Following Patterns of Inheritance in Humans Chapter 5 ~ Section 5.3 Following Patterns of Inheritance in Humans

Review - Key Ideas Section 5.1 Section 5.2 Mendel’s experiment with Pea Plants = Dominant & Recessive Traits Monohybrid Cross Mendel’s Law of Segregation Differences between genotype & phenotype Section 5.2 Use of Punnett Squares to analyze and predict the inheritance of traits Law of Independent Assortment Dihybrid Crosses Phenotype @ 9:3:3:1 Chromosome Theory of inheritance

Introduction Controlled breeding of plants & animals has allowed scientists and researchers to come across many genetic discoveries Breeding experiments are NOT ethical or possible for human genetics So they use a flow chart called a Pedigree to illustrate inheritance patters with colours and symbols between generations

411 on Pedigrees Is a way to analyze how a trait “runs in the family” Used by geneticists to determine patterns of inheritance of a particular trait that is controlled by a 1 or more genes Help uncover the genotype of a particular member of a family Can be used with a Punnett Square to determine the probability of a specific genotype / phenotype in an offspring Mainly used to determine the presence / absence of an allele linked to a disease

411 on Pedigrees

Autosomal Inheritance Autosomal Chromosomes = any chromosomes other than Sex chromosome Autosomal Inheritance = the traits that are found on autosomal chromosomes (1 to 22) Autosomal genes are also responsible for many inherited disorders which can be classified as autosomal Dominant or Recessive

Autosomal Inheritance

Autosomal Inheritance: Dominant A pedigree can determine whether the inheritance pattern of a disorder is dominant or recessive You can have both parents affected by a gene (heterozygous dominant) and yet their child may not be (homozygous recessive)

Autosomal Inheritance: Recessive In order for someone to have an autosomal recessive disorder, BOTH their parents must be carriers of the disorder, via: Heterozygous dominant (Aa) Homozygous recessive (aa) People who are heterozygous (Aa) for a disorder are not first hand affected by it, even though they are “carriers”

Genetic Testing There are lots of different ways individuals who are at risk of developing genetic disorders, or of passing these disorders on to their off spring can be tested Once geneticists are able to identify the chromosome and eventually the gene responsible for a disorder, more detailed analyses are possible

Types of Genetic Tests – pg. 224 Method What is Analyzed Example Karyotype Chromosome Structure Chromosome Number F.I.S.H Details of chromosome abnormalities Target a specific region on a chromosome Gene Testing Mutation (s) in the DNA sequence of a gene Biochemical Testing Abnormal enzymes and proteins are visible due to mutation in protein synthesis

Genetic Testing At work Read pgs. 221-224 Explain the genetic defects of Huntington’s Disease and Cystic Fibrosis Explain how genetic testing was used to identify them

Genetic Testing At work Huntington’s Disease Cystic Fibrosis

Genetic Counsellors Are a health care professional with specialized training in human genetics and in counselling people and their families who may have or be at risk for a genetic disorder They too use Pedigrees to determine the genotypes of family members and provide options for genetic testing to explain the possibility of them passing on a disorder to their children

Gene Therapy: A Cure for Genetic Disorders? While genetic testing give people options for people carrying a genetic disorder, their greatest HOPE can lie within gene therapy Gene Therapy – a technique aimed at correcting the effects of a mutated gene that’s related to a disorder by introducing the correct form of the defected gene in a patient’s genome

Gene Therapy: A Cure for Genetic Disorders? Works by having a copy of the NORMAL gene inserted into a vector , who carries the gene into the cell Once inside, the correct protein can be made from the right information!

Gene Therapy: A Cure for Genetic Disorders?

The Future of gene Therapy Researchers have been working with Gene Therapy since 1990 – yet is still very “experimental” This is because of 2 reasons: Use of viruses to send the right gene onto the cell can sometimes be “attacked” by the immune system as it is a virus & foreign to the cell Benefits are Short-lived Difficulty integrating the correct gene into the cell’s chromosomes, which means the correct gene does not reproduce / fix the problem

STSE: Gene Therapy Case Study – p. 232