Genetics

•Father of Genetics – Gregor Mendel•Studied garden pea plant•Genes are passed from one generation to the next•Genes have different forms called alleles

•Dominant allele•Recessive allele

genetics

http://www.sumanasinc.com/webcontent/animations/content/mendel/mendel.html

Genotype vs. Phenotype

•Genotype refers to the alleles- Heterozygous – Hh- Homozygous – HH – dominant

hh – recessive

•Phenotype refers to the appearance

Example: Genotype - PhenotypeWW - person has a widow’s peakWw - person has a widow’s peakww - person has a straight hair line

http://www.sumanasinc.com/webcontent/animations/content/independentassortment.html

Patterns of Heredity

Incomplete Dominance – blending Co-Dominance – stripes

Multiple Alleles – blood types

Each human body cell has 23 pairs of homologous chromosomes (46 total)

Half of the chromosomes are from the mother and half are from the fatherKaryotype

Trisomy 21

Trisomy 18 & Monosomy 15

http://www.sumanasinc.com/webcontent/animations/content/mistakesmeiosis/mistakesmeiosis.html

The Human GenomeDefined as the sum total of genes in a human

Estimates are 30,000 genes in each human controlling production of approximately 2 million different proteins

Each gene consists of an average of several thousand bases

Total number of nucleotides is about 3 billion per human cell

Human Genome Project

The project began in the late 1980s supported by 15 billion dollars

Goal of the project was to sequence the roughly 8 billion chemical letters in DNA that comprise the genetic code of humans

Many scientists said it could not be done

Project was completed in 2000.

Genetic Testing

• Now have DNA tests for 30 - 40 diseases–Cystic fibrosis, some forms of breast

cancer, Huntington disease• Tests are up to 99% accurate• Tests can be run on embryos created

by in-vitro fertilization prior to implantation

Issues about Genetic Testing

• What if the news is bad? Should the fetus be aborted or allowed to live with a “cruel” disease?

• Should insurance coverage provide care for a child having a genetic disease that was diagnosed before birth?

• Should blood relatives be warned?• Should our genetics be part of our records?• Should employers be allowed to consider

genetically based diseases in hiring employees?

• Will eugenics (manipulation of the hereditary qualities of a race) be practiced?