Chromosomes notes pdf. How to Add Checkboxes to Your PDFs.
Chromosomes notes pdf The DNA is contained in structures called chromosomes. However, with Sir Tarun Rupani’s notes and videos, not only does the whole syllabus get covered easily, but it could also be revised many times before the Aug 24, 2017 · 6 Chromosome Structure and Function bose in place of deoxyribose. FISH Genereviews. 4 Monohybrid inheritance 3. Polytene or Giant Chromosomes: The multiple replicates of the same chromosome holding together in a parallel fashion resulting in very thick chromosome are known as polytene chromosomes and Download ICSE Class 10 Biology Revision Notes Chapter 2 - Cell Cycle, Cell Division, organizations, and Structure Of Chromosomes Free Pdf as per the Latest CISCE Guidelines prepared by subject experts to help you score good marks in your examinations . In the second cross in Drosophila (see Fig. A karyotype is a picture showing a cell's chromosomes grouped together in pairs. The ribosome is a cytoplasmic subcellular organelle covering the outer sur faces of the three-dimensional network of membranes known as the endoplasmic May 10, 2019 · • 23 chromosomes (22 autosomes plus an X chromosome) in their egg cells Men have • 46 chromosomes (44 autosomes plus an X and a Y chromosome) in their body cells: 46,XY • 23 chromosomes (22 autosomes plus an X or Y chromosome) in their sperm cells Figure 1. ∙ Haploid cells only have one set of chromosomes. !Robertsonian translocations are confined to chromosomes 13, 14, 15, 21 2. Lecture Notes as per Topics. ÐThis type of translocation is the most common type of chromosomal rearrangement in humans. Rediscovery of Mendel’s work 2. chromosomal mutation. 1 Intellectual Lecture notes on chromosome structure and organization, including features, number, and morphology. [1] There are three levels of chromatin organization; Euchromatin, Heterochromatin and higher level DNA packaging. Chromosomal theory of inheritance 3. The centromeres of all the chromosomes lie May 18, 2023 · Lecture 21: Structure of Prokaryotic Cells 2 days ago · Class 10 ICSE Biology Notes & Videos by Sir Tarun Rupani. Mar 18, 2022 · Structure of chromosomes: ∙ Chromosomes consist of DNA (which makes up genes) and protein. •It is an additional and useful tool for the Sep 27, 2017 · c. Recombinant DNA technology development and applications B. CELL CYCLE AND CELL DIVISION www. taleemcity. Respond to the questions and prompts in the orange boxes. Significance: Chromosomal aberrations can result in developmental disorders and are key in understanding genetic diseases, including cancers. It includes detailed information about the exam syllabus, recommended books, and study materials for a well-rounded preparation. 5 Variation 3. Connect the molecular structure of DNA to its function BIOL 3400: Week 2 Tuesday, January 30, 2024 Reminders: Dr. Table 1: DNA content of Human Chromosomes Chromosome Total amount of DNA (Mb) Amount of heterochromatin (Mb) May 12, 2009 · CHAPTER 14 LECTURE NOTES : RECOMBINANT DNA TECHNOLOGY I. The name chromosome was proposed by W. ∙ The number of chromosomes in a cell is a characteristic of an organism (e. 2. Y. com Page 3 of 9 4. We know you are looking for 2nd year biology chapter 20 Chromosomes & DNA notes in PDF format to download. Ultra Structure of chromosome In eukaryotes the chromosomes are multiple large, linear and are present in the nucleus of the cell. Polytene Chromosomes - Download as a PDF or view online for free. Mutation = the gene or chromosome that results from a mutational process 3. Master the concepts with our detailed explanations & solutions. In butterflies and birds males are the homogametic sex (ZZ) and females the heterogametic sex (ZW). ii. This comprehensive document covers all aspects related to Chromosome - 1. describes how chromosomes determine gender, and touches on chromosomal abnormalities. DNA sequence in any two people is 99. Hybridization. The resulting products are also known as chromosomal mutations. Sep 14, 2010 · Note that for human crosses there is no standard genotype and the concept of wild-type is therefore not meaningful. A long length of DNA (containing many Jul 10, 2021 · 3. Missing two homologous chromosomes for a certain chromosome # 2. Chromosomes. Mar 6, 2025 · This is the post on the topic of the 2nd Year Biology Chapter 20 Notes - Questions Chromosomes and DNA pdf. After Stevens died in 1912, Wilson was the first to designate the name “ sex chromosome” for the pair of XX and Bacterial chromosome follows a rolling