Quantitative genetics

Question 1

What is discontinuous variation?

Answer 1

Discrete classes of phenotype
NO intermediates
Follows Mendelian ratios
Simple genetic basis, limited effect of environment

Question 2

What is discrete data?

Answer 2

Can be categorised into a classification

Question 3

What is continuous variation?

Answer 3

Also Quantitative or complex
Phenotypes do not fall into classes
Offspring of intermediate phenotype
Can’t observe Mendelian ratios
Complex genetic basis, plus effect of the environment

Question 4

What are quantitative traits?

Answer 4

Measurable phenotype that depends on the cumulative actions of many genes and the environment. These traits can vary among individuals, over a range, to produce a continuous distribution of phenotypes

Question 5

What is threshold variation?

Answer 5

appears like a discontinuous trait BUT is caused by a continuous distribution

• distribution is called liability
• phenotype depends on critical threshold
• no simple segregation in families

Question 6

What is the normal distribution?

Answer 6

Fully described by mean and standard deviation (or variance= sd2)
Mean = centre
Standard deviation and variance are measures of spread

Question 7

How many genotypes for two alleles?

Answer 7

3

Question 8

How are quantitative traits influenced?

Answer 8

By both the environment and genetics, combined effects of several polymorphic loci result in a nearly continuous distribution

Question 9

Why might you be more similar in height to a sibling than to a random stranger?

Answer 9

Due to:
Nature: Have some of the same alleles from parents
Nurture: grew up in the same environment