8th Grade: Genetics and Heredity

trait

a characteristic of an organism that is passed down from parents to offspring.; Can be determined by genes, the environment, or a combination of both.

genetics

the study of how traits are passed from parent to offspring

heredity

the passing of traits from parents to offspring

true-breed/homozygous

possesses the same alleles; Example: RR, rr

hybrid/heterozygous

combination of different alleles; Example: Rr

dominant

allele that blocks or "covers up" the weaker alleles; when present it will always show in the phenotype; represented by an upper-case letter

recessive

allele that is weaker and is "hidden/covered up" by the stronger allele: represented by a lower-case letter

allele

different forms of a gene

genotype

genetic make-up of an organism; determines the phenotype

phenotype

the physical appearance of an organism; based on the genotype

Punnett Square

a tool used to predict the genetic outcomes of a cross between parents' traits

Dihybrid Cross

a Punnett Square when two traits are crossed

Incomplete Dominance, Codominance, Polygenic Inheritance

Complex Patterns of Inheritance

Incomplete Dominance

an inheritance pattern when a combination of different alleles makes a blended result; example: white flower + red flower = pink flower

Codominance

an inheritance pattern when both alleles are strong and expressed; Example: cow with a red coat + cow with a white coat = offspring with a speckled coat

Pedigree

a diagram used to show the inheritance of traits over generations of a family

Polygenic Inheritance

an inheritance pattern in which multiple genes determine the phenotype of a trait; Example: Weight, height, eye color, skin color

Gregor Mendel

Austrian monk who used pea plants to predict the inheritance of traits; known as the "Father of genetics"

Reginald C. Punnett

developed a chart to determine the combination of parents' alleles

They reproduce quickly, their traits are easily observed, and he could easily control which pairs of plants reproduced.

Why did Mendel choose pea plants?

A gene is a section of DNA on a chromosome.

How is a gene, DNA, and chromosome related?

He concluded that two factors (alleles) control each inherited trait, that each organism contributes one allele for each trait, and that there are dominant and recessive traits.

What did Mendel conclude from his experiments?

growth, gender, and appearance (know examples of each from your notes.

How can the environment have an effect on phenotype?

Give an example of how is gender determined in another species other than humans.

Watch the TedEd.com Sex determination video

Adenine, Cytosine, Guanine, and Thymine

Four Chemical Bases of DNA

Thymine

Chemical base that always pairs with Adenine

Cytosine

Chemical Base that always pairs with Guanine

Double Helix

Shape of DNA

Makes bodies develop and function in different ways.

What is the function of DNA?

What does DNA stand for?

Deoxyribonucleic Acid