Skip to main content

8th Grade Science Help

Go to Google and type Punnet Square online game, (There are tons of them!)

www.neok12.com/Genetics.htm (videos and quiz games)

Genetics Animations http://www.dnalc.org/resources/animations/index.html

*Heredity: Passing traits from parents to offspring.

*Trait: How something looks, (short, tall, green, yellow, curly hair or straight hair)

*Genetics: The study of how traits are passed from parents to offspring.

Fertilization: When the sperm combines its chromosomes with the egg's chromosomes to make a zygote.

A zygote is a fertilized egg.

Purebred: An organism that only has one form of gene for each trait.

*Gene: The DNA instructions (recipe) for specific traits.

*Alleles: Different forms of a gene, for example tall vs short.

*Dominant allele: This form of the gene will always control the trait if it is present.

*Recessive allele: This form of the gene will only be expressed if there are two copies. If there is one

copy, it will be covered up by a dominant allele.

Hybrid: Organisms that have two different alleles for many traits because they were made from two very

different purebred parents. This is done in plant breeding.

*Chromosomes: This is where the genes are found. The sperm and the egg both have one copy of each

chromosome to give to their baby. You have two copies of each chromosome, one from your mom and one

from your dad.

*Mendel: Mendel was a monk who discovered dominant and recessive alleles by breeding pea plants. He

is considered the father of genetics

Probability: How likely a certain event will occur.

Punnet square: A chart that shows all the possible combinations of alleles from a genetic cross.

*Phenotype: How an organism looks.

*Genotype: The actual genes an organism has.

*Homozygous: Both alleles are the same.

*Heterozygous: The two alleles are different.

*Codominance: Both alleles are expressed, like a black and white chicken.

*Incomplete dominance: When two forms of a gene combine to make an in-between trait, red + white

makes pink, curly hair + straight hair makes wavy hair.

*Multiple alleles: Three or more forms of the gene for a single trait, like blood type.

*Multiple genes: Traits that are controlled my many genes, like height, skin, hair and eye color, disease

resistance, speed. These are all traits that show a lot of variation within a group.

Sex chromosomes: The X and Y chromosomes determine if a person is male or female. XX = female and

XY = male in humans. It is different in birds and insects.

*Sex-linked gene: Genes found on the X or Y chromosome, like colorblindness, baldness.

1. Where did you get your genes from?

2. What gives the instructions for any inherited trait?

3. How many copies do we have of every gene?

4. List two traits are controlled by more than one gene.

5. What is DNA and where is DNA found?

6. What is the difference between asexual and sexual reproduction?