HeredityS7L3. Students will recognize how biological traits are passed on to successive generations.

S7L3.a Explain the role of genes and chromosomes in the process of inheriting a specific trait. S7L3.b Compare and contrast that organisms reproduce asexually and sexually (bacteria, protists, fungi, plants & animals). S7L3.c Recognize that selective breeding can produce plants or animals with desired traits.

Important Vocabulary

• Genetics- the study of heredity

• Heredity- Passing of traits from parent to offspring.

• Trait- physical characteristic– Ex: brown hair, red hair

Offspring

• Organism that is the result of reproduction

How do you inherit traits?

• Meiosis

• Occurs in gametes (sex cells): sperm in males & egg in females

• results in 4 cells with ½ as many chromosomes

• New cells are genetically different

Who was Gregor Mendel?

How Mendel's pea plants helped us understand

genetics

Who was Gregor Mendel?

• Discovered the principles of heredity

• Performed experiments with pea plants

• Realized that offspring

inherit traits from their

parents

• Father of Genetics• Austrian monk• born in 1822 • known for research and teaching• after his death (1884) acknowledgment of his

discoveries in 1900

What decides what traits get passed down?

Dominant trait

• Trait that masks or covers the other form of the trait

• Represented with a capitol letter– Examples

• Round seed –R• Tall plant--T• purple flower—F

Recessive trait

• Trait that is masked or covered by a dominant trait

• Represented with a lower case letter

• Examples– Wrinkled seed—r– Short plant—t– White flower--f

genes• Your traits are determined by your

genes.

• Instructions for an inherited trait

• Each parent gives

one set of genes to the

offspring

• Offspring has 2 forms

of the same gene

for every characteristic

allele

• Different forms of a gene are called alleles.

• Can be dominant alleles or recessive alleles

• Example

–Tt

– Dominant allele recessive allele

Practice

• Monster # 1 has Rr or 1 dominant and 1 recessive allele

• How many eyes will this monster have???

• Monster # 2 has RR or 2 dominant alleles

• How many eyes will this monster have???

• Monster #3 has rr or 2 recessive alleles

• How many eyes will this monster have?

Baby Boom Genetics Activity• http://www2.edc.org/weblabs/BabyBoom/BabyBoom

LabMenu.html

• Choose 2 aliens that will mate to create an offspring

• Flip the coin to choose the alleles that will combine to create traits

• Use the “screen clipping” option in Microsoft word to create a 1 page document of the parents and their offspring

• After your teacher has checked your document you may print.

Exceptions to the rules

• Incomplete dominance- there is a blending of traits expressed; neither trait is fully expressed

• Codominance- both alleles are shown

Genotype

• Combination of genes for a specific trait

• Example: – TT, Tt, tt

** expressed

in letters

Phenotype

• Physical appearance of the trait

• Examples: purple flowers, white flowers, yellow seeds, white seeds

Answer the following questions on the back of your

Alien Offspring Print out

1. What is the difference between genotype and phenotype?

2. Give an example of when dominant allele masked a recessive allele in your offspring.

3. What recessive traits did your offspring inherit from their parents?

Punnett Squares

• Tool used to organize all possible combinations of offspring from particular parents

Homozygous genotype

• Two same alleles for a trait

• aka—Purebred

• Examples: TT, tt

Heterozygous genotype

• 2 different alleles for the same trait

• aka hybrid

• Example: Tt