Question

dominant vs. recessive traits
learning target: i can explain why only some inherited genes become visibly expressed traits.
do now
what combination of traits do you have? complete the survey to find out.
widows peak
dimples
brown/black hair
freckles
brown eyes
detached earlobe
why do you think some traits are more common in the class than other traits?

Explanation:

To complete this survey (the "Do Now" activity) and answer the follow - up question, here's what you can do:

Step 1: Conduct the Survey

• For each trait (Widow’s Peak, Dimples, Brown/Black Hair, Freckles, Brown Eyes, Detached Earlobe), ask your classmates (or record your own response if it's a self - survey) whether they have the trait. Mark the number of students who answer "Yes" and "No" in the corresponding columns. Then, for the "Number of students trait" column, you can calculate it as the sum of the "Yes" and "No" responses for each trait (or it might be intended to be the number of students with the trait, i.e., the "Yes" count, depending on the exact meaning of the column header). For example, if 15 students have a Widow’s Peak and 10 do not, the "Number of students trait" (assuming it's the number with the trait) would be 15.

Step 2: Analyze the Trait Frequencies

• After collecting the data, look at which traits have a higher number of students with the trait. Traits that are dominant in the population are more likely to be more common. Dominant traits are expressed when at least one dominant allele is present in the genotype. For example, the allele for Widow’s Peak is dominant (let's say allele \( W \) is dominant and \( w \) is recessive). So, individuals with genotypes \( WW \) or \( Ww \) will have a Widow’s Peak. Recessive traits (like attached earlobes, where the allele \( e \) is recessive and \( E \) is dominant, so only \( ee \) individuals have attached earlobes) are less common because they require two recessive alleles. So, if a trait is dominant, it has a higher chance of being expressed in the population, which can lead to it being more common in the class. Also, the frequency of the alleles in the class population (which is a sample of the larger human population) can affect how common a trait is. If a dominant allele is more prevalent in the class's gene pool, its associated trait will be more common.

Answer:

ing the Question "Why do you think some traits are more common in the class than other traits?"

• Some traits are more common because they are controlled by dominant alleles. Dominant alleles are expressed in the phenotype even when only one copy is present (in heterozygous individuals). So, for example, if the allele for brown eyes (let's assume \( B \) is dominant for brown eyes and \( b \) is recessive for blue eyes) is more common in the class, more students will have brown eyes. Also, the initial genetic makeup of the class (the frequency of different alleles in the students' genotypes) plays a role. If a large proportion of students have at least one dominant allele for a particular trait, that trait will be more common. Recessive traits are less common because they need two recessive alleles to be expressed, so they are only seen when both parents pass on the recessive allele, which is less likely if the recessive allele is not very common in the population.

If we assume we have collected the following sample data (just for illustration purposes):

Trait	Yes	No	Number of students trait (Yes)
Dimples	9	11	9
Brown/Black Hair	18	2	18
Freckles	7	13	7
Brown Eyes	16	4	16
Detached Earlobe	14	6	14

From this data, traits like Brown/Black Hair, Brown Eyes, and Widow’s Peak (to some extent) are more common. This is likely because the alleles for these traits are dominant and/or more prevalent in the class's gene pool. For example, the allele for brown hair and brown eyes are often dominant and relatively common in many human populations, so in a class, we would expect to see more students with these traits.

If you want to fill in the table with actual data, you need to conduct the survey in your class.