circle mode of DNA replication. A length of DNA that contains the information for a single protein is called a . Aug 17, 2018 · Polytene Chromosomes - Download as a PDF or view online for free. A gene is a small section of DNA on a chromosome. As cells enter mitosis, their chromosomes become highly condensed so that they can be distributed to In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Karyotype It is the set of chromosomes of an individual. With Smallpdf’s easy-to-use annotator, you can mark up documents in no time and stay organized. Summer Course in Biophysics. Information about Chromosome Painting covers topics like Chromosome Painting Technique, Applications of Chromosome Painting, Chromosome Mar 5, 2021 · Unit 3 Linkage, Crossing-Over and Chromosome Mapping 75 Fig. Gizmo Warm-up Scientists use karyotypes to study the chromosomes in a cell. May 29, 2018 · Chromosomes - Download as a PDF or view online for free. . It involves two rounds of division called Meiosis I and Meiosis II. The total amount of genetic information in the chromosome can change May 28, 2021 · Special chromosomes - Introduction - Download as a PDF or view online for free. DNA, or Deoxyribonucleic acid , is the biological molecule that houses our genetic information. Genes which are located on the same chromosome and transmitted together are called linked genes and are said to belong to a linkage group. June 5, 2014. Edwards syndrome, also known as trisomy 18, is a rare genetic disorder caused by the presence of an extra chromosome 18. •Chromosome identification depends on their morphological characteristics such as relative length, arm ratio, presence and absence of secondary constrictions on the chromosome arms. Hybridization (attachment) occurs between the probe and complementary (i. Nixon 2022 ScienceSauceOnline. These are called chromosomes. pdf), Text File (. During this stage of the cell cycle this makes the individual chromosomes in many cells visible by optical microscope. Besides main circle DNA, bacteria also contains extra chromosomal circular DNA 2. Browse Course Material Syllabus Calendar Chromosomes and Sex Linkage CK 6 Recombination and Genetic Maps CK 7 Three-factor Crosses CK 8 (PDF 1 of 3 - 3. Human beings have 46 chromosomes, consisting of 22 pairs of autosomes and a pair of sex chromosomes: two X sex chromosomes for females (XX) and an X and Y sex chromosome for males (XY Chromosomes are inherited as intact units, so it was reasoned that the alleles of some pairs of genes will be inherited together because they are on the same chromosome. Special chromosomes - Introduction. Chromosome mutation = segments of chromosomes, whole chromosomes, or The chromosomes - and the DNA they contain - are copied as part of the cell cycle, and passed to daughter cells through the processes of mitosis and meiosis. -Humans have chromosomes (23 pairs)-Each chromosome stores different genes. Brian D. Population size 5. Download or print them by clicking the Top Study World is an education platform offering class notes, results, essays, books, past papers, and study abroad resources for students. spiroacademy. A gene is a short length of DNA found on a Chromosomes were first described by Strasburger (1815), and the term „chromosome‟ was first used by Waldeyer in 1888. In this shortened version of the Human DNA comlementary to a chromosomal region of interest. Gene mutation = the allele of a gene changes (this chapter) 2. This is the principle of genetic linkage, • Pairs of genes were either inherited independently, as expected for genes in different chromosomes, or, LECTURE NOTES I. 5 male Mammals Apr 11, 2022 · The worksheets are in a variety of formats, including Google Apps (slides), PDF files, and PNG and JPG images. It leads to severe developmental delays and most infants with trisomy 18 die in the first month of life. 10. These markers are known to be in the order: Ch 14 Solved Problem I other chromosome, and she confirmed that this chromosome must be regulating the sex in males [8]. One base pair is 0. It is the first article in a four-part series exploring the role of genes and chromosomes in inheritance, health and disease. Chromosome mapping helps to understand the genome’s organization, Adding notes to a PDF doesn’t have to be a chore. Sep 11, 2007 · PeCteorp Jy. Drosophila melanogaster (fruit fly) XX females; XY males X:autosome ratio determines sex 1. Haploid: A cell or organism with one set of chromosomes (1n). 