Science: Genetics and Heredity
Traits, genes, inheritance, and variation
Science: Genetics and Heredity
Traits, genes, inheritance, and variation
Science - Grade 6-8
- 1
Define heredity in your own words.
Think about how children can have traits similar to their parents.
Heredity is the passing of traits from parents to their offspring through genetic information. - 2
What is a gene, and what does it do in a living organism?
A gene is a section of DNA that contains instructions for a trait or for making a product in the body. Genes help determine how an organism grows, functions, and looks. - 3
Explain the difference between a trait and an inherited trait.
One word describes any characteristic, and the other tells where it came from.
A trait is any characteristic of an organism, such as eye color or height. An inherited trait is a characteristic passed from parents to offspring through genes. - 4
What role does DNA play in heredity?
DNA stores the genetic instructions that are passed from parents to offspring. These instructions help determine inherited traits. - 5
Describe what chromosomes are and where they are found in a cell.
They carry many genes together in one structure.
Chromosomes are organized structures made of DNA and proteins. They are found in the nucleus of a cell. - 6
A plant has tall stems because it inherited that trait from its parent plants. Is stem height an example of heredity, environment, or both? Explain.
Stem height can be an example of both heredity and environment. Genes influence how tall the plant can grow, but water, sunlight, and soil conditions also affect its actual height. - 7
What is the difference between dominant and recessive alleles?
Think about which allele can mask another one.
A dominant allele can show its effect when only one copy is present. A recessive allele usually shows its effect only when two copies are present. - 8
If B represents a dominant allele for brown eyes and b represents a recessive allele for blue eyes, what eye color phenotype would a person with genotype Bb most likely have?
A person with genotype Bb would most likely have brown eyes because the dominant allele B masks the recessive allele b. - 9
Explain the difference between genotype and phenotype.
One refers to genes, and the other refers to what you can observe.
Genotype is the genetic makeup of an organism, such as Bb or bb. Phenotype is the observable trait that results, such as brown eyes or blue eyes. - 10
Two parents each have the genotype Tt for a trait where T is dominant. List the possible genotypes of their offspring.
The possible genotypes are TT, Tt, and tt. These combinations come from the different allele pairs the offspring can inherit from the parents. - 11
In the cross Tt x Tt, what fraction of offspring would be expected to show the recessive phenotype?
Make a Punnett square with T and t across the top and side.
One out of four offspring, or 1/4, would be expected to show the recessive phenotype. The recessive phenotype appears only in offspring with the genotype tt. - 12
Why are siblings from the same parents not usually genetically identical?
Siblings are not usually genetically identical because each parent passes on a different combination of alleles to each child. This creates variation among offspring. - 13
Give one example of a trait influenced by both genes and the environment, and explain how both affect it.
Think of a characteristic that can change depending on conditions or lifestyle.
Human height is influenced by both genes and the environment. Genes affect a person's growth potential, while nutrition and health affect how fully that potential is reached. - 14
A scientist says that mutations can sometimes be passed to offspring. Explain what a mutation is.
A mutation is a change in the DNA sequence. If a mutation occurs in reproductive cells, it can be passed from parents to offspring. - 15
Summarize how genes, DNA, chromosomes, and traits are connected.
Start with DNA, then explain how it is organized and how it affects characteristics.
DNA is the molecule that stores genetic information. Genes are sections of DNA, chromosomes are structures that contain many genes, and traits are characteristics influenced by those genes.