Which one of the following are not hallmarks used to identify genes in an unknown eukaryotic sequence?

a) operator sequences
b) regulatory sequences (promoters, enhancers, and silencers)
c) 5' and 3' intron splice sites
d) orfs (open reading frames)

The correct answer is A) operator sequences

Explanation:

An operator sequence is a sequence that regulates the transcription of genes present in an operon. These operons are mainly found in prokaryotes. An operon consists of closely bound structural gene which have its own operator, and promotor and these genes are transcribed together.

An operator sequence overlaps the promoter sequence. Regulatory proteins binds to these operator sequence and prevents the binding of RNA polymerase on the promoter thereby inhibits the transcription initiation of operon in prokaryotes.

So as operator sequence is mainly found in prokaryotes so they are not hallmarks used to identify genes in an unknown eukaryotic sequence.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation: