Genes, Population and Ecosystems

Question 1

What is epistasis?

Answer 1

The expression of a gene which mutes/silences the expression of the other
(Think of the yellow and black Labrador dogs!)

Question 2

What is co-dominant alleles?

Answer 2

When both alleles are dominant therefore expression is phenotypical mixture (both alleles are expressed)
Think of red+white cows (determines colour of fur of cow) or blood groups (determines the antigens available on the surface of the blood cells)

Question 3

Monohybrid Inheritance

What is it? And the definitions of the terms associated with it?

Answer 3

Inheritance of one gene at a time
Homozygous - same AA, aa
recessive - requires two to be expressed
Dominant - is always expressed
Heterozygous - Aa (two alleles, dominant allele expressed)

Question 4

What is dihybrid inheritance? What is a typical phenotopic ratio?

Answer 4

Inheritance of two genes
eg: pea colour and shape (yellow/green , smooth/wrinkled)
YY, Yy = yellow
yy= green
RR, Rr = wrinkled
rr= smooth, rounded

9:3:3:1

Question 5

What is autosomal linkage?

Answer 5

When two genes are located (their locus) is on one chromosome, and are therefore often inherited together.
the closer their locus is, the more likely they are inherited together.
This is not considered in a traditional punnet square

Question 6

What is sex linkage

Answer 6

When a gene is linked/ locus is on a sex chromosome

Think of the calico cats! Why is it incredibly rare to get a male calico (tortoise shell) cat
or male linked red-green colourblindness
- males only have one X chromosome, therefore fertilised cell with female carrier means X^r Y therefore only recessive allele expressed

Question 7

What is multiple alleles?

Answer 7

When there are more than 2 different alleles (alleles = versions of a gene)

Question 8

Mark release & recapture

• What is it?
• What does it measure
• How is it done?
• Any assumptions in the experiment?

Answer 8

• a practical method of measurement
• measures a rough estimate of a population
• 1. Set ethical trap in location. 2. Derive sample. 3. Count mark ethically, release. 4. Wait for a period of time and reset traps. 5. Derive next sample, counting those who were recaptured. 6. Repeat over 30x times and average results.
• Assumption: no death, birth or migration of an individual within the species has occurred.
• Ethical traps for moving organisms (animals), quadrants for plants