A. Changes Involving Number of Genes i) Deletion or deficiency It signifies the loss or absence of a section of a chromosome and may involve one or more genes. ii) Duplication. It represents a gain in chromosomal material and in this case a part of a chromosome is present in excess of the normal amount. … Read more
Stages of Chromosomal Pairing Chromosomal pairing proceeds through several stages: 1. Recognition and Alignment of Homologs 2. Homology Search 3. Synapsis (Formation of Synaptonemal Complex) 4. Recombination (Crossing Over) Key Molecular Players in Chromosomal Pairing Molecule/Structure Function Spo11 Creates DSBs for initiating recombination Rad51, Dmc1 Catalyze strand invasion and homology search Cohesin Maintains sister chromatid … Read more
A Chromosome – B-chromosomes 3-M- Chromosome 4- Mega chromosome Lampbrush chromosomes Salivary gland chromosomes Fig. Salivary gland chromosome from nucleus of female Drosophila Fig. Balbiani rings Sex chromosomes 1. Normal chromosomes in an organism are called: A) B-chromosomesB) A-chromosomesC) G-chromosomesD) Polytene chromosomesAnswer: B 2. B-chromosomes are also called: A) Accessory chromosomesB) AutosomesC) Sex chromosomesD) Satellite … Read more
Introduction Fig. A standard map of the banding pattern of each chromosome in the human karyotype. G-Banding Q- Banding Fluorochrome banding has some drawbacks – Both Q and G bands correlate with the centromeres observed in leptotene and pachytene chromosomes during meiosis. Q and G banding pattern are generally similar and correspond to the intercalary … Read more
This is Two type (A) Symmetrical karyotype (B) Asymmetrical karyotyping – The karyotype of the human female contains 23 pairs of homologous chromosomes: The karyotype of the human male contains: Process of Karyotyping Sterilization– Sampling and Culture– Cell Synchronization- Harvesting and Slide preparation– Observation in microscope – Photography- Karyotype Evolution 🔹 1. The karyotype is … Read more
Heterochromatin Function Types of Heterochromatin Constitutive heterochromatin Facultative heterochromatin Euchromatin Structure Appearance Function 🔹 1. Who first defined heterochromatin in 1928? A. WatsonB. Heitz ✅C. CrickD. Morgan🧠 Explanation: Heitz first described heterochromatin based on its staining properties. 🔹 2. Euchromatin is characterized by: A. Dense stainingB. Peripheral localizationC. Loose DNA packing ✅D. Inactive genes🧠 Explanation: … Read more
Nucleolus Evolution Number and Structure Structure Morphologically nucleolus consists of three regions: Fibrillar regions: Granular regions : Protein region: Chromatin part: Perinucleolar Chromatin: Intranucleolar chromatin: Functions: Chemical Composition of nucleolus: Function of Nucleolus: Ribosomal RNA Genes Fig Biogenesis of ribosomes MCQ 🧪 PART A: Simple Conceptual MCQs (1–30) 1. Who discovered the nucleolus? A. Robert … Read more
MOLECULAR ORGANISATION OF CENTROMERE AND TELOMERE Centromere (i) Conserved element I (CDE I): (ii) Conserved element II (CDE II): (iii) Conserved element III (CDE III): Telomere 🔹 PART A: CENTROMERE STRUCTURE & FUNCTION Q1. What is the primary function of the centromere in a chromosome?A. RNA synthesisB. DNA replication✅ C. Attachment site for spindle fibersD. … Read more
Nucleosome Chromatin → Nucleosomal monomers Containing the spacer DNA (160 base pairs) → Core nucleosomes (140 base pairs) → Subnucleosomal particles 🔹 PART A: Basic Concept of Nucleosome Q1. The term “nucleosome” was first coined by:A. Olius and Woodcock✅ B. Oudet et al.C. Watson and CrickD. Hershey and Chase Q2. … Read more
CHROMOSOME STRUCTURE Detailed structure of chromosome Chromatid 1- Sister chromatid 2-Non sister chromatid Chromonema – Centromere/Primary constriction – According to the no. of centromere these are the following types According to the position of centromere chromosomes are following types 1. Telocentric – 2. Acrocentric 3. Sub metacentric 4. Metacentric 4. Kinetochore – 5. Chromomere – … Read more
