1
Q
Imcomplete Domiance/Semi-domiance
A
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.
2
Q
Codominance
A
- 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.
3
Q
Sex linkage
A
- 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
4
Q
Hemizygous
A
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.
5
Q
A
