can u help me with this qs
pure breeding white budgies were crossed with pure breeding yellow and green budgies. all the F1 offspring were yellow and green. the F1 was then testcrossed with pure breeding white budgies, and the offspring were as follows:
Green and Yellow 25
White 27
Blue and White 23
Yellow and White 24
Explain these results using symbols and statistics. Provide the genotypes of the parents, F1 and progeny from the testcross and
corresponding phenotypes (5 marks)
To explain the results, we need to look at the genotypes of the parents, F1, and progeny. Let's assign the symbols G for green, Y for yellow, W for white, and B for blue.
1. Pure breeding white budgies crossed with pure breeding yellow and green budgies:
White (WW) x Yellow (YY/GG)
Gametes: W, Y/Y, G
The F1 offspring are all yellow (YG). This means that the genotype of the F1 would be YG, which represents a heterozygous yellow budgie.
2. F1 testcrossed with pure breeding white budgies:
Testcross: F1 (YG) x White (WW)
Gametes: Y, G/W
The expected phenotypic ratios can be derived using Punnett square analysis.
Possible genotypes and corresponding phenotypes:
- Yellow (YY) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
- Yellow (YG) x White (WW)
- Gametes: Y, W
- Offspring: Yellow (YW) - expected to be yellow
- Yellow (YG) x White (WW)
- Gametes: G, W
- Offspring: Green (GW) - expected to be green
Now, let's summarize the observed phenotype frequencies from the testcross:
Green and Yellow: 25
White: 27
Blue and White: 23
Yellow and White: 24
From the expected phenotypic ratios, we can see that the observed frequencies match our expectations. The result indicates that the white budgies (WW) can be the pure-breeding white parents, the yellow and green budgies (YY/GG) can be pure-breeding yellow and green parents, and the F1 (YG) can be the first-generation offspring resulting from the white and yellow/green cross.
Therefore, the genotypes of the parents are WW (white), YY/GG (yellow or green), the F1 is YG (yellow and green), and the genotypes of the progeny from the testcross are YW (yellow and white), GW (green and white), and YW (yellow and white).
In order to explain the results and determine the genotypes of the parents, F1, and the progeny from the testcross, we need to understand the principles of inheritance and the patterns of genetic inheritance in budgies.
First, let's assign symbols to represent the different alleles:
- W: represents the allele for white feathers
- Y: represents the allele for yellow feathers
- G: represents the allele for green feathers
- B: represents the allele for blue feathers
Now, let's analyze the given information step by step:
1. Pure breeding white budgies were crossed with pure breeding yellow and green budgies.
Based on this statement, we can conclude that the white budgies are homozygous for the white allele (WW), and the yellow and green budgies are either homozygous for their respective color alleles (YY or GG), or they are heterozygous (YG).
Therefore, we can represent the genotypes of the parents as follows:
- White budgies: WW
- Yellow/green budgies: YY or GG or YG
2. All the F1 offspring were yellow and green.
Since all F1 offspring were yellow and green, it means that they must have inherited one yellow allele (Y) and one green allele (G) from their parents. This indicates that the yellow and green alleles are both dominant over the white allele.
Therefore, the genotype of the F1 generation can be represented as YG.
3. The F1 was then testcrossed with pure breeding white budgies.
A testcross involves crossing an individual with an unknown genotype (in this case, F1 generation) with an individual with a known homozygous recessive genotype (pure breeding white budgies: WW).
Now, let's analyze the offspring from the testcross:
- Green and Yellow: 25
- White: 27
- Blue and White: 23
- Yellow and White: 24
To determine the genotypes and corresponding phenotypes, we need to consider the possible combinations of alleles that can result from the testcross.
The F1 generation (YG) can produce four possible genotypes:
- YW (yellow feathers, heterozygous for white)
- YY (yellow feathers, homozygous for yellow)
- GW (green feathers, heterozygous for white)
- GG (green feathers, homozygous for green)
Using these genotypes, we can assign colors to each genotype:
- YW: Yellow and White
- YY: Yellow
- GW: Green and White
- GG: Green
Given the number of individuals in each category, we can now determine the genotypes for the testcross progeny:
- Green and Yellow: 25 (GG and YW)
- White: 27 (WW)
- Blue and White: 23 (BW)
- Yellow and White: 24 (YW)
The blue feathers observed in the testcross progeny indicate that there is a blending of the yellow and green alleles, resulting in a blue phenotype. However, the specific genotype for blue feathers cannot be determined without further information.
To summarize:
- Genotypes of parents: White budgies (WW), Yellow/Green budgies (YY or GG or YG)
- Genotype of F1: Yellow and Green (YG)
- Genotypes of testcross progeny: GG, YW, WW, BW, YW
- Corresponding phenotypes: Green, Yellow and White, White, Blue and White, Yellow and White