Chapter 11 Heredity

I.Genetics A. Inheriting Traits - Heredity – the passing of traits from parent to offspring. 1. What is genetics? a) alleles – the different forms of a trait a gene may have. -ex: Trait: Dimples Alleles: Present or Missing b) genetics – the study of how traits are inherited through interactions of alleles

B.Genetics in a Garden 1. Dominant and Recessive Factors a) Dominant – form that covers up the over form b) Recessive – the form that gets covered up c) letters represent dominant and recessive alleles -Capital letters represent dominant alleles -Lowercase letters represent recessive alleles

d) genotype – letters making a code showing genetic makeup e) phenotype – the way an organism looks or behaves as a result of its genetic makeup

f) homozygous – having two of the same alleles for a trait (TT or tt) -purebred – having the same alleles for a trait g) heterozygous – having two different alleles for a trait (Tt) -hybrid – having two different alleles for a trait

2. Using Probabilities to Make Predictions -Using a Punnett Square, we can make predictions about what possible traits an offspring might have.

3. Punnett Square – a tool used to predict possible traits an offspring might have. a) The genotype of one parent goes on top of the grid. b) The genotype of the 2 nd parent goes on the side of the grid. c) Bring alleles down and across to fill in the grid. Link to Punnett Square worksheet Link to Punnett Square Practice Problems

4. Principles of Heredity (Mendelian) a) Traits are controlled by alleles on chromosomes. b) An allele’s effect is dominant or recessive. c) When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate reproductive cells.

II.Genetics Since Mendel A.Incomplete Dominance -ex: 4 o’clock flowers -incomplete dominance – when the offspring of 2 homozygous parents show an intermediate phenotype 1. Multiple Alleles – a trait that is controlled by more than two alleles -ex: Blood types: Type A and Type B are dominant and Type O is recessive Link to incomplete dominance ws

B. Polygenic Inheritance – when a group of pairs acts together to produce a trait -the effects of many allele produce a wide variety of phenotypes -ex: height, eye color, skin color, hair color, fingerprints -the environment plays a role in how some of your genes are expressed or whether they are expressed at all

C.Human Genes and Mutations -Mutations occur when errors occur in the DNA when it is copied inside a cell -Mutations can be caused by chemicals, x-rays, radiation and sunlight -Mutations can be helpful, harmful, or have no effect at all.

1. Chromosome disorders a) Mistakes in meiosis can result in a new organism with fewer or more chromosomes. -Down Syndrome – 3 chromosomes in pair 21 -Klinefelter’s Syndrome – males have XXY chromosomes

D.Recessive Genetic Disorders -Some genetic disorders are the result of receiving 2 recessive alleles. -Cystic Fibrosis – a thick mucus is produced in the lungs making it hard to breath

E.Sex Determination -Females are XX and Males are XY for 23 rd pair of chromosomes -Males determine the sex. F.Sex-Linked Disorders -sex-linked gene – an allele inherited on a sex chromosome -ex: colorblindness, hemophilia, calico cats -only occurs on X chromosome Link to Sex Chromosomes and Linkage Worksheet

G.Pedigrees Trace Traits -Helps determine who has had a trait in a family over several generations. -Helps determine if a trait is dominant, recessive, or sex-linked. -Helps to predict probability offspring will be born with a specific trait. Link to Pedigree Worksheet

III.Advances in Genetics A.Genetic Engineering – scientists are experimenting with biological and chemical methods to change arrangement of DNA that makes up a gene. -creates medicines, improves crop production, and makes disease resistant crops.

1. Recombinant DNA – inserting useful segment of DNA into a bacterium -creates insulin 2. Gene Therapy – a normal allele is placed in a virus and the virus infects cells with normal alleles 3. Genetically Engineered Plants – selective breeding of crops produces crops with specific traits -corn, wheat, rice, tomatoes