protein synthesis

Question 1

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Central Dogma of protien synthesis

Answer 1

A eukaryotic organism’s genome is found within the nucleus

Proteins are synthesized by ribosomes either on the ER or in the cytoplasm

The information for protein synthesis is specified by DNA, but this DNA is not allowed to leave the nucleus

DNA is copied to single-stranded RNA to leave the nucleus

Question 2

Main process of Protien synthesis

Answer 2

DNA is copied as a single-stranded messenger RNA molecule (transcription)

The ribosomes then have to translate the messages into polypeptide chains, which are processed into proteins (translation)

Question 3

One Gene – One Polypeptide Hypothesis

Answer 3

rior knowledge:
- Genes direct the production of proteins
- Proteins determine the phenotypes of organisms.
- Dominant alleles produce proteins, recessive alleles do not.

Based on this knowledge and the Central Dogma, the One Gene – One Polypeptide Hypothesis was developed:
- one gene codes for one polypeptide (or protein)

Question 4

RNA – Ribonucleic Acid

Answer 4

3 types:
- Messenger RNA (mRNA) – carries the code from DNA to the ribosome
- Transfer RNA (tRNA) – carries amino acids to the ribosome
- Ribosomal RNA (rRNA) – makes up part of the ribosome (the rest is protein), construction site for proteins

Differences from DNA:
- OH on 2ʹ carbon in ribose sugar
- A pairs with U (uracil)
- Single Stranded

Question 5

Transcription overall

Answer 5

Transcription involves the copying of the information encoded in DNA into messenger RNA (mRNA)

When you transcribe, you copy from one medium to another
In this case from DNA to RNA

DNA: 3’ ATG – GCA – TAC 5’
RNA: 5’ UAC – CGU – AUG 3’

Question 6

Translation overall

Answer 6

Translation involves ribosomes using the messenger RNA (mRNA) as a blueprint to synthesize a protein composed of amino acids

When you translate, you convert into a different language
In this case the language of mRNA is translated into the language of amino acids

mRNA: 5’ AUG – CAU – UAA 3’
amino acids: Met – His – stop

Question 7

how DNA and mRNA is read

Answer 7

DNA is read from 3-5; the mRNA is read from 5-3!!
mRNA is anti-parallel to DNA

Question 8

mRNA codons you should know

Answer 8

• Start Codon- AUG
  *signal initiation
• Stop Codons- UGA, UAA, UAG
  *signal termination
• Multiple codons for the same amino acid.
• *to have “backup” if a point mutation occurs

Question 9

Overview of Transcription

Answer 9

The Major Steps in Transcription are:
- Initiation
RNA polymerase binds to the DNA at a specific site called the promoter, near the beginning of the gene
- Elongation
Using the DNA as a template, the enzyme RNA polymerase puts together the appropriate ribonucleotides and builds the mRNA transcript
- Termination
Shortly after the RNA polymerase passes the end of a gene, it recognizes a signal to stop transcribing

The mRNA is then released from the DNA and will eventually exit the nucleus

Question 10

Overview of Translation

Answer 10

The major steps in translation are:
- Initiation
Occurs when a ribosome recognizes a specific sequence on the mRNA and binds to that site
- Elongation
The ribosome then moves along the mRNA three nucleotides at a time
Each set of three nucleotides codes for an amino acid
A tRNA delivers the appropriate amino acid and the polypeptide chain is elongated
- Termination
When the ribosome reaches a special three-base nucleotide sequence that does not code for an amino acid, this provides the “stop” signal
The ribosome falls off the mRNA and the polypeptide chain is released