Question

A) Which of these groups is known from fossils in both Europe and Africa from 200,000 years ago?

• A. Homo heidelbergensis
• B. Neandertals
• C. Anatomically modern Homo sapiens
• D. Denisovans

B) What did the discovery of Neanderthal DNA in modern human genomes tell us about gene flow as Homo sapiens emerged from Africa?

• A. All of the human variation that exists today was derived from the variation that existed in the population of Homo sapiens that first emerged in Africa; there is no evidence of interbreeding with other hominin populations.
• B. Very little human variation is derived from what was present in the population of Homo sapiens that first emerged in Africa; a significant amount of variation was introduced after interbreeding with Neanderthals and Denisovans.
• C. Human variation is largely derived from what was present in the population of Homo sapiens that first emerged in Africa, but a limited amount of variation has been passed from Neanderthals and Denisovans through interbreeding after Homo sapiens emerged from Africa.
• D. Although DNA extraction techniques continue to improve, there are not enough data to provide conclusive evidence about whether modern humans interbred with Neanderthals.

C) The LCT allele for persistence of lactase until adulthood is today found at high frequency (40-100%) in various populations of Europe, where dairy farming has been practiced for thousands of years. Which of the following is our current understanding of the origins of the allele in Europe.

• A. The allele originated in Europe after hunter-gatherers began keeping dairy cattle and the mutation went to high frequencies quickly under strong selection.
• B. The allele spread from the Near East via farmers who also introduced crops, animals and agricultural technology to Europe around 7,500 years ago.
• C. The allele was present at low frequency in cattle and sheep herding nomads that spread to Europe from the Russian steppe 4,500 years ago.
• D. The allele spread to Europeans via introgression from Neandertals.

D) Which of the following are real limitations of direct-to-consumer percentage ancestry tests? Select all that apply.

A. A SNP may occur at appreciable frequency in multiple geographically distant populations, which can lead to incorrect estimates of trace percentages.
B. The reference populations to which test subjects are compared may fail to include the genetic variation most relevant to the individual being tested and may include misclassified reference individuals.
C. The composition of the reference population varies among companies, which can lead to an individual receiving different estimate from different tests.
D. There are not enough variable SNPs in the human genome to identify individual relatives with certainty.

Answer 1

A) Correct answer: C-Anatomically modern homo sapiens are the fossils found in both Europe and Asia from 200,000 years ago. They are believed to have first emerged out of Africa around 200,000 years ago and then expanded from Africa throughout Europe and Asia.

A. Homo heidelbergensis: This is the extinct species or subspecies of archiac humans in the genus Homo radiated in middle Pleistocene from about 700,000 to 300,000 years ago. They were dispersed throughout Eastern and Southern Africa as well as in Europe.

B. Neandertals: These are the extinct species or subspecies of archiac humans who lived in Eurasia until about 40, 000 years ago. They were hunter-gatherers. They probably were extinct due to competition with immigrating modern humansor due to climate change and diseases.

D. Denisovans: They are the extinct species or subspecies of archiac humans which ranged across Asia during lower and middle Paleolithic 30-14,500 years ago. They lived in a wide variety of habitats such as forests, tundras, mountains and jungles. They had dark skin, eyes and hair and Neandertals-like build and facial features but with larger molars.

B) Correct answer: B. Studies since 2010 have refined the picture of interbreeding between Neandertals, Denisovans and anatomically modern homo sapiens. Interbreeding occured asymmetrically among the ancestors of modern-day humans. Though significant amount of variation were introduced after interbreeding with Neandertals and Denisovans, some of the genes may have been detrimental and selected out. Thus only about 20% of Neandertals genome survived today in modern humans.

C) Correct answer: B. Lactase persistence is only favoured in culture practising dairying. The LCT allele for lactase persistence first underwent selection among dairy farmers around 7,500 years ago in the central Balkans. From the Near East via farmers who also introduced crops, animals and agricultural technology the allele spread to Europe.

D) Correct answer: B, C and D. Direct-to-costomer percentage ancestory test provides access to their genetic information without the involvement of healthcare provider or health insurance company. But it can be false because not many SNPs are reported in the databank, so if there is a SNP in the genome of an individual it may be considered deleterous and may increase concern in the individual. Moreover the reference individuals to against whose genome the test sample is studied may vary from company to company. This may creat confusion among the individuals.