Question

bioi 210 chapter 8 quiz 1 november 4, 2023

1. the following pertain to ribosomes during protein synthesis except

a) they participate in both transcription and translation
b) they participate only in translation
c) they scan the mrna for an aug codon
d) they are composed of ribosomal rna and protein
e) they shift to the right along the mrna strand from one codon to the next

1. which of the following is incorrect about termination codons?

a) where the bond between the final trna and the finished polypeptide chain is broken
b) include aug
c) include uaa, uag, and uga
d) do not have corresponding trna
e) can also be called nonsense codons

1. a sequence of bases on a cukaryotic gene that does not code for protein is called a/an

a) promoter
b) operator
c) operon
d) exon
e) intron

1. a mutation that changes a normal codon to a stop codon is called a

a) point mutation
b) silent mutation
c) back mutation
d) missense mutation
e) nonsense mutation

1. a bacteriophage transfers dna of the previous host to the current host. this is an example

of
a) conjugation
b) generalized transduction
c) specialized transduction
d) a reaction of an hfr cell
e) none of the choices are correct.

1. bacterial conjugation involves

a) bacteriophage carrying donor dna to the recipient cell
b) a donor cell with a plasmid that synthesizes a pilus
c) naked dna fragments from a lysed donor cell taken up by a recipient cell
d) new progeny cells with genes from two parent bacterial cells
e) none of the choices are correct.

Explanation:

1. Ribosomes are involved in translation only. Transcription occurs in the nucleus (in eukaryotes) and involves RNA - polymerase.
2. Termination codons (UAA, UAG, UGA) do not code for amino acids (so no corresponding tRNA), break the bond between tRNA and polypeptide, and are also called nonsense codons. AUG is a start codon.
3. Introns are non - coding sequences in eukaryotic genes. Promoters are regulatory regions, operators are in operons (prokaryotic), exons are coding sequences.
4. A nonsense mutation changes a normal codon (coding for an amino acid) to a stop codon. A point mutation is a single - base change (a more general term), silent mutation does not change the amino acid, back mutation reverses a previous mutation, missense mutation changes the amino acid.
5. Generalized transduction is when a bacteriophage transfers random DNA from the previous host (after lysis) to the current host. Conjugation is direct cell - to - cell transfer (via pilus), specialized transduction transfers specific DNA near the prophage site.
6. Bacterial conjugation involves a donor cell (usually with an F - plasmid) that synthesizes a pilus to transfer DNA (usually plasmid DNA) to a recipient cell. Transduction involves bacteriophages (A), transformation involves uptake of naked DNA (C), and conjugation does not directly produce new progeny cells with genes from two parents in the way sexual reproduction does (D is more related to sexual reproduction in some organisms).

Answer:

1. A
2. B
3. E
4. E
5. B
6. B