Topic 3: Polygenic Inheritance

Question 1

Define phenotype. (2 points)

Answer 1

1. the observable appearance of a characteristic or organism,
2. as a result of the expression of the alleles present (genotype) and also
   sometimes the environment.

Question 2

The epigenome can be involved, because the environment (eg. a person’s diet, exposure to pollutants), can affect the _________.

Epigenetic markers (the epigenome) can be inherited along with ______.

Answer 2

epigenome

genes

Question 3

Give 3 examples of phenotypes

Answer 3

1. Eye colour (polygenes only)
2. Height (polygenes and environment- diet & health)
3. Human skin colour (polygenes and environment- UV light)

Question 4

Define polygenetic inheritance (2 points)

Answer 4

1. multiple genes for a single characteristic, at more than one locus,
2. which interact in the inheritance of the characteristic to produce a phenotype, giving rise to continuous variation

NOTE: poly = many

Question 5

Key Summary: How does polygenic inheritance lead to continuous variation within a phenotype?
(6 steps)

Answer 5

1. many genes are involved (definition - multiple genes for a single characteristic, at more than one locus)
2. genes interact
3. each gene has a very small effect
4. additive effect of the alleles of many genes produces many different genotypes (the more genes involved, the greater the number of possible genotypes)
5. the effects of environment cause even more variation
6. resulting in a huge continuous range of phenotypes with many intermediates

Question 6

Give 2 examples of characteristics that show continuous variation

Is it:

Genes only OR genes + environment?
One gene OR polygenes (many)?
Discrete groups OR range of values?
Quantitative OR Qualitative data?

Answer 6

1. Human height
2. weight

genes and environment
polygenetic (many)
range
quantitative

Question 7

Give 2 examples of characteristics that show discontinuous variation

Genes only OR genes + environment?
One gene OR polygenes (many)?
Discrete groups OR range of values?
Quantitative OR Qualitative data?

Answer 7

1. Blood group
2. Gender

Genes only
One gene
Groups
Qualitative

Question 8

Human height is controlled partly by ________ - _________

It is also affected by the ___________ – diet, health etc

Human height shows __________ variation.

Answer 8

genotype - polygenes

environment

continuous