Brooklyn College BIOL 1010 : Investigations

Investigations : Genetics (Patterns of Inheritance)

Text:  Pages to reference will be given in class.

Web:  Science at a Distance - Brother Gregory Investigates
http://www.brooklyn.cuny.edu/bc/ahp/SCI/Science1/Sci1.HP.html

Lab Notes - Genetics

Background

Brother Gregory wants you to investigate the patterns of inheritance seen in his pea hybrids as the traits are inherited through two generations (called the F1 and F2 generations).

If he is right, and the form of a trait is controlled by a 'transmission element', an offspring receives one 'element' from its male parent and a second 'element' from its female parent.

Once in the body of the offspring, these 'elements' direct the development of the traits they control. It should be possible to determine what 'elements' each offspring inherits by the numbers, and ratios, of the offspring showing those traits.

Following a 'pattern of inheritance' requires:

  • two parent plants that are 'pure breeding',
  • performing a genetic cross using these plants to produce the F1 hybrids,
  • recording the form(s) of the trait seen in the F1 generation of plants,
  • using some of these F1 plants as parents in a second series of genetic crosses to produce the F2 hybrids,
  • counting the number of times a version of a trait occurs in the F2 hybrids,
  • calculating the ratios of plants showing one form to those plants showing the alternate form of a trait.

Question

What different patterns of inheritance can be seen during genetic crosses, and how can these patterns be interpreted?

Assignment

First Genetic Cross - to produce F1 hybrids

  • Select "pure breeding tall plant" from the Special Peas menu. This will become "TRAIT ONE" of Parent One (or Parent Two).
  • Select "short plants" from the Traits menu.
    • Click on "TRAIT ONE" of the other Parent.
  • You should now have two parent plants. You know that the 'tall' plant is 'pure breeding', but what do you know about the 'short' plant? Is it 'pure breeding'? How would you know? (Hint: haven't you checked this already?).
  • Carry out the genetic cross by clicking on the "Collect Peas" box, collecting the seeds and then clicking on the "Plant Peas" button. The new peas will grow and number and type of offspring will appear in the boxes underneath.
  • Write down, and record
    1. what you did, and
    2. what results you obtained on the tables provided at the end.
  • Repeat this type genetic cross experiment five times, and then use the other 'special pea' that is 'pure breeding for the purple flowered plant'. The other parent in this cross should hold the 'white flowers' trait.

This is now the data for the 'pattern of inheritance' seen as Mendel's transmission elements are passed from the original parent plants into the first generation of hybrids, the F1 hybrids.

Second Genetic Cross - to produce F2 hybrids

One of the F1 hybrid plants (produced in the first round of genetic crosses) must be one of the parents in the second round of genetic crosses.

To do this,

  • click on the 'special pea' called "an F1 seed from a tall/short cross" and this version of the trait will become one of the parents.

You can now cross this F1 hybrid plant with three other types of plant:

  1. another F1 hybrid plant from a tall/short cross. To do this click again on that 'special seed'. Both parents should now be these F1 hybrids.
  2. a 'tall plant' selected from the Traits menu.
  3. a 'short plant' selected from the Traits menu.

Repeat these genetic cross at least 5 times each. Record all the results on the tables provided at the end.

Assignment Questions:

  1. What did you find?
  2. Which of the 'F1 crosses' produced consistent results?
  3. Which of the "F1 crosses' produced inconsistent results?
  4. How do you explain your results?

Portfolio

Create and submit an individual portfolio containing the results of your investigation.

A proper answer should include the following:

  • The data collected in your experiment.
  • Your results or conclusions based on the data.
  • And answers to any questions presented in the investigation.

Investigations are due the next scheduled lab period.

Late investigations will NOT be accepted!

Lecture

Lab

Investigations

Investigations (hardcopy)