The lambda phage that has been studied in the laboratory possesses an isometric head of diameter 650 Å and a tail 1,500 Å long and 170 Å wide. A tail fiber extends an additional 200 Å from the tail. This tail fiber makes a specific contact with a porin protein found in the outer membrane of the host cell, and the phage DNA is injected through the tail into the cell. Apparently in an early isolation of lambda, investigators chose a mutant form of the virus that lacked tail fibers. The natural form possesses a number of tail fibers that attach the phage to something other than the porin protein. The DNA within the phage particle is double-stranded and linear, with a length of 48,502 base pairs. This is roughly 1% the size of the Escherichia coli chromosome. Intracellularly, lambda DNA exists as monomeric circles or polymeric circular forms, but during encapsidation, unit-length lambda linear genomes are cut out of the polymeric forms (Fig. 1). The cuts of the two DNA strands are offset from one another by 12 bases. Thus the ends of the encapsidated phage DNA are single-stranded and complementary.

Fig1. Cleavage at two cos sites between the R and A genes generates lambda monomers from oligomers during encapsidation of lambda DNA. Because each cos site is cut with a 12 base staggered cleavage, complementary end sequences are generated.

Roughly half the mass of a lambda particle is DNA and half is protein. Consequently, the particle has a density in CsCl halfway between the density of DNA, 1.7 gm/cm³, and the density of protein, 1.3 gm/cm³. This density facilitates purification of the phage since isopycnic banding in CsCl density gradients easily separates the phage from most other cellular components.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم الشؤون الدينية يوزع أكثر من ألفي وجبة طعام للمعزين في ذكرى عاشوراء بنينوى

قسم الشؤون الطبية يواصل تقديم خدماته الصحية لزائري عاشوراء

جموع المعزين تحيي مراسم يوم العاشر من شهر المحرم عند المرقدين الطاهرين

قسم العلاقات يطلق محطات فتية الكفيل الثقافية في محافظة نينوى

المزيد

الآخبار الصحية

لهذا السبب.. إغلاق 25 مركزًا لعلاج الإدمان في مصر ؟

خلافا للاعتقاد الشائع.. علماء يكشفون أسرار بذور البطيخ ؟!

هذا ما يحدث لجسمك عند تناولك الطماطم بانتظام !

تعرف على أطعمة تسرّع "تعافي الجسم" من حروق الشمس

المزيد

الآخبار التكنلوجية

الثلوج تغطي الصحراء الأكثر جفافا في العالم!

بتلسكوب "ألما".. التقاط صورا غير مسبوقة لبدايات الكون !

هل هاتفك مراقب؟.. 5 علامات خطيرة تكشف التجسس عليك

دبي تطلق أول رحلة تجريبية للتاكسي الجوي

المزيد

مواضيع ذات صلة

Genotoxicity Through Potential Off-target Nuclease - Induced Double - Strand Breaks

A Broad Range of Genomic Changes by Homologous Recombination–Mediated Genome Editing

Early Transcription of Genes N and Cro

Lambda’s Relatives and Lambda Hybrids

The Genetic Structure of Lambda

Other Attenuated Systems: Operons, Bacillus subtilis and HIV

Coupling Translation to Termination

trp Multiple Secondary Structures in trp Leader RNA

Early Explorations of the Hypersynthesis

The Serendipitous Discovery of trp Enzyme Hypersynthesis

Rapid Induction Capabilities of the trp Operon

The Aromatic Amino Acid Synthetic Pathway and its Regulation