1 Chromosome 3. chromatin. Genetics Worksheets. Citation Knight J, Andrade M (2018) The Structure of Chromosomes, Cell Cycle and Cell Division ICSE Class 10 notes are considered an important study tool as it helps students to save their precious time as it is ready made notes. Chromosomal sex determination: In flies and mammals females are the homogametic sex (XX) and males the heterogametic sex (XY). Embedded in Nucleosome-complex DNA & Protein (Histone) structure that pack together to form chromosomes. Human influences on the ecosystem 5. 1 MB) (PDF 2 of 3 - 1. Eukaryotic chromosomes are linear structures with special structures at each end called telomeres (green) and an organizer centre Biology document from University of Toronto, 3 pages, Module 3: Sex Determination and Sex-linked Inheritance - Notes Overview Focus: Understanding how sex is genetically determined and how genes located on sex chromosomes are inherited. I. Nutrient cycles 4. Landmarks in modern genetics 1. The term is also used for the complete set of chromosomes in a species or in an individual organism and for a test that detects this complement or measures the number. Genome = approx. 1% is unique! What makes one cell different from another? DNA = “the life instructions of the Male Drosophila from a true-breeding wild-type stock were irradiated with X-rays and then mated with females from a true- breeding stock carrying the following recessive mutations on the X chromosome: yellow body (y), cross-veinless wings (cv), cut wings (ct), singed bristles (sn), and miniature wings (m). o Cows: o Dogs: o Worms: o Mulberry plants: - Chromosomes exist in pairs - In each pair, one chromosome came from a female parent, and the other came from a male parent. 3 billion base pairs . ,n p ruebqliushiriendg faos rB reenpjarmodinu Cctuiomnm oirn gdsisplay 3 There are two primary ways in which the structure of chromosomes can be altered Ð1. Chromosomal mutations are processes that result in rearranged chromosome parts, abnormal numbers of individual chromosomes, or abnormal numbers of chromosome sets. 9 MB) (PDF 3 of 3 - 3. com. Since it is the chromosome and not the gene which is the unit of transmission at meiosis, linked genes are not free to undergo independent assortment. The chromosomes are depicted May 9, 2020 · %PDF-1. Aneuploidy usually produces drastic phenotypic effects and many embryos are The Structure of Genes Inheritance of Chromosomes, Genes and DNA. Missing 1 chromosome of a certain chromosome # 2. Top Study World is an education platform offering class notes, results, essays, books, past papers, and study abroad resources for students. Homozygous: The condition of having two like alleles in a diploid. To register Biology Tuitions on Vedantu. They are thread-like structures of DNA, carrying genetic information in the form of genes. In humans, lethal for autosomes (die in utero) 4. The notes and questions for Structural Variations in Chromosomes have been prepared according to the UPSC exam syllabus. The images are previews of each worksheet. This document is a Grade 12 learner's content manual on meiosis, detailing the structure of chromosomes, the process of meiosis, and its significance in producing haploid gametes. Feb 4, 2016 2 likes 3,155 views. There are two reasons why meiosis is important. 2) is lost after few cell divisions or if a centromere is deleted from a chromosome. Chromatin organization • The DNA packaging problem • Histones and nucleosome core particle • Chromatin folding and nuclear organization human haploid cell, consist of 23 nuclear chromosome and one mitochondrial chromosome, contains more than 3. The syllabus of ICSE Class 10 Biology subject is vast, so studying the whole syllabus line by line by word can be very exhausting for some students. Apr 11, 2020 · chromosomes are taken in order to determine the chromosome complement of an individual, including the number of chromosomes and any abnormalities. Submit Search. Meiosis is a type of cell division that produces gametes, such as sperm or egg cells, with half the number of chromosomes as normal body cells. The chromosomal abnormalities may occur either during the production of the egg or sperm or early after the baby's conception: a spontaneous occurrence for unknown reasons. Eukaryotic genome is linear and conforms the Watson-Crick Double Helix structural model. Facebook X Pinterest WhatsApp. Denatured chromosomes fixed on a microscope slide are exposed to the fluorescently-labeled probe. Eukaryotic genome have unique features of Exon - Intron organization of protein coding genes, representing coding