Q: A researcher wants to estimate the proportion of West African ancestry in a new sample using the same approach as the Four Cities Study. Which formula would best represent the calculation of ancestry proportion using AIMs and STRUCTURE software?

$$p_{WA} = \sum_{i=1}^{n} q_{i,WA}$$,\text{ where } q_{i,WA} \text{ is the estimated proportion for individual } i$

Question 1

Which of the following best explains why skin color is considered an imprecise proxy for genetic ancestry in biomedical research, according to the Four Cities Study?

Accepted Answer

Skin color does not capture the heterogeneity in ancestral genomic contributions within populations.

Question 2

In the Four Cities Study, which city’s participants had the highest average inner arm melanin index, indicating the darkest constitutive skin pigmentation?

Accepted Answer

Cincinnati, Ohio

Question 3

Which of the following statements about the relationship between skin color, sex, and marital status is supported by the study’s findings?

Accepted Answer

Men with darker skin and women with lighter skin were more likely to be married.

Question 4

Which method was used to estimate proportions of West African, Native American, and European genetic ancestry in the study participants?

Accepted Answer

A supervised model-based clustering algorithm using ancestry informative markers (AIMs)

Question 5

Based on the study, which group was most likely to have higher West African ancestry and darker skin pigmentation?

Accepted Answer

Participants who self-identified as African American

Question 6

Which of the following best describes the relationship between occupation, skin color, and ancestry found in the study?

Accepted Answer

Skilled and professional individuals were darker and had more West African ancestry than unskilled individuals.

Question 7

Which historical event is most closely associated with the presence of Native American ancestry among Black residents in Oklahoma?

Accepted Answer

The Trail of Tears

Question 8

Why is it important for biomedical research to consider both genetic ancestry and local historical/social context, rather than relying solely on skin pigmentation?

Accepted Answer

Because genetic ancestry and social context can influence disease risk and social outcomes independently of skin color.

Question 9

Which statistical method was used to analyze the relationship between skin color and socioeconomic status (SES) in the study?

Accepted Answer

Multinomial logistic regression

Question 10

A researcher wants to estimate the proportion of West African ancestry in a new sample using the same approach as the Four Cities Study. Which formula would best represent the calculation of ancestry proportion using AIMs and STRUCTURE software?

Accepted Answer

$$p_{WA} = \sum_{i=1}^{n} q_{i,WA}$$,	ext{ where } q_{i,WA} 	ext{ is the estimated proportion for individual } i$

Question 11

Which of the following findings from the study challenges the common assumption that lighter skin is always associated with higher social attainment?

Accepted Answer

Darker skinned participants in some cities were more educated and held skilled or professional jobs.

Question 12

Which of the following best describes the relationship between self-identified race/ethnicity (SIRE) and genetic ancestry in the study?

Accepted Answer

SIRE is largely based on skin color and may not precisely reflect genetic ancestry.

Question 13

If a participant from New York self-identifies as 'mixed,' what is the most likely pattern of genetic ancestry based on the study’s findings?

Accepted Answer

More European than Native American ancestry

Question 14

Which of the following is a plausible explanation for the higher proportion of West African ancestry among participants in Ohio compared to those in New York?

Accepted Answer

Less gene flow (admixture) with Europeans and Native Americans due to historical opposition to ending slavery

Question 15

Which of the following equations best represents the calculation of the melanin index (MI) as used in the study?

Accepted Answer

$$MI = \frac{	ext{Sum of three measurements at a site}}{3}$$

Question 16

A participant has a melanin index of 47 on the inner arm and 0.72 proportion West African ancestry. Based on the study, which occupation category is this participant most likely to belong to?

Accepted Answer

Skilled or Professional

Question 17

Which of the following best summarizes the main conclusion of the Four Cities Study?

Accepted Answer

Black U.S. populations are heterogeneous and should not be treated as a monolithic group in research.

Question 18

Which of the following is a limitation of the Four Cities Study as described in the article?

Accepted Answer

Skin color data was not collected for Oklahoma participants.

Question 19

Which of the following best describes the use of mitochondrial DNA haplogroups in the study?

Accepted Answer

They were used to identify maternal lineages and infer regional ancestry patterns.

Genetic Ancestry, Skin Color, and Social Attainment in U.S. Black Populations: Insights from the Four Cities Study

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