LS1+(9-11)+-+2

**Students demonstrate an understanding of the molecular basis for heredity by …**

2a describing __the DNA structure and relating the DNA sequence to the genetic code.__

2b explaining how DNA may be altered and __how this affects genes/heredity__ (e.g. substitution, insertion, or deletion).

2c describing how __DNA contains the code for the production of specific proteins.__

=GSE LS1 (9-11)-2=
 * Assessment target: Explain or justify with evidence how the alteration of the DNA sequence may produce new gene combinations that make little difference, enhance capabilities, or can be harmful to the organism (e.g., selective breeding, genetic engineering, mutations).**
 * Students demonstrate an understanding of the molecular basis for heredity by …**
 * **2a describing the DNA structure and relating the DNA sequence to the genetic code**
 * **2b explaining how DNA may be altered and how this affects genes/heredity (e.g. substitution, insertion, or deletion).**
 * **2c describing how DNA contains the code for the production of specific proteins.**

From the RISTA Workshop, December 2009.



Concepts contained in 2a:

 * DNA is found in chromosomes, which are in the nucleus. DNA is smaller than the nucleus and the cell.
 * DNA is a double helix, like twisted ladders, 98% of which is not genes (in humans).
 * DNA is enormous, for a molecule, but still really small. Sense of relative scale.
 * DNA is made of long chains of small chemical units called nucleotide bases.
 * The order of the nucleotide bases in DNA carries information, like the order of letters in words and sentences.
 * There are only four ‘letters’ in the DNA alphabet, g, a, c, t, and they pair in the double helix as g-c, a-t.
 * Groups of three letters are read as ‘words’ called codons. Each codon codes for an amino acid.

Concepts contained in 2b:

 * What are the kinds of mutations, frame shift, addition, subtraction, substitution?
 * What are the effects of those mutations? No effect. Effects that are passed on, effects that are advantageous, effects that are disadvantageous, fatal effects.
 * Where and when will mutations matter? Mutations in gametes can be passed on, otherwise not. Some mutations do not change amino acids, due to synonomous codons. Sometimes, mutations have no effect on protein function.

Concepts conatined in 2c:

 * DNA is transcribed into a portable molecule called RNA
 * messenger RNAs carry instructions for making a protein
 * ribosomal RNA makes up a large part of the protein making machines, ribosomes
 * transfer RNAs bring amino acids to the protein making machinery
 * RNA messages are translated into proteins
 * Students need to be able to code and decode DNA into amino acids
 * Students should know the special codes for stop and start
 * Teachers should learn about introns and exons, and how the coding of DNA is an interrupted process. Eukaryotic gene sequences are not continuous.

**What ideas to students need to understand before they can address the topics described above?**
Students need to know":
 * that differences between organisms are important, and do matter.
 * Organisms that are more fit will tend to survive and reproduce more often.
 * Transcription and translation processes.

**What misconceptions are students likely to have about these topics?**
Students often believe (erroneously):


 * Mutations are always bad,
 * mutations cause super powers,
 * mutations are the same as cancer.
 * Students misunderstand scale of DNA.

**What phenomena and representations help students understand these topics?**

 * 3-D models are important to understand double helix structure.
 * Have students make mutations to DNA.

**What activities or activity sequences can be used to address these GSEs?**

 * students build model of DNA from paper or clay
 * Connects has a DNA model
 * Students send mesages in amino acid form, coding and decoding.
 * Students will research a particular mutation, and find out the effects.(We will provide list of disorders, cystic fibrosis, polydactly, albinism, sickle-cell anemia, etc….)