11.1 Heredity

Genetics-the study of how traits are inherited

A. Heredity

1. Passing of traits from parent to offspring

2. Genes on chromosomes control the traits that show up in an organism

3. Different forms of traits are called alleles (alleles = letters)

4. Each sex cell contains 1 allele for each trait

B. Genetics

1. Gregor Mendel: “Father of Genetics”

-1st to use mathematics of probability to explain genetics and trace traits through generations (used Pea Plants for his

experiments)

C. Terms

1. Probability- helps you predict the chance that something will happen

2. Hybrid- organism that receives different genetic information from each parent

3. Genotype- the genetic make-up4. Phenotype- the way an organism

looks or behaves as a result of the genotype (like a photo)

D. Punnett Squares

1. Helps to predict traits of offspring2. Dominant alleles: uppercase (T)

-covers up the other trait3. Recesive alleles: lowercase (t)

-trait seems to disappear4. Homozygous- two alleles that are the

same (TT or tt)5. Heterozygous- two different alleles (Tt)

E. Example

T t

T

t

11.2 Genetics Since Mendel

A. Incomplete Dominance

1. Neither allele is dominant

2. The phenotype is in between the two homozygous parents

Ex: red plant + white plant = pink

B. Multiple Alleles

1. More than two alleles that control a trait

2. Produce more than three phenotypes

C. Polygenic Inheritance

1. A group of gene pairs act together to produce a trait, which creates more variety

Ex: hair color, eye color, skin color

2. Environmental factors also play a role such as sunlight.

D. Mutations

1. Genes that are altered or copied incorrectly

2. Harmful, helpful, or have no effect3. Chromosomal disorders

-more or fewer chromosomes than normal

-Down’s Syndrome (extra 21st chromosome) ** Causes:

-mutagens, heredity, errors in DNA

E. Recessive Genetic Disorders

1. Both parents have the recessive allele (heterozygous)

2. Both parents show no symptoms3. Child receives both recessive alleles

and displays the symptoms4. These children rarely live to

reproductive age5. Ex: Cystic Fibrosis

F. Gender Determination

XXGirl

XYBoy

G. Sex-linked disorders

-found on the X-chromosome-more common in males since they only

have 1 X-less common in females b/c they would

have to inherit the gene on both XX’s-examples: Calico Cats

Color-blindness Baldness

H. Pedigrees-used like family trees-horizontal line =

marriage-vertical line = kids-square = boy-circle = girl-follow family traits-predict traits of

offspring

11.3 Genetic Engineering

-changing the arrangement of DNA that makes up a gene

1. Recombinant DNA-insertion of a useful segment of DNA into a bacteria (insulin)

2. Gene Therapy-a normal allele is placed into a virus, which delivers it when it infects its target cell (cystic fibrosis)

3. Genetically Engineered Plants-created by inserting the genes that produce desired traits in one plant into a different plant