Question

I have an essay I need to write about this article(https://www.sciencenews.org/article/tibetans-live-high-life-thanks-extinct-human-relatives), but I'm having a hard time understanding the details in it. Could I get some help?

Answer 1

I will answer any specific questions about what is confusing you. I will be careful though because I do not want to do anything that would allow you to cheat on your paper (not saying you would/will, just letting you know). @GodGirl360

Answer 2

I understand about the whole "cheating" thing? Please, give me a minute to figure what exactly I don't understand-if you get what I mean. :)

Answer 3

No problem.

Answer 4

"The researchers compared a stretch of DNA surrounding EPAS1 that is 32,700 DNA letters long from 40 Tibetans and 40 Han Chinese, who are close genetic relatives of Tibetans. A distinctive pattern of single DNA letter changes, or SNPs, set the Tibetans apart from other groups."
First, what are DNA letters?

Answer 5

While we're at it, could we talk about SNPs and what they are exactly as well?

Answer 6

They are referring to the nucleotide bases in DNA as "letters". When you get a sequence of DNA back from a sequencing machine (Illumina, 454, Sanger, what ever other method), you get some that looks like "AATGCGTGGTCAAAGTC". That's why they are saying letters. What they really mean is that there are changes in the sequence.

SNPs stands for "single nucleotide polymorphism". Let's say they had three sequences, human 1, human 2, Devonian 1 and each had a region of DNA we are looking at.
human 1: AATGCGTGGTCAAAGTC
human 2: ggTGCGTaGGTCAAA-TC
devonian 1: gATGCGTGGTCAAA-TC

I have used lower case to indicate changes and - to indicate deletions. In my above sequences, human 2 and human 3 have two SNP sites in common, when compared to the first sequence. The first A in the human 1 is "g" in 2 and devonian 1, and the last "G" in human 1 has been lost in human 2 and devonian 1. The odds of enough of these SNPs occurring randomly is very low, so we know human 2 is more closely related to devonian 1 than human 1.

Answer 7

@GodGirl360

Answer 8

Opps, no human 3 I meant devonian 1

Answer 9

Sorry, that's a mouthful. Just trying to take it in.

Answer 10

Ok that's all my questions. After rereading the article and getting help from you, I'm pretty sure I understand.

Answer 11

Thank you

Answer 12

@GodGirl360 No problem. Post again if you have other questions.