Introduction to Bioinformatics Lecture 4: Genetics and Inheritance, Study notes of Bioinformatics

Download Introduction to Bioinformatics Lecture 4: Genetics and Inheritance and more Study notes Bioinformatics in PDF only on Docsity! 1 BCB 444/544 – Introduction to Bioinformatics Lecture 4 • Basic Genetics Overview #4_Aug28 Overview • What is genetics? • Genetics and inheritance • Case study from the textbook • Slides adapted from a presentation by Erin Garland from the Genome Sciences Centre in Vancouver Inheritance Gregor Mendel (1860s) Inheritance occurs in a discrete manner Cross offspring - get ¾ purple Cross purple and white - get all purple Pea flowers can be purple or white Mendelian inheritance A A a a • There are 2 copies of each gene in each cell, and a single gene determines a single trait phenotype genotype • Genes have alleles that are dominant or recessive A adominant allele recessive allele A A A a A a a a Alleles reassort randomly in offspring Homozygous = the individual has the same two alleles for a gene Heterozygous = the individual has two different alleles for a gene Hemizygous? In a family with 4 children, what is the probability that all 4 are female? Non-Mendelian inheritance Some traits are determined by 2 or more genes, each with multiple alleles 3 different genes determine color and pattern in the foxglove flower Continuous traits are determined by large numbers of genes Human height is a continuous trait 2 Genetics and environment Phenotype is determined by BOTH genotype AND environment Example: Adult onset diabetes • Susceptibility genes are inherited • Environmental factors influence disease onset (eg. obesity) Genetic structures Cells Chromosomes Genes DNA Human chromosomes 22 pairs of autosomes + 2 sex chromosomes (XX or XY) X-linked traits • Many genes are carried on the X and not the Y chromosome Example: red-green color blindness is X-linked • Recessive alleles on the X will appear dominant in males (no other allele present to mask the recessive phenotype) Carriers • Females can be carriers for X-linked traits • Carriers have one copy of the recessive allele and one copy of the dominant allele • What is the disease status for a carrier? Carriers usually show no disease symptoms Our story so far… • Little boy BB has some serious problems • BB’s little brother is behind in development as well • BB has two older sisters with no apparent health problems • BB’s oldest sister is married with one healthy daughter and one baby on the way • An uncle of BB’s died at 20 years old from a disease similar to BB’s • Other males in BB’s family have also died as young adults