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Molecular basis of inheritance Flashcards

1
Q

what gave the most conclusive evidence about DNA being the genetic material?

A

The Hershey and Chase experiment in bacteriophages

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2
Q

What is the Griffith’s experiment?

A

This is an experiment in which Griffith proves that DNA is the genetic material and not the proteins. S straina and R strain.

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3
Q

What is transformation?

A

The phenomenon by which DNA when isolated from cell is introduced into the other , it bestows some of its properties to the other cell.

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4
Q

What is the Avery,McCleod and McCarry’s experiment?

A

In this experiment three scientists performed these experiments in-vitro and after transferring the genetic material of the S cell to the R cell, he realised that the R cell transformed into the S cell. He treated the extract with DNAase which prevented the transfer of species , he also treated it with proteases and found that nothing happened.

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5
Q

What was the Hersheys and Chase exp. ?

A

It was the exp. that dealt with the T2 Bacteriophage.

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6
Q

Why was the T2 Bacteriophage used?

A

It was used because it contained only two things, a protein head and genetic material inside.

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7
Q

What were the two virus strains created for the experiment.

A

Since sulphur was not found in DNA, proteins were labelled with radioactive sulphur and DNA with radioactive phosphorus.

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8
Q

What properties must a molecule have in order to act as genetic material?

A
  • Replication
  • Chemically and structurally stable
  • expression in the form of mendelian characters
  • It should be able to mutate
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9
Q

Which molecules are the foundation of life?

A

Nucleic acids

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10
Q

What are nucleic acids?

A

They are large polymeric molecules composed of repeating units called nucleotides

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11
Q

What is a nucleotide composed of ?

A
  • Nitrogenous base
  • Pentose sugar
  • Phosphate
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12
Q

Where does DNA occur?

A
  • Chromosomes
  • Plastids
  • Mitochondria
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13
Q

Where does RNA occur?

A
  • Chromosomes
  • Nucleoli
  • Cytoplasm
  • Ribosomes
  • Plastids
  • Mitochondria
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14
Q

What is Chargaff’s rule?

A

This rule states that the ratio of purines to pyrimidines is one. i.e. , the no. of A is equal to the no. of T etc.

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15
Q

What did Franklin and Wilson notice about the structure of DNA?

A
  • Helical
  • Diameter 20Å
  • The distance between successive nucleotides 3.4Å
  • This helix makes one complete turn every 34Å
  • There are ten nucleotides per turn
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16
Q

What did Watson and Crick propose?

A

They proposed the double helix model of DNA

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17
Q

What should you mention describing the structure of DNA?

A
  • Its dimensions given by Wilkin and Franklin
  • Double stranded(fulfilling density requirements)
  • Hydrogen bond
  • Sugar-Phosphate alternate backbone
  • Antiparallel
  • Complementary
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18
Q

What are the different types of RNA?

A
  • Ribosomal RNA
  • Messenger RNA
  • Transfer RNA
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19
Q

In which ways do these types of RNA vary ?

A

In size and function.

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20
Q

Which is the largest RNA?

A

rRNA

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21
Q

Where is mRNA produced?

A

The nucleus

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22
Q

Just a note:

A

mRNA is specific for each protein

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23
Q

Which is the most abundant RNA?

A

Ribosomal

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24
Q

Which is the stable form of RNA?