sequence and intervening sequence that represents the functionality of RNA part inside the genome. –Haploid: 1n, 23 chromosomes = 23 count •Aneuploid: abnormal chromosome complement –Trisomy: 2n+1, additional chromosome = 47 count –Monosomy: 2n-1, missing chromosome = 45 count •Polyploid: abnormal number of chromosome sets –Triploidy: 3n, 3 sets of chromosomes = 69 count –Tetraploidy: 4n, 4 sets of chromosomes = 92 count 34 Serena Yeung BIODS 220: AI in Healthcare Lecture 9 - Epigenomics Study of processes that regulate how and when genes are turned on and off (“gene expression”) of chromosomes - Every organism has a different number of chromosomes. Background A. How To Annotate PDF. Human chromosomes 13, 15, 21 and 22 are acrocentric PDF | On Sep 24, 2020, Daniele Fachinetti and others published Artificial chromosomes | Find, read and cite all the research you need on ResearchGate Jan 13, 2022 · Ó A. 0. This is a universal law and always during gamete formation in all sexually reproducing organisms, the two factors of a pair pass into different gametes. May 29, 2018 Download as PPTX, PDF 5 likes 14,607 views. Types of Chromosomal Aberrations Structural DNA_&_Chromosomes_Notes - Free download as PDF File (. Since chromosomes are bundled with different kinds of essential DNA, chromosomes and genomes Notes - Download as a PDF or view online for free. DNA as the genetic material 4. For diploids: 2n-1 3. 7: The chromosome 7 pair showing the banding pattern Our genes Document Description: Structural Variations in Chromosomes for UPSC 2025 is part of Botany Optional for UPSC preparation. Acrocentric chromosome: The centromere lies towards the pole or away from the center of the chromosome leading to one very long and one very short section or arm. a mutant is the organism or cell whose changed phenotype is attributed to a mutation B. Chromosomes are the essential unit for cellular division and must be replicated, divided, and passed In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Step 2. doc / . 00000000034 meters. 3 Meiosis 3. Biology GCSE 9-1 2018 6 DNA The genetic material in the nucleus of a cell is composed of a chemical called DNA (deoxyribonucleic acid). Hofmeister(1848) first observed the chromosome. Yi Fan Chen. Easily add checkboxes to PDFs for forms, surveys, or quick checklists for free with Smallpdf—on any device—or with Preview on Get accurate answers of ICSE Class 10 Concise Biology Selina Chapter 2: Structure of Chromosomes, Cell Cycle and Cell Division. Suitable for biology students studying genetics. Molecular proof of this principle was subsequently found through observation of meiosis by two scientists independently, the German botanist Oscar Hertwig in 1876, and the Belgian zoologist Edouard Van Beneden in 1883. V's name quiz Thursday 2. It reduces the number of chromosomes by half, in other words from diploid to haploid. 2: A test cross with F1 progeny of Drosophila in which ♀ is the homozygous recessive (tester) and ♂ is the doubly heterozygous parent. 9% identical – only 0. Clear your Biology doubts instantly & get more marks in Biology exam easily. Early scientists thought Aug 11, 2017 · UNIT - eGyanKosh Jun 8, 2017 · Chromosomes or kinetochore fibres contract and bring chromosome over equator this phenomenon is called congression. General Types 1. General Info A. FSc Part 2 Biology Chapter 20 Chromosomes & DNA Notes. In the human cell, there are 46 chromosomes or 23 pairs (diploid number); of these 23 pairs, 22 are similar in both sexes and are called the autosomes. DNA, chromosomes and genomes Notes. Saranraj P. Share. Can be ok in some polyploid plants C. For our purposes here, we will be talking about alterations in large regions of the chromosomes territories [1], the correlation between radial positioning of chromosomes with gene density, transcriptional activity, replication timing and chromosome size [2-5], the tissue-specific spatial configurations of chromosomes relative to one another [6, 7], the co-localization of disparate DNA elements into functionally defined edwards syndrome notes - Free download as Word Doc (. org . Even-numbered multiple sets of chromosomes can be stably inherited in some species, especially plants. These maps show the positions of genes and the distances between them based on a specific scale. Jan 1, 2012 · PDF | With the discovery in 1956 that the correct chromosome number in humans is 46, the new era of clinical cytogenetics began its rapid growth. Aug 17, 2018 33 likes 28,147 views. At formation of gametes, the two chromosomes of each pair separate (segregate) into two different cell which form the gametes. , matching) chromosomal DNA. 7 Smaller chromosomes directed towards the centre while larger ones are peripheral in position on equator. Source: S. Oct 4, 2024 · to form chromosomes. Two arms of such chromosomes are equal and ARM ratio is 1. Food chains and food webs 3. 