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Chromosomes
This document summarizes key information about chromosomes. It defines chromosomes as carriers of genetic information visible during cell division. It describes the differences between prokaryote and eukaryote chromosomes. It discusses chromosome number, size, and types (autosomes and sex chromosomes). It explains cell division processes like meiosis and fertilization. It provides examples of human chromosomal abnormalities including both numerical disorders like Down syndrome and structural disorders. It describes chromosome structure and banding patterns used to identify chromosomes. It concludes with references for further reading.
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Chromosomes
- 1. A Seminar on CHROMOSOMES Presented By K. GANAPATHIRAO (13031D6003) Presence of Miss. CH SILPA CHAKRA (HOD) CNST-JNTUH IST
- 2. OUTLINE • • • • • • • • Introduction. Chromosome. Types Of Chromosomes. CellDivision. Meiosis And Fertilisation. Human Chromosomal Abnormalities. Chromosomes Structure. Structural Chromosomes Disorders.
- 3. CELL • Basic unitof building the body
- 4. Chromosomes In DifferentCells PROKARYOTES EUKARYOTES single chromosome plus plasmids many chromosomes circular chromosome linear chromosomes made only of DNA made of chromatin, a nucleoprotein (DNA coiled around histone proteins) found in cytoplasm found in a nucleus copies its chromosome and divides copies chromosomes, then the cell immediately afterwards grows, then goes through mitosis to organise chromosomes in two equal groups
- 5. Chromosome • Chromosomes arethe rod-shaped, filamentous bodies present in the nucleus, which become visible during cell division. • They are the carriers of the gene or unit of heredity. • Chromosome are not visible in active nucleus due to their high water content, but are clearly seen during cell division. • Chromosomes were first described by Strausberger in 1875. • The term “Chromosome”, however was first used by Waldeyer in 1888. Chromo=colour Soma=body Chromosome
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- 7. NUCLEOSOMES 30 NM SOLENOID/ CHROMATINFIBER CHROMATIN FIBER LOOPS
- 8. No of chromosomes •Normally, all the individuals of a species have the same number of chromosomes. • Presence of a whole sets of chromosomes is called euploidy. • When a change in the chromosome number does not involve entire sets of chromosomes, but only a few of the chromosomes - is Aneuploidy. • Gametes normally contain only one set of chromosome – this number is called Haploid • Somatic cells usually contain two sets of chromosome – 2n - Diploid – 3n – triploid – 4n – tetraploid
- 9. No of chromosomes Roundworm Onion Tomato 2 16 24
- 10. Chromosome Size In contrastto other cell organelles, the size of chromosomes shows a remarkable variation depending upon the stages of cell division. • Interphase: chromosome are longest & thinnest • Prophase: there is a progressive decrease in their length accompanied with an increase in thickness • Anaphase: chromosomes are smallest. • Metaphase: Chromosomes are the most easily observed and studied during metaphase when they are very thick, quite short and well spread in the cell.
- 11. Can distinguish chromosomesby “painting” – using DNA hybridization + fluorescent probes
- 12. Types of Chromosomes •Autosomes – Paired chromosomes with the same length, shape, centromere location, and genes – Any chromosome other than a sex chromosome – Determine size, colour, hair of a body. • Sex chromosomes – Members of a pair of chromosomes that differ between males and females HOMOGAMETIC SEX HETEROGAMETIC SEX SEX DETERMINATION Female XX Male XY Presence of Y-chromosome = maleness (mammals and fish) Presence of second X-chromosome = femaleness (Drosophila, the fruit fly) Male ZZ Female ZW Birds, amphibians, reptiles, butterflies, moths. Female XX Male Xo Grasshoppers
- 13. CELL DIVISIONS • Meiosis: – – – – Aspecial type of cell division Used to make sex cells Meiosis halves the numbers of chromosomes Meiosis picks one chromosome from each pair at random and places them in a sex cell. This results in enormous variation amongst the sex cells • Mitosis: – Normal cell division – Chromosomes are duplicated and distributed equally
- 14. Meiosis and fertilisation Mother Father 23pairs of chromosomes 23 pairs of chromosomes Meiosis 23 unpaired chromosomes 23 unpaired chromosomes 23 unpaired chromosomes Fertilisation 23 pairs of chromosomes Child 23 unpaired chromosomes
- 16. The inheritance ofgender Is it going to be a boy or a girl?
- 17. The inheritance ofgender Mother Father XX XY X X X X Fertilisation Y X XX XY X XX XY Y Possible children Chance of a girl 50% Chance of a boy 50%
- 18. Human chromosomal abnormalities Numerical(Chromosomal Disorders) • • • • Trisomy = 3 copies of a single chromosome 47 Monosomy = 1 copy of a single chromosome 45 Triploidy = 3N Tetraploidy = 4N Structural (Chromosomal Disorders) – Deletion – Duplication – Translocation (involves 2 chromosomes)
- 19. Causes of ChromosomalDisorders • Ionising radiation, autoimmunity, virus infections and chemical toxins in the pathogenesis of certain disorders.
- 20. Some Numerical Disorders XXY = Klinefelter’s syndrome male Feminine character. Tall, Normal Intelligence. XXX = Trisomy X female Produce healthy female. XYY = Jacob’s syndrome male Height, more active. Slightly learning disability. Normal intelligence. X/XO = Turner syndrome female • Webbed neck. • Short height. • Immature females.
- 21. Chromosomes Structure – – – – Centromere p arm qarm Telomeres
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- 24. Some Structural Disorders •Cri-Du-Chat Syndrome – – – – #5q Deletion Moon-shaped face, Heart disease Mentally retarded, Malformed larynx Normal lifespan • Aniridia-Wilms Tumor Syndrome – – – – #11p Deletion Mentally retarded, Growth retarded Blindness, Tumors on kidneys Short lifespan • Thirteen Q Deletion Syndrome – Mentally retarded, Deformed face – No thumbs, Heart disease – Short lifespan
- 25. Some Structural Disorders •Prader-Willi Syndrome – – – – #15q Deletion Small bird-like head, Mentally retarded Respiratory problems Obesity, Short lifespan • Eighteen Q Deletion Syndrome – – – – – #18q Deletion Mentally retarded, Heart disease Abnormal hands and feet Large eyes, Large ears Normal lifespan • Burkitt Lymphoma – Translocation of the Myc gene on chromosome 8 – Translocated Myc genes don’t function properly – Leads to cancer of the lymph nodes
- 26. Some Structural Disorders •Cat-Eye Syndrome – – – – #22q Deletion Fused fingers and toes Mentally retarded, Small jaw Heart problems, Normal lifespan • Patau’s Trisomy Syndrome – – – – – – #13 Trisomy Nondisjunction Small head, Small or missing eyes Heart defects, Extra fingers Abnormal genitalia, Mentally retarded, Cleft palate Most die a few weeks after birth • Four-Ring Syndrome – – – – #4 Inversion Cleft palate, Club feet Testes don’t descend Short lifespan
- 27. Videos 1. What IsA Chromosome. 2. How Dna Is Packaged (Advanced). 3. Chromosome Disorder Outreach Video. 4. Unique Children With Rare Chromosome Disorders.
- 28. REFRENCE • Human Chromosomesby Orlando J. Miller, • Chromosome biology by R. Appels, • http://www.chromodisorder.org/CDO/ • http://www.genome.gov/26524120 • http://www.youtube.com/watch?v=zf7tbymrv9 o • http://www.johnkyrk.com/chromosomestructu re.html
Editor's Notes
- #6 Their number can be counted easily only during mitotic metaphase.