Transcript Introducing genes

Introducing genes
• Genetics is the study of
inherited traits and their
variations.
• Genetics is not
genealogy!
• Genealogy is the study
of family relationships
• What types of
characteristics can be
inherited? Name some.
• What types of
characteristics are not
inherited? Name some.
Introducing genes (continued)
• Genes are the units of
heredity (Heredity is the
transmission of inherited
traits)
• They are biochemical
signals that provide
instructions to the cell
on how to manufacture
proteins.
• The central dogma of
genetics is
genes→proteins →you!
Introducing genes (continued)
• How is that possible?
Proteins are responsible
for your physical
characteristics.
• This happens mainly
through the action of a
special class of proteins
called enzymes, which
control chemical
reactions in the cell.
• More on that later!
Introducing genes (continued)
• Genes are long
molecules of DNA or
deoxyribonucleic acid
• The complete set of
genetic instructions for an
individual is called the
genome.
– The entire human genome
has been decoded by the
research of the Human
Genome project.
– This effort has located
20,325 protein encoding
genes!!
Introducing genes (continued)
• Comparing genomes
of individuals can
reveal information
about relationships.
Introducing genes (continued)
• The development of the
field of genetics has
forced us to wrestle with
concepts such as benefit
and risk , right and wrong.
• The field of bioethics
was founded in the
1970’s to address ethical
questions surrounding
genetics and medical
technology.
Levels of genetics
• Through this course we
will examine the
transmission of traits at
several levels
– The molecular level
– The body (cells, tissues,
and organs)
– Within families
– Within populations and
the evolution of species.
Levels of genetics (continued)
• At the molecular level…
• Genes are regions of
DNA
• They are made up of
different sequences of the
bases that make up DNA
• A = adenine
• T = thymine
• C = cytosine
• G = guanine
Levels of genetics (continued)
• In addition to DNA, there
is another molecule in
cells that codes for
proteins: RNA
• DNA is located inside the
nucleus of cells, RNA is
located both in the
nucleus and cytoplasm.
Levels of genetics (continued)
• The same protein
encoding gene may vary
from person to person
• For example, all people
have genes that code for
eye color, but some of
them have genes for blue
eyes, while others have
genes that code for
brown
• Variants of a gene are
called alleles.
Levels of genetics (continued)
• How do these variants
arise?
• Through mutation.
• Mutation can be defined
as an error in the
copying of DNA.
• Some mutations have no
effect, some can create
harmless variations of a
trait (such as brown to
blue eyes) and some can
cause disease (such as
sickle cell anemia or
Down syndrome. )
Levels of genetics (continued)
• All genes (which means
all DNA) are stored in the
nucleus in the form of
chromosomes.
• Chromosomes are made
up of a strand of DNA
wound around proteins,
much in the same way
that thread is wound
around a spool.
• The proteins around
which the DNA is wound
are called histones.
Levels of genetics (continued)
• Different species of
organisms have different
numbers of
chromosomes.
• Humans have 23 pair for
a total of 46
chromosomes a person.
• In humans, 22 pair (44
total) are autosomes.
These are the same in
both genders. The
remaining two are sex
chromosomes (X and
Y).
Levels of genetics (continued)
• Moving from the molecular
level to the whole body
level….
• The human body consists
50 to 100 trillion cells!
• All of these (except red
blood cells) contain all
your genetic information.
• However, cells differ in
appearance (there are only
260 types of cells that
make up four basic tissue
types)
• Why is that?
Levels of genetics (continued)
• Because cells only use
some of their genes….
• For example, an adipose
cell is filled with fat, but a
skin cell is filled with a
scaly protein keratin.
• Therefore, genetic
defects can affect some
parts of your body
while others remain
healthy!
Levels of genetics (continued)
• Many organs include
rare, unspecialized cells
called stem cells.
• These cells are special
because they are
undifferentiated and
can became many
different cell types.
• These cells are at the
forefront of genetic and
medical research and
Levels of genetics (continued)
• Moving from the body to
the family level….
• Many genes are inherited in a
dominant/recessive fashion
• Each person has two copies of
each gene in their bodies
• If one copy masks the other,
the alleles is said to be
recessive
• If only one copy of the gene
needs to be present in order
for a trait to be expressed then
the allele is said to be
dominant
Levels of genetics (continued)
• We can trace the
inheritance of these types
of genes within a family
lineage using a chart
called a pedigree.
• These charts can also
help us predict future
inheritance of traits within
a family.
Levels of genetics (continued)
• Moving from the family
level to the population
level….
• In much the same way
that we can use an entire
genome to determine
how closely individuals
are related, we can apply
the same principle to
determine how closely
different species are
related to one another.
• In this way we can make
hypotheses about
evolutionary
relationships between
species.
Levels of genetics (continued)
• The evolution of
populations can also be
described using genetics.
• If the physical
characteristics of a
population begin to
change, then we know
that represents a change
at the genetic level.
• Therefore, evolution can
be defined as a change
in genes over time.
• Mutations drive
evolution!