Mendelian Inheritance by B. Korf | OPENPediatrics скачать в хорошем качестве

Mendelian Inheritance by B. Korf | OPENPediatrics

Learn about the patterns of single gene inheritance. Please visit: www.openpediatrics.org OPENPediatrics™ is an interactive digital learning platform for healthcare clinicians sponsored by Boston Children's Hospital and in collaboration with the World Federation of Pediatric Intensive and Critical Care Societies. It is designed to promote the exchange of knowledge between healthcare providers around the world caring for critically ill children in all resource settings. The content includes internationally recognized experts teaching the full range of topics on the care of critically ill children. All content is peer-reviewed and open access-and thus at no expense to the user. For further information on how to enroll, please email: [email protected] Please note: OPENPediatrics does not support nor control any related videos in the sidebar, these are placed by Youtube. We apologize for any inconvenience this may cause. My name is Bruce Korf, I'm a medical geneticist in the Department of Genetics at University of Alabama at Birmingham. This talk will focus on the principles of Mendelian inheritance. We'll first describe the basic patterns of Mendelian inheritance that is autosomal recessive, autosomal dominant, and sex-linked. We'll explain the concepts of penetrance and expressivity and then the notion of x chromosome inactivation. Basic Patterns of Mendelian Inheritance. The basis for Mendelian Inheritance is the fact that humans are a diploid organism. We call the non-sex chromosomes autosomes, and any individual will have inherited one copy of each autosome from each parent. That is, one from mother, one from father. The sex chromosomes consist of two Xs in females, and an X and a Y chromosome in males. If one focuses on any particular gene, it's possible that both copies, each one inherited from one of the parents, are the same, which we refer to as homozygous. Or they can be different from one another, in which case we say the individual is heterozygous. The two copies of any particular gene are called allelels, and the particular allelels for any particular gene locus refer to the individual's genotype. The physical expression of a genotype is the phenotype. In this case, for example, having blue eyes or brown eyes. The first major pattern of genetic transmission we'll consider is autosomal recessive. In this case, a particular genetic mutation needs to be present in a homozygous form in order for phenotype to occur. The dominant version is referred to here is big A, the recessive is little a. So only the homozygote for little a shows the phenotype. The heterozygote does not, and of course the homozygote for big A also does not. If one looks at a family tree, both parents are heterozygous carriers, and they have a one in four chance at they both transmit the little a to a child, and that child will be affected. That is, will show the phenotype. There's a one-in-two chance that either of them, but not both, transmits little a, in which case, the child is heterozygous. And a one in four chance that a child inherits big A from both parents. And that child, too, will be unaffected. For rare autosomal recessive traits, there tends to be an increased frequency of consanguinity. That is, where the parents may be close relatives. This is an example where this child is homozygous for little a, and her great grandfather was heterozygous for what may be an exceedingly rare allele on the population. But he transmitted little a to his daughter, who in turn transmitted it to her son, who transmitted it to this child. And simultaneously was transmitted from him to his son, then to his daughter, and then, finally, to this child. Certainly not all instances of consanguinity result in homozygosity for medically significant traits, and not all instances of homozygosity are the consequence of consequently. But again, for rare traits, one tends to see an increased frequency of consanguinity.