Transcript Human Genetics

Aim: How do your genetics
play a role in the person
you are today?
 Do Now: What similarities do you
have with your parents or
siblings?
 Homework:Textbook 126-132 #1-5
Human Genetics
What is Heredity?
 The transfer of characteristics from one
generation to the next
What are Traits?
 A characteristic that is determined by
your genes
 A pair of genes will determine the trait
 Examples:
 Tongue rolling
 Earlobes
 Widow’s Peak
 Hair Whorl
 Dimples
What is genetics?
 The science of how traits are inherited
How are traits determined?
 Dominant Genes – the traits that will
usually appear in the individual
(represented by an uppercase letter)
 If an organism has a gene for blue or
brown eyes, usually it will have brown
eyes because it is the dominant gene
 Recessive Genes – The gene hidden by
the dominant gene
(represented by a lowercase letter)
 Blue-eyed people need two recessive
genes to show the blue-eyed trait
Who is Gregor Mendel?
 “Father of Genetics”
 Studied pea plants
 He crossed pea plants with different
characteristics and studied their offspring
 He was able to determine how
traits get passed on from
generation to generation
What is a Punnett Square?
 A table that shows
the possible results
when the genes of
two parents are
crossed
 It shows the
probability of a trait to
be expressed in the
offspring
B
B
B
BB
BB
b
Bb
Bb
B – Brown Eyes
b – Blue Eyes
What is a genotype?
 The genetic code or make up of the
individual
 Examples: BB, Bb, bb
What is a genotype?
 Homozygous dominant
– a pair of dominant genes (BB)
 Homozygous recessive
– a pair of recessive genes (bb)
 Heterozygous or hybrid
– a mixed pair of one dominant gene and
one recessive gene (Bb)
What is a phenotype?
 The way an organism looks or behaves
 Examples:
Genotype Phenotype
BB
Brown Hair
Bb
Brown Hair
Lets try some Punnett Squares!
B = Brown Eyes
b = Blue Eyes
What we are looking for:
1. Genotypes
2. Phenotypes
3. Percentage Brown
eyes
4. Percentage Blue Eyes
Examples:
 BB x bb
 Bb x bb
 Bb x Bb
 bb x bb
 BB x BB
 BB x Bb
Pedigree Charts
Allow us to trace
certain traits.
Helpful for tracking
genetic disorders
passed down
through
generations.
Ex: Colorblindness
DNA Structure
A double helix made of a sugarphosphate backbone bound in the
middle by nucleotide base pairs
-The backbone is made up of
molecules that have phosphates and
sugars – basically the sides of the
ladder
-The nucleotides,
which come in
pairs, make up
each step of the
ladder
Nucleotides
Everything that determines what we look like, our
likes, our dislikes, whether we’re a morning person or
we like to sleep in is largely determined by four
nucleotides that are repeated over and over again
inside each and of one of our cells.
Adenine
Cytosine
Guanine
Thymine
These four molecules hold our
DNA together by binding together
in pairs. Adenine and Thymine will
always be paired. Cytosine and
Guanine will always be paired.
**Guanine will not pair with
Adenine, nor Thymine with
Cytosine!!!!
Protein Building
So how does our DNA actually
determine why we are made this
way?
Earlier in the year, we learned
about ribosomes – who synthesize
proteins. They get their orders from
the DNA.
How??
The ribosomes will read sections of DNA, and every
time it reads three nucleotides, it goes and gets an
amino acid.
Once it has a few amino acids lined up, it chains
them together, forming a protein. That protein then
goes out to do it’s job, building your body from the
ground up!
Remember – proteins come in many different forms,
think of them like tools – many shapes and sizes, all
with very different jobs.
Protein Building
Replication
When DNA is copied, it is “unzipped”, separating the
two strands of DNA.
Once separated, ribosomes work to create a
complementary strand.
As the complementary strand is formed, the DNA and
the new strand are “zipped” together, creating two
separate strands of the same DNA.
Sometimes, errors occurs. These errors are called
mutations
Mutation
Mutations can happen for a variety of reasons. Some are
good, some are bad. Our DNA has methods built in to find and
correct mutations, but not all of them are corrected in time.
If mutations are good, helping the organism to survive, there is
a chance that they will be passed on to the offspring. This is a
gradual change, that ultimately results in evolution over
several generations of a species.
Restriction Enzymes
 Enzymes that cut DNA at specific
locations.
Genetically Engineered
Bacteria
Genetically Engineered
Bacteria
 Plasmid (loop of DNA) is
removed from bacterial cell
 A specific gene is removed
from an animal cell
 Animal gene is spliced into
plasmid
 Recombinant DNA is inserted
into
bacterial cell
 Bacteria and it’s descendants
will now produce an animal
protein
DNA Fingerprinting