Modern Genetics

Human Inheritance A. Traits Controlled by Single Genes 1. traits are controlled by 2 alleles on a single gene 2. these traits have 2 distinctly different phenotypes 3. ex: widow’s peak, dimples

Section 1: Human Inheritance B. Multiple Alleles 1. some traits are controlled by a single gene with more than one allele 2. because chromosomes exist in pairs, a person can carry only 2 of these alleles 3. ex: blood types

Blood Types

Section 1: Human Inheritance C. Traits Controlled by Many Genes 1. some human traits show a large number of phenotypes because the traits are controlled by many genes. The genes act together as a group to produce a single trait 2. ex: at least 4 genes control height, at least 3 genes control skin color

Human Inheritance D.The Effect of the Environment 1. effects of genes can be altered by the environment 2. ex: height can be affected by diet

Human Inheritance Male or Female? 1. one of the 23 pairs of chromosomes is called the sex chromosomes 2. sex chromosomes are the only chromosomes that don’t always match (as in males) – Y is much smaller than X 3. eggs and sperm cells can each have only one chromosome; females always contribute an X, while males may contribute an X or a Y 4. XX = female XY = male

Human Inheritance F. Sex-Linked Genes 1. alleles are passed from parent to child on sex chromosomes 2. because females have 2 matching X chromosomes, a dominant allele on one can mask a recessive allele on the other 3. in males any allele on the X chromosome – even a recessive one – will produce a trait 4. ex: color-blindness 5. carrier = person who has one recessive allele for a trait and one dominant one. doesn’t have trait but can pass it on

Human Genetic Disorders 1.genetic disorders are abnormal conditions that a person inherits through genes or chromosomes 2. are caused by mutations or changes in a person’s DNA

Cystic Fibrosis carried on a recessive allele causes body to produce a thick mucus in lungs and intestine no cure Cystic fibrosis website

C c C c CCCc cc Carriers!

Sickle-Cell Disease carried on a codominant allele prominent in Africans causes body to produce an abnormal form of hemoglobin red blood cells become sickle shaped and do not carry oxygen as well no cure – treatments available Sickle-Cell Website

sickle cell

Hemophilia carried on a recessive allele on the X chromosome causes blood to clot slowly or not at all can be treated with clotting protein Hemophilia website

Human Inheritance Pedigrees 1. a chart or family tree that tracks which members of a family have a particular trait

The Walker Family Tree Rick James HenryChristine Marie “Judy” DennisNancyStevenAndreaBrentJoyceLisa MollyClarkBrent Sharum EmilyBrentAprilSteven Eden Neil Sharum

Down Syndrome caused by an extra copy of chromosome 21 causes distinctive appearance and usually some mental retardation Down Syndrome Website

Diagnosing Genetic Disorders amniocentesis = fluid containing baby’s cells is removed and analyzed karyotype = a picture of the chromosomes arranged in pairs Karyotype website

The Blue Fugates the methemoglobinemia gene

Genetic Counseling Doctors use karyotypes, pedigrees and Punnett squares to help couples understand their chances of having a child with a particular genetic disorder

Section 3: Advances in Genetics For thousands of years people have tried to produce plants and animals with desirable traits

Selective Breeding the process of selecting a few organisms to serve as parents of the next generation Inbreeding crossing two individuals that have identical or similar sets of alleles reduces an offspring’s chances of inheriting new allele combinations increases the probability that organisms may inherit alleles that lead to genetic disorders

ProsCons INBREEDING (Mating of closely related individuals) Produces uniform or predictable offspring. Hidden (recessive) genes show up and can be eliminated. Individuals will "breed true" and are "pure." Doubles up good genes. Eliminates unwanted traits. Doubles up on faults and weaknesses. Progressive loss of vigor and immune response. Increased reproductive failures, fewer offspring. Emphasis on appearance means accidental loss of "good" genes for other attributes. Genetically impoverished individuals.

Hybridization breeders cross two genetically different individuals hybrid organisms that result are bred to have the best traits of both parents

California Schnoodles Mom & Dad

Cloning A clone is an organism that is genetically identical to the organism from which it was produced 1. Cloning Plants a. cutting 2. Cloning Animals a. much more difficult (Dolly)

Cloning

Genetic Engineering Defined: genes from one organism are transferred into the DNA of another; also called gene-splicing 1. Genetic Engineering in Bacteria a. segments of human DNA can be spliced into bacterial chromosomes. the bacteria then produce human hormones 2. Genetic Engineering in Other Organisms a. genes from one organism can be inserted into another to achieve desired traits 3.Gene Therapy a. inserting working copies of a gene directly into cells in an attempt to correct a genetic disorder

Genetic Engineering First human somatic gene therapy – On September 14, 1990, the first human gene therapy experiment was conducted on four year-old Ashanti Desilva who suffered from ADA deficiency. Dr. W. French Anderson performed the experimental therapy by infusing white blood cells (with the correct genetic composition) into Ashanti to correct her immunodeficiency. While the therapy did not yield a complete cure, it did help correct the deficiency so that Ashanti only takes small, weekly doses of the traditional PEG- ADA drug.

First gene therapy death – In September 1999, 18 year-old Jesse Gelsinger was the first reported death to be directly caused by gene therapy treatment. Jesse suffered from OTC disease (ornithine transcarboxylase deficiency), a liver disorder that results in poisonous levels of ammonia build-up in the body. His disorder was being controlled through diet and medication. Although he was healthy and full of life, he chose to participate in the gene therapy study because of his desire to help others with same disease. Four days after starting treatment, he died of multiple organ failure. His death is thought to be a result of a severe immune response to the adenovirus carrier (the vector used to carry the altered genes to his liver).

DNA Fingerprinting no two people, except identical twins, have the same DNA DNA in blood, skin, saliva, hair, etc can be used to solve crimes

The 1 st DNA Fingerprint! Who Did It?

The Human Genome Project genome = all the DNA in one cell of an organism the main goal of the human genome project is to identify the DNA sequence of every gene in the human genome and discover what the genes do

Are They Real???