Pediatric Tutorial PDF

 Cellular and molecular biology and principles of genetics ----------------- ▪ Course code: IMP-07- 010106 ▪ Phase: I ▪ Year/ semester: 1nd year / Semester (1) ▪ Credit hours: 2 Hr. ▪ Course duration: 7weeks. Clinical aspects of chromosomal abnormal...

 Cellular and molecular biology and principles of genetics ----------------- ▪ Course code: IMP-07- 010106 ▪ Phase: I ▪ Year/ semester: 1nd year / Semester (1) ▪ Credit hours: 2 Hr. ▪ Course duration: 7weeks. Clinical aspects of chromosomal abnormalities Prof. Ensaf Khalil Mohamed Professor of Pediatrics Faculty of Medicine (for Girls)- Al-Azhar University Wednesday 10/12/2020 Intended Learning Outcomes (ILOs) ▪ On completion of this lecture, the student will be able to: ▪ Define chromosome and chromosome abnormalities or syndromes. ▪ Describe and distinguish different chromosomal aberrations in man with examples. ▪ Understand the causes for chromosomal anomalies. ▪ Understand the consequences of chromosomal aberrations. Information: ▪ Human beings have cells with 46 chromosomes; these consist of 2 chromosomes that determine what sex they are (X and Y chromosomes), and 22 pairs of nonsex (autosomal) chromosomes. ▪ Males are 46,XY and females are 46,XX. Chromosome: ▪ A chromosome is the most condensed structure of a DNA molecule with protein. Gene: ▪ Genes are sections or segments of DNA that are carried on the chromosomes and determine specific human characteristics such as height or hair color. Genetic Disorders: A genetic disorder is a disease that is caused by a change, or mutation, in an individual’s DNA sequence. There are three main categories: ▪ Single gene disorders caused by defects in one particular gene, often with simple and predictable inheritance patterns. ▪ Chromosome disorders resulting from changes in the number or structure of the chromosomes. ▪ Multifactorial disorders caused by changes in multiple genes, often in a complex interaction with environmental and lifestyle factors such as diet or cigarette smoke, for example: cancer. Chromosomal abnormalities: 1. Numerical Abnormalities: Abnormal number a. Trisomy Definition: One chromosome is represented by 3 copies “extra-chromosome”. Examples: Autosomes: Trisomy 21, 18 & 13 (i.e., Down, Edward & Patau Syndromes). Sex chromosomes: Klinefelter (XXY), triple X (XXX female), (XYY male). b. Monosomy: Definition: One chromosome is represented by 1 copy “absent chromosome”. Examples: Autosomes: Monosomy 21, 22. Sex chromosomes: Turner syndrome (XO) ▪ 2. Structural Abnormalities: A chromosome's structure can be altered in several ways. ▪ Deletions: A portion of the chromosome is missing or deleted. ▪ Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material Translocations: A portion of one chromosome is transferred to another chromosome. There are two main types of translocation: ▪ Reciprocal translocation ▪ Robertsonian translocation ▪ Inversions: A portion of the chromosome has broken off, turned upside down, and reattached. As a result, the genetic material is inverted. ▪ Down syndrome is an example of a condition caused by numerical abnormalities, which is marked by: ▪ Mental retardation ▪ Learning difficulties ▪ A characteristic facial appearance ▪ Poor muscle tone (hypotonia) in infancy Clinical features of Down’s syndrome Edward syndrome trisomy 18 Patau syndrome trisomy 13 ▪ Turner syndrome: In this chromosomal disorder there is the absence of one X chromosome in females. Hence, decreasing the chromosomes count to 45 (44 + X0). Such females are: Sterile Have rudimentary ovaries Absence of secondary sexual characters ▪ Klinefelter syndrome: This genetic disorder arises due to the presence of an additional X chromosome in males. Such a person has:  Example of structural chromosomal abnormalities ▪ Cri-du-chat syndrome Cri-du-chat syndrome is an autosomal deletion syndrome caused by a partial deletion of the p arm of chromosome 5 (5p) and is characterized by a distinctive, high-pitched, catlike cry in infancy with growth failure, microcephaly, facial abnormalities, and mental retardation throughout life. Self assessment Questions: Down’s syndrome is due to ▪ a) crossing over ▪ b) linkage ▪ c) sex-linked inheritance ▪ d) nondisjunction of chromosomes A section of chromosomes that codes for a trait can be called a: ▪ a) nucleotide ▪ b) base-pair ▪ c) gene ▪ d) nucleus A person with Klinefelter syndrome ▪ a) is a sterile male ▪ b) is a sterile female ▪ c) can be either a sterile male or female ▪ d) is neutral (neither male or female) Learning Resources: https://medlineplus.gov/ency/article/002048.htm https://www.yourgenome.org/facts/what-is-a- chromosome-disorder https://learn.genetics.utah.edu/content/basics/