Genetics

Mendel's Laws

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Session Overview

Genetics_sess_1.jpg

This session will cover the background and assumptions that Mendel made regarding the inheritance of particular traits, the hypotheses he developed, the experiments he performed to test the hypotheses, and the conclusions he made. In addition, how offspring acquire genes (and thus traits) from parents by inheriting chromosomes, and how the movement of chromosomes during meiosis is related to Mendel’s rules of inheritance will be emphasized.

Learning Objectives

  • To understand how experimentation resulted in Mendel’s laws of inheritance.
  • To accurately use common genetic terms.
  • To predict the outcome of genetic crosses involving one, two or three unlinked genes.
  • To design a genetic cross that can determine whether a trait is dominant or recessive.
  • To design a genetic cross that can determine the genotype of an individual.
  • To understand the relationship of meiosis to Mendelian inheritance and Punnett Squares.

Session Activities

Lecture Video

Watch the lecture video excerpt

Check Yourself

You are working with the following pea plants:

  • Plant 1: Purple flowers
  • Plant 2: Purple flowers
  • Plant 3: White flowers

You set up three mating experiments using these plants and obtain the following results:

  Ratio of plants with following Phenotype
Experiment Purple flowers White flowers
#1: P1 with P2 100 0
#2: P1 with P3 100 0
#3: P2 with P3 50 50
Question 1

Which phenotype is dominant?

Purple flowers check
White flowers close
Check Show Solution

Experiment #2 demonstrates that purple flower color is dominant to white flower color.

Question 2

What is the genotype of Plant 1 with respect to flower color?

PP 1 check
Pp 2 close
pp 3 close
Check

Question 3

What is the genotype of Plant 2 with respect to flower color?

PP 1 close
Pp 2 check
pp 3 close
Check

Question 4

What is the genotype of Plant 3 with respect to flower color?

PP 1 close
Pp 2 close
pp 3 check
Check

Session Activities

Lecture Video

Watch the lecture video excerpt

Check Yourself

You are studying two true-breeding varieties of plants. Flower size is controlled by the A gene and flower color is controlled by the B gene.

Parent 1: small yellow flowers
Parent 2: large red flowers

Question 1

You cross the two true-breeding parental plants, and find that **all** the F1 progeny have small red flowers. Which of the following phenotypes are dominant?

large red close
large yellow close
small red check
small yellow close
Check

Question 2

You cross the two true-breeding parental plants, and find that **all** the F1 progeny have small red flowers. What is the genotype of Parent 1 with respect to flower color and size? Use A and B for the dominant traits, a and b for the recessive traits.

AABB 4 close
AAbb 5 check
AaBb 8 close
aaBB 6 close
aabb 7 close
Check

Question 3

You cross the two true-breeding parental plants, and find that **all** the F1 progeny have small red flowers. What is the genotype of Parent 2 with respect to flower color and size? Use A and B for the dominant traits, a and b for the recessive traits.

AABB 4 close
AAbb 5 close
AaBb 8 close
aaBB 6 check
aabb 7 close
Check

Question 4

You cross the two true-breeding parental plants, and find that **all** the F1 progeny have small red flowers. What is the genotype of F1 progeny with respect to flower color and size? Use A and B for the dominant traits, a and b for the recessive traits.

AABB 4 close
AAbb 5 close
AaBb 8 check
aaBB 6 close
aabb 7 close
Check

Question 5

You cross an F1 plant with a true breeding plant that has large yellow flowers and obtain 1000 progeny. Assume that the two genes assort independently. The progeny from this cross could show how many different phenotypes?

1 close
2 close
3 close
4 check
5 close
6 close
Check

Question 6

You cross an F1 plant with a true breeding plant that has large yellow flowers and obtain 1000 progeny. Assume that the two genes assort independently. Of the 1600 progeny plants, approximately how many would be expected to have large yellow flowers?

100 close
1600 close
300 close
400 check
900 close
Check

Session Activities

Practice Problems

Further Study

Study Guides

Suggested topics for further study in an introductory-level Biology textbook

  • Mendel’s laws of inheritance
  • Common genetic terms
  • Genetic crosses
  • Punnett Squares
  • Meiosis, and its relationship to Mendelian inheritance and Punnett Squares.

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Learning Resource Types

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