Genetic Variation
Organizing Data About Expressed Traits
rganizing Data About Expressed Traits Quick Check
In a certain population of rabbits, the ratio of the phenotypes of brown fur and white fur is 1:1. ?What is the frequency of the white fur trait in the rabbit population? (1 ?point)
1%
100%
25%
50%
The Correct Answer and Explanation is:
Correct Answer: 50%
Explanation:
In genetics, a phenotype refers to the observable characteristics or traits of an organism, such as fur color in rabbits. When organizing data about expressed traits, especially in a population, we often use ratios and percentages to describe the frequency of each phenotype.
In this scenario, we are told that the ratio of brown fur to white fur in a rabbit population is 1:1. This means for every 1 brown-furred rabbit, there is 1 white-furred rabbit.
Let’s break this down numerically:
- Suppose there are 2 rabbits: one with brown fur and one with white fur.
- The total number of rabbits is 2.
- The number of white-furred rabbits is 1.
To calculate the frequency (or percentage) of rabbits with white fur, we use the formula: Frequency (%)=(Number of white-fur rabbitsTotal number of rabbits)×100\text{Frequency (\%)} = \left( \frac{\text{Number of white-fur rabbits}}{\text{Total number of rabbits}} \right) \times 100 =(12)×100=50%= \left( \frac{1}{2} \right) \times 100 = 50\%
So, 50% of the rabbit population has white fur.
This 1:1 ratio is often seen in simple Mendelian inheritance when both parents are heterozygous (carrying one dominant and one recessive allele). For example:
- B = dominant allele for brown fur
- b = recessive allele for white fur
When two Bb (heterozygous) rabbits are crossed, the offspring have these genotype possibilities:
- 25% BB (brown fur)
- 50% Bb (brown fur)
- 25% bb (white fur)
However, if the ratio of phenotypes is already stated as 1:1, it may also suggest a test cross between a heterozygous (Bb) and a homozygous recessive (bb) rabbit. This cross would produce:
- 50% Bb (brown fur)
- 50% bb (white fur)
Hence, the 1:1 ratio supports that 50% of the rabbits have white fur.