Genetics Since Mendel

Incomplete Dominance Occurs when neither allele for a trait is dominant. The phenotype produced is intermediate between the two homozygous parents Ex. Coat color in purebred dogs

Multiple Alleles More than 2 alleles are multiple alleles Traits controlled by multiple alleles produce more than 3 phenotypes. In humans, blood type is controlled by 3 alleles (A,B,)- A & B are dominant. O is recessive

Polygenic Inheritance A group of gene pairs acts together to produce a trait, which creates more variety in phenotypes. Many human traits are controlled by polygenic inheritance, such as hair and eye color, height, body build, shape of eyes, lips and ears.

*Height is controlled by four genes working together. *Skin color is controlled by at least three genes, each one containing two different alleles. Various combinations of alleles produce the many skin colors in humans

Mutations- genes that are altered or copied incorrectly A mutation can be harmful, helpful, or have no effect Chromosome disorders- caused by more or fewer chromosomes than normal Down Syndrome- caused by 3 copies of chromosome 21

Significance of Mutations Most are neutral Eye color Birth marks Some are harmful Sickle Cell Anemia Down Syndrome Some are beneficial Sickle Cell Anemia immune to Malaria Immunity to HIV

What Causes Mutations? There are two ways in which DNA can become mutated: Mutations can be inherited. Parent to child Mutations can be acquired. Environmental damage Mistakes when DNA is copied

Chromosome Mutations Down Syndrome Chromosome 21 does not separate correctly. They have 47 chromosomes in stead of 46. Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.

Chromosome Mutations Cri-du-chat Deletion of material on 5th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps

Recessive Genetic Disorders Both parents have a recessive allele responsible for the disorder and pass it on to their child. Because parents are heterozygous, they don’t show symptoms Cystic Fibrosis is a homozygous recessive disorder

Recessive Genetic Cont. Genes that determine the sex of an organism are XX in females and XY in males. Males determine the sex of the offspring Females produce eggs with x chromosomes only. Males produce sperm with either an x or a y chromosome.

Sex Linked Disorders 1. An allele inherited on an X or Y chromosome is a sex linked gene. Colorblindness is a sex linked disorder caused by a recessive allele on the X chromosome. More common in males- females have to inherit it on both x’s.

Example of sex-linked trait controlled by a recessive allele: red-green color blindness Affects more males than females

What is a pedigree chart? Pedigree charts show a record of the family of an individual They can be used to study the transmission of a hereditary condition They are particularly useful when there are large families and a good family record over several generations. © 2007 Paul Billiet ODWS

Symbols used in pedigree charts A marriage with five children, two daughters and three sons. The eldest son is affected by the condition. Eldest child  Youngest child Normal male Affected male Normal female Affected female Marriage © 2007 Paul Billiet ODWS

Organising the pedigree chart A pedigree chart of a family showing 20 individuals © 2007 Paul Billiet ODWS

Organising the pedigree chart Generations are identified by Roman numerals I II III IV © 2007 Paul Billiet ODWS

Organising the pedigree chart Individuals in each generation are identified by Arabic numerals numbered from the left Therefore the affected individuals are II3, IV2 and IV3 I II III IV © 2007 Paul Billiet ODWS

Advances in Genetics Genetic Engineering: Genes from one organism are transferred into the DNA of another organism Used to produce medicine(insulin), improve crops, and cure genetic disorders

Bright face of genetically modified corn plant: pest-infected non-GM (left) and pest-free GM plant (right) planted side-by-side in a field trial. (photo: Dr. Yu Jialin, China Agricultural University)

                                                                                                                    French genetic researchers created Alba for artist Eduardo Kac. Thanks to genes borrowed from a jellyfish, the albino rabbit glows green when placed under special lighting. In regular light, Alba appears like any other furry white rabbit. But place her under a black light, and her eyes, whiskers and fur glow a otherworldly green.

http://www.fluorescentpets.com/index.htm

Gene Therapy A normal allele is placed into a virus, which delivers the normal allele when it infects its target cell. May be used to control cystic fibrosis and other genetic disorders

Selective Breeding: Breeding organisms with desired traits so that their offspring will have those traits Hybridization: Breeding two genetically different individuals

SELECTIVE BREEDING The Liger is the result of breeding a female Tiger to a male Lion. The liger has both stripes and spots. The stripes are inherited from its tiger parent and the spots from the lion parent. On their hind legs, ligers stand approximately 12 feet tall. At most, ligers may weigh up to 1,000 pounds.

The Cama is the result of breeding a Llama to a Camel The Cama is the result of breeding a Llama to a Camel. Parents in background of picture.

The Zebroid is the result of breeding a female Horse and a male Zebra. The Zedonk / Zonkey is the result of breeding a female Donkey and male Zebra.

The Mule is the result of breeding a female horse (mare) to a male donkey (jack). The mule is superior to the horse in strength, endurance, intelligence and disease resistance.

The Human Genome Project: The main goal of the human genome project is to identify every gene in human DNA. How can this help improve modern medicine?