 Gregor Mendel is known as the Father of Genetics. With his research he concluded that organisms receive units of inheritance from each parent.  The inherited factors are called genes, which are found in the chromosomes in the nucleus of the cell.  Most of the time chromosomes are not visible but are dispersed within the nucleus as chromatin material. When a cell is about to divide the chromatin condense and chromosomes become visible under a microscope

 A gene provides each cell in the body with instructions for making a particular protein for a particular characteristic.  Except for sex cells, all cells contain the same set of about 30,000 genes.

 Except for the sex cells, all human cells contain 46 chromosomes that occur in pairs. These 46 chromosomes make up the human karyotype.  Each pair has a similar appearance and are called a homologous pair. There are 23 homologous pairs of chromosomes in human cells.  Of these 23 pairs, 22 pairs are called autosomes. The 23 rd pair determines the sex of the individual. In the female karyotype there are 2 X chromosomes and in the male there is one x and one y. Female XX, Male XY.

Is this a male or female karyotype? How do you know?

How is this karyotype different from the last slide?

 Genes for a particular feature occur in pairs. One gene on each chromosome of the homologous pair. These paired genes are called alleles.  Homozygous alleles are an identical pair. They have the same DNA sequence.  Heterozygous alleles consist of different alleles. For instance, one for blue eyes and one for brown eyes.  One allele may be dominant (preference to the characteristic) or recessive (“weaker”) How many of you have 12 fingers on one hand? Would this be the dominant or recessive trait?

 It is the DOMINANT trait!!! Just because something is common (10 fingers) does not make it dominant. There are so few of the dominant (12 finger) genes in the population that it does not show up often.

Answer at your table: 1. Every person has ______ chromosomes in every cell nucleus. 2. The pair of chromosomes that determines whether you are male or female is called the _______ chromosomes. 3. The 22 pairs of chromosomes that are not sex chromosomes are called _____________. 4. ________ have a long X chromosome and a short Y chromosome. 5. ________ have two long X chromosomes. 6. Inheritance of genes on the autosomes is called _________________________. 7. In ____________ inheritance, only one copy of the gene is needed to see the trait. 8. In ____________ inheritance, two copies of the gene are needed to see the trait. 9. Although there are some traits and diseases that are caused by a single gene, most traits and diseases are caused by _______ genes. 10. The goal of the __________________________ is to create a map of where each gene belongs on a chromosome. Word Bank autosomes dominant sex Human Genome Project females many males 46 recessive

 Genotype: the genetic constitution of an individual. It indicates the combination of alleles.  Phenotype: the individual’s observable characteristics resulting from his/her genotype.

HUMAN GENOME PROJECT One of the purposes if this decades long research was to find all of the genes that make up a human and to map their locations on the appropriate chromosomes.) One of the positive outcomes of this project has been, to begin identifying, where on our chromosomes certain diseases are carried. This chart shows the locations of some of these.

 Genetically-linked disease (or genetic tendency): makes a person more likely than most to develop a specific disease. Factors other than genetics, such as lifestyle or environmental exposure, are contributing causes. ▪ Ex: coronary artery disease and obesity  Genetic Disease: a disease that is determined by a person’s genes. If you have those genes, you will develop the disease  Dominant genetic diseases show up in every generation, because it only takes one dominant gene to cause the disease ▪ Example: Huntington’s Chorea  Recessive genetic diseases are caused by two recessive genes. The parent can pass on a recessive gene without having the disease. Disease can skip generations, because both parents must provide the recessive gene. ▪ Examples: Tay Sachs Disease  Congenital Disease: Disease present at both but not part of the genetic make-up of the individual. Caused by birth injury or something introduced during pregnancy ▪ Examples: Fetal Alcohol Syndrome an d Cerebral Palsy  Sex-linked Disease: Disease caused by recessive or dominant traits that are linked to the X chromosome and more rarely to the Y chromosome. ▪ Example Hemophilia

With your table, complete the Pedigree Chart Act ivity