Study questions for the lectures 1-4
1. What information(s) could you obtain from a genetic approach of
studying mutants defective in a particular process?
a. Function and importance of a protein. (Isolation, identification, permissiveness
b. Number of genes involved in a certain process.
c. Location of the genes in the process (Complementation analysis)
d. Interactions between different genes by using genetic suppression.
N.B: Remember b, c & d by Lac Operon
2. How would you define permissive conditions in respect to temperature
Permissive conditions are those under which a mutation is silenced. Eg: In
temperature sensitive mutations, at low temperature (permissive conditions), the
mutation will be almost silent and the organism will be able to survive. On the other
hand, at higher temperatures, the organism will fail to survive due to loss of
3. Define (or compare and contrast): a) gene expression; transcription;
replication; translation; b) gene; allele
Gene Transcription Replication Translation
Def Process by The process of The process of The process of
which formation of forming formation of
information on RNA from DNA multiple copies protein from
DNA is made by RNA of DNA by mRNA.
into a polymerase semi-
functional gene conservative
Cell Cycle Occurs mainly Occurs in the S Occurs in all
in interphase phase of the phases of the
cell cycle cell cycle b) Gene: The sequence of nucleotides that code for a particular protein or RNA. It
includes the regulatory molecules involved. So in other words, it’s the entire DNA
sequence required for production of a functional protein or RNA.
Allele: Variants of a single gene.
4. Explain by using your own words the meaning/significance of gene
Gene expression forms the central dogma of life. Without gene expression, there
would be no passing of genetic information to off springs, no formation of proteins
and life will cease to exist. Moreover, all cells in an organism contain the same DNA,
however, not all cells carry out the same functions. The process of gene expression
is selective. Different tissue types express different proteins depending on their
function. This selectivity of the gene expression helps the cell conserve energy and
resources by not forming unwanted proteins and therefore, increases the viability of
5. What are the roles of model organisms in molecular biology studies?
Choose two model organisms and explain your reasoning.
Carrying out experiments on molecular level may not always be very feasible and the
experiments are simplified by using less complex organisms and extrapolating the
results to the more complicated organisms. This is done because:
a. They are simple
c. Short reproductive period
d. Relatively small
e. Easy to maintain
f. There is lots of data available to aid the researcher
g. The results can be extrapolated to higher organisms
The mouse is used as a model for human development. The mouse shows similar
genetic defects but it would be impossible to cage human beings and monitor their
development and therefore, the mouse is used instead. All the above 7 factors apply
Yeast (Saccharomyces cervisiae) is a single celled eukaryotic cell with mutants
readily available and easily induced and can therefore be used to study the effects of
6. What are three main functions of DNA? Explain the importance of each
a. Stores information. DNA stores information for the production of all proteins required for life.
These instructions are then passed on to daughter cells providing them
with the essential information to synthesize their own required proteins.
b. Replicates faithfully.
DNA replicates by a semi-conservative mechanism. That is, the two
strands separate and each is used to form a second strand. This
mechanism ensures that both the parent and the new strand are exactly
identical. It also ensure that if a mutation were to occur, it would only be
replicated on one of the two new strands.
c. Can mutate.
The only source of variability in DNA is mutations. Mutation can lead to
the formation of new alleles which if selected for by the natural selection
process can result in evolution.
7. What is (are) the role(s) of phospho-diester bonds in DNA structure?
What is (are) the role(s) of hydrogen bonds in DNA structure? What is
(are) the role(s) of hydrophobic interactions in DNA structure?
Phospho-diester bonds form between the 5’ phosphate group on one sugar and the
3’ OH group on the next sugar, they form the sugar-phosphate backbone of DNA and
Hydrogen bonds help in base pairing. A binds with T with 2 hydrogen bonds, C binds
with G with 3 hydrogen bonds. Hydrogen bonds also help stabilize the molecule by
formind hydrogen bonds with different molecules.
Hydrophobic interactions are non-polar Vander Waal interactions. They are
temporary and are formed by small dipole moments that occur due to the random
movement and distribution of electrons. They help stabilize DNA structure by forcing
the bases to join inwards away from the polar water molecules.
8. What noncovalent interactions are involved in maintaining the double-