Chapter 4: HereditySection1- Genetics Life Science Lesson Plan
Inheriting Traits • Create a short list of characteristics about yourself…
Heredity • Heredityis the passing of traits from parents to offspring. • Inherited Traits- Traits that are passed from parents to their offspring (through fertilization)
Genes are passed down… but what are genes? • Genes - Sections of DNA on a chromosome. • Genes on chromosomes control the traits that show up in an organism. • There are hundreds of genes on a chromosome
Alleles are different forms of a trait that a gene may contain. • There are TWO alleles for every trait • Example: Height • 1 allele is tall (T) • 1 allele is short (t)
alleles a gene Alleles
GENETICS • Genetics- the study of inherited traits. • Gregor Mendel-The Father of Genetics “The Man”
Mendel’s Experiment • Mendel studied the traits of Pea Plants • Look Page 105 • Crossed 2 Plants with different expressions of the trait • Example- Tall (T)& Short (t) • Round (R) & Wrinkled (r)
Mendel’s Experiment • When the plants were crossed he discovered that the new plant formed looked like one of the two parents. • Take a look… Mendel’s Tall vs. Short Plants
Mendel used pollen from both Tall and Short Plants to pollinate by hand the flowers. • Cross-Pollination- the pollination of two different plants together • http://www2.edc.org/weblabs/Mendel/MendelMenu.html
Hybrid vs. Purebred • 3.Purebreds- offspring that receives two of the same alleles for a trait (TT or tt)
Hybrid vs. Purebred • 4. Hybrids- offspring that receives two different alleles for a trait (Tt)
Check out these websites! • http://www.switcheroozoo.com/zoo.htm • http://www.buildyourwildself.com/
2 Types of Alleles a. Dominantallele- covers up or dominates the other trait. Represented by a CAPITAL b. Recessive allele- the trait seems to disappear Represented by a lower case
Homozygous vs. Heterozygous • Homozygous – an organism with 2 alleles for one trait that are the same (written TT) 6 • Heterozygous – an organism with 2 alleles for one trait that are different (written Tt)
Phenotype vs. Genotype • Genotype-the genetic-makeup of an organism (types of letters used)
Phenotype vs. Genotype • Phenotype- the way an organism physically looks/behaves as a result of its genotype. • Types of Words used: Tall, Short, Blonde, Brown, etc.
The Use of Punnett Squares • A Punnett Square can help you predict what an offspring will look like. • For example, Male and Female Chromosomes
Chapter 4Part 2- Genetics Since Mendel Life Science
Question… • If you crossed Purebred Red four- o’clock plants with Purebred White four-o’clock plants, what would the offspring look like?
Incomplete Dominance-when two homozygous parents combine, the offspring results in a mixed (or blended) phenotype • Remember the chickens?!?!
When neither allele for a trait is Dominant. • The phenotype produced is a blending between the two homozygous parents. • The combining of Purebred Red & Purebred White produced PINK plants.
Although Mendel studied peas that were controlled by two alleles, many traits can be controlled by more than two alleles…
Multiple Alleles • A trait that is controlled by Having more than two alleles is controlled by Multiple Alleles. • Traits controlled by Multiple Alleles produce more than threephenotypes of that trait.
Example of Multiple Alleles… • Blood Types: A, B, AB, and O. • The O allele is recessive to both A and B
Other Worksheet… • Phenotype A - AA or Ao Genotype • Phenotype B – BB or Bo Genotype • Phenotype AB – AB • Phenotype O – oo Genotype
Polygenic Inheritance • Polygenic Inheritance- when a group of gene pairs acts together to produce one trait. • Which creates more variety in phenotypes
What would be an example? • Many traits such as…Eye Color, Hair Color, Skin tone, & Handspan are traits produced by a combination of genes.
Human Genes & Mutations • What are Mutations?!?!?
Mutations • Mutations - a permanent change in the DNA sequence • A mutation can be harmful, beneficial, or cause no effect.
Chromosome Disorder • Chromosome disorders- caused by more or fewer chromosomes than normal • Downs Syndrome- caused by an extra chromosome (trisomy) at Chromosome 21
Recessive Genetic Disorders • Recessive Genetic Disorders are disorders passed through the Recessive alleles. • Both parents contain the recessiveallele (containing the disorder) that comes together in the offspring.
When both parents are Heterozygous, they do not show any symptoms • (Called “carriers” for the trait.) • Example- Cystic Fibrosis is a homozygous recessive disorder.
Sex-Linked Disorders • An allele inherited on a sex chromosomes ( X or Y ) is called a sex-linked gene. • Inherited conditions are linked with the X and Y chromosomes.