Chapter 2 Molecular and Cellular Biology: Genomics

Question 1

What are the four bases of DNA (and which two are purines vs pyrimidines)

Answer 1

Purines:

Adenine

Guanine

Pyrimidines:

Cytosine

Thymine

Question 2

Which DNA bases bind to each other and how many hydrogen bonds are there in each pair?

Answer 2

Adenine - Thymine (two hydrogen bonds)

Guanine - Cytosine (three hydrogen bonds)

= “Watson-Crick rules” that those pairs bind to each other

Question 3

List three ways in which RNA differs from DNA.

Answer 3

1. Base pairs linked by ribose rather than deoxyribose (hence RiboNucleic Acid vs Deoxy-riboNucleic Acid)
2. RNA is single stranded
3. Thymine base is replaced by uracil.

RNA more susceptible to degradation by nucleases.

Question 4

How many chromosomes do dogs and cats have?

Answer 4

Dogs 39 chromosomes

Cats 20 chromosomes

(Humans 23 chromosomes)

Question 5

What is chromatin?

Answer 5

Condensed complex of DNA + protein that makes up the chromosomes in the eukaryotic nucleus

Question 6

What does the “central dogma of molecular biology” state?

Answer 6

That DNA can be copied to DNA (DNA replication), and that DNA can be copied to messenger RNA (mRNA) (transcription), and that proteins can be synthesized using the information in messenger mRNA as a template (translation), but that the information cannot be transferred back from protein to nucleic acid, or from RNA to DNA

Process:

• Transcription
• Splicing
• Translation

Re Figure: The central dogma of molecular biology. Genomic DNA (gDNA) is transcribed to messenger RNA (mRNA), starting at the first exon (E1), after the initiation of transcription. The whole gene sequence, not including the promoter region (P), is transcribed before splicing removes the introns (I). Translation of the mature mRNA sequence produces the protein

Question 7

Which enzyme mediates DNA trascription?

Answer 7

RNA polymerase

Question 8

Whats are the terms for coding vs non-coding sections of genomic DNA?

Answer 8

Exons (=coding) and introns (=non-coding)

Question 9

What is the term used for the base triplet upon which an amino acid is determined?

Answer 9

Codon

Question 10

What is the specific RNA base triplet (i.e. codon) that signifies the start and give an example of a stop codon (there are 3 in total)

Answer 10

Start = AUG

Stop = UAA, UAG, UGA

Question 11

What is a haploid

Answer 11

Half of usual number of chromosomes i.e. after meiosis

Question 12

There are exceptions to central dogma meaning DNA can begenerated from RNA. What is the name of the enzyme responsibe?

Answer 12

Reverse transcriptase

Question 13

What are transcription units?

Answer 13

The segments of DNA sequence transcribed into mRNA (they are irregularly spaced along the DNA sequence).

These units act as templates for the synthesis of RNA by RNA polymerases. The position of the transcription unit and the start of the gene are identified by short specific sequences upstream of the coding sequence of the gene collectively termed the promoter. The promoter sequences are bound by transcription factors (also termed DNA binding factors), which are proteins designed to bind specific DNA sequences. Their action is to promote (an activator) or block (a repressor) the recruitment of RNA polymerase to the gene in question.

They represent excellent targets to manipulate healthy and diseased cells, e.g. tamoxifen

Question 14

What is teratogensesis?

Answer 14

Interference by exogenous factors in normal embryologic development

Question 15

What is the genome?

Answer 15

Genetric sequence on one set of chromosomes

Question 16

What is a missense mutation and what is a non-sense mutation?

Answer 16

Mis-sense mutation = change in amino acid codon, which may alter protein activity

Non-sense mutation = Normal amino acid codon replaced with stop codon e.g. MDR1 gene mutation causing ivermectin toxicity

Question 17

What is the most common type of genetic mutation?

Answer 17

Missense/nonsense mutations = 59% of all mutations.

(deletions 21%, insertions 7%)

Question 18

Briefly descripe te process of PCR (3 key steps)

Answer 18

1. Denaturation (i.e. heated so DNA splits into single stand)
2. Annealing (cooling to allow primer to bind to target sequence)
3. Elongation/Extension (DNA polymerase synthesises new DNA)

Question 19

What does ELISA stand for?

Answer 19

Enzyme

Linked

Immuno-

Sorbent

Assay

Question 20

What does MALDI-TOF stand for

Answer 20

Matrix

Assisted

Laser

Desorbtion/

Ionization

Time

Of

Flight