AP Biology:: Gene Expression Regulation

What is the CENTRAL DOGMA of molecular biology, describing the general flow of genetic information within a cell?

- **A)** DNA is TRANSCRIBED into RNA, and RNA is then TRANSLATED into PROTEIN -- describing the general one-way flow of genetic information from the genetic code to a functional gene product
- **B)** The central dogma describes only a single step, with no distinction between transcription and translation
- **C)** Protein is transcribed into RNA, and RNA is translated into DNA (the reverse of the actual flow described by the central dogma)
- **D)** This concept has no actual relationship to how genetic information flows from DNA to a functional protein

What is DNA REPLICATION, and why is it described as 'SEMICONSERVATIVE'?

- **A)** This process has no actual relationship to producing new copies of a DNA molecule
- **B)** The process of COPYING a DNA molecule to produce two identical DNA molecules; it is 'semiconservative' because EACH resulting DNA molecule consists of ONE original ('parental') strand and ONE newly synthesized strand
- **C)** DNA replication is called 'semiconservative' because BOTH resulting DNA molecules consist entirely of newly synthesized strands, with no original strands retained at all
- **D)** Semiconservative replication means only HALF of a DNA molecule ever gets replicated, with the other half permanently lost

What is the role of DNA HELICASE during DNA replication?

- **A)** An enzyme that UNWINDS and SEPARATES the two strands of the DNA double helix, breaking the hydrogen bonds between base pairs to create a 'replication fork' where new strands can be synthesized
- **B)** DNA helicase always RE-JOINS two separated DNA strands back together, rather than separating them
- **C)** This enzyme has no actual relationship to unwinding or separating DNA strands
- **D)** DNA helicase functions to ADD new nucleotides to a growing DNA strand, rather than to unwind the double helix

What is the role of DNA POLYMERASE during DNA replication?

- **A)** DNA polymerase always synthesizes a new strand in the 3' to 5' direction, rather than 5' to 3'
- **B)** An enzyme that SYNTHESIZES a new DNA strand by adding complementary nucleotides one at a time, reading an existing (template) strand and building a new strand in the 5' to 3' direction
- **C)** DNA polymerase functions to unwind the DNA double helix, rather than to synthesize new DNA strands
- **D)** This enzyme has no actual relationship to building a new DNA strand during replication

Why does DNA replication proceed CONTINUOUSLY on the 'LEADING STRAND' but DISCONTINUOUSLY (in short 'Okazaki fragments') on the 'LAGGING STRAND'?

- **A)** This difference has no actual relationship to the antiparallel structure of the DNA double helix
- **B)** DNA polymerase can synthesize new DNA equally well in either direction, making the leading/lagging strand distinction irrelevant
- **C)** The lagging strand is always synthesized MORE quickly and continuously than the leading strand, the reverse of the actual relationship
- **D)** Because DNA polymerase can only synthesize new DNA in the 5' to 3' direction, and the two template strands run ANTIPARALLEL to each other, one new strand (leading) can be synthesized continuously toward the replication fork, while the other (lagging) must be synthesized in short, separate fragments moving AWAY from the fork

What is TRANSCRIPTION, the first major step of gene expression?

- **A)** Transcription always produces a new DNA molecule, rather than an RNA molecule
- **B)** This process has no actual relationship to copying genetic information from DNA into RNA
- **C)** The process of SYNTHESIZING an RNA molecule using a DNA sequence as a TEMPLATE, carried out by the enzyme RNA POLYMERASE, essentially 'copying' the genetic information from DNA into a mobile RNA transcript
- **D)** Transcription refers to synthesizing a PROTEIN using an RNA template (this actually describes translation, not transcription)

What is a PROMOTER, in the context of transcription?

- **A)** A promoter is located at the very END of a gene, signaling transcription to STOP rather than start
- **B)** A specific DNA sequence located NEAR the beginning of a gene that RNA polymerase (often with help from other proteins) BINDS to in order to correctly initiate transcription of that gene
- **C)** This DNA sequence has no actual relationship to where RNA polymerase binds to begin transcription
- **D)** A promoter refers only to the final RNA product of transcription, with no relationship to initiating the process

What is RNA PROCESSING (in eukaryotes), and what are TWO common modifications made to a newly transcribed RNA molecule (pre-mRNA) before it becomes a mature mRNA ready for translation?

- **A)** RNA processing refers only to translating the RNA directly into protein, with no modification steps occurring beforehand
- **B)** This process always REMOVES the coding exon regions, keeping only the non-coding intron regions in the final mature mRNA (the reverse of the actual process)
- **C)** RNA processing has no actual relationship to modifying a newly transcribed RNA molecule
- **D)** The addition of a protective '5' CAP' and a 'POLY-A TAIL' to the ends of the pre-mRNA, along with SPLICING OUT non-coding regions (introns), leaving only the coding regions (exons) joined together in the final mature mRNA