Multicellular Organisms - Variation and Inheritance

Question 1

• What is a phenotype?
• What is a genotype?

Answer 1

• Observable characteristics of an organism
• Combination of alleles an organism inherits from its parents.

Question 2

Describe Discrete variation in terms of:
* Definition
* Controlled by
* Type of Inheritance

Answer 2

• Characteristics with phenotypes that fall into distinct categories
• Single gene
• Single gene inheritance

CAN BE SHOWN IN A BAR CHART

Question 3

Describe Continuous variation in terms of:
* Definition
* Controlled by
* Type of Inheritance

Answer 3

• Characteristics that have phenotypes showing a range of values
• Several genes
• Polygenic inheritance

CAN BE SHOWN USING A HISTOGRAPH

Question 4

• Define the term ‘Homozygous’
• Define the term ‘Heterozygous’

Answer 4

• Homozygous - Genotype in which the two alleles for a characteristic are identical.
• Heterozygous - Genotype in which the two alleles for a characteristic are different.

Question 5

What is a Monohybrid cross?

Answer 5

Way of showing how a specific characteristic is passed from parents to offspring.

Question 6

• What is a Punnet Square?
• Give 2 reasons as to why predicted phenotype ratios not always achieved?

Answer 6

• Grid that shows the possible combinations of alleles that can result at fertilisation.
• Fertilisation is a random process, sample sizes not big enough

Question 7

• What is a dominant allele?
• What is a recessive allele?

Answer 7

• Allele that always expresses itself whether it is partnered by a recessive allele or by another like itself.
• Allele that is suppressed in the presence of the dominant variant and will remain dormant unless paired with another recessive gene.