14. THE MOLECULAR BASIS OF INHERITANCE Flashcards
1
Q
- What happened with DNA during the 20th Century?
A
- the identification of the molecules of inheritance was a
major challenge to biologists
2
Q
- What did Thomas Hunt Morgan’s research show?
A
- it showed that genes are located on chromosomes
3
Q
- Which 2 compounds of chromosomes became candidates for genetic material?
A
- DNA
- Proteins
NB:
- Protein was the stronger candidate
4
Q
- What three characteristics did the Genetic Material have to have?
A
- Contain information
- Be easy to copy
- Be variable to account for the diversity between
species
5
Q
- How was the the role of DNA in heredity first discovered?
A
- by studying bacteria and viruses
- this is because they were a much simpler organism
than plants, insects and animals
6
Q
- When was the Griffith Experiment conducted?
A
- it was conducted in 1928
7
Q
- What did the Griffith experiment prove?
A
- it proved that DNA can transform bacteria
8
Q
- What is meant by Transformation is genetic terms?
A
- it is the genetic alteration of a cell
- this is due to the uptake and incorporation of
exogenous and foreign DNA
9
Q
- What did Griffith do during his experiment?
A
- he mixed 2 strains of Streptococcus Pneumonia
- this is a type of Bacteria
- he mixed a heat-inactivated pathogenic strain with
living bacteria - this living bacteria comes from a harmless, non-
pathogenic strain
10
Q
- What did Griffith observe at the end of his experiment?
A
- some of the living cells became pathogenic
- the transforming substance in Griffith’s experiment
was later found to be DNA
11
Q
- When did Hershey and Chase conduct their experiments?
A
- they conducted them in 1952
12
Q
- What were Hershey and Chase’s Experiments?
A
- they studied viruses that infect bacteria
- these viruses are known as Bacteriophages
13
Q
- What did Hershey and Chase conclude?
A
- they found evidence that viral DNA can program cells
14
Q
- What did Erwin Chargaff report in the year 1950?
A
- he reported that the DNA composition varies between
species - this is evidence of diversity in the DNA
15
Q
- What does DNA structure have a role in?
A
- it has a role in inheritance
16
Q
- What did Maurice Wilkins and Rosalind Franklin study?
A
- they studied in King’s College
- this is in London
17
Q
- What did Maurice Wilkins and Rosalind Franklin do?
A
- they used a technique called X-Ray Crystallography
- they used this to study the molecular structure of DNA
18
Q
- What did Watson and Crick produce in the year 1953?
A
BASED ON ROSALIND’S RESEARCH:
- they produced the double helical model for the DNA
structure
- they discovered the 3 dimensional structure of DNA
- they did not do a single one of the experiments
NB:
- most of the experiments were performed by Rosalind
Franklin
- she died of Cancer before the awarding of the Nobel
Peace Prize for Physiology and Medicine in 1962
19
Q
- What is the structure of DNA?
A
- it is composed of 2 strands forming a double helix
shape - these 2 strands are antiparallel
- they also from the sugar-phosphate backbone
- the DNA structure also consists of the nitrogenous
base pairs - these are found in the molecule’s interioir
20
Q
- What did Watson and Crick determine with regards to the Nitrogenous bases?
A
- Adenine (A) only pairs with Thymine (T)
- Guanine (G) only pairs with Cytosine (C)
21
Q
- What is Chargaff’s Rule?
A
- this is a rule that was proven by the Watson-Crick DNA
model
IT STATES THAT:
- there is an equal number of A and T bases in every
species
- there is an equal number of G and C bases in every
species
22
Q
- Does this diagram make sense?
A
- yes
23
Q
- What is DNA?
A
- this is the substance of inheritance
- hereditary information is encoded in DNA
- this information is reproduced in all cells of the body
24
Q
- What does the DNA program and information direct?
A
IT DIRECTS THE DEVELOPMENT OF:
- biochemical traits
- anatomical traits
- physiological traits
- behavioural traits (to some extent)
25
Q
- What forms the double helix shape of DNA?
A
- the 2 polynucleotides
- they spiral around an imaginary axis
- they have a sugar phosphate backbone on the
outside - the 2 strands run in an antiparallel manner
- one strand runs from a 5’ to 3’ direction
- the other strand runs from a 3’ to 5’ direction
26
Q
- Provide the labels for the parts numbered 1-3.
A
- Sugar-Phosphate Backbone
- Nitrogenous Bases
- Hydrogen Bond
27
Q
- What kind of Model is this?
A
- space filling model
28
Q
- What are the monomers of DNA?
A
- Nucleotides
29
Q
- What components does a Nucleotide consist of?
A
- A nitrogenous base
- A pentose sugar
(this can be deoxyribose or ribose) - a phosphate group
30
Q
- What is a Nucleoside?
A
- this is a nitrogenous base and a pentose sugar
- it does not have a phosphate group
31
Q
- What is the sugar in DNA?
A
- Deoxyribose
32
Q
- What is the sugar in RNA?
A
- Ribose
33
Q
- What can be said about the 2 polynucleotide strands that form the DNA double helix shape?
A
- they are complementary
- this means that if we know the one sequence
- we can derive the sequence of the other strand
34
Q
- What holds the Nitrogenous bases together?
A
- Hydrogen bonds
- there are two hydrogen bonds holding Adenine and
Thymine together - there are three hydrogen bonds holding Guanine and
Cytosine together
35
Q
- What creates nucleotide polymers?
A
- the Phosphodiester bonds
- the nucleotides are connected in a 3’-5’
Phosphodiester bond to create a polymer
36
Q
- What is a Phosphodiester bond?
A
- it is a bond that is found between the 3’-OH group of
the sugar molecule of one nucleotide
AND - the 5’ Phosphate group of the Second nucleotide
