The history of DNA : Important figures

Question 1

What did Greg Mendell do?

Answer 1

He did experiments with pea plants to understand how traits were inherited.

Question 2

In regards to Mendell’s experiment, what laws were involved?

Answer 2

Law of inheritance, which branched out to law of segregation and law of independent assortment

Question 3

What did Greg Mendell observe about traits?

Answer 3

That certain traits, which he labelled as “dominant” would mask the expression of the “recessive” trait.

Question 4

What was the hereditary material that Mendell determined?

Answer 4

Chromosomes

Question 5

Why were chromosomes determined to be the hereditary material in Mendell’s experiment?

Answer 5

Because Chromosomes contain protein and nucleic acids, which therefore one of these must be the genetic material.

Question 6

Harmless bacteria changed into …

Answer 6

deadly bacteria

Question 7

What was Federick Griffith experiment?

Answer 7

Griffith worked with two strains of bacteria—one deadly (smooth) and one harmless (rough) and used them on mice.

Question 8

What did Federick Griffith discover?

Answer 8

Bacterial transformation and transforming principle, but he did not know DNA was responsible for it

Question 9

What are the two strains that Griffith worked with?

Answer 9

S-strain, which is known as the smooth strain and the deadly one. The R-strain, also known as the rough strain and is the harmless one.

Question 10

What did Avery and McCarty do?

Answer 10

Repeated Griffith’s experiment and they aimed to identify they “transforming principle” that Griffith had discovered. They found and provided first strong evidence that DNA, not protein, is the molecule responsible for heredity

Question 11

What were the testing components for Avery and McCarty’s experiment?

Answer 11

Protease (to destroy proteins),
RNase (to destroy RNA),
DNase (to destroy DNA).

Question 12

What were the different changes that Avery and McCarty made from using Griffith’s experiment?

Answer 12

Avery, MacLeod, and McCarty took the deadly (smooth) bacteria that Griffith used and extracted different components—proteins, RNA, and DNA—from these bacteria.

Question 13

What was Hershey and Chase’s doings?

Answer 13

Hershey and Chase conducted an experiment strong evidence that DNA, not protein, is the genetic material in organisms.

Hershey and Chase worked with bacteriophages, viruses that infect bacteria.

Question 14

What was Hershey and Chase’s experiment?

Answer 14

Hershey and Chase grew two batches of bacteriophages, labeling each one with a different radioactive marker.

Question 15

What were the two radioactive marker that Hershey and Chase labelled?

Answer 15

Radioactive sulfur (³⁵S) to label proteins, since sulfur is present in proteins but not in DNA.

Radioactive phosphorus (³²P) to label DNA, since phosphorus is in DNA but not in proteins.

Question 16

What was Hershey and Chase’s conclusion or discovery?

Answer 16

Hershey and Chase concluded that DNA, not protein, is the genetic material that viruses inject into bacteria to replicate, providing further proof that DNA is the hereditary material in living organisms.

Question 17

What was Miescher contribute to the history of DNA?

Answer 17

He was the first to isolate DNA, he Obtained it from white blood cells from pus filled bandages.

Question 18

What was Miescher’s experiment?

Answer 18

Miescher isolated the nuclei of the white blood cells by breaking down the cell membranes with a salt solution.

Question 19

What did Miescher discover or concluded?

Answer 19

Miescher discovered a unique substance that was neither a protein nor a lipid, containing large amounts of phosphorus and no sulfur. He named it “nuclein” (now known as nucleic acid, specifically DNA).

Question 20

What did Levene discover?

Answer 20

discovered two types of nucleic acids, DNA and RNA.

He also discovered that DNA had one less oxygen in the sugar compared to RNA, called RNA’s sugar Ribose and DNA’s sugar Deoxyribose.

Moreover, he discovered that both DNA and RNA are composed of nucleotides.

Question 21

What was Levene’s conclusion?

Answer 21

Distinction Between DNA and RNA:

Levene differentiated between DNA and RNA by identifying their respective sugars, deoxyribose and ribose, a key insight into their structural differences.

Question 22

What did Chargraff do?

Answer 22

Chargaff decided to look for
differences in the DNA of a
variety of different species

Question 23

What was Chargaff’s experiment?

Answer 23

Chargaff isolated DNA from various organisms and analyzed the quantity of each nitrogenous base (adenine, thymine, cytosine, and guanine) within DNA samples from different species.

Question 24

What was Chargaff’s conclusion?

Answer 24

Organisms differ in their
proportions of each base (ex.
Yeast and Humans have a
different % of Adenine)

Regardless of organism, the
% of A always corresponded
to the % of T and G and C
corresponded.

Question 25

What was Franklin’s experiment?

Answer 25

Extracted DNA and took pictures of it using a beam of x- rays.

Question 26

What was Franklin’s conclusion?

Answer 26

The x-rays scattered producing a pattern which provided clues to the 3-D structure of DNA.

Question 27

What is X-Ray Diffraction?

Answer 27

X-Ray diffraction works by sending an x-ray through an isolated biological molecule

Question 28

What were Franklin’s discoveries?

Answer 28

From these x-rays she concluded that DNA was in fact a double helix. She also concluded, by observing DNA interact with water, that the bases are on the inside and the sugar phosphate backbone was on the outside.

Question 29

What did Crick and Watson do?

Answer 29

built models of DNA and matched it to the patterns in the x-ray photograph.

Question 30

What did Crick and Watson discover?

Answer 30

Double Helix Structure: By building a three-dimensional model, Watson and Crick discovered that DNA is a double helix, with two strands twisting around each other in a spiral.

Base Pairing Rules: They showed that adenine (A) always pairs with thymine (T), and cytosine (C) pairs with guanine (G).