Week 9

Question 1

Imcomplete Domiance/Semi-domiance

Answer 1

ncomplete dominance is when a dominant allele does not completely
mask the effects of a recessive allele, and the organism ’s resulting physical
appearance shows a ‘blending’ of both alleles.

Question 2

Codominance

Answer 2

• In codominance, both alleles can be seen in the phenotype at the same time.
• Instead of being uniformly pink, a flower with red and white alleles that show
  codominance will have patches of red and patches of white.
• As with incomplete dominance, the F2 generation from heterozygous plants will
  have a ratio of 1:2:1 of red, spotted, and white flowers.
• Codominance is also shown in humans with AB blood type; the alleles for blood
  types A and B are both expressed.

Question 3

Sex linkage

Answer 3

• Sex linked genes are genes that are in the sex chromosomes and that are
  therefore inherited differently between males and females.
• In mammals, where the female has two X chromosomes (XX) and the male has
  one X and one Y chromosome (XY)
• Sex-linked genes on the X-chromosome are X-linked genes. Genes on the Ychromosome are Y-linked.
• Females have two X-chromosomes. Males have one X and one Y-chromosome.
• With both an X and a Y-chromosome, males inherit both X and Y-linked traits,
  while females only inherit X-linked traits
• Common examples of sex-linked genes are those that code for colorblindness or
  those that code for hemophilia (inability to make blood clots) in humans

Question 4

Hemizygous

Answer 4

Hemizygous means having only a single copy of a gene
instead of the customary two copies. All the genes on the
single X chromosome in the male are ‘hemizygous.