Alleles A and a are located on a pair of metacentric chromosomes. Alleles B and b are located on a pair of acrocentric chromosom
es. A cross is made between individuals having the genotypes Aa Bb and aa bb. Label the gametes of the aa bb parent with the chromosomes carrying the correct alleles.
1 answer:
Answer:
See the second attached image showing the gametes from the parent with the location of the centromere indicating the type of chromosome
Explanation:
According to the position of the centromere, chromosomes can be of 4 types namely:
- Metacentric
- Acrocentric
- Telocentric
- Sub-metacentric
A metacentric chromosome is a chromosome that has no short or long arm. The arms are equal in length with the centromere joining the two sister chromatids located at the center.
Acrocentric chromosomes have unequal arm lengths with the centromere skewed towards one end of the chromosome.
Telocentric chromosomes have their centromeres at one end of the chromosome.
Sub-metacentric chromosomes have unequal arm lengths but the centromere is not as skewed to one end of the chromosome length as found in acrocentric chromosome.
The only possible gamete from <em>aa bb</em> parent is <em>ab</em>. Recall that the allele <em>a </em>is located on a metacentric chromosome while allele <em>b </em>is located on acrocentric chromosome.
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The correct answer is 9:3:3:1
When two homozygotes for two traits cross, the phenotypic ratio of the offspring is 9:3:3:1 ( unless other factors like epistatic interaction change the inheritance model).
In our case, we have two simple traits of seed color and seed shape that follow the Mendelian model of inheritance.
In this dihybrid cross, we have
9/16 of the offspring expressing both dominant traits ( yellow and round seeds)
3/16 expressing one dominant and one recessive trait ( yellow and wrinkled)
3/16 expressing the other dominant and recessive trait (green and round)
1/16 expressing both recessive traits ( green and wrinkled)
When two homozygotes for two traits cross, the phenotypic ratio of the offspring is 9:3:3:1 ( unless other factors like epistatic interaction change the inheritance model).
In our case, we have two simple traits of seed color and seed shape that follow the Mendelian model of inheritance.
In this dihybrid cross, we have
9/16 of the offspring expressing both dominant traits ( yellow and round seeds)
3/16 expressing one dominant and one recessive trait ( yellow and wrinkled)
3/16 expressing the other dominant and recessive trait (green and round)
1/16 expressing both recessive traits ( green and wrinkled)