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Genetics is the
study of DNA, chromosomes, and genes - and how those genes are expressed as
(Deoxyribonucleic Acid) is
the blueprint for life. It is a long, thin strand that contains four "bases":
adenine (A), thymine (T), cytosine (C), and guanine (G). These four bases are
used to create codes for everything that happens inside of your body - every
structure and every chemical reaction.
long, coiled up strands of DNA. Different species have different numbers of
chromosomes - humans have 46. Our 46 chromosomes are really two sets of 23 -
one set we get from our mothers, the other from our fathers. So, we usually say
that humans have 23 pairs of chromosomes.
gene is a segment of DNA (in a chromosome) that codes for a
certain trait/characteristic. There are genes for hair color, eye color,
handedness, height, build, even musical ability. Most genes come in different
"flavors". For example, different versions of the eye color gene can code for
brown, blue, or green eyes. These different forms of the same gene are called
Some alleles are dominant, and
some are recessive. This means that if you happen to have one
dominant allele and one recessive allele, the recessive trait will be masked
(hidden) by the dominant trait. Check out this example:
In pea plants, there are two versions of the height gene:
tall and short. The tall gene (T) is dominant over the short
(t) gene. Since pea plants have two copies of each gene (just
like humans), they may have any of these three combinations of alleles:
TT - The plant will be tall.
t - The plant will be tall.(The "short" trait is
hidden by the "tall.")
t t - The plant will be
Homozygous means that
both alleles are the same. In the above example, TT is homozygous dominant and tt is homozygous recessive.
Heterozygous means that the alleles are different. In this
case, Tt is heterozygous. These codes are
the plant's genotype (the genes that are
present). The phenotype is the physical
characteristic that shows up (tall or short).
Engineering & Genomics
genome is your entire set of genes. The study of genomes is
Genetics Resources Online
- Blood Typing Using Eldoncard (3:18) - There are four spots on the card: Anti-A (reacts if the A-tag is present), Anti-B (reacts if the B-tag is present), Anti-D (reacts if the Rh tag is present), and control (does not react - for comparison).
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