DNA Isolation

Question 1

what was the purpose of this lab?

Answer 1

-to isolate DNA from plant tissue

Question 2

what is DNA?what does it do? where do you find DNA?

Answer 2

deoxyribonucleic acid

• it is a macromolecule
• it carries genetic information required for growth/development/function/and reproduction of living organisms
• find DNA in every cell of plants and animals

Question 3

what is the structure of DNA?

Answer 3

DNA is made of nucleotides that pair to form a double helix

Question 4

how many DNA are there in a eukaryotic chromosome?

Answer 4

each chromosome contains a single linear DNA double helix

Question 5

How is DNA compacted? what is the resulting product called? why does DNA compact?

Answer 5

-DNA compacts by wrapping around histone proteins
-the DNA + proteins = chromatin
-DNA compacts to take up less space
as well as the helical shape that DNA strands take can compress tighter

Question 6

what organism was used in the this lab? what is its scientific name?

Answer 6

strawberries

-Fragaria ananassa

Question 7

why were strawberries used for this lab? what does this mean?

Answer 7

because they are octoploid (have 8 of each type of chromosome in each cell) ie. they have large genomes
-meaning that they yield more DNA, making it easier to be observed

Question 8

what was the purpose of first mashing the strawberries before adding anything to them?

Answer 8

-the smashing mechanically breaks apart the tough cell walls, freeing the cell contents (including the DNA)

Question 9

what 2 liquids were added to the mashed strawberries?

Answer 9

3% Sodium chloride (NaCl) - ie. salt solution

liquid detergent

Question 10

what is the purpose of adding liquid detergent to the strawberries?

Answer 10

it dissolves the phospholipids that make up the cell membrane –> releasing the contents of the cell

Question 11

what is the purpose of adding NaCl (salt) to the strawberries?

Answer 11

NaCl dissolves to form a sodium ion (Na+), which shields the negative charges of the DNA by bonding to the phosphate groups –> allowing the DNA to clump together

Question 12

what is the purpose of heating the strawberry solution?

Answer 12

1. it will denature the proteins
2. it will improve the emulsification of lipids (breaking down of fats)
3. inactivates any enzymes (DNases) that may be present that could degrade the DNA

Question 13

what happens to the mixture upon cooling?

Answer 13

the proteins and lipids precipitate from the solution –> leaving the DNA behind

Question 14

after the strawberry filtrate is cooled, what liquid is added? why is this added?

Answer 14

• ice cold 95% ethanol

- DNA remains dissolved in the aqueous strawberry solution, but DNA in not soluble in alcohol

Question 15

why is it important that the ethanol is cold?

Answer 15

-the colder the alcohol, the less soluble the DNA is in it –> so ice cold temperature will enhance the precipitation

Question 16

after stirring at the interface of the strawberry solution and ethanol, what should you expect to see? what is this?

Answer 16

• a white sticky precipitate (looks like snot) should form

- this is the isolated DNA

Question 17

what else may be present in the resulting precipitate?

Answer 17

-not pure DNA, also contains histones (the proteins that DNA wraps around)