Unit 6 topic 3-4

List and describe the steps in translation.

1. Initiation: Transcription begins when RNA polymerase molecules attach to a promoter region of DNA. In eukaryotes, they use transcription factors to help them bind to the TATA box. In prokaryotes, they bind directly to a promoter. 2. Elongation: RNA polymerase opens the DNA and reads the triplet code of the template strand. It moves downstream in the 3' to 5' direction and pairs complementary RNA nucleotides. (The mRNA transcript elongates 5' to 3'.) The growing mRNA strand peels away from the DNA template strand. The double helix then reforms. 3. Termination: In eukaryotes, RNA polymerase transcribes a sequence of DNA called the polyadenylation signal sequence, which codes for a polyadenylation signal (AAUAAA). This releases the pre-mRNA from the DNA, which must undergo modifications before translation. In prokaryotes, transcription proceeds through a termination sequence, which causes a termination signal. RNA polymerase detaches, mRNA transcript is released and proceeds to translations. mRNA does NOT need modifications

Referring to question 10, imagine if the coding strand were transcribed and translated instead. Determine the mRNA sequence and translate it. How would this error affect the polypeptide produced?

3'-CAACACUAA-5' this would produce the incorrect polypeptide because we have the incorrect codons

An mRNA sequence reads 5'- CGAUGCAGA-3'. Translate assuming you are downstream of the start codon

3'-GUACGUCU-5'

A section of the template strand of DNA reads 5'°-CAACACTAA-3' Determine the mRNA sequence and translate it.

3'-GUUGUGAUU-5'

If the tRNA anticodon reads 3'-CUU-5' then what does the mRNA codon read that it can bind to? Knowing this, what amino acid will the tRNA be carrying?

5'-GAA-3"; Glu

Poly-A tail

50-250 adenine nucleotides added to the 3' end of the pre-mRNA

What is a promoter region? Are they upstream or downstream of the gene?

A promoter region is an area on DNA strand where RNA polymerase attaches; in eukaryotes they are the TATA box. They are located upstream.

Referring to question 3, what is the codon that the RNA binds to?

AUG

What does it mean that DNA strands are complementary and antiparallel?

DNA is complementary because the bases A and T always pair and C and G always pair. It is antiparallel because one strand runs from the 3' to 5' end and the other strand runs from 5' to 3'.

True or false: the genetic code is read in groups of 2 nucleotides at a time called the doublet code.

False! 3; triplet code

Describe the consequences of a chemical that prevents the 5' cap and poly A tail from forming on eukaryotic mRNA.

If the 5' cap and poly A tail did not form, the mature mRNA could not leave the nucleus as easily, it would not be protected from degredation, and ribosomes would have trouble attaching to the 5' end of the mRNA when it reaches the cytoplasm.

What would be the immediate effect on transcription if a cell was exposed to a drug that mutated the promoter region?

If the promoter region was mutated, then RNA polymerase would not be able to bind to the DNA and transcription would not be able to OCCUr.

Why do introns exist if they are just spliced out of the mRNA during pre MRNA modifications?

Introns exist so that there will be more genetic variation in the DNA; a single gene can produce many different proteins due to splicing.

Referring to question 3, which amino acid does this tRNA carry?

Methionine

The very first tRNA will enter at which site?

P site

RNA splicing

Process by which introns are removed and exons are joined together.

Identify the major classes of macromolecules and identify their monomers and polymers

Proteins: monomers=amino acids, polymers-polypeptides Carbohydrates: monomers-monosaccharides, polymers=polysaccharides Lipids: monomers=glycerol and fatty acids, no true polymers Nucleic acids: monomers=nucleotides, polymers=DNA and RNA

Why is redundancy in the genetic code important?

Redundancy is so important because it prevents single mutations from being detrimental and lessens the likelihood of a harmful mutation occUrIng

In eukaryotic cells, where does transcription occUr?

The nucleus

Trace the path of a newly produced polypeptide that will leave the cell?

The polypetide folds into an active protein and goes on to perform its functions within the cell

Summarize the purpose of translation in 1-2 sentences.

The process of translating mRNA to a sequence of amino acids during protein synthesis. The genetic code shows the sequence of base pairs in a gene and the corresponding amino acid sequence it encodes.

True or false: only the template strand is transcribes during transcription.

True

Using a codon chart determine what UAU codes for

Tyr

5' Cap

a modified guanine nucleotide "cap" attached to the 5' end of the pre mRNA

Anticodon

a region of tRNA that consists of three bases complementary to the codon of mRNA

Alternative splicing

a single gene can code for more than one kind of polypeptide

tRNA has an _ region which is complementary and antiparallel to

anticodon; the mRNA codon

Where does translation occUr?

at the ribosome in the cytoplasm

Stop codon

codons that do not code for amino acids; signal for a release factor which hydrolyzes the bond that holds the polypeptide to the P site, the polypeptide releases, and all transitional units disassemble; UAA, UAG, UGA

The mRNA nucleotide triplets are called . These code for

codons; amino acids

tRNA

each carries a specific amino acid and attach to mRNA through their anticodon, a complementary codon to mRNA

rRNA

helps form ribosomes and helps link amino acids together through dehydration synthesis

How does transcription and translation differ between prokaryotes and eukaryotes?

in eukaryotes the processes take place in different cellular compartments whereas both processes share space and time in prokaryotes. RNA is processed in the nucleus in eukaryotes and the cytoplasm for prokaryotes.

Codon

mRNA nucleotide triplets that code for amino acids

mRNA

messenger RNA; synthesized during transcription using a DNA template; carries information from the DNA at the nucleus to the ribosomes in the cytoplasm

Redundancy

more than one codon codes for each amino acid

Reading frame

the codons on the mRNA must be read in the correct groupings during translation to synthesize the correct proteins

Template strand

the one strand of DNA that is being transcribed into mRNA; also known as the noncoding strand

Gene expression

the process by which DNA directs the synthesis of proteins

Transcription

the synthesis of RNA using information from DNA; allows for the message of the DNA to be transcribed

Translation

the synthesis of a polypeptide using information from the mRNA

Protein synthesis occUrs in 2 stages:

transcription, translation

The process of DNA to RNA. The process of turns RNA into proteins. converts

transcription, translation

tRNA

transfer RNA; type of RNA that has am anticodon region that binds to mRNA via their codon; carries amino acids

When does translation stop?

when a stop codon is reached