Video Transcript
Which of the following best
describes the term chromosome? (A) A protein that DNA wraps around
to increase its stability. (B) A threadlike structure of
tightly coiled DNA that contains many genes. (C) A tightly coiled section of DNA
that codes for a particular protein. Or (D) an alternative form of a
gene.
The genetic information of our
cells is located in its DNA. If we were to take all of the DNA
in a human cell and stretch it all out together, all of the strands together would
be about two meters long. However, the DNA in human cells is
split into 46 different strands. Each strand of DNA contains many
different genes. Each gene codes for the production
of a particular protein. The proteins produced can be
structures, for different purposes in development, growth, and repair, or they can
be enzymes to catalyze particular reactions, or hormones, and so on.
Although all members of a
particular species will have the same genes, they very likely may have different
forms of those genes. That is why two individuals of the
same species may have different colors of fur, even though they both have what we
might call the fur color gene. These different forms of a gene are
called alleles.
In order to keep the strands of DNA
from tangling up with each other in the cell’s nucleus, DNA is generally stored in a
highly coiled and condensed form when not in use. In order to get into this state,
the strand of DNA coils around proteins called histones to create what is called a
nucleosome. And then nucleosomes bundle
together to create a chromatin fiber. When chromatin fibers bundle
together to create the highly coiled and condensed version of DNA, this is called a
chromosome.
So, looking at our answer choices,
(C) could be the definition of a gene. (D) is the definition of an
allele. (A) is the definition of a
histone. And (B) is the definition of a
chromosome. So the correct answer to this
question is (B). A chromosome is a threadlike
structure of tightly coiled DNA that contains many genes.
