Biology Unit 5 Quiz 2
What is an anti-codon?
-On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA -Sequence of 3 bases in the tRNA molecule at the site where the tRNA and mRNA bind; complementary to the codon in the mRNA
What can happen to polypeptide chains?
After a polypeptide chain is synthesized, it may undergo additional processes.
What happens in the first step of translation?
After mRNA leaves the nucleus, it moves to a ribosome, which consists of rRNA and proteins. The ribosome reads the sequence of codons in mRNA. Molecules of tRNA bring amino acids to the ribosome in the correct sequence.
What is an amino acid?
An organic molecule containing a carboxyl group and an amino group; serves as the monomer of proteins (there are 20)
What is a polypeptide?
Chain of amino acids that alone or with other such chains makes up protein
What happens in the second step of translation?
Each tRNA molecule has an anticodon for the amino acid it carries. An anticodon is a sequence of 3 bases, and is complementary to the codon for an amino acid.
What is the second step of transcription? What happens?
Elongation is the addition of nucleotides to the mRNA strand. RNA polymerase reads the unwound DNA strand and builds the mRNA molecule, using complementary base pairs. There is a brief time during this process when the newly formed RNA is bound to the unwound DNA. During this process, an adenine (A) in the DNA binds to an uracil (U) in the RNA.
What is RNA polymerase?
Enzyme that transcribes DNA, making mRNA
Where does translation take place?
In the cytoplasm and ribosomes
Where does transcription take place?
In the nucleus
What is the first step of transcription? What happens?
Initiation is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter. This signals the DNA to unwind so the enzyme can ''read'' the bases in one of the DNA strands. The enzyme is now ready to make a strand of mRNA with a complementary sequence of bases.
What is mRNA?
Messenger RNA; type of RNA that copies genetic instructions from DNA in the nucleus and carries them to the cytoplasm
What is a ribosome?
Organelle inside all cells where proteins are made; site of protein synthesis
What bond forms in translation? What does this form?
Peptide bond forms a polypeptide chain which is a protein
What is protein synthesis?
Process in which cells make proteins; includes transcription of DNA and translation of mRNA
What is transcription?
Process in which genetic instructions in DNA are copied to form a complementary strand mRNA
What is translation?
Process in which genetic instructions in mRNA are read to synthesize a protein
What is the last step of transcription? What happens?
Termination is the ending of transcription, and occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA.
What is tRNA?
Transfer RNA; type of RNA that brings amino acids to ribosomes, where they are joined together to form proteins.
What happens in the third step of translation?
While bound to the mRNA, the tRNA gives up its amino acid. Bonds form between adjacent amino acids as they are brought one by one to the ribosome, forming a polypeptide chain. The chain of amino acids keeps growing until a stop codon is reached.