|I was just wondering how many chromosomes it
takes to make one strand of DNA? Thanks,
hopefully you reply soon.
|Question Date: 2012-03-14|
That seems like an easy question, doesn't it?
There are 23 pairs of chromosomes. There are
about 20,000-25,000 genes. So a quick answer to
your question would be about 1,000 genes.
Here are a few wrinkles, though. A gene is
basically a recipe for a protein. A lot of each
chromosome is DNA that is not recipes. This part
of the collection of DNA (the genome) may have
directions on which part of the chromosomes to
read. These would be sort of like switches that
turn on to get the cell to use a particular
recipe. So every chromosome has more DNA than is
contained in the recipes.
are also different sizes. Chromosome 1 is much
larger than chromosome 22, for example. There's
even a pair of chromosomes that may be different
sizes. In females, chromosome pair 23 is two X
chromosomes. For males, pair 23 is one X and one
Y. The X is much larger and contains around 2,000
genes. The Y is quite small and only has about 86
genes that make about 23 proteins, which basically
say be male.
Look up the number of genes
that a few different species have. You will
notice that the number of genes or chromosomes
will not let you predict how large or complex
Do you think there's a lower
limit to the size of a chromosome? What about an
upper limit? Why don't we just have one or two
big chromosomes? Think about how cell division
works and see if that gives you some
ideas.Thanks for asking.
Actually, chromosomes are just one very long
strand of DNA wound together in a manageable
shape. Chromatids, a pair of identical
chromosomes, contain two strands of DNA.
You've got it the wrong way around: chromosomes
are composed of DNA (and other things). That said,
each chromosome consists of one very long DNA
strand, which loops back on itself many times to
make the chromosome.
Actually, a chromosome is a bundled up strand
of DNA! If you take a double-helix of DNA, and
wind it up really tightly into itself, you get a
Actually, when we talk about "strands of DNA",
this can refer to DNA molecules of any length
(measured in single A,T,G, or C nucleotides known
as "base pairs"). Human cells contain two sets of
23 chromosomes, one set inherited from each parent
(46 total). These chromosomes are large "chunks"
of DNA wound tightly together, and range in size
from 51 million to 245 million base pairs each.
As a whole, the whole human genome is 3.3 billion
base pairs long! If you put all this sequence
information into a text file, it would just barely
fit onto one CD (~800 megabytes). Best,
One chromosome has 2 strands of DNA in a
double helix. But the 2 DNA strands in chromosomes
are very, very long. One strand of DNA can be very
short - much shorter than even a small chromosome.
Strands of DNA are made by joining together the 4
DNA bases in strings. The 4bases are A, C, G, and
T. So a short strand of DNA might be AAGCCTTGCAAT
- or any other string of those 4 DNA
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