Week 2 (Chapters 1.4, 1.5, 1.7, 1.8)

Question 1

What are the properties of prokaryotes?

Answer 1

• Spherical, rodlike or corkscrew-shaped
• Small
• Contain a tough protective coat (or cell wall) surrounding the plasma membrane which encloses a single compartment containing the cytoplasm and the DNA
• Cells reproduce rapidly by dividing in two

Question 2

What are the names of the two domains prokaryotes can be divided into?

Answer 2

Archaea & Bacteria

Question 3

The distinction between prokaryotic and eukaryotic cells is based on _________________

Answer 3

Structural complexity

Question 4

What is the name of the species that live in extremely inhospitable environments?

Answer 4

Extremophiles

Question 5

What are some examples of extremophiles?

Answer 5

• Methanogens (convert CO2 and H2 gases into methane CH4)
• Halophiles (live in extremely salty environments)
• Acidophiles (acid-loving prokaryotes)
• Thermophiles (live at very high temperatures)

Question 6

_________ are the only known prokaryotes to lack a cell wall and to contain a genome with fewer than 500 genes

Answer 6

Mycoplasma

Question 7

What are the properties of Cyanobacteria?

Answer 7

• The most complex prokaryotes
• Contain elaborate arrays of cytoplasmic membranes where photosynthesis occurs
• Photosynthesis occurs by splitting water molecules

Question 8

What are the characteristics of Protists?

Answer 8

• Eukaryotic (contain a nucleus)
• Most have mitochondria
• Can be parasites
• All prefer aquatic or moist environments

Question 9

What is the process by which specialised cells are formed?

Answer 9

Differentiation

Question 10

What are the model organisms and their applications?

Answer 10

• Bacterium (E.Coli) - Mechanisms of replication, transcription and translation
• Budding Yeast - Identification of genes through the use of mutants
• A flowering plant - An unusually small genome, a rapid generation time
• Nematode - Easily cultured, kept alive in a frozen state, transparent cell wall, short generation time and genetic analysis
• Fruit fly - genetics & development study
• House mouse - easily lab bred and able to accept human tissue grafts that are not rejected

Question 11

What are the health conditions related to genetic changes in MLH1 gene?

Answer 11

Lynch syndrome (also known as hereditary nonpolyposis colorectal cancer (HNPCC)) and Ovarian cancer

Question 12

Gene transfer approach using recombinant DNA technology is being used to study human neurodegenerative disorders, what are some examples?

Answer 12

Huntington disease
Machado-Joseph disease
Myotonic dystrophy
Alzheimer disease

Question 13

What is “Huntington disease” and what causes it?

Answer 13

Huntington disease is a progressive brain disorder that causes uncontrolled movements, emotional problems and loss of thinking (cognition). Individuals have trouble walking, speaking, swallowing, thinking and reasoning.

Mutations in the HTT gene cause Huntington disease. The HTT gene provides instructions for making a protein called huntingtin and is located on chromosome 4 (short arm)

Question 14

What is “Machado-Joseph” disease and what causes it?

Answer 14

Machado-Joseph disease is a condition characterised by progressive problems with movement.

Symptoms:
- Problems with coordination and balance (ataxia)
- Speech difficulties, uncontrolled muscle tensing (dystonia), muscle stiffness (spasticity), rigidity, tremors, bulging eyes, double vision
- Restless leg syndrome (numbness or tingling in the legs accompanied by an urge to move the legs to stop the sensations) and REM sleep behaviour disorder

It results from a mutation in the ATXN3 gene known as ‘trinucleotide repeat expansion’ which increases the length of the repeated CAG segment. This is on the long (q) arm of chromosome 14.

Question 15

What is ‘Myotonic dystrophy’ and what causes it?

Answer 15

Myotonic dystrophy is characterised by progressive muscle wasting and weakness. Individuals have prolonged muscle contractions (myotonia) and are not able to relax certain muscles after use.

