You Are Attempting to Generate a Physical Map of the Bacteriophage

question 19

Essay

You are attempting to generate a physical map of the bacteriophage $\lambda$ genome using restriction enzyme digestions. You digest the phage DNA with EcoRI or NcoI or both, and observe the fragment sizes listed below. You know that bacteriophage $\lambda$ has a linear, not circular, genome. $$\begin{array} { l l l } { \text { EcoRI } } & { \text { NcoI } } & { \text { EcoRI/NcoI } } \\\hline { 21.2 \mathrm {~kb} }&{ 19.3 \mathrm {~kb} } &{ 19.3 \mathrm {~kb} } \\7.4 \mathrm {~kb} & 16.4 \mathrm {~kb} & 7.4 \mathrm {~kb} \\5.8 \mathrm {~kb} & 4.6 \mathrm {~kb} & 5.1 \mathrm {~kb} \\5.7 \mathrm {~kb} & 4.2 \mathrm {~kb} & 3.9 \mathrm {~kb} \\4.9 \mathrm {~kb} & 4.0 \mathrm {~kb} & 3.5 \mathrm {~kb} \\3.5 \mathrm {~kb} & & 2.7 \mathrm {~kb} \\& & 2.2 \mathrm {~kb} \\& & 1.9 \mathrm {~kb} \\& & 1.8 \mathrm {~kb} \\& & 0.7 \mathrm {~kb}\end{array}$$ a. How many times does the EcoRI enzyme cut the $\lambda$ DNA? How many times does the NcoI enzyme cut the $\lambda$ DNA?
b. Use the fragment size data to generate a physical map of the bacteriophage $\lambda$ genome, indicating the order and relative positions of the restriction enzyme recognition sites.

---

Definitions:

Brittle Bone

Also known as osteogenesis imperfecta, a genetic disorder characterized by bones that break easily due to a collagen defect.

Hydroxyapatite Crystals

Mineral complexes primarily of calcium and phosphate that form the hard structure of bones and teeth.

Compression Strength

The capacity of a material or structure to withstand loads tending to reduce size, measured in force per unit area.

Chondroblasts

Cells that produce cartilage, developing into chondrocytes which are the cells primarily found in cartilage.