Chapter 17: Gene Expression

links between genotype and phenotype

proteins

determine how genes are expressed as traits

proteins

The process by which DNA directs the synthesis of proteins

gene expression

what are the two stages of gene expression

transcription and translation

what did beadle and tatum experiment on

neurospora

what is neurospora

bread mold

George Beadle and Edward Tatum exposed Neurospora to what

x-rays

what happened when George Beadle and Edward Tatum exposed Neurospora to X-rays

mutants were created that couldn't survive on minimal media

what were the mutants created by beadle and tatum missing

arginine

what conclusion did beadle and tatum come to

one gene-one enzyme

each gene controls the production of a specific enzyme

one gene one enzyme

what is the central dogma order

DNA to RNA to protein

DNA → mRNA

transcription

mRNA → polypeptide (protein)

translation

what does transcription start with

DNA

what does transcription create

mRNA

what does translation start with

mRNA

what does translation end with

polypeptide

transcription and translation occur simultaneously

prokaryotes

why do transcription and translation happen at the same time

because there is no nucleus

transcription and translation happen at different times

eukaryotes

The instructions for making proteins are encoded in the

sequence of nucleotides in DNA

Each group of 3 nucleotides (codon) corresponds to one amino acid

triplet code

3 nucleotides

codon

4 bases → ____ possible codons

64

what are the three stop codons

UGA, UAA, UAG

Multiple codons can specify the same amino acid

redundant

can more than one codon code for the same amino acid

yes

each codon has ____ meaning(s)

1

does each codon always code for the same amino acid

yes

Codons must be read in the correct 3-letter grouping

reading frame

Start codon

AUG

what does AUG code for

methanionine

is the genetic code universal for all living things

yes

DNA → RNA

transcription

what direction is mRNA built

5' to 3'

how is DNA read

5' to 3'

does RNA polymerase need a primer

no

enzyme in eukaryotic cells that transcribes DNA into messenger RNA

RNA polymerase II

RNA polymerase II binds to the promoter region of a gene

initiation of transcription

what does RNA polymerase II bind to

promoter region of a gene

It reads the DNA template strand and builds a complementary RNA strand by adding RNA nucleotide

elongation of transcription

Transcription ends once Pol II reaches a termination signal, and the RNA strand is released

termination of transcription

when does termination end in transcription

when RNA polymerase II reaches termination signal

Transcription factors bind to promoter → form

transcription initiation complex

DNA sequence in the promoter that tells RNA polymerase II where to start

tata box

RNA polymerase moves along DNA, unzipping and adding ribonucleotides to growing RNA

elongation in transcription

Termination sequence signals polymerase to stop

termination in prokaryotes

Polyadenylation signal (AAUAAA) tells polymerase to release RNA

termination in eukaryotes

Modified guanine added to protect RNA and help ribosome binding

5' cap

50-250 adenines added to 3' end → protects mRNA from degradatio

poly a tail

Removes introns (noncoding) and joins exons (coding)

rna splicing

added to 5' end

5' cap

Helps the ribosome recognize and attach to the mRNA to start translation

5' cap

added to 3' end

poly a tail

special modified guanine nucleotide

5' cap

It's a long chain of adenine (A) nucleotides

poly a tail

Helps the mRNA exit the nucleus

poly a tail

noncoding

introns

coding

exons

how is RNA splicing done

through splicesome

allows one gene to code for multiple polypeptides

alternative splicing

RNA → Protein

translation

where does translation occur

ribosomes

carries codon instructions

mRNA

brings specific amino acids

tRNA

forms ribosomal structure

rRNA

Has an anticodon that pairs with complementary mRNA codon

tRNA

how does tRNA pair with complementary mRNA codon

through an anitocodon

tRNA enters

a site

holds growing polypeptide chain

p site

tRNA exits

e site

what binds to mRNA in Ribosome binds mRNA, start codon AUG, methionine added

initiation in translation

Codon-anticodon pairing, peptide bond formation, ribosome moves

elongation in translation

Stop codon, release factor, water added

termination in translation

Small ribosomal subunit binds to the mRNA

initation in translation

Initiator tRNA (carrying methionine) binds to the start codon using its anticodon (UAC).

initiation in translation

Translation complex forms

initiation in translation

A new tRNA enters the A site of the ribosome, matching its anticodon with the next codon on the mRNA

elongation in translation

Stop codon (UAA, UAG, or UGA) enters the A site

termination in translation

is there a tRNA for stop codons

no

A release factor protein binds instead

termination in translation

the ribosome disassembles and falls off the mRNA.

termination in translation

Change in a single nucleotide pair in a gene

point mutation s

No change in amino acid

silent mutation

Changes one amino acid

missense mutations

Creates a premature stop codon → shortened, nonfunctional protein

nonsense mutation

May cause frameshift mutation

insertions and deletions

Process by which DNA directs synthesis of proteins (transcription + translation).

gene expression

Synthesis of RNA from DNA template.

transcription

Synthesis of polypeptide from mRNA.

translation

Three-nucleotide sequence on mRNA that codes for a specific amino acid.

codon

Three-nucleotide sequence on tRNA complementary to mRNA codon.

anticodon

Enzyme that synthesizes mRNA from DNA template in eukaryotes.

rna polymerase II

Promoter DNA sequence that helps position RNA polymerase.

TATA box

Noncoding regions removed during RNA splicing.

introns

Coding regions of a gene that remain after splicing.

exons

Complex that removes introns and joins exons.

splicesome

Modified guanine added to 5' end of mRNA.

5' cap

String of adenine nucleotides added to 3' end of mRNA.

poly a tail