1. Genetics Since Mendel Page 2

2. Environmental Role
The environment plays a role in how some of your genes are expressed.
These influences may be internal or external.
Example: Some people may be at risk for skin cancer. These people need to limit their exposure to the Sun.

3. Polygenic Inheritance
Poly is a prefix meaning more than one.
Polygenic inheritance occurs when a group of gene pairs act together to produce a trait.
Eye color, height, hair color, and skin color are examples of polygenic inheritance.

5. Recessive Genetic Disorders
Both parents have a recessive allele that is responsible for the disorder and pass it on to the child.
Because the parents are heterozygous, they don’t show symptoms.
Treat this as dominant/recessive when working Punnett square problems.

6. Will the offspring be male or female?
Chromosomes/genes that determine the sex of an organism are XX in females and XY in males.
Females produce eggs with an X chromosome only.
Males produce sperm with either an X or a Y chromosome.
Who determines the sex of the offspring?

7. Mutations
Mutations occur when a gene is altered or copied incorrectly.
A mutation may be harmful, beneficial, or have no effect.
Chromosome disorders are caused by more or fewer chromosomes than normal.
These can occur because of mistakes during the process of meiosis. (Which would pass this disorder to the offspring.)

8. Pedigree A pedigree follows a trait through generations of a family.

9. Selective Breeding
Involves selecting qualities within individuals of a breed that are desired so that these qualities may be passed on to the next generation.
Inbreeding produces individuals with similar characteristics.

10. Selective Breeding
Hybridization involves crossing individuals with different traits.
This is done with the hope of producing offspring with the best traits of both organisms.

11. What is genetic engineering?
Today scientists can use biology or chemistry to change the arrangement of DNA that makes up a gene.
This is used today for many reasons. One of those reasons is to produce larger volumes of medicine.
Cloning is a type of genetic engineering.
In cloning, the genetic information from a single cell of an organism is used to produce another organism with the same genetic information.

12. What other ways can genes be used?
Genes can be changed by scientist to make plants more resistant to disease.
Genes from one type of plant may be inserted into another type of plant to help fight crop diseases!