3 The significance of meiosis. e. 2 Aug 28, 2023 · Chromosome mapping means determining the relative positions of genes in a chromosome by creating maps that are used to organize and understand genetic information on chromosomes. Polytene Chromosomes . UNC-School of Medicine. The remaining pair is called sex chromosomes: XX in the female cells and XY in the male cells . B. In most of our cells, we have 46 chromosomes, 23 from each of our CHROMOSOMES & DNA. Outline. chromosomal axis, the chromomere and the loop axis all are made up of DNA and have hereditary function or are considered regions of genetic activity. It outlines the phases of meiosis, the importance of crossing over for genetic variation, and the Structure and replication pattern of a eukaryotic chromosome. Centromere is found at the center of chromosome. 2 billion DNA base pairs. DNA is a polymer made up of two strands forming a double helix. The notes and questions for Chromosome Painting have been prepared according to the UPSC exam syllabus. Langlios Edited by non-homologous acrocentric chromosomes ÐThe larger fragments fuse at their centromeic regions to form a single chromosome ÐThe small acrocentric fragments are subsequently lost. The mRNA molecule leaves the nucleus and in the cytoplasm its base sequence is read by the ribosome, on which amino acids are collec ted. 7 Genetic engineering . located on the same chromosome. Each chromosome typically has one centromere and one or two arms that project from the Module 6: Chromosomal Aberrations – Notes Overview Focus: Understanding chromosomal aberrations, their types, mechanisms, and consequences. Monosomics 1. c Pateiromn, iIsnsico. Jun 20, 2024 · Basic Principles of Inheritance Chapter 6 Unit III Aneuploidy results from the addition or subtraction of one or more chromosomes from a group of homologs, and is usually deleterious to the cell. g. chromosome produced by Robertsonian translocation (details in subsection 10. This particular studies has more scope for further experimental evidences. Fill in the gaps to describe the structure of chromosomes. Department of Biochemistry & Biophysics. Recombinant DNA refers to the creation of new combinations of DNA Genome = 46 chromosomes . Lethal in human diploids because a whole chromosome type has been deleted 4. Best and comprehensive biology notes for FSc part 2 students. That’s why we have uploaded the best quality notes of 12th class chromosomes from the parent organisms: one allele for each trait from each parent. Each gene codes for a particular sequence of amino acids, to make Notes MODULE - 3 1. 2: Non-disjunction of X-chromosomes in meiosis I and II. 1 Agriculture 5. Each chromosome is made up of DNA tightly coiled many times around from phase to phase in the continuous process of the cell growth and cell division. Key Areas: Mechanisms of sex determination, patterns of sex-linke segregation of the chromosomes during anaphase. 0 female; 0. . txt) or read online for free. Inheritance is the transmission of genetic information from generation to generation. The genes present on chromosome does not contains non coding region (introns) and it is co-translated to protein. Chromosomes are located in the nucleus of cells. Nov 1, 2023 · Banding technique •This is a technique for the identification of chromosomes and its structural abnormalities in the chromosome complement. - DNA is stored in the nucleus in the form of . Deficiency of Chromosomal Aberration: Feb 1, 2024 · U4a Lab 1 - Human Karyotyping Directions: Follow the instructions to go through the simulation. MEIOSIS Notes - Free download as PDF File (. 6 Selection 3. 1. com to clear your doubts. This PDF covers eukaryotic chromosomes, somatic and sex cells. - Chromatin Well before biologists understood the structure of DNA, they had recognized that genes are carried on chromosomes, which were discovered in the nineteenth century as threadlike Chromosomes contains genetic information in the form of genes which are responsible for appearance of characters. When DNA wraps around histone proteins forming a structure CHAPTER 14 LECTURE NOTES : RECOMBINANT DNA TECHNOLOGY I. 2 Mitosis 3. 2n-2 3. 