• The passing of traits from parents to offspring– Genes on chromosomes control the traits that

show up in organisms

Heredity

• The father of genetics• First to use

mathematics of probability to explain heredity and to trace one trait for several generations

Gregor Mendel

• Different forms of a trait that a gene may have

Alleles

• The study of how traits are inherited is

genetics

• covers up or dominates other allele

Dominant allele

• the trait seems to disappear unless the organism has TWO copies

Recessive allele

• receive DIFFERENT genetic information for a trait from each parent

Hybrids

Punnett Square

• the genetic makeup of an organism

Genotype

– an organism with two alleles for one trait that are the SAME

Homozygous

– an organism with two alleles for one trait that are the DIFFERENT

Heterozygous

• the way an organism looks and behaves as a result of its genotype

Phenotype

Cross Bb and BB

Cross Bb and BB

BB BbBB Bb

B b

B

B

What Percentage of Offspring are Homozygous recessive?

BB BbBb bb

25%

If B is allele for pink flowers, and b is the allele for white, what is the probability of having offspring that are pink?

BB BbBb bb

75%

B and b show incomplete dominance. If B is allele for red flowers, and b is the allele for white, what is the probability of having

offspring that are pink?

BB BbBb bb

50%

B and b show codominance. If B is allele for pink flowers, and b is the allele for white, what is the probability of having offspring

that are pink?

BB BbBb bb

25%

• When the offspring of two homozygous parents show an intermediate phenotype– Such as flower color in some plants, coat of some

horse breeds

Chesnut horse Cremello horse Palomino horse

Incomplete dominance

• When the offspring of two homozygous parents show an intermediate phenotype– Such as flower color in some plants, coat of some

horse breeds

Chesnut horse Cremello horse Palomino horse

• Occurs when a group of gene pairs act together to produce a trait

• The effects of many alleles produce a wide variety of phenotypes– Ex: height, eye and skin color

Polygenic Inheritance

• Occurs when a group of gene pairs act together to produce a trait

• The effects of many alleles produce a wide variety of phenotypes– Ex: height, eye and skin color

• plays a role in how genes are expressed– Ex: some people have genes that make them at

risk for developing skin cancer, but if they limit their exposure to the sun, they may never get cancer

Environmental Impact

• Environment plays a role in how genes are expressed– Ex: some people have genes that make them at

risk for developing skin cancer, but if they limit their exposure to the sun, they may never get cancer

• Genes that are altered or copied incorrectly– Can be harmful, beneficial, or have no effect– Can be caused by x-rays or radioactive substances

Bruce Banner was exposed to Gamma Radiation, turning him into the Hulk.

Mutations

• Genes that are altered or copied incorrectly– Can be harmful, beneficial, or have no effect– Can be caused by x-rays or radioactive substances

Bruce Banner was exposed to Gamma Radiation, turning him into the Hulk.

• Mistakes in meiosis can result in new organism with more or fewer chromosomes than normal– Usually fatal to unborn fetus, but not always– Ex: Down Syndrome

Chromosome Disorders

• Mistakes in meiosis can result in new organism with more or fewer chromosomes than normal– Usually fatal to unborn fetus, but not always– Ex: Down Syndrome

• These disorders occur when both parents have a recessive allele responsible– Because parents heterozygous, they don’t show

symptoms• Ex: cystic fibrosis

Recessive Genetic Disorders

• Some recessive genes are result of a mutation• These disorders occur when both parents have

a recessive allele responsible– Because parents heterozygous, they don’t show

symptoms• Ex: cystic fibrosis

• Chromosomes that determine the sex of an organism are XX in females and XY in males

• Females produce eggs with X chromosome only and males produce sperm with X or Y.

Sex Determination

• Chromosomes that determine the sex of an organism are XX in females and XY in males

• Females produce eggs with X chromosome only and males produce sperm with X or Y.

• an allele inherited on a sex chromosome

Sex Linked Disorders

• Sex-linked gene- an allele inherited on a sex chromosome– Ex: color blindness trait

for color blindness recessive on X chromosome. Because men only have one X chromosome, a male with this allele is color blind.

• A visual tool for following a trait through generations of a family

Pedigree

• A visual tool for following a trait through generations of a family

• When scientists experiment with biological and chemical methods to change the arrangement of DNA that makes up a gene– Can be done to find new ways to improve crop

production and quality, including the development of plants that are resistant to disease

Genetic Engineering

• When scientists experiment with biological and chemical methods to change the arrangement of DNA that makes up a gene– Can be done to find new ways to improve crop

production and quality, including the development of plants that are resistant to disease

• made by inserting a useful segment of DNA from one organism into a bacterium– ex: large quantities of human insulin are made by

genetically engineered organisms

Recombinant DNA

• a normal allele is placed in a virus. The virus then delivers the normal allele when it infects target, and the normal allele replaces defective one.– Used to test ways of controlling cystic fibrosis and

cancer

Gene therapy

• In the past, improvements to plants were result of selecting plants with most desirable traits and breeding them

Selective Breeding

Genetically Modified Organism (GMO)

Benefits• More nutritious food• Tastier food• Disease- and drought-resistant plants

that require fewer environmental resources (water, fertilizer, etc.)

• Decreased use of pesticides• Increased supply of food with

reduced cost and longer shelf life• Faster growing plants and animals• Food with more desirable traits, such

as potatoes that absorb less fat when fried

• Medicinal foods that could be used as vaccines or other medications

Risks• Modified plants or animals may

have genetic changes that are unexpected and harmful.

• Modified organisms may interbreed with natural organisms and out-compete them, leading to extinction of the original organism or to other unpredictable environmental effects.

• Plants may be less resistant to some pests and more susceptible to others.