Session 12 ILOs - Genotype, Phenotype and Inheritance

Question 1

Clearly define genotype and phenotype

Answer 1

Genotype: the DNA sequence of an organism that codes for the specific characteristics seen (phenotype)

Phenotype: the observable characteristics of an individual that are directly influenced by the genotype AND/OR their environment

Question 2

Clearly define gene and allele

Answer 2

Gene: a specific DNA sequence at a specific chromosomal location that carries the code for a polypeptide or untranslated RNA

Allele: a version/variant of a gene

Question 3

Describe and explain monogenic (Mendelian) inheritance patterns and list the types of Mendelian inheritance patterns (both autosomal or sex-linked)

Answer 3

Mendelian inheritance pattern, for any given phenotype, an individual inherits one gene from each parent so that the individual has a pairing of two genes - only looks at 1 gene

Types of mendelian inheritance patterns:

1. Autosomal domniant
2. Autosomal recessive
3. X-linked dominant
4. X-linked recessive
5. Y-linked

Question 4

Describe mitochondrial inheritance

Answer 4

Mitochondrial inheritance - where the mitochondrial DNA is passed on through the mother only. If the mother’s mitochondrial DNA is affected, all her children will be affected. If the father’s mitochondrial DNA is normal, then all the children will not be affected!

Question 5

Explain and describe in general terms polygenic and multifactorial inheritance

Answer 5

Polygenic/multifactorial inheritance is more complicated than Mendelian inheritance.

Polygenic inheritance involves complex traits that are determined by many genes at different loci, without the influence of the environment
Whereas, Multifactorial inheritance describes a trait whose manifestations are determined by two or more genes, accompanied by environmental factors

EXAMPLE: Albinism is an example of polygenic inheritance and is inherited in a recessive manner and involves multiple genes therefore the ratio of gametes is not 1:1:1:1