Chapter 3

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Questions and Answers

What is the term used to describe the individual organisms that contribute genetic material to offspring?

Biological parents

Genetic parents (correct)

Legal parents

Social parents

Which type of trait is cleft chin?

Heterozygous trait

Recessive trait

Dominant trait (correct)

Homozygous trait

What does it mean when someone is homozygous for a specific allele?

They have one dominant and one recessive allele for that gene

They have two copies of the same allele for that gene (correct)

They have two different alleles for that gene

They have a combination of alleles for that gene

If a person with a cleft chin mates with a person with a smooth chin, what type of chin will their offspring have?

Heterozygous chin Signup and view all the answers

If a person with a cleft chin (genotype BB) has offspring with someone with a smooth chin (genotype bb), what is the chance of their offspring having a cleft chin?

50% Signup and view all the answers

In the context of Punnett squares, what does the lowercase 'b' represent?

The recessive allele Signup and view all the answers

What would be the expected outcome if a person with genotype Bb (heterozygous for cleft chin) has offspring with someone who is also heterozygous for cleft chin (Bb)?

50% chance of cleft chin, 25% chance of smooth chin, 25% chance of different phenotype Signup and view all the answers

How does sickle-cell anemia illustrate the concept of genetic disorders caused by the pairing of two recessive genes?

Heterozygous carriers develop a lethal blood disorder Signup and view all the answers

What is the main function of dendrites in a neuron?

Serving as input sites to receive signals from other neurons Signup and view all the answers

What is the role of the myelin sheath in the nervous system?

Acting as an insulator to increase the speed of signal transmission Signup and view all the answers

What are the small gaps in the myelin sheath known as?

Nodes of Ranvier Signup and view all the answers

How does PKU, a genetic disorder, affect white matter cortical and subcortical structures?

It leads to a reduction in myelin and abnormalities in these structures Signup and view all the answers

What is the main function of glial cells in the nervous system?

Providing insulation to neurons Signup and view all the answers

Why is the nearly 1:1 ratio of glial cells to neurons important?

It suggests that human brains may be more similar to primate brains than previously thought Signup and view all the answers

What is the role of a neuron's semipermeable membrane?

Regulating the passage of molecules based on size and charge Signup and view all the answers

What do neurons serve as in the nervous system?

Information processors Signup and view all the answers

Study Notes

Genetics and Heredity

The term used to describe individual organisms that contribute genetic material to offspring is parents.
A cleft chin is an example of an autosomal dominant trait.
When someone is homozygous for a specific allele, they have two copies of the same allele (e.g., BB or bb).

Inheritance Patterns

If a person with a cleft chin (genotype BB) mates with a person with a smooth chin (genotype bb), their offspring will have a cleft chin (genotype Bb).
The chance of their offspring having a cleft chin is 100%, since the dominant allele (B) will always be expressed.
In Punnett squares, the lowercase 'b' represents the recessive allele.

Punnett Squares and Inheritance

If a person with genotype Bb (heterozygous for cleft chin) has offspring with someone who is also heterozygous for cleft chin (Bb), the expected outcome is a 3:1 ratio of cleft chin to smooth chin in the offspring.

Genetic Disorders

Sickle-cell anemia illustrates the concept of genetic disorders caused by the pairing of two recessive genes.
PKU (Phenylketonuria) is a genetic disorder that affects white matter cortical and subcortical structures in the brain.

Nervous System and Neurons

The main function of dendrites in a neuron is to receive signals from other neurons.
The myelin sheath insulates the neuron and increases the speed of signal transmission.
The small gaps in the myelin sheath are known as nodes of Ranvier.
The main function of glial cells is to provide support and maintenance functions for neurons.
The nearly 1:1 ratio of glial cells to neurons is important because glial cells play a crucial role in maintaining the health and function of neurons.
A neuron's semipermeable membrane allows for the selective passage of ions and molecules.
Neurons serve as the primary functional units of the nervous system, transmitting and processing information.

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Test your knowledge about the interaction between glial cells and neurons and their roles in the nervous system. Learn about recent research challenging the long-standing assumption about the ratio of glial cells to neurons.