Chapter 4: HereditySection1- Genetics

Life Science

Lesson Plan

Inheriting Traits Create a short list of characteristics

about yourself…

HeredityHeredity is 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)

Allelesalleles

a gene

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)

OR……

Check out these websites!

http://www.switcheroozoo.com/zoo.htm

http://www.buildyourwildself.com/

2 Types of Allelesa. Dominant allele- 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

Check out the Punnett Square

Screencast!

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?

Actually… they were Pink !?!?!

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 three phenotypes 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?!?!?

MutationsMutations - 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 recessive allele (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.

Example- Color Blindness and Hemophilia

Pedigree- used to follow or trace traits through generations of a family.

Section 3

III. Advances in Genetics

A. Genetic Engineering- experimentations that changes the arrangement of DNA that makes up a gene.

Types:

1. Recombinant DNA

Inserting a useful section of DNA into a bacteria

Example- Creating Insulin (Page 143)

2. Gene Therapy- When a “normal allele” is placed into

a virus, the virus then delivers the normal allele when it infects a specific cell. (Figure 13 Page 144)

May be used to control Cystic Fibrosis and other disorders.

3. Genetically Engineering Plants- Plants are created by genetically inserting

the desired genes of one plant into another plant you want to show those genes.

Also genetically engineered: ANIMALS “Cloning”

Works Cited www.coolclips.com http://kentsimmons.uwinnipeg.ca/

cm1504/mendel.htm www.classzone.com www.dkimages.com www.virtualsciencefair.org

www.scienceray.com