Genes and Inheritance [1]: DNA (High band Biology)
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Genes and Inheritance [1]: DNA (High band Biology)


A Level Biology: Genes and Inheritance 1 – DNA Hi! Welcome to my first video on this topic
of Genes and how they affect you. This first video will be looking at the structure of
DNA and how it is organized within your cells. The first thing to establish is what makes
you unique or what makes you “you”. The two things that determine an individual’s
characteristics are the environment and their genes. Through genes you received from your
parents and therefore, they are inherited. The environment is essentially all of the
stimuli that you receive from outside. It could be things like your exposure to light;
it can be the amount of food that you are exposed to and your experiences in general. Your genes are basically your blueprint. They
enable you to make things called proteins. Proteins are the building blocks for life.
They’re the structure that you are made of and they are the chemicals that control
the reactions in your body. Your genes, I said before, are set of instructions for making
these proteins. The smallest sub-unit of genetic material
is called DNA. This diagram here represents the DNA found within your cells. If we take
one of the sections here or pieces of DNA here, there are 3 billion of those in virtually
every cell within the human body. These are what are known as bases. These bases come
in four different varieties: Adenine, thymine, guanine and cytosine. You notice that they always pair together
in a very, very specific way. One in which they always go together is the adenine always
binds to the thymine and the cytosine always binds to the guanine and you can see that
represented here with these different-colored bases. For instance here, the guanine in green
and the cytosine is in red and you notice that those two always bind together. The thymine
in yellow and the adenine in blue; they always bind together. In a DNA, you do not only have the bases in
the middle, but you also have two other sections that are represented by this gray strip here.
That’s a phosphate group and a ribose sugar joined together. The three major parts of a DNA are ribose
sugar, phosphate group and the bases that you have here. You may have heard of DNA being referred to
as a double helix. All that simply means is that it has two strands that are connected
together that twist around one another; a bit like a coiled spring and hence, the name
double helix. This diagram here has nine nucleotide bases
joined up. The next major sub-unit of genetic material is called a gene. A gene is something
which codes for a particular characteristic; be that eye color or hair color. A gene usually
consists of tens of thousands of nucleotide bases and pieces of DNA joined together. So you start to get an idea of just how small
the piece of DNA actually is. In summary, your DNA which is the smallest
sub-unit of genetic material is referred as deoxyribonucleic acid or DNA for short. It
is made up of nucleotide bases and which therefore are adenine, thymine, cytosine and guanine,
ribose sugar and phosphate group and the bases always pair up in a particular way so the
adenine always binds to the thymine and the cytosine always binds with the guanine and
they form a structure called a double helix which basically looks like a coiled spring
wrapped around. A gene, which codes for a particular characteristic;
this could be something like an eye color or hair color and a gene is made of lots of
pieces of DNA and in some cases, up to tens of thousands of pieces of DNA. [end of audio – 04:23]
A Level Biology: Genes and Inheritance 1 – DNA Page…1

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