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aksuggie@gmail.com H1 Histone protein binds to the linker DNA. Structure of chromatin: • Within the cell nucleus, the DNA is wrapped in 1.8 loops, around a core of histone proteins • This DNA which encircles the histone proteins consists of 147 base pairs. ◦ The core histone proteins consist of 2 sets each of the histone proteins H2A, H2B, H3 and H4, giving a total of 8 histone proteins known as the histone octamer. ◦ This DNA-histone complex is known as the nucleosome. • The nucleosomes are connected by DNA segments called linker DNA. Both together constitute the chromatin, giving the appearance of "beads on string, where the beads represent nucleosomes and the string represents the linker DNA. • The H1 histone protein binds to the linker DNA and helps stabilize the overall chromatin architecture. ◦ Notably, the histone proteins are positively charged, which facilitates the compaction of the negatively charged DNA.

SNPs are said to be bi-allelic. The two most common genetic variations or polymorphisms are ◦ Single-nucleotide polymorphisms (SNPs) ◦ Copy number variations (CNVs) A. SNPs ◦ These are variations in a single nucleotide that occurs at a specific position (locus) in the genome • They are always bi-allelic, that is, only two choices exist at a given locus in a populati (-CorA-). The image below shows a C/A SNP. The upper DNA molecule differs from the lower DNA molecule at a single base-pair location.

Ans. is 'd" i.e., High risk of malignacy o Malignancy is rare in harmartomatous polyps of Peutz-Jeghers syndrome. . Other three options are correct

45-year-old woman having salt and pepper appearance in skull with dentine defects and loss of lamina dura most likely suggests hyperparathyroidism Radiological features of hyperparathyroidism: ◦ Classical and pathognomonic feature of hyperparathyroidism is sub-periosteal cortical resorption of middle phalanges, seen especially in the second and third fingers. This feature can also be visualised in lateral end of clavicle and symphysis pubis ◦ Loss of lamina Dura (thin cortical bone of tooth socket surrounding teeth is seen as thin white line) ◦ Generalized osteopenia, thinning of cortices, and indistinct bony trabeculae ◦ Expansile lytic lesion, otherwise known as brown's tumor generally affecting maxilla/mandible ◦ Salt and pepper appearance of skull

Correct Answer - A Ans. is 'a' i.e., Coagulative necrosis Coagulative necrosis * This is most common type of necrosis. * This type of necrosis is most frequently caused by sudden cessation of blood flow (ischemia) in organs such as heart (MI), Kidney (ATN), adrenal gland, and spleen. Note: Brain is the only exception, i.e.,. It is the only solid organ in which ischemia leads to liquifactive necrosis not coagulative necrosis. * It is also seen with other types of injury e.g.,liver necrosis in viral hepatitis, Coagulative necrosis of skin after burns (Thermal injury). Why there is predominant protein denaturation and no enzymatic digestion ? Hypoxia causes intracellular acidosis (has been explained earlier) > .t pH results in denaturation ofproteins which includes not only structural proteins hut also enzymes So, there is no enzymatic digestion. o The necrotic cells retain their cellular outline for several days. Liquefactive necrosis * It is the necrotic degradation of tissue that rapidly undergo softening and liquefaction

Correct Answer is D