Inquiry in the Natural World – Spring 2003

Student Topic Guide #10: Inheritance

Topic objectives:

1. Know what factors contributed to the success of Mendel’s investigations of inheritance.

2. Understand how Mendel’s hypothesis explains why children don’t always resemble either of their parents, and how traits can skip a generation.

3. Be able to describe how scientists came to the conclusion that genes are on chromosomes.

4. Know how the work of (a) Avery, Macleod and McCarthy; (b) Chargaff; and (c) Franklin contributed to Watson and Crick’s development of a model for the structure of DNA.

5. Know the structure of DNA, including the basic structure of nucleotide building blocks, how nucleotides are linked to form DNA strands, and how bases pair in the DNA double helix.

6. Be able to explain how DNA is replicated, how the information in DNA is “transcribed” to make messenger RNA, and how the information in messenger RNA is “translated” into the amino acid sequence of a protein.

7. Be able to describe some of the ways that the scientific method, and other considerations, influenced Watson and Crick’s work on the structure and function of DNA.

Day 2 (Monday, 31 March):

Reading assignment:

Trefil and Hazen. 2001. The Sciences, 3rd edition. Chapter 23

Learning Exercises:

1. Explain how each of the following factors contributed to the success of Mendel’s experiments:

Use of an organism with several easy-to-distinguish traits

Use of pure-breeding stocks as the parental (P) generation

Continuance of experiments for at least two generations (F1 and F2 generations)

Quantitative analysis of results

Ability to formulate a testable hypothesis

2. Briefly explain how Mendel’s hypothetical genetic “elements” (now called “genes”) later came to be identified with (A) the nucleus; and then (B) chromosomes; and then (C) DNA molecules

Day 3 (Wednesday, 2 April):

Readings (all from the 17 Feb 2003 issue of Time magazine):

Lemonick, M.D. “A twist of fate”

Lemonick, M.D. “You have to be obsessed”

Golden, F. “Beyond the double helix”

Grossman, L. “Mystery woman”

Learning exercises:

1. A. Fill in the blanks in the exercise on mechanisms of replication, transcription and translation on the back of this page. B. Identify and explain three interesting possible consequences of a “point mutation” (= a change in one base) in the “original” DNA strand that serves as the template for the mRNA?

2. Based on the Time magazine readings concerning the discovery of the structure of DNA... A. identify a hypothesis that proved false, and describe how the investigators responded; B. identify two examples of preconceptions entering the process; C. describe the roles of arrogance and obsession; D. describe the importance of scientific meetings; and E. identify two things that scientists do besides “investigate” that contribute to the progress of science.

Replication-Transcription-Translation exercise – Sp 2003

(NB: The first tRNA should correspond to the first “start” codon in the mRNA)

Complementary

DNA: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Original DNA: G T C A T A C G C A C T C G T G T T C A T C G G T

(template for

mRNA)

Messenger RNA: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(mRNA; codons)

Transfer RNA’s:_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(tRNA’s;

anti-codons)

Amino acids:

(use “genetic code” table

in text – p. 520)