Establishing DNA as hereditary material Flashcards
(129 cards)
1
Q
What do Darwin’s genetics say?
A
‘Gemmules’ in cells are inherited.
2
Q
How is Mendel’s Law of Inheritance named alternatively?
A
Law of segregation.
3
Q
What does the Law of segregation say?
A
Gametes only had one version of allele for each gene.
4
Q
What did Darwin’s and Mendel’s Laws do?
A
They overlap.
5
Q
What is characterised as ‘The missing link’?
A
Friedrich Miescher’s composition of lymphoid/pus.
6
Q
What did biochemists do?
A
They isolated protein.
7
Q
What does make biology more interesting except DNA isolation?
A
Other molecules’ isolation.
8
Q
When did Griffith do his experiment?
A
In 1928.
9
Q
What was Griffith’s experiment about?
A
Streptococcus pneumoniae in mice.
10
Q
What did Grififth do in his experiment?
A
Grew bacteria on agar plate.
11
Q
Why did Griffith experienced bacterial growth on agar plates in mice?
A
To check if Streptococcus pneumoniae was lethal in mice.
12
Q
What strains did Griffith use in his experiment with bacteria and mice?
A
Rough strain.
Smooth strain.
13
Q
What did Griffith realise as an outcome of his strain experiment in mice?
A
Only smooth strain killed mice.
14
Q
What was the characteristic of smooth strains in the experiment?
A
Smooth colonies were identified in agar plate.
15
Q
How did smooth strains kill mice?
A
Produced polysaccharide –> immune response in organism –> does not see it –> kill it.
16
Q
What did Griffith manage to grow in his experiment?
A
Live cells.
Dead cells.
Whole cells.
17
Q
What did Griffith do with mice in his experiment?
A
Took blood from mice –> in agar –> colonies growth.
18
Q
What was the control Griffith used in his experiment?
A
Blood of live cells –> injected in mice –> in agar –> colonies growth.
19
Q
What happened when killed cells were injected in mice?
A
Mice killed.
20
Q
What happened when heat killed cells where injected in mice?
A
Mice died.
Colonies grew.
21
Q
What does the ‘Transforming principle’ say?
A
Smooth cell gradient –> into rough cell –> produce polysaccharide.
22
Q
What happens when bacteria take DNA from environment?
A
They produce proteins.
23
Q
What did Griffith show with his experiment?
A
Something (DNA) could be transferred –> change phenotype –> genetic information.
24
Q
What do different enzymes do?
A
Destroy different molecules: sugars, polysaccharides, DNA, proteins.
25
What is the advantage of destroyed proteins?
They still work.
26
What happens when degraded RNA is transferred to a sample?
Smooth cells appear.
27
How many experiments occurred in biomolecules and genetics for DNA?
A lot.
28
What happened when material were incubated with DNA?
Mixture did not transform cells in smooth cells.
29
What was the outcome of the experiments in DNA?
DNA carries the information only not another molecule.
30
With which factors did Hershey and Chase work their experiment?
E. coli.
| T2 (agar plate).
31
When did the Hershey and Chase experiment take place?
In 1952.
32
Who was Chase?
One of the most important women in genetics.
33
What substances did Hershey and Chase used in their experiment?
Radioactive phosphate and sulphur.
34
How did Hershey and Chase use E. coli in their experiment?
E. coli culture + phage --> mixed --> on agar plate.
35
What did Hershey and Chase measure when E. coli and phage were added on an agar plate after they mixed?
Bacterial growth.
| A hole.
36
How did Chase and Hershey use an initial virus infection?
Virus' DNA injected in --> cell --> replication --> maturation --> lysis --> blended food process.
37
What appears most in DNA? Phosphate or protein?
Phosphate.
38
How where E. coli and phage mixed?
In a tube.
39
What happened when DNA was injected in a cell?
Some DNA found in progeny.
40
Where was DNA transferred from a parent?
In a cell, not in progeny.
41
What was the outcome of Hershey and Chase experiment?
Only DNA is transferred in generations, not proteins.
42
What is DNA after these experiments?
Carrier of genetic information.
43
What we must use to understand something difficult?
A simple system.
| Model systems.
44
Why should we use model systems in biomedicine?
To understand human diseases.
45
From where can we isolate DNA in an organism?
From any organ.
46
Why would we isolate DNA from an organism?