Type 1 is caused by mutations in the DMPK gene and appears to be important for the correct functioning of cells in the heart, brain and skeletal muscles and may play a role in communication within cells. Type 2 is caused by mutations in the CNBP gene found in heart and skeletal muscles where is helps regulate the function of other genes.

DMPK gene is located on the long (q) arm of chromosome 19. CNBP gene is located on the long (q) arm of chromosome 3.

Question 16

What is the difference between Type 1 and Type 2 Myotonic dystrophy?

Answer 16

Type 1 affects the lower legs, hands, neck and face whereas Type 2 affects the muscles of the neck, shoulders, elbows and hips.

Question 17

The mutations of which genes are associated with Alzheimer Disease?

Answer 17

• B-amyloid precursor protein gene (APP - 21q)
• Presenilin 1 gene (PSEN1 - 14q)
• Presenilin 2 gene (PSEN2 - 1q)

Question 18

Describe the cause of Alzheimer disease

Answer 18

The mutated genes cause large amounts of amyloid beta peptide to be produced in the brain which build up in the brain to form amyloid plaques. The buildup of toxic amyloid beta peptide and amyloid plaques may lead to the death of nerve cells and the progressive signs and symptoms of AD.

Question 19

What does IDDM stand for?

Answer 19

Insulin-dependent diabetes mellitus

Question 19

What are the stages of Type 1 diabetes?

Answer 19

1. Autoreactive T cells destroy the islet cells of the pancreas
2. This causes decreased insulin in the blood vessels
3. Increased glucose due to low insulin
4. Muscle is unable to use glucose due to low insulin

Alternative: Glycogen and protein breakdown causing ketone-acidosis that leads to muscle being unable to use glucose due to low insulin

Question 19

What are the stages of Type 2 diabetes?

Answer 19

1. The pancreas secretes sufficient insulin in the blood stream
2. Increased glucose in the blood stream
3. Antibodies to insulin receptors interfere with insulin binding
4. Muscle is unable to use glucose due to insulin resistance

Alternative: Obesity, inheritance & other factors lead to insulin resistance which leads to muscle unable to use glucose due to insulin resistance

Question 20

In type 2 diabetes, what directly prevents cells from intaking insulin from the blood stream?

Answer 20

Antibodies to insulin receptors interfere with the insulin binding process which play a pathogenic role

Question 21

What causes IDDM?

Answer 21

Autoimmune destruction of islet B cells in the pancreas causes deficiency in insulin production which disrupts the regulation of anabolism and catabolism causing metabolic changes similar to those shown in starvation. This usually results from a combination of genetic susceptibility and subsequent environmental insult and very rarely from just one of the two.

Question 22

What are the two units most commonly used to measure cells?

Answer 22

micrometer and nanometer

Question 23

What are the main symptoms of diabetes?

Answer 23

• Polydipsia (excessive thirst)
• Polyphagia (excessive food intake)
• Lethargy (tiredness)
• Stupor (unresponsiveness)
• Blurred vision
• Weight loss
• Acetone breath
• Kussmaul breathing
• Nausea
• Vomiting
• Abdominal pain
• Polyuria (excessive urination)
• Glycosuria (presence of reducing sugars in the urine)

Question 23

What are the sizes of some cell components and what equipment do you need to see them?

Answer 23

Electron Microscope:
DNA molecule - 2nm
Myoglobin - 4.5nm
Ribosome - 30nm
HIV - 100nm
Light Microscope:
Bacterium - 1um
Mitochondria - 2um
Chloroplast - 8um
Lymphocyte - 12um
Epithelial cell - 30um
Human eye:
Paramecium - 1.5mm
Frog egg - 2mm

Question 23

What is the structure of a virus?

Answer 23

• Protective shell (Capsid) is made of many identical protein subunits which protects the genetic material, is symmetrically organised and is 50% of the weight
• Envelope is a lipid containing membrane that surrounds some virus particles that is acquired during viral maturation