The breast cancer gene BRCA1 has a very similar sequence in humans, mice, and gorillas, due to its origination in a common ancestor. The BRCA1 genes in these species are examples of __________________.

Question

A.  orthologs
B.  paralogs
C.  polyploidy
D.  synteny

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?
 
Gather Content
· What do you already know about homology?
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

A.  orthologs

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses homology.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.
· What key words does the question contain and what do they mean?
        o A common ancestor is an extinct species that gave rise to a set of modern species being compared.
 
Gather Content
· What do you already know about homology?
        o Homologous genes arose from one original gene.
        o There are two kinds of homology: paralogy and orthology.
        o Two genes within an organism that have arisen from the duplication of a single gene in an ancestor are called paralogs.
        o In contrast, orthologs reflect the inheritance of a single gene from a common ancestor — a conserved gene.
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o Would we call the BRCA1 genes paralogs? No, because each species only has one copy of the gene.
        o Would we call the BRCA1 genes an example of polyploidy? No, because that refers to multiple copies of the genome in one species.
        o Would we call the BRCA1 genes an example of synteny? No, because that refers to a set of multiple genes that retained their order on the chromosome during recombination.