GENE3734 Semester TEST 2 Questions

SEMESTER TEST 2 QUESTIONS
POSSIBLE QUESTIONS AND ANSWERS

1.1. Discuss the variations on Mendelian inheritance patterns. (3)
Any 3, with correct definitions:
- Incomplete dominance
- Co-dominance
- Epigenetics
- Y-chromosome inheritance
- Mitochondrial Inheritance

1.2. Discuss the threshold model by using an example. (3)
Any 2, plus appropriate example.
- Discontinuous variation  discrete classes
- Degree of relatedness can increase incidence
- Additive genetic and environmental influences
- Crossing over threshold, fall into affected class
- E.g. Schizophrenia (predisposing additive genes, plus traumatic environmental influence). 2


1.3. Discuss the sources of genetic variation to a phenotype. (3)
Any 3, plus correct definitions:
- Mutations
- Silent / synonymous
- Missense / Nonsynonymous
- Nonsense / Null mutations
- Indels
- Frameshift
- Lethal mutations
- Hypomorphic mutations
- Hypermorphic mutations

1.4. In a homogenous population, a percentage of individuals show the same phenotype. This is an
example of: (1)
a. Pleiotropy
b. Inbreeding
c. Penetrance
d. Expressivity

1.2. Name and define the forms of inheritance that does not follow Mendelian principles. (4)
List & define any 4:
 Incomplete dominance
 Co-dominance
 Epigenetics
 Complex / Poligenic / Multifactorial
 Epistasis
 Pleiotropy

,  GEC / GEI
 Y-chromosome / Mitochondrial
 Genomic imprinting

1.3. Explain how additive and interactive genetic mechanisms work by applying it to the Gene-
Environment Correlation and Gene-Environment Interaction. Make use of examples. (5)
 GEC = additive  genes for IQ + studying more = higher IQ
 GEI = interactive  alcoholism genes + alcohol = alcoholic (both necessary for phenotype!)

1.4. Discuss the evolutionary significance of mutations. (3)
 Define mutation
 Adaptation to environment
 Natural selection
 Example

2.1. Explain how genetic engineering works, as well as its application. (4)
Change genes in living cell by putting desired gene in by means of viral vector
• Somatic
• Targets the genes in specific organs and tissues of the body of a single existing person
without affecting genes in their gametes.
• Still under trial
• Germline
• Targets the gametes, or very early embryos.
• Alterations affect every cell in the body of the resulting individual, and are passed on to all
future generations.
• Banned in most countries.


2.2. Discuss additive and interactive genetic mechanisms. (6)
Additive:
- Accumulation of genetic and/or environmental influenced on a phenotype, increasing the severity
of the disease or disorder
- Co-dominance and Incomplete dominance
- Intermediate phenotypes
- Gene-environment correlation

Interactive:
- Dependence between genes and/or environmental influences for the manifestation of a phenotype
- Epistasis and Dominance
- Masking of one gene or allele by another gene or allele
- Gene-environment Interaction


2.3. Explain how epigenetics can contribute to penetrance and expressivity. (8)
- Epigenetics: Change in phenotypic expression with no change to DNA sequence
- Penetrance: Percentage of individuals sharing a genotype displaying the phenotype.  DNA
methylation.