Question

why are well - defined reading frames critical in protein synthesis?
a) without a well - defined reading frame, the resulting protein would be transported to the cell surface.
b) without a well - defined reading frame, the ribosome is unable to bind to the mrna.
c) without a well - defined reading frame, the mrna would be transcribed back into dna.
d) without a well - defined reading frame, the peptide made from a given sequence could be completely different.
question 7 (5 points)
listen
what are the two main phases of the cell cycle?
a) prophase and anaphase
b) multiplication phase and division phase
c) interphase and mitosis
d) renlication phase and recombination nhase

Explanation:

First Question (Protein Synthesis Reading Frames)

• Option A: Protein transport to the cell surface is not related to the reading frame of mRNA during translation. The reading frame is about how codons are read, not protein transport.
• Option B: Ribosome binding to mRNA is mediated by the ribosome - binding site (like the Shine - Dalgarno sequence in prokaryotes or the 5' cap in eukaryotes), not the reading frame.
• Option C: mRNA being transcribed back into DNA is reverse transcription, which is a different process (done by reverse transcriptase in retroviruses, for example) and not related to the reading frame in translation.
• Option D: The reading frame is the way the mRNA codons (groups of three nucleotides) are read. If the reading frame is not well - defined (e.g., a frameshift mutation), the sequence of amino acids (and thus the peptide/protein) will be completely different because the codons being read will be different.

Second Question (Cell Cycle Phases)

• Option A: Prophase and anaphase are stages of mitosis (a part of the cell cycle), not the two main phases of the entire cell cycle.
• Option B: There is no "multiplication phase" as a standard term for the cell cycle. The cell cycle has interphase (where the cell grows and replicates DNA) and the mitotic (M) phase (where cell division occurs).
• Option C: The cell cycle is mainly composed of interphase (G1, S, G2 phases - where the cell prepares for division) and mitosis (or M phase, where the cell divides).
• Option D: "Replication phase" is part of interphase (the S phase), and "recombination phase" is not a main phase of the normal cell cycle (recombination is more associated with meiosis or DNA repair in some cases).

Answer:

D) Without a well - defined reading frame, the peptide made from a given sequence could be completely different.