To use the information --> make a standard genetic tool --> transfer it in other organisms --> investigate DNA functions.
47
What is DNA?
Carrier of inherited information.
48
What was the hypothesis of Darwin?
Cells contain 'gemmules'.
49
What where the 'gemmules' of cells responsible for?
Inheritance of variation.
| Phenotype.
50
By what were gemmules produced?
By adult tissues.
51
Where were gemmules incorporated?
In developing eggs.
| Sperm.
52
When did gemmules spread from egg and sperm?
During offsspring development.
53
From what did gemmules produce?
By both parents.
54
Where were gemmules mixed?
In offspring.
55
What does the process of gemmules production from both parents and mixed in offspring explain?
Inheritance patterns.
56
What experiments did Mendel do?
Pea experiments.
| Crossbreeding of different pea.
57
When did Mendel was doing corss-breeding of different peas?
During reproduction.
58
What did Mendel show with his experiment in peas?
Pieces of genetic information from parents --> mixed --> different combinations in offspring.
59
What did Mendel establish?
Inheritance principles.
| Genetic traits transmission before gene identification.
60
How is Mendel's Law of inheritance called?
Law of dominance and uniformity.
61
What was said in Mendel's ingeritance law about alleles?
Some are dominant.
| Some are reccessive.
62
What will an organism with at least one dominant allele display?
Dominant allele effect.
63
What was another one of Mendel's law of inheritance?
Law of segregation.
64
What is law of segregation say?
Gamete formation --> alleles for each gene segregate --> each gamete carries one allele for each gene.
65
What is the third Mendel's law of inheritance?
Law of independent assortment.
66
What dies Lae of independent assortment say?
Genes of different traits segregate independently during gamete formation.
67
How are characters characterised?
Unitary.
68
What do genetic characteristics have?
Alternate forms.
69
From where are genetic characteristics inherited?
From one of 2 parents.
70
What does phenotype reflect?
Dominant allele.
71
By what are gametes generated?
Rabdom segregation.
72
What do different traits have?
Independent assortment.
73
Why do different traits have independent assortment?
Gene are unlinked.
74
What happened in the 20th century?
Darwin's and Mendel's work combined.
| Developed in Modern Synthesis.
75
When was DNA discovered?
In 1869.
76
Who discovered DNA?
Friedrich Miescher.
77
How did Friedrich Miescher discover DNA?
Studied lymphoid cells' composition.
| Isolated DNA with cell nuclei's associated proteins.
78
Which material were considered as carriers of genetic information instead of DNA back in 1869?
Carbohydrates.
Lipids.
Proteins.
79
Why did proteins, carbohydrates and lipids were considered as carriers of genetic information instead DNA in 1869?
Because they were variable.
80
Who did Frederick Griffith demonstrate in 1928?
Genetic information could be transferred between cells without sexual replication.
81
How was Griffith's demonstration known as?
'Transforming principle'.
82
What did Griffith's experiment prove?
DNA, not proteins or biopolymers, was the carrier of genetic information.
83
What model did Griffith use?
2 strains of Streptococcus pneumoniae and mice.
84
Where does S. pneumoniae reside?
In healthy carriers asymptomatically.
85
What can S. pneumoniae cause?
Serious diseases in neonates, children, elderly, immunocompromised, mice.
86
How can strains be differentiated?
Based on infection severity.
Immunological response.
Colony morphology.
Staining behaviour.
87
Which where the isolates Griffith worked with?
Smooth.
| Rough colony morphologies.
88
What is an injection of wild-type S. pneumoniae S strain for mice?
Lethal.
89
What can mice survive?
Injection of R strain.
90
What does wild-type S strain produce?
Polysaccharide capsule around cell.
91
What does the capsule S strain produces, prevent?
Detection.
| Clearance by host immune system.
92
What happened in Griffith's experiment?
1. Mice injected with live/dead cultures of S and R strains.
2. Blood recovered from survived mice and mice died of pneumonia.
3. Blood checked for S and R strains on agar plates.
93
What did mice survive?
R strain injection.
94
What could viable R strain cells be recovered from?
Blood samples.
95
When did mice die?
After S strain injection.
96
From what did viable S strain cells recovered?
Post-mortem blood samples.
97
What happens when mice were injected heat-killed S strain cells?
Survived.
98
What happened to the viable S strain cells when mice died from injected heat-killed S cells?
