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Lec 29 Flashcards

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1
Q

When was DNA first identified and by who?

A

In 1860 by a Swiss chemist, Frederick Miescher

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2
Q

What is the nuclein ? And what was it named after?

A

Some chemical substance from the nucleus of human WBCs
Nucleic acid , then deoxyribonucleic acid DNA

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3
Q

What flu was common in 1929?

A

Pneumonia

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4
Q

What did Dr Griff , a British bacteriologist try to develop?

A

A vaccine for pneumonia that was caused by streptococcus pneumonia

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5
Q

What’s the Dr. Griff notice?

A

That there are different strains of streptococcus pneumonia, which are:
rough strain (R) & smooth strain (S)

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6
Q

What are the characteristics of rough strain (R) ?

A

1- non pathogenic bacteria
2- Without a polysaccharide capsule

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7
Q

What are the characteristics of smooth strain (S) ?

A

1- pathogenic bacteria
2- Has polysaccharide capsule

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8
Q

When a rat is injected with rough strain what will happen to him?

A

He will survive

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9
Q

When a rat is injected with smooth strain, what will happen to him?

A

He will die

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10
Q

When a rat is injected with smooth strain that has been heated what will happen to him ?

A

He will survive because the bacteria is dead

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11
Q

What will happen to a rat when ( the S heated bacteria are mixed with R bacteria ) and injected to him ?

A

He will die

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12
Q

According to Griff, why did the rat when he was injected with the heat killed pathogenic S bacteria mixed with R bacteria not die?

A

Dr. Griff proposed that some chemical substances present in the heat killed pathogenic S bacteria transformed the living non-pathogenic R bacteria into pathogenic bacteria.

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13
Q

What did Dr Griff name the unknown chemical substance?

A

The transforming factor

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14
Q

Dr. Avery was a bacteriologist trying to develop a ?

A

Vaccine for pneumonia

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15
Q

Doctor Oswald Avery heat killed virulent strain bacteria and added enzymes that destroy { RNA , proteins , DNA , lipids , carbohydrates } what were his results?

A

The DNase culture had only R strain bacteria
And the rest cultures contained transformed S strain bacteria

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16
Q

Dr. Avery proposed that the transforming factor present in the heat killed bacteria was ?

A

DNA

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17
Q

Why did scientists disagree with Dr. Avery?

A

1- DNA was the genetic material only in bacteria and not in eukaryotes
2- there were some proteins present in the sample which may have transformed the non-pathogenic to pathogenic
3- many scientists believed in those days that proteins were the genetic material

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18
Q

Hershey and Chase were American —-

A

Virologist

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19
Q

What did Hershey and Chase use to demonstrate whether DNA or protein were the genetic material?

A

Bacteriophages ( virus )

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20
Q

They labelled virus with radioactive —— & another one with radioactive——

A

S35
P32

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21
Q

They allowed the virus to multiply into —— inside the——-

A

Bacteriophages
Bacteria

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22
Q

Hershey and Chase observed the presence of only radioactive —— inside the bacterial cell

A

P32

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23
Q

What did Dr Hershey receive for the discovery of DNA carrying genetic material and not protein?

A

Nobel prize

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24
Q

Who was the first doctor who proposed the chemical composition of nuclein or DNA?

Study These Flashcards
A

Dr Phoebus levene

25
Dr Levine proposed that the DNA has a ?
Repeating sequence of four nucleotides each nucleotide is composed of { deoxyribose , phosphate , base —> such as adenine thymine guanine cytosine } accordingly DNA was made up of equal amounts of the bases
26
Chargaff of was an American —— ? Who said that DNA was
Scientist Not made up of repeating sequences of 4 nucleotides as Dr Levine proposed
27
In 1950 chargaff proposed
2 base equivalency rules 1- Adenine = thymine & guanine = cytosine 2- the numbers of each base are not the same among species ( they vary from species to species ;however, they are constant in all cells of a species , and together they are total to 100% )
28
Chargaff ——— rules provided the clue for the first time that in a DNA strand
Equivalency rules Adenine always base pairs with thymine Guanine always base pairs with cytosine
29
What are purines?
Adenine and guanine , which have a double carbon ring
30
What are pyrimidines?
Thymine and cytosine, which have a single carbon ring
31
Roseland Franklin was an English
Chemist and x-ray crystallographer
32
In 1951 Franklin and Wilkins were trying to identify DNA —— in King’s College , London .
Structure
33
Franklin used———- to identify the structure of the DNA
x-ray the diffraction experiment
34
Based on the result of x-ray diffraction on DNA Franklin proposed that
DNA is composed of two strands which are twisted around each other like coils of a spring and in the middle of the two strands the purine and pyrimidines bases hold the two strands together
35
James Watson, an American , and Francis Crick , a British , were trying to identify the structure of —— from Cambridge University
DNA
36
Based on leven’s , Franklin’s , chargaff’s experiment results Watson and Crick built a
3 dimensional model ( using wires and hardboard ) , which demonstrated the structure of DNA , now called Watson and Crick model of DNA
37
What is the structure of the deoxyribonucleotide?
1- pentose sugar 2- nitrogenous base ( purine or pyrimidines ) 3- phosphate group
38
What is the structure of a nucleoside? And what is it for a nucleotide?
1- nitrogenous base 2- pentose sugar ( 5 carbon sugar ) For a nucleotide the two mentioned before are in it + phosphate group
39
Adenine & thymine bases are held together with —— hydrogen bonds
2
40
Guanine & cytosine are held together with —— hydrogen bonds
3
41
Different number of hydrogen bonds between bases ensure that
Bases pair together correctly
42
The DNA has
Two grooves ( major and minor )
43
Where does the major groove occur?
We backbones are far apart
44
Where does the minor groove occur?
Where they are close together
45
Where do proteins bind to regulate the gene expression?
Grooves
46
A DNA molecule has a —— between two strands and a —— turn of one helix ,as well as ——between two bases
Diameter ( 2nm ) Complete ( 3.4nm ) Spacing ( 0.34nm )
47
Nucleotides are linked together by ——— bonds between sugar of one nucleotide and phosphate of another nucleotide
Phosphodiester
48
The two strands run
Antiparallel 5’ to 3’ in one strand and 3’ to 5’ on the other strand
49
James Watson , Francis Crick , Maurice Wilkins won the
Noble prize
50
Why didn’t Roseland Franklin get a noble prize?
Because she died in 1958 and could not receive the award
51
What are the functions of DNA?
1- replication 2- transcription
52
What is DNA replication?
The process by which DNA makes a copy of itself during cell division , it is semiconservative
53
During ——— each strand serves as a template for the replication of a new complimentary strand
Replication
54
One strand of the parent double helix is —— in each new DNA molecule
Conserved
55
What happens during transcription?
Many RNA’s are transcribed from DNA such as: messenger RNA { mRNA } transfer ribonucleic acid { tRNA } ribosome RNA { rRNA }
56
What is mRNA?
Large family of RNA molecules that carry the genetic information from DNA for particular protein synthesis occurring in ribosome
57
What are tRNA?
Participants in protein synthesis tRNA recognises each mRNA codon and provides the corresponding amino acid
58
What is rRNA?
A part of protein synthesising organelle / ribosome helps translating the codon in mRNA into protein

Biology (20 decks)

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