MGD S11 L2 (Chromosomal Abnormalities) Part 2.pdf

University Of Basrah Ministry Of Higher Education Al-Zahraa College Of Medicine And Scientifi c Research Module: Molecule, Gene and Disease Semester: 2 Session: 11 Lecture: 19 , 20 (Part 2) Duration: 1 hr...

University Of Basrah Ministry Of Higher Education Al-Zahraa College Of Medicine And Scientifi c Research Module: Molecule, Gene and Disease Semester: 2 Session: 11 Lecture: 19 , 20 (Part 2) Duration: 1 hr Lecture Title: Chromosomal abnormalities Module staff: Dr. Farqad M. Al-Hamdani Dr. Ilham Mohamed Jawad Dr. Wameedh Hashim Alqatrani Dr. Ban M. Saleh Dr. Abeer Laily Mohammed Dr. Hamed Jaddoa Dr. Hazim T. Thwainy Dr. Shant Sunbat Dr. Zainab Muzahim Dr. Zainab Ahmad Dr. Hussein K. Abdul-Sada Dr. Myada Abd Allah Dr. Amani Niama Ass.Lect Eatidal Akram Farhan This Lecture was loaded in blackboard and you can find the material in: (Lippincott’s Illustrated Reviews: Cell and Molecular Biology Chapter 5). For more detailed instructions, any question, or you have a case you need help in, please post to the group of session  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Lecture 19, 20 Learning Outcomes: 4. Provide an overview of the different genetic tests available for the detection of chromosomes abnormalities. (LO 11.4) 5. Be familiar with the concept of karyotyping. (LO 11.5) 6. Recognize, comprehend and apply chromosome nomenclature. (LO 11.6) 7. Outline the reasons for referral of patients for karyotyping. (LO11.7) 8. Explain how fluorescent in situ hybridization (FISH) works and recognize its importance in the detection of chromosomal abnormalities. (LO 11.8) 9. Show an appreciation of the ethical issues associated with genetic testing. (LO 11.9)  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Genetic tests available for the detection of chromosomes abnormalities LO 4 Genetic testing is a type of medical test that identifies changes in chromosomes, genes or proteins. Genetic tests examine a person's DNA in a variety of ways. They are all designed to identify a particular gene that may cause a genetic disorder.  Gene tests look for abnormalities in DNA taken from a person's blood, body fluids or tissues.  There are different types of genetic testing which include: 1) Molecular genetic tests (or gene tests) Such as PCR, Southern blotting, Gene cloning and Gel electrophoresis.  These look at single genes or short lengths of DNA taken from a person's blood or other body fluids (for example, saliva) to identify large changes, such as:  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research  A gene that has part of it missing or a section added; or LO 4  Small changes, such as a missing, added or altered part within the DNA strand. An example of a genetic disorder that is tested in this way is cystic fibrosis. 2) Chromosomal genetic tests These look at the features of a person's chromosomes, including their structure, number and arrangement.  There are different ways in which chromosome tests can be undertaken. These include: Karyotyping - this test results in a picture of all of a person's chromosomes. It can identify changes in the number of chromosomes (for example, Down's syndrome in which there is an extra chromosome number 21).  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 4 Fluorescent in situ hybridisation (FISH) analysis - this test looks at certain parts of the chromosomes and can detect very small pieces of chromosomes that are either missing or extra (for example, Duchenne muscular dystrophy). 3) Biochemical tests  Biochemical tests look at the amounts or activities of key proteins.  These types of tests are often used for newborn baby screening. For example, biochemical screening can detect infants who have a condition affecting one of the many essential chemical reactions in the body (metabolic condition) such as phenylketonuria.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Karyotype LO5 Karyotype: is a pictorial presentation of an individual’s chromosomes, taken from microphotographs and arranged in a numeric sequence that aligns the chromosomes from largest to smallest.This standardized presentation allows the geneticist to analyze an individual’s chromosomal profile. Somatic cells used to get Karyotype:  Peripheral blood.  Amniotic fluid.  Chorionic Villi.  Tumor Cells.  Bone marrow cells. Amniocentesis  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research How to get Karyotype? Amniocentesis LO 5  To investigate chromosomes there is usually a need for dividing mitotic cells.  Cells are collected from tissues samples (e.g. blood or bone marrow, or for fetal cells, amniotic fluid or chorionic villus) and cultured in vitro.  Cells are then arrested when most cells are in late prophase or early metaphase, when chromosomes are highly condensed and replicated, but not yet organized along the metaphase plate.  