function, their promoter site, and the operator all function together as a(n)_____________ .

operon

Mutations that change one or just a few nucleotides in a gene on a chromosome are called [random / point] mutations.

point

The three genes are located next to each other and all are controlled by the same_________site.

promoter

A(n) ______________is a protein that binds to an operator and physically blocks RNA polymerase from binding to a promoter site.

repressor

If a mutation causes a gene containing the nucleotide sequence ACA to become ACT, he mutation is called a [substitution / deletion] mutation.

substitution

gene expression

the entire process by which proteins are made

translation

the process of reading instructions on an RNA molecule to put together the amino acids that make up protein

transcription

the process of transferring a gene's instructions for making a protein to an RNA molecule