Ch. 4-1 Mendel’s WorkKey Concepts: What were the results of Mendel’s experiments, or

crosses?

Discover Activity: What Does the Father Look Like?

Observe the colors of the kitten’s coat colors and patterns. 1. Record any coat colors and patterns that you observe. Include as many details as

you can. ____________________________________________________________________________________________________________________________2. Observe the mother cat, record her coat color and pattern.

____________________________________________________________________________________________________________________________3. Infer: Describe what you think the kitten’s father might look like. Identify the

evidence on which you based your inference. ____________________________________________________________________________________________________________________________ ______________________________________________________________

http://www.youtube.com/watch?v=5Rylcijkp9c&feature=related

Mendel’s Experiments

Heredity: The passing of physical

characteristics from parents to

offspring

Trait: Characteristic

that an organism can pass on to its

offspring

Genetics: The scientific study

of heredity

Key Terms:

For Mendel’s Experiment he “cross-pollinated” pea plants with

contrasting traits. For example: short and tall plants

Mendel started with purebred plants.

Mendel’s ExperimentsThe F1 Offspring: In one experiment, Mendel crossed purebred tall plants with purebred short plants. These plants were known as the parental generation (p generation). Their offspring are the first filial generation (F1 generation)

The F2 Offspring: In the next test when the F1 generation plants were full-grown Mendel self-pollinated the plants.

Result: All the offspring in the F1 generation were tall.

Result: The short trait reappeared. The F2 generation was a mix of tall and short plants.

P Generation F1 Generation F2 Generation

Mendel’s ConclusionsMendel crossed pea plants with other contrasting traits. In all of Mendel’s

crosses, only one form of the trait appeared in the F1 generation. However, in the F2 generation, the “lost” trait reappeared in one fourth of the plants.

1. What did Mendel find when he crossed purebred tall plants with purebred short plants

________________________________________________

2. When Mendel crossed the F1 Generation with one another was the trait for shortness lost?

_________________________ 3. Are the plants in the F1

generation purebred plants? _________________________

Dominant and Recessive Alleles

Gene: factors that control a traitAlleles: different forms of a gene

An organism’s traits are controlled by the alleles it inherits from its parents. Some alleles are dominant, while other alleles are recessive.

Dominant Allele: one whose trait always shows up in the organism when the allele is presentRecessive Allele: trait that is hidden whenever a dominant allele is present.

The purple corn ears were produced by the F2 generation. The purple color is produced

by the dominant allele, and yellow is controlled by the recessive allele.

Trace back the inheritance of the dominant and recessive alleles for kernel color.

F2 generation: both purple ___________F1 parents: both purple ___________P parents: one purple ____________ one yellow ___________

P = Purple p = Yellow

Predicting In fruit flies, long wings are dominant over short wings. A

scientist crossed a purebred long-winged male fruit fly with a short-winged female. Predict the wing length of the F1 offspring. If the scientist crossed a hybrid male F1 fruit fly with a hybrid F1

female, what would their offspring probably be like?

Long Winged = L

Short Winged = l

Parental Generation

F1

F2

Mendel’s Experiments

Hybrid: Organism that

has two different alleles

for a trait

Example:

Symbols for AllelesGeneticists use

letters to represent alleles. Dominant

represented by capital letter.

Recessive represented by

lowercase of same letter.

Key Term:

Chapter 4 Section 1 Assessment

On a separate piece of paper answer: Page 115 Questions 1 and 2