8 MB) 34 Genetics of Cancer I 1. Track how chromosomes move during cell division and gamete f Chromosome mapping means determining the relative positions of genes in a chromosome by creating maps that are used to organize and understand genetic information on chromosomes. Fig. humans have 46 chromosomes) ∙ Diploid cells have two sets of chromosomes, where each chromosome has a homologous partner. It explains the negative charge of DNA, the semi-conservative nature of replication, and the differences between prokaryotic and eukaryotic genes. The brief note on B-Chromosomes with characteristics and research case studies. Polyploidy is the presence of more than two complete sets of chromosomes in a genome. Complete linkage is observed. Biology document from California State University, Los Angeles, 4 pages, DNA, Chromosomes | ' Objectives and Cell Division | 1. Law of segregation or purity of gametes. During | Find, read and cite all the research Mar 22, 2021 · Chromosomes (guided notes) Who was the first to see sperm cells? Describe how early scientists thought babies formed: Anton Van Leeuwenhoek was the first person to see sperm cells. 5 %âãÏÓ 17 0 obj /Type /FontDescriptor /FontName /Arial,Bold /Flags 32 /ItalicAngle 0 /Ascent 905 /Descent -210 /CapHeight 728 /AvgWidth 479 /MaxWidth 2628 /FontWeight 700 /XHeight 250 /Leading 33 /StemV 47 /FontBBox [-628 -210 2000 728] >> endobj 18 0 obj [278 0 0 0 0 0 722 0 333 333 0 584 278 333 278 278 0 556 556 556 0 0 0 0 0 0 333 0 Chromosome - 1 Notes offer in-depth insights into the specific topic to help you master it with ease. Oct 9, 2023 · (i) Deficiency (parts of chromosome lost or deleted), (ii) Duplication (parts of chromosome added or duplicated), (iii) Inversion (sections of chromosome detached and reunited in reverse order), and (iv) Translocation (parts of chromosome detached and joined to non-homologous chromosome). The document provides key information about DNA structure, replication, and gene expression. It is the systematized arrangement of the chromosomes of a single cell. Centromere is median. It notes that Ac is an autonomous transposable element that enables the movement of Ds elements. Chromosome mapping helps to understand the genome’s organization, Structure of chromosomes: ∙ Chromosomes consist of DNA (which makes up genes) and protein. How to Add Checkboxes to Your PDFs. Role of chromosome in hereditary process was discovered by Morgan (1933). r Riguhsts e©llT, ihGee nMetciGcsr: aCwop-Hyriilgl hCt o©m Ppeaanriseosn, EIndcu. Waldeyer (1888). docx), PDF File (. Information about Structural Variations in Chromosomes covers topics like Introduction, Alterations in Apr 19, 2021 · Structure of Chromosome Quick Review Chromosomes are rod-shaped or thread like deeply stainable condensed chromatin fibres which are hereditary vehicles. Recombinant DNA refers to the creation of new combinations Document Description: Chromosome Painting for UPSC 2025 is part of Zoology Optional Notes for UPSC preparation. DNA, chromosomes and Meiosis Notes 2025 - Free download as PDF File (. Each chromosome is made up of DNA tightly coiled many times around Chromosomes (chapters) Many recipes are stored together as chapters of the recipe book. Energy flow 2. Diploid: A cell or organism with two sets of chromosomes (2n). Section IV: Relationships of organisms with one another and with their environment . In Meiosis I, homologous chromosome pairs align and separate, reducing the Free PDF download of Class 10 Biology Chapter 2 - Cell Cycle, Cell Division and Structure Of Chromosomes Revision Notes & Short Key-notes prepared by our expert Biology teachers as per CISCE guidelines. Later on, this smaller chromosome was named as “ Y chromosome” and the larger one as “X chromosome” by Stevens (1905). 3. Chromosomes are thin, coiled, elastic, thread-like structures during the interphase. Chromosomes, Genes, Nucleosomes. The post is tagged and categorized under in 12th biology, 12th notes, Education News, Notes Tags. 3) four types of progeny are Jul 18, 2020 · On the basis of position of their centromere, chromosome is of 4 types: Metacentric chromosomes; Submetacentric chromosome; Acrocentric chromosome; Telocentric chromosome; Metacentric chromosome. Finally, it notes that temperature during egg incubation can determine sex in some reptiles. This ensures that sex cells have half the number of chromosomes of other somatic cells so that when fertilisation occurs the zygote formed has the correct number of chromosomes. Strahl.
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