Protein Synthesis Flashcards
What is meant by “the genetic code is universal” and why is this significant?
It is used by all known organisms as the code for the DNA, mRNA, and tRNA. It is like a universal language.
What is transcription?
The copying of the info. in DNA to mRNA.
What is translation?
The ribosomes using the mRNA as a blueprint to synthesize a protein.
What does mRNA stand for and what does it do?
Messenger RNA. It copies DNA’s code & carries genetic info. to ribosomes.
What does rRNA stand for and what does it do?
Ribosomal RNA. Along with protein, makes up ribosomes.
What does tRNA stand for and what does it do?
Transfer RNA. Transfers amino acids to ribosomes where no proteins are synthesized.
RNA polymerase
An enzyme that transcribes DNA into complementary mRNA.
Describe tRNA.
- clover leaf shape
- single stranded with attachment site at one end for amino acid
- opposite end has 3 nucleotide bases called anticodon
What is the codon and what is its function?
A sequence of 3 bases in DNA or complementary mRNA that serves as a code for a certain amino acid. It designates amino acids.
What is a start codon and stop codon?
A start codon signals the ribosome that the translation starts here and a stop codon does the opposite.
Describe mRNA
- long straight chain
- made in nucleus
- sequence of 3 bases (codon)
- AUG (methionine) is start codon
- UAA,UAG or UGA are stop condons
Describe rRNA
- made in nucleus
- site of protein synthesis
How many amino acids are there and how many possible combinations of codons are there?
20 amino acids and 64 possible codons
Can an amino acid have more than 1 codon?
Yes
List the codons for these amino acids:
Gly-Phe-Lys
Glycine
Phenylalanine
Lysine
What are the possible sequences for:
Gly-Phe-Lys
GGG, GGC, GGA, GGU
UUU, UUC
AAA, AAG
What is the first major step of protein synthesis? Briefly describe it.
Initiation. The enzyme RNA polymerase binds to the DNA double helix and unwinds the strand exposing the template strand.
What is the central dogma?
It states that DNA -> RNA -> protein.
Why does RNA polymerase bind “upstream” of the DNA.
The upstream region consists of mainly A and T base pairs with 2 H bonds. It takes less energy to break them apart so less energy is expended opening the helix.
What is the second step of protein synthesis?
Elogation. mRNA is synthesized in the direction of 5’ to 3’ using one strand as a template. RNA polymerase synthesizes mRNA. Termination sequence is reached.
Is it in DNA replication or protein synthesis that RNA polymerase does not require a primer?
Protein synthesis.
What is the third step of protein synthesis?
Termination. RNA synthesis ceases. The mRNA and RNA polymerase are released.
Differences of DNA replication and transcription.
- Rep. occurs in preparation for cell division
- Tran. in preparation for protein translation
- Rep. for regulating growth/division of cells
- Rep will not occur is certain growth factors are missing
- Tran. Regulate gene expression
- Tran. only occurs when gene is activated
Similarities between DNA replication and transcription
- involve binding complementary nucleic acids
- yield a new strand of info.
- can both lead to errors that cause change in gene
Role of template strand?
The strand of DNA that the RNA polymerase uses as a guide to build the mRNA.
Role of a ribosome?
Synthesizes the assembly of proteins.
What is a DNA triplet?
A group of 3 bases that code for an amino acid.
How does a DNA triplet differ from a codon?
3 bases on mRNA and complementary to DNA triplet.
How does a DNA triplet differ from a anticodon?
3 bases on tRNA and complementary to a codon.
What are nucleotides?
Form the basic structure of DNA. They are composed of a phosphate group, a sugar and a nitrogenous base.
