AP Biology · Topic 6.8
Biotechnology Practice
Part of Gene Expression and Regulation.(IST-2.D)
Practice questions
36
Sample questions
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Sample 1difficulty 1/5
EcoRI recognizes the palindromic sequence GAATTC and cuts both strands between G and A, generating four-nucleotide 5' overhangs.
What feature of EcoRI's cleavage pattern enables ligation between two DNA molecules cut by the same enzyme?
- A
EcoRI methylates the overhangs to enhance ligation.
- B
EcoRI cuts both strands at the same position, creating blunt ends that randomly join.
- C
The ends are phosphorylated by EcoRI.
- Dcheck_circle
Both fragments have complementary single-stranded overhangs that can anneal.
Why
EcoRI cleaves between G and A on both strands, leaving 5' AATT overhangs. Identical sticky ends from any source can base-pair and be sealed by DNA ligase, the basis of recombinant DNA cloning.
- A
Sample 2difficulty 1/5
The plasmid map shows an origin of replication (ori), an ampicillin-resistance gene (amp^R), a multiple cloning site (MCS), and an EcoRI site.
Why is the amp^R gene important when cloning a foreign gene into this plasmid?
- A
It is the origin of replication for the plasmid.
- B
It cuts the foreign gene to insert it.
- C
It encodes the foreign protein of interest.
- Dcheck_circle
It serves as a selectable marker so only transformed bacteria grow on ampicillin plates.
Why
Selectable markers like amp^R allow researchers to grow only cells that took up the plasmid by plating on antibiotic-containing media. The ori drives replication; the MCS provides cloning sites.
- A
Sample 3difficulty 2/5
Lane 2 shows two bands, while Lanes 1 and 3 each show one. What does the Southern blot most likely indicate about Patient 2?
- Acheck_circle
Patient 2 is heterozygous for two restriction-fragment alleles at this locus.
- B
Patient 2 has no DNA in the lane.
- C
Patient 2's DNA was not digested.
- D
Patient 2 is homozygous and has a deletion.
Why
Southern blots detect specific DNA fragments by hybridization to a labeled probe. Two bands of different sizes in one lane suggest a heterozygote inheriting two distinct alleles distinguished by a restriction-site polymorphism.
- A
Sample 4difficulty 2/5
A DNA sample run alongside a size ladder produces two visible bands.
Approximately what fragment sizes does the sample contain?
- A
Both bands are below 0.2 kb
- Bcheck_circle
About 6 kb and about 0.5 kb
- C
Cannot estimate without sequence data
- D
Both bands are 10 kb
Why
DNA migrates toward the positive electrode; smaller fragments travel farther. Comparing to the ladder, the sample bands fall between 5-10 kb (<del>6 kb) and between 1-0.2 kb (</del>0.5 kb).
- A
Sample 5difficulty 2/5
A genetic test for sickle-cell disease uses restriction enzymes that cut the normal beta-globin allele but not the sickle (HbS) allele. The gel below shows results for four family members along with a size ladder.
Which children are heterozygous (carriers)?
- A
Both children are heterozygous.
- B
Only C1 is a carrier.
- Ccheck_circle
Both parents are heterozygous; C1 is HbS/HbS and C2 is HbA/HbA.
- D
C1 and C2 are both unaffected and homozygous normal.
Why
Both parents show two bands (1.3 uncut and 0.7 cut), indicating heterozygotes. C1 shows only the 1.3 uncut band (HbS/HbS); C2 shows only the 0.7 cut band (HbA/HbA).
- A