Learning Outcomes - Week 1 - Introduction to Molecular Biology & Bioinformatics

Question 1

DNA:
–Its basic structure
–Its building blocks
–Where we can find it in organisms
–what is it packaged into/how is it packaged?

Answer 1

• DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix.
• Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) or thymine (T).
• Is found in the nucleus of eukaryotes and in the cytoplasm (in the plasmid) of prokaryotes
• See image

Question 2

Chromosomes:
–Basic structure / ’anatomy’

Answer 2

Question 3

The concept of ‘information flow’ from DNA to RNA to protein - draw

Answer 3

Question 4

Define replication

Answer 4

DNA is unwound and copied on both strands in opposing directions (DNA polymerase does copying - on 3’ to 5’ strand it, just like the other strand, copies in reverse - needs to stop and move back to before fresh copy as it has nothing left to copy - called okizaki fragments which are then ‘stitched’ back together at end by DNA ligase)

Question 5

Define transcription

Answer 5

• Transcription is the first step in gene expression. It involves copying a gene’s DNA sequence to make an RNA molecule.
• Transcription is performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand (using a DNA strand as a template).
• Transcription has three stages: initiation, elongation, and termination.
• In eukaryotes, RNA molecules must be processed after transcription: they are spliced and have a 5’ cap and poly-A tail put on their ends.
• Transcription is controlled separately for each gene in your genome.

Question 6

Define translation

Answer 6

Code in mRNA is used by the ribosome in the cytoplasm to ‘build’ amino acid chains from amino acids that tRNA get for the ribosome to use

Question 7

Define intron

Answer 7

a segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.

Question 8

Define exon

Answer 8

a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.

Question 9

Define poly-a tail

Answer 9

A long stretch of (about ten to 200 or more) adenine nucleotides added to the “tail” or 3′ end of the pre-mRNA via the process called polyadenylation catalyzed by the enzyme, polyadenylate polymerase (PAP).

Question 10

Define amino acids

Answer 10

a simple organic compound containing both a carboxyl (—COOH) and an amino (—NH2) group.

Question 11

Define pre-protein

Answer 11

A polypeptide chain that is in the process of growing into a protein by the addition of successive amino acid moieties

Question 12

Define signal peptide

Answer 12

A signal peptide is a short peptide (usually 16-30 amino acids long) present at the N-terminus

Acts like a postage stamp on a letter, targeting the protein for secretion or for relocation to different organelles within the cell

Question 13

Define post-translational modification, where does it take place, and give examples

Answer 13

Post-translational modifications take place in the ER and include folding, glycosylation, multimeric protein assembly and proteolytic cleavage leading to protein maturation and activation. They take place as soon as the growing peptide emerges in the ER and is exposed to modifying enzymes.

Phosphorylation.
Acetylation.
Hydroxylation.
Methylation.

Question 14

In-depth understanding of gene structure (e.g., promoter, splicing, introns,
exons, UTRs, CDS, difference between transcription and translation)

Answer 14

Question 15

Answer 15

c

Question 16

Which nucleotides are pyrimidines and which nucleotides are purines?

(a) Pyrimidines: C, A. Purines: T, G.
(b) Pyrimidines: C, T. Purines: A, G
(c) Pyrimidines: A, G. Purines: C, T.
(d) Pyrimidines: C, G. Purines: A, T.

Answer 16

B