L
Modern Genetics Study Sheet
Know this information (Also: Study the vocabulary sheet , your homework answers , and handouts/worksheets .) Be sure to know how to "read" a pedigree . Know the meanings of the symbols used (circles, squares, shading, lines, etc.)
Section 1. Human Inheritance
1.
Some human traits are controlled by a single gene that has more than two alleles or forms.
These three or more forms of a single gene are called multiple alleles . Human blood type is an example of at trait controlled by multiple alleles.
2.
Polygenetic traits are traits produced by multiple genes. Skin color, eye color, and height are examples of polygenetic traits. These genes act together as a group to produce a single trait.
3.
Traits are often influenced by the organism’s environment . Height is an example of a trait that can be modified by an organism’s environment. If a proper amount of food is available, a person will probably reach his/her potential height.
If nutrition is poor the person may end up shorter that his/her potential height.
4.
Males have one X chromosome and one Y chromosome. Females have two X chromosomes. ( Male = XY; Female = XX )
5.
The X and Y chromosomes are the 23 rd
pair of chromosomes in the human genome. These chromosomes are called the sex or gender chromosomes .
6.
Males are more likely than females to have a sex-linked trait controlled by a recessive allele such as colorblindness. This is because the Y chromosome is shorter that the X chromosome. If the X chromosome has a defective gene, and there is no homologous gene on the Y chromosome to override it, the male will have the condition caused by the defective gene.
7.
A pedigree is a chart that shows several generations of a family. Geneticists use pedigrees to trace the inheritance pattern of a particular trait through a number of generations of a family.
Section 2. Human Genetic Disorders
1.
Genetic disorders are abnormal conditions that are caused by mutations or changes in an organism’s DNA in a gene or chromosome. In some cases, these mutations can be passed on from one generation to the next.
2.
Commonly known genetic disorders include cystic fibrosis, sickle-cell anemia, hemophilia, and Down syndrome. There are many others that are not well known to the general public such as Williams disorder and Turner syndrome.
3.
Amniocentesis is a test used to diagnose genetic disorders . During amniocentesis a small amount of fluid (amniotic fluid) surrounding the developing fetus is extracted and analyzed to see if any abnormalities are present in the fetus’s chromosomes.

4.
Karyotyping is another tool used to diagnose genetic orders. A sample of DNA is taken from a white blood cell. The chromosomes are photographed, organized in pairs, and examined for abnormalities.
5.
Genetic counselors are professionals who help couples understand their chances of having a child with a genetic disorder.
Section 3. Advances in Genetics
1.
Selective breeding is the process of selecting a few organisms with desired traits to serve as parents of the next generation . Farmers and animal breeders have used selective breeding to improve plants and animals for thousands of years.
2.
Cloning is a technique used to produce an organism that is genetically identical to the organism from which it was produced.
The process involves removing the nucleus from an egg cell, replacing it with the nucleus of the organism to be cloned, then placing the egg cell with the new nucleus into compatible female organism for gestation.
3.
Genetic engineering involves the transfer of a gene from the DNA of one organism into another organism . Genetic engineering can be used to produce medicines and to improve crops. Genetic engineering is responsible for tomatoes with fish genes that can resist cold, and goats that produce spider silk or medicine in their milk!
4.
Gene therapy involves the insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder. Results have been mixed regarding the success of this strategy for curing diseases.
5.
DNA fingerprinting can be used to help determine whether material found at a crime scene came from a particular suspect. DNA can be extracted from urine, semen, saliva, blood, hair, and skin cells. DNA "fingerprints" are images of sequences of DNA. No two individuals, except for identical twins, have the same
DNA sequences.
6.
Polymerase Chain Reaction (PCR): A method used by scientists to increase the amount of DNA. This is important when only a small amount of DNA from blood or saliva is found at a crime scene. PCR allows forensic scientists to provide enough DNA to test.
7.
The goal of the Human Genome Project was to identify the DNA sequence of every gene in the human genome . This has been accomplished. Scientists are working on or have completed the genomes of other species such as bacteria, fungi, many plants and some animals – many invertebrates and some vertebrates like dogs, mice, etc.