So called ‘metaphase spreads’ (chromosomes in metaphase nicely spread out) can then be analyzed using a wide variety of staining procedures (including G-banding).  Karyotypes can be produced by ‘cut & paste’ (either by hand or computer) of chromosomes pictures into a systematically organized set of metaphase chromosomes organized in pairs and groups, chromosome 1 in the top left corner and the sex chromosomes in the bottom right corner.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 5 G-Banding  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 5 G-Banding  Dye gives chromosomes a striped appearance because it stains the regions of DNA that are rich in adenine (A) and thymine (T) base pairs.  Regions that stain as dark G bands replicate late in S phase of the cell cycle and contain more condensed chromatin, while light G bands generally replicate early in S phase, and have less condensed chromatin.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 5 Chromosomes are numbered and grouped according to their size and the position of their centromere.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 5  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Karyotype of a normal male LO 5  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Karyotype of a normal female LO 5  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Karyotype of a female Down syndrome LO 5  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Karyotype nomenclature: LO 6  The karyotype formula start with the total number of chromosomes in the cell, followed by a comma, then the X chromosomes and then the Y chromosomes (e.g. a normal female is 46,XX and a normal male is 46,XY).  Other notations will follow this, each time separated by a comma.  The plus (+) or minus (-) sign followed by a number indicate an extra or missing entire chromosome. When a piece of a chromosome is missing the chromosome number is indicated followed by a ‘p’ or ‘q’ and a minus (-) sign (e.g. 5p- means ‘missing a segment of the p-arm of chromosome 5’).  Other notations include ‘del’ (deletion), ‘dup’ (duplication), ‘inv’ (inversion),‘s’ (satellite) and ‘t’ (translocation).  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 7 Outline the reasons for referral of patients for karyotyping. There is main Indications for routine chromosomal investigation: 1. Constitutional (congenital) abnormalities: A. Prenatal screening:  Down’s syndrome, especially raised maternal age (>35 years).  Family history of chromosome abnormality.  Abnormal ultrasound scan of fetus. B. Birth defects:  Malformations  mental retardation  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Down Syndrome LO 7 (47, XY, +21) (47,XX, +21)  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research Malformations LO 7 Micrognathia (47, XX, +9)  UNIVERSITY OF BASRAH Ministry of higher Education AL-Z AHR A A MEDICAL COLLEG E and Scientific Research Malformations LO 7 Clinodactyly (47, XX, +21) Low set Ears (47, XY, +21)  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 7 1. Constitutional (congenital) abnormalities: cont. C. Abnormal sexual development: Delayed puberty:  Klinefelter’s syndrome (47, XXY)  Turner syndrome (45, X) D. Infertility. E. Recurrent fetal loss. 2. Acquired abnormalities:  Leukemia and related disorders.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 7  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 7  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 7 Diagnosis of Chromosome Abnormalities enables: 1. Accurate diagnosis/prognosis of clinical problems in patients. 2. Better management of affected patients e.g. hormone treatment in some sex chromosome abnormalities. 3. Understanding of future reproductive risks for carriers. 4. Prenatal diagnosis and possible termination of affected pregnancies.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 8 Explain how fluorescent in situ hybridization (FISH) works and recognize its importance in the detection of chromosomal abnormalities.  This technique allows the investigation of specific DNA sequences on chromosomes inside the cell.  Fluorescent probes for a specific gene (or several genes) can be used or probes for specific DNA stretches on chromosomes, like telomeres or centromeres.  For chromosome investigation chromosome painting is often used, whereby each chromosome is visualized using a different colored fluorescent probe.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 8 Detection centromeric region Detection telomeric region by FISH Technique by FISH Technique  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research LO 9 Show an appreciation of the ethical issues associated with genetic testing.  Privacy.  Access to care.  Autonomy in decision making.  Protection against discrimination.  UNIVERSITY OF BASRAH AL-ZAHRAA MEDICAL COLLEGE Ministry of higher Education and Scientific Research 12