Chapter 5.6 Polygenetic Inheritance ✓

Question 1

Define polygenetic inheritance

Answer 1

The inheritance of more than one gene that affects the inheritance of a single characteristic

Question 2

Define polygene

Answer 2

A gene whose alleles have a small, additive effect of a phenotype

Question 3

What is an example of polygenetic inheritance and why?

Answer 3

Human height is a polygenetic because multiple genes are involved, polygenic traits do not follow the patterns of Mendelian inheritance

Question 4

Define continous variation

Answer 4

Variation in a phenotype characteristic that shows a smooth range

Question 5

Draw a table and write down the difference between continuous and discontinuous variation.
-Type of inheritance
-Cause
-Description
-Type of graphical representation
-Examples

Answer 5

Continuous variation
-Type of inheritance: Polygenetic (multiple alleles for each gene and several genes)
-Cause: genetic and environmental factors
-Description: Variation shows gradual changes from one trait to another. Differences are slight, along a continuum.
-Type of graphical representation: Histogram
-Examples: height, weight, skin colour

Discontinuous variation
-Type of inheritance: Single-gene inheritance (but multiple alleles)
-Cause: Genetic factors
-Description: Variation that shows clear and discrete changes between traits. There is no intermediate form
-Type of graphical representation: Bar graph
-Examples: Ability or inability to tongue roll; attached or detached earlobes; blood groups A, B, AB and O.

Question 6

Distinguish between multiple alleles and polygenes

Answer 6

-Multiple alleles is when there are more than two versions of any one gene.
-Polygenic inheritance is when a trait is controlled by more than one gene.
-Multiple alleles involve the same DNA strand, whereas polygenic inheritance involves multiple DNA strands.

Question 7

Explain why some phenotypes, such as height, can show continuous variation yet others show discontinuous variation

Answer 7

-Some phenotypes, like height, show continuous variation because they are influenced by multiple genes (polygenetic inheritance) and environmental factors, resulting in a wide range of possible values.
-In contrast, phenotypes with discontinuous variation are controlled by a single gene with distinct alleles, resulting in distinct categories (e.g. blood type)

Question 8

Provide a human and non-human example of polygenetic inheritance controlling a trait.

Answer 8

Humans
-Skin colour
-Height
-Eye colour
-Hair colour
Non-human
-Coat colours in dogs
-Grain colour in wheat
-Size and colour of fruits e.g. tomatoes, apples.