Investigating Spider Inheritance

• Describe the relationship between genes and traits.

• Differentiate between inherited and acquired traits.

• Explain how sexual reproduction contributes to genetic variation in a population.

• Use Punnett squares to predict the probability of traits in offspring.

Key Vocabulary

Trait

A specific characteristic of an organism, like your eye color or your overall height.

Heredity

This is the process of passing traits from parents to their offspring through their genes.

Gene

A section of DNA on a chromosome that has the specific instructions for a trait.

Allele

Alleles are the different forms of a gene, like having a tall or short allele.

Dominant Allele

An allele that masks the effect of a recessive allele, represented by a capital letter.

Recessive Allele

An allele whose effect is hidden by a dominant allele, shown by a lowercase letter.

Key Vocabulary

Genotype

The genetic makeup of an organism, represented by its combination of alleles like Tt or RR.

Phenotype

The observable physical traits of an organism, such as its height, that result from its genotype.

Genetic Variation

The differences in genes and traits that exist among individuals within the same species.

Punnett Square

A chart scientists use to predict the possible genotypes of offspring from a genetic cross.

Inherited Traits

• ​These are traits passed from parents to their children through genes.

• ​​You are born with these traits and they are part of your DNA.

• ​Examples: natural hair color, eye color, and whether your earlobes are attached.

Acquired Traits

• ​These are traits that you are not born with.

• ​​You develop or learn them throughout your life experiences.

• ​Examples: the ability to ride a bike, scars, or a tattoo.

Asexual Reproduction

• Involves only one parent to create a new organism or offspring.

• The offspring produced is genetically identical to the single parent.

• There is no mixing of genetic material from different parents.

Sexual Reproduction

• Involves two parents who combine their genetic material to produce offspring.

• The offspring inherits a unique combination of genes from both parents.

• This creates genetic differences, which helps a species survive and adapt.

Using Punnett Squares to Predict Traits

• A Punnett square is a chart for predicting genetic cross outcomes.

• It shows the probability of an offspring’s genotype and phenotype.

• Put one parent’s alleles on top and the other parent’s on the side.

• A tall (TT) and short (tt) plant cross results in all Tt offspring.

• Inherited traits are passed from parents to offspring through genes.

• Genes have versions called alleles, which can be dominant or recessive.

• Genotype is the genetic makeup; phenotype is the physical appearance.

• A Punnett square helps predict the probability of offspring inheriting traits.