They were not recovered from blood samples.
99
What happened to mice when they were injected a mixture of living R cells and heat-killed S strain cells?
Died.
100
What happened to the viable R and S strain stain cells when mice died from living R cells and heat-killed S cells?
They were recovered from blood samples.
101
What did the testing of R and S strains demonstrate?
Transfer of information from dead S cell preparation to live R cells in mice.
Live S cells production.
102
What can DNA released by dead S cells be taken up by?
Living R cells.
103
Where do living R cells incorporate DNA by dead S cells?
R cells chromosome.
104
How are bacteria, S. pneumoniae are transformed?
Naturally.
105
What happens to Escherichia coli?
Forced to take-up exogenous DNA chemically/electrochemically.
106
Why did Griffith extent his experiment?
To identify what 'transforming principal' was.
107
How did Griffith extend his experiment?
Heat-killed S strain cultures material --> digested with various enzymes of treatments --> destroy DNA, RNA, lipids, proteins --> leave behind carbohydrates and combinations.
108
What happen to the extended Griffith experiment?
Mice died when injected living R cells + protease-treated heat-killed S strain extract.
Viable R and S strain cells --> recovered from blood samples.
109
What was the outcome of Griffith's extended experiment?
Protein was not the transforming principal.
110
What happen to mice when injected living R cells + ribonuclease-treated heat-killed S strain extract?
Mice died.
| Viable R and S strain cells -- recovered from blood samples.
111
hat was the second outcome of Griffith's extended experiment based on R cells + RNAase?
RNA was not the transforming principal.
112
What happen to mice when injected living R cells + deoxyribonuclease-treated heat-killed S strain extract?
Mice survived.
| Viable R cells --> recovered from blood samples.
113
What was the 3rd outcome of Griffith's extended experiment based on R cells + DNAase?
DNA was the transforming principal.
114
Why carbohydrate could not be the transforming principal?
It was still in DNAse treated mixture.
115
What was the Avery-MacLeod-McCarty's key finding?
DNA, not RNA, proteins, lipids, carbohydrate, was the transforming principal in S. pneumoniae S strain - R strain transformation in mice.
116
When did Avery, MacLeod and McCarty finding occur?
In 1944.
117
Who did finally proof that DNA is the carrier of inherited information?
Alfred Hershey.
Martha Chase.
In 1952.
118
What did Hershey and Chase use?
Bacteriophage T2.
119
What does bacterial virus T2 infect?
Escherichia coli.
120
What did Hershey and Chase do in their experiment?
1. Labelled T2 phage proteins : 35S and DNA with 32P.
| 2. Tracked where molecules went during early life cycle stages.
121
How did Hershey and Chase's experiment begin?
Initial attachment of phage to bacterial cell.
122
What can happen to attachment of T2 phage with bacterial cell?
Fragile.
| Broken by vigorous mixing with blender.
123
What happened in the experiment of Hershey and Chase in the end?
Labelled phage produced.
Growing generation of phage in E. coli with growth media of 32P or 35S.
Purified new phage.
124
What was the pathway of Hersey and Chases' experiment?
1. Phage attaches host's surface.
2. Viral DNA enters host cell.
3. DNA phage replicates.
4. Phage proteins made.
5. New phage particles assembled.
6. Cell lyses.
7. Release newly made phage.
125
How this experiment occurred with using 32P and 35S material?
1. One phage labelled 32P.
2. Incorporated in DNA.
3. Another phage labelled 35S.
4. Incorporated in protein coat.
5. Bacteria infected with phage.
6. Identify if viral DNA/viral protein entered host cell.
7. Cultures blended.
8. Centrifuged.
9. Separated phage from bacteria.
10. Separated lighter phage from heavier bacterial cells.
11. Bacteria infected with phage 32P-labelled DNA.
12. Produced 32P-labelled phage.
13. Bacteria with 35S-labelled phage.
14. Produced unlabelled phage.
126
What was the outcome of Hershey and Chase's experiment?
DNA, not protein, is the carrier of inherited information.
127
What did the use of simple model systems form?
Basis of many ground-breaking experiments in molecular biology and genetics.
128
How can E. coli cells produce genetically modified 'transformants'?
DNA can be introduced into specially prepared E. coli.
129
What can DNA introduction to specially-prepared cells do?
Gene cloning.
