Protein Synthesis

Ribosome sites

- A site: tRNA docks - P site: tRNA with growing polypeptide - E site: exit

Transcription

- DNA to RNA - mRNA product of transcription - begins at promoter region - rewrites code - only 1 strand is transcribed

Translation

- RNA to protein - info in mRNA is delivered to ribosome to produce proteins - a cell translates mRNA into protein with the help of tRNA

tRNA

- carries specific amino acids to the ribosome - not identical - specific amino acid and anticodon that corresponds with its amino acid

Effects of Mutations

- could be fatal - adaptations

RNA splicing

- introns (noncoding) removed - exons (expressible) joined

new polypeptide chain will undergo modification

- primary: polypeptide chain - secondary: alpha coils & beta pleated sheets - tertiary: 3D structure - quaternary: complex of multiple proteins

Insertions & Deletions Mutations

- results in frameshift mutations - missense and nonsense

Substitution Mutation

- silent: no affect, same amino acid - missense: diff amino acid - nonsense: stop codon

promoter regions

- where RNA Polymerase binds - A & T pairs

Steps of Transcription

1. Initiation - RNA Polymerase binds at promoter 2. Elongation - add nucleotides 3. Termination - enzyme detaches

# of amino acids

20

The genetic code uses ________ nucleotide(s) to specify one amino acid.

3

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

Alteration of mRNA ends

5' end Guanine cap 3' end 20 - 250 adenine nucleotides

If transcription is like copying out a recipe and translation is like baking the cake, what is a mutation like?

An error in the recipe's list of ingredients.

Which statement about the genetic code is false?

Codons code for amino acids only.

Structural damage to DNA resulting from exchange of fragments between non-homologous chromosomes is potentially very harmful, some causing cancer. This is called what?

Crossing over

A spontaneous mutation usually originates as an error in

DNA replication

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

THE DOG SAT changes to THE DOG TAS

Point Mutation

Differences between DNA and RNA

RNA has ribose, uracil, and is single-stranded

Which of these is a mutagen (anything that can cause genetic mutation)?

UV

In eukaryotes, translation takes place

at ribosomes

RNA Polymerase

binds to promoter region to open up double helix

mRNA

carries DNA message to the ribosome

Induced Cause of Mutation

caused by physical or chemical agents called mutagens

During translation, the nucleotides that make up the mRNA are read in groups of three. These groups are called

codons.

The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon.

A frameshift mutation could result from

either an insertion or a deletion of a base.

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes

excision of introns.

What are the coding segments of a stretch of eukaryotic DNA called?

exons

What type of gene mutation results from the insertion or deletion of nucleotides and alters the entire amino acid sequence from that point forward

frameshift

Spontaneous Cause of Mutation

occurs during DNA replication, recombination, or repair

Sickle-cell disease is probably the result of which kind of mutation

point and missense

Messenger RNA molecules contain information that is used to synthesize ________.

polypeptides

To begin transcription, RNA polymerase must bind to a segment of DNA called the ________.

promoter

In eukaryotes, pre-mRNA processing may involve all of the following except

removal of exons from the pre-mRNA

The polypeptide-making organelles, which consist of protein combined with RNA, are called

ribosomes

Point mutations include

substitutions, insertions, deletions

A & T pairs are easier to open because

they only have 2 hydrogen bonds

2 stages of protein synthesis

transcription and translation

During ________, a ribosome assembles a polypeptide whose amino acid sequence is specified by the nucleotide sequence in a molecule of mRNA.

translation

Many mutations are neutral, some are disadvantageous, and others are beneficial. (T/F)

true

rRNA

type of RNA that makes up part of the ribosome