A

Ribosomal

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25
Which RNA has the highest molecular weight?
Ribosomal
26
What helps in the binding of the mRNA and tRNA?
The rRNA molecule helps in the of mRNA and tRNA to the ribosome. This bond occurs using a Mg2+ linkage btw the phosphate molecules of the two RNAs.
27
Which RNA is the most heterogenous is size and stability?
mRNA
28
Where does mRNA occur?
It occurs in the nucleolar region and the cytoplasm
29
IMP things about an mRNA molecule.
* Its size varies depending on the protein it codes for * It carries coded message from a DNA molecule to a Ribosome and instructs the amino acids to sequence in protein synthesis * mRNA is short lived * Hence it does not accumulate in cells
30
The matching of anticodon with amino acid is done by...?
Amino acyl- tRNA synthetase
31
What method did Watson and Crick propose for the replication of DNA?
They proposed the semiconservative method of replication.
32
What was the Meselson- Stahl experiment?
E.coli cultures with heavy and light Nitrogen isotopes.
33
In the Meselson- Stahl experiment how were the DNA strands analysed?
They used a CsCl density gradient centrifugation technique.
34
Which enzymes are used in DNA replication?
* Primases * Helicases * Topoisomerases * DNA polymerases * DNA ligases * Repair enzymes
35
What is the origin of replication?
It is the initiation site at which replication occurs
36
What are replicons?
LInearly arranged units that undergo replication.
37
What is a primer?
The primer is a short stretch of RNA formed on DNA.
38
What does the primase enzyme do?
This enzyme polymerises A U G C into the primer.
39
What is the sense strand?
It is the DNA strand which serves as a template for W
40
What principle governs the process of transcription?
The principle of complementarity
41
Why does only strand code take part in transcription.
* This is because if both strands of DNA coded for proteins they would be coding for different proteins. Which would complicate the process. * The two RNA strands formed would be complementary to each other and form a double stranded DNA
42
What purposes do deoxyribose triphosphates serve in DNA replication?
They have a dual function, i.e.They act as substrates for reactions and also provide energy for polymerisation reactions. (High energy phosphates)
43
The term genetic code was coined by whom?
The term genetic code was coined by George Gamow
44
What is the transcriptional unit?
the transcriptional unit is a structure that consists of * the promotor * The structural gene * A terminator
45
What is the template strand?
The strand whose polarity is 3' to 5' and that strand which acts as the template strand.
46
What is the template strand also called?
The template strand is also called the non coding strand.
47
What is the coding strand
This is the strand with the desired code for the RNA. It is also called the sense strand or non- template strand.
48
Which provides for the binding site of RNA polymerase?
The promoter contains a DNA sequence that does so.
49
AN IMP NOTE:
It is the position of the promoter strand that determines the coding and template strands.
50
Certain short sequences of the promoter that are conserved are called...?
Recognition sequence
51
What does the Terminator do?
It defines the end of a process
52
What is the functional unit of inheritance
gene
53
What is a cistron?
This is functional unit of a gene. It is a segment of DNA that codes for a polypeptide.
54
The structural gene in prokaryotes is usually..... and in eukaryotes is usually ...... ?
polycistronic | monocistronic
55
What are exons?
These are the coding sequences present in a mature or processed RNA.
56
What are introns?
Exons are interrupted by introns which are intervening sequences that do not appear in mature/sequenced RNA.
57
Just a note:
This structure of a DNA is called the split gene arrangement.
58
Where do transcription and translation occur?
In eukaryotes Transcription occurs the nucleus and translation in the cytoplasm.
59
In which way does the sigma factor help in transcription?
It gives specificity to the initiation process. Without it , initiation could've started anywhere.
60
What is hnRNA synthesised by?
RNA Polymerase II
61
What are the processes involved in post transcriptional processing?
* 5' capping | * Tailing and Splicing
62
What happens in 5' capping?
Methyl guanosine triphosphate is added to the 5' end of an hnRNA. This is catalysed by guanylyl transferase. The cap is necessary for the formation of the mRNA ribosome complex.
63
What is tailing?
It is the addition of 200-300 adenylate residues to the 3' end in a template independent manner with the help of Poly A Polymerase
64
What is splicing?
It is the process of removal of introns. It is done by SnRNA and SnRNPs.
65
What does splicing represent?
It represents the dominance of the RNA world.
66
How are the the protein and DNA arrange in a bacterial cell.
They are collinear
67
What are the 5 histone proteins?
H1,H2A,H2B,H3,H4
68
what is the nucleosome?
It is he combination of an acidic DNA molecule and a basic histone protein
69
just a note:
200 bp are involved in wrapping around the histone octamer by 7/4 turns
70
What are the dimensions of a nucleosome?
110 x 60 angstrom
71
What is the DNA present in btw to nucleosomes
This is the linker DNA
72
What causes the beads on string appearance?
nucleosomes which coils to form a solenoid
73
What is the definition of a codon?
A sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule.
74
What is the genetic code?
The order of base pairs along a DNA molecule controls the kind and order of aas found in the protein of an organism.

Biology (6 decks)

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