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1

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

The Hershey and Chase experiment in bacteriophages

2

What is the Griffith's experiment?

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

3

What is transformation?

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

4

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

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.

5

What was the Hersheys and Chase exp. ?

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

6

Why was the T2 Bacteriophage used?

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

7

What were the two virus strains created for the experiment.

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

8

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

* Replication
*Chemically and structurally stable
*expression in the form of mendelian characters
*It should be able to mutate

9

Which molecules are the foundation of life?

Nucleic acids

10

What are nucleic acids?

They are large polymeric molecules composed of repeating units called nucleotides

11

What is a nucleotide composed of ?

*Nitrogenous base
*Pentose sugar
*Phosphate

12

Where does DNA occur?

*Chromosomes
*Plastids
*Mitochondria

13

Where does RNA occur?

*Chromosomes
*Nucleoli
*Cytoplasm
*Ribosomes
*Plastids
*Mitochondria

14

What is Chargaff's rule?

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.

15

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

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

16

What did Watson and Crick propose?

They proposed the double helix model of DNA

17

What should you mention describing the structure of DNA?

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

18

What are the different types of RNA?

*Ribosomal RNA
*Messenger RNA
*Transfer RNA

19

In which ways do these types of RNA vary ?

In size and function.

20

Which is the largest RNA?

rRNA

21

Where is mRNA produced?

The nucleus

22

Just a note:

mRNA is specific for each protein

23

Which is the most abundant RNA?

Ribosomal

24

Which is the stable form of RNA?

Ribosomal

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