'लैम्प ब्रश' गुणसूत्र से क्या तात्पर्य है? इसके संरचना और कार्यात्मक महत्व की व्याख्या करें। (What is meant by a ‘Lamp brush' chromosome? Explain its structure and functional significance.) (UPSC 2017,10 Marks,)

What is meant by a ‘Lamp brush' chromosome? Explain its structure and functional significance.