Investigating Spider Inheritance

Investigating Spider Inheritance

Middle School

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Learning Objectives

• 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

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Trait

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

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Heredity

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

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Gene

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

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Allele

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

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Dominant Allele

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

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Recessive Allele

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

Key Vocabulary

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Genotype

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

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Phenotype

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

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Genetic Variation

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

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Punnett Square

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

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Inherited vs. Acquired Traits

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.

Multiple Choice

What is the primary difference between an inherited trait and an acquired trait?

• Inherited traits are passed from parents, while acquired traits are developed during life.

• Inherited traits are learned, while acquired traits are present at birth.

• Inherited traits only affect appearance, while acquired traits affect abilities.

• Inherited traits come from DNA, while acquired traits come from the environment.

Multiple Choice

Which of the following is an example of an inherited trait?

• The ability to ride a bike

• A scar on your knee

• Eye color

• A tattoo

Multiple Choice

A person with natural brown hair learns to speak Spanish. Which statement correctly classifies these two traits?

• The ability to speak Spanish is an acquired trait, while the person's natural hair color is an inherited trait.

• Both speaking Spanish and having natural brown hair are inherited traits.

• Both speaking Spanish and having natural brown hair are acquired traits.

• Natural hair color is an acquired trait, while the ability to speak Spanish is an inherited trait.

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Reproduction and Genetic Variation

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.

Multiple Choice

What is the main difference between asexual and sexual reproduction?

• The number of parents involved in the process.

• The amount of time it takes to create an offspring.

• The environment where the parents live.

• The size of the offspring that are produced.

Multiple Choice

What is the key outcome of two parents combining their genetic material?

• It results in offspring that are genetically different from the parents.

• It creates offspring that are genetically identical to one parent.

• It allows a single parent to produce many offspring quickly.

• It ensures that all offspring will have the same traits.

Multiple Choice

If a new disease threatens a population of organisms, which method of reproduction is more likely to help the species survive, and why?

• Sexual reproduction, because genetic variation increases the chance that some offspring can survive the disease.

• Asexual reproduction, because creating identical offspring ensures they will all be protected from the disease.

• Sexual reproduction, because it always produces a greater number of offspring.

• Asexual reproduction, because the offspring will be an exact copy of the surviving parent.

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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.

Multiple Choice

What is the primary purpose of a Punnett square?

• To show an animal's complete family history

• To predict the outcomes of a genetic cross

• To list all the dominant genes in a species

• To describe the traits of a single parent

Multiple Choice

What information does a Punnett square reveal about potential offspring?

• The exact traits an offspring will have for sure

• The number of chromosomes an offspring will receive

• The probability of an offspring's genotype and phenotype

• The environment where an offspring will best survive

Multiple Choice

Based on a genetic cross between a parent with TT alleles and a parent with tt alleles, what is the only possible outcome for their offspring?

• All offspring will have the TT genotype

• All offspring will have the tt genotype

• Half the offspring will be TT and half will be tt

• All offspring will have the Tt genotype

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Common Misconceptions

Misconception	Correction
Dominant traits are always more common in a population.	A trait's frequency depends on many factors, not just its dominance.
You only inherit traits from the parent you look more like.	You inherit a unique combination of genes from both of your parents.
All traits are determined by just one gene.	Many traits are influenced by several different genes working together.

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Summary

• 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.

Poll

On a scale of 1-4, how confident are you about using a Punnett square to predict traits?

• 1 (Not confident at all)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)