u4: dna structure

Question 1

reasons to study DNA

Answer 1

• DNA mutations can lead to cancer/diseases
• genetically engineered crops
• forensic science

Question 2

when was DNA accepted as hereditary info? what was accepted before that?

Answer 2

• 1952
• before, it was thought that proteins gave genetic material

Question 3

why was griffith’s experiment in 1920s significant

Answer 3

first experiment suggesting that bacteria was capable of transferring genetic info via transformation

Question 4

griffith’s conclusion

Answer 4

• a heritable factor was transformed from the S strain to the R strain
• the heritable factor must have been DNA, not protein because heat kills protein

Question 5

heritable factor

Answer 5

something that is passed on

Question 6

explain hershey and chase experiment 1952

Answer 6

• used a bacteriophage to infect a bacterial cell
• wanted to see if the protein or DNA was responsible for infection of the bacteria, nd thus viral reproduction
• labelled viral protein coats with radioactive isotopes (easy to see)

Question 7

what did hershey and chase observe?

Answer 7

• protein coat stayed outside of the cell
• DNA was injected into the cell
• virus reproduction followed
• bacteriophages with 32P infected bacteria = all radioactive bacterial cells
• bacteriophages with 35S infected bacteria and virus coats removed = no radioactive bacterial cells

Question 8

hershey and chase’s conclusion

Answer 8

DNA is the hereditary material

Question 9

shape of DNA

Answer 9

• double helix polymer
• both helices are antiparallel to each other

Question 10

antiparallel

Answer 10

both strands run in opposite directions

Question 11

what is DNA made up of?

Answer 11

nucleotide monomers

Question 12

what are nucleotide monomers made up of?

Answer 12

• deoxyribose + phosphate group = sugar-phosphate backbone
• nitogenous base pairs (ATCG)

Question 13

chargaff’s rule

Answer 13

• A always binds to T
• G always binds to C

Question 14

purines/pyramidines

Answer 14

• purines have two rings (A, G)
• pyramidines have one ring (T, C)

Question 15

why does chargaff’s rule work?

Answer 15

• if two purines bonded together, the DNA would be wider than 2nm at some pts
• if two pyramidines bonded together, the DNA would be less than 2 nm at some pts
• bases bonded by hydrogen bonds, wihch only happen at ATCG arrangement

Question 16

diameter of DNA + who discovered this

Answer 16

• constant at 2nm
• found by rosalind franklin and maurice wilkins via x-ray diffraction

Question 17

width/length of DNA

Answer 17

• 0.34 nm between base pairs
• 3.4 nm length of each full turn

Question 18

two types of bonds in DNA

Answer 18

• phosphodiester bond
• hydrogen bond

Question 19

phosphodiester bond

Answer 19

• holds sugar-phosphate backbone together
• strong bond/difficult to break

Question 20

hydrogen bonds

Answer 20

• holds nucleotide bases together
• weaker bond/easier to breal

Question 21

how many chroomosmes do all human body cells (except sex cells) have?

Answer 21

46 chromosomes

Question 22

chromosome

Answer 22

DNA that has been wound/wrapped with protein

Question 23

why does DNA need to replicate itself in mitosis and meiosis

Answer 23

so that daughter cells have correct amount of DNA (46 in body, 23 in sex)