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Genes and
Heredity
Outline
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What are genes?
Gregor Mendel
Where can we find our genes?
What do our genes do?
Our Genes
Genetic Trait Tree
Where do we get our genes from?
Inheritance
Predicting Inheritance
Modern uses of DNA technology
What are genes?
• Heredity: the passing of
genes from parents to
offspring
• Gene: a specific part of
DNA that controls a
hereditary trait
• What are hereditary traits?
– characteristics that can be
passed from parents to their
offspring (children)
– Examples:
• hair color
• eye color
• height
Gregor Mendel
• Austrian monk
• Considered to be the
father of modern
Genetics
• Used pea plants to
demonstrate how
certain characteristics
were passed through
generations
– Seed shape, seed color,
flower color, pod shape,
pod color, and stem
height
Mendel’s Work
Where can we find our genes?
• Each chromosome in a cell contains 100’s
and 1000’s of genes
• Each gene is found at a specific place on a
specific chromosome
– What does that mean?
• They all have a certain part of a chromosome where
they are found
• So we know where to find them all at
• Everyone has different combinations of
traits, but…
– The genes for those traits are on the same
parts of chromosomes in everyone
What do our genes do?
• Genes determine the traits
that we have
– We are most familiar with
physical traits
– So basically…
• Our genes determine what we
look like
• Physical traits are
observable characteristics
– Things that we can see
– examples: hair color, eye
color, tongue rolling, ear
lobes, hairline
Our Genes
• We have 2 copies of
each gene in our
chromosomes
– Every cell in our body
has the same 2 copies
in it
• How many genes do
humans have?
– www.ncbi.nlm.nih.gov/b
ooks/bv.fcgi?rid=gnd.c
hapter.272
Our Genes
• We have 2 copies of each
gene.
• Each gene has 2 or more
variations for what we
see
– We can inherit the same or
different variations
– examples:
• Hair color – brown, black,
red, blonde
• Tongue rolling – can do it,
can’t do it
Genetic Trait Tree
• We are going to be
creating a Genetic Trait
Tree to examine certain
characteristics (traits)
within our class
• For this activity we will
be examining 3 traits
– Free or attached ear
lobes
– Widow’s peak
– Tongue rolling
Where do we get our genes from?
• ½ comes from mother
– 23 single chromosomes in
the egg cell
• ½ comes from father
– 23 single chromosomes in
sperm cell
• When the sperm and egg
cell combine they form 1
cell with 46 single
chromosomes (23 pairs).
– All humans have started as 1
cell just like that
Inheritance
• The characteristics seen in us depend
on 2 things.
1. the combination of gene variations we get
from our parents
2. how those gene variations interact with each
other
• 2 basic gene variations
– Dominant: the trait/characteristic that is always
seen or observed
– Recessive: the trait/characteristic that is only seen
or observed when the dominant variation is not
present
Inheritance
• Example of dominant and
recessive variations
– A person can have a widow’s
peak (dominant) or a
straight hairline (recessive)
– 2 dominant variations = a
person with a widow’s peak
– 1 dominant and 1 recessive
variation = a person with a
widow’s peak
– 2 recessive variations = a
person with a straight
hairline
Predicting Inheritance
• Punnett Square: a tool to
predict the
characteristics a child
can inherit from its
parents
W = dominant
w = recessive
– Use the gene variations
each parent has to
determine the possible
combinations that can be
passed to offspring
– Capital letters represent
dominant variation
– Lower case letters
represent recessive
variation
Punnett Square Example
• Example using hairline
– Mother has the following
combination – Ww
– Father has the following
combination – ww
– They each pass 1 variation
(letter) on to their
offspring
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Draw a Punnett Square
Label sides
Add parent variations
Fill in the square
MOTHER
W
F
A
T
H
E
R
w
w
Ww
Ww
w
ww
ww
Punnett Square Example
• What does this show
us?
– Ww would have a widow’s
peak
– ww would have straight
hairline
– 2 of 4 children have Ww
and 2 have ww
– 50% chance of having a
child with a widow’s peak
– 50% chance of having a
child with straight
hairline
MOTHER
W
F
A
T
H
E
R
w
w
Ww
Ww
w
ww
ww
Modern uses of DNA Technology
• Forensic Science
– What shows on TV have you seen that use
this?
– DNA Fingerprinting
• Identifying people based on their DNA
• Create cures for diseases
• Genetic Engineering
– Has been used to create better plants and
vegetables
• Grow faster, bigger, in tougher conditions, and
resistant to insects
– Could we genetically engineer people?
Forensic Science Pictures
Forensic Science Pictures
Modern uses of DNA Technology
• Stem Cell Research
– Newest of the items on the list
– Take an undifferentiated cell (one that hasn’t
changed into a specific type of cell) and then
turn it into a specific type of cell
– What can it be used for?
• Create new organs to replace damaged ones
• Replace damaged nerve cells in a spinal cord
• Replace damaged brain cells
– There are problems with it though
Stem Cells
Modern Uses of DNA Technology
• Cloning
– Creating an exact copy of an existing
organism
– Dolly (a sheep) was the first cloned animal
to survive the process
• Happened in 1997
– How is it done?
– There are problems with it though
Cloning
Cloning