Download Genetics and Heredity

Genetics and Heredity
Ch. 7A
Vocab
• Heredity: the passing of
traits from parents to
offspring (kids)
• Genetics: the study of
how traits are inherited
through the interaction of
alleles
Genetics
• Inherited Traits
– Eye color, nose shape,
and many other
physical characteristics
are some of the traits
inherited from parents
to the offspring
– An organism is a
collection of traits, all
inherited from the
parents
How are traits passed on?
• Each parent has two genes for a trait. These
specific genes are called alleles.
• During Meiosis, the alleles for different traits
are mixed up and separated randomly to insure
that the offspring will be a genetically diverse
individual
• Genes are passed on once Meiosis and
fertilization takes place
Gregor Mendel
• Gregor Mendel is known as Father of
Genetics
– Austrian Monk
– Worked with garden peas at a monastery
• Noticed and studied patterns in plant traits & people
– He was the first to use the mathematics of
probability to explain heredity
– He was also the first to trace one trait
through several generations
Alleles
• Alleles are different forms of a trait
that a gene may have
– Ex of a Trait: EYE COLOR
– Ex of a allele: blue eyes, green eyes, hazel
and brown
• Alleles are represented by various
letters of the alphabet
– T, t, R, r, W, w, B, b
Pattern of Inheritance
• Some traits are expressed in an organism
through different patterns of inheritance
• One pattern is know as Dominant and
Recessive
Dominant Traits
• Dominant trait – the trait that will physically
be seen in an organism
– Capital letters are used to represent Dominant
alleles. When these alleles are present, they take
over or show
– Only requires one of the alleles present in the
genotype to show up in the appearance
– Dominant Traits:, W -widows peak,
F- freckles, G – 6 fingers?!
Recessive Traits
• Recessive trait: trait that hides in the
background or is NOT always physically
seen
– Recessive alleles are represented by
Lowercase letters and are the weaker of the
alleles
– Rec. trait will only appear when there’s two
recessive alleles
– Recessive Traits: w -no widows peak, f no freckles, d – 5 fingers
Genetic Cross
• A cross – is the deliberate breeding of
two different individuals that results in
offspring that carry part of the genetic
material of each parent
Genotype and Phenotype
• Genotype: inherited combination of
alleles
– Actual genes
• Example: Bb, Ll
• Phenotype: the organism’s physical
appearance
– What the organism looks like
• Blue eyes, brown hair, smooth chin
Purebred and Hybrid
• Purebred: an organism that has two
alleles that are the SAME
– Also called homozygous
– Ex: bb, TT, DD
• Hybrid: an organism that has two
DIFFERENT alleles for a trait
– Also called heterozygous
– Ex: Bb, Tt, Dd
Punnett Squares
• Punnett Squares are
used to visually show
all possible
gene/allele
combinations of a
cross for ONE
offspring (organism)
Probability
• Probability: chance that an event will
occur
– After solving Punnett squares, questions
will often ask you to predict the probability
of one of the traits.
– Ex: What’s the chance of a child having a
smooth chin? Expressed like so:
0%, 25%, 50%, 75%, or 100%
(0/4) (1/4) (2/4) (3/4) (4/4)
End Notes
• More about Punnett Squares later… 
Sex linked traits
• If a gene is found only on the X chromosome
and not on the Y chromosome, it is said to be
a sex linked trait.
• Because the gene controlling the trait is
located on the sex chromosome, sex linkage
is linked to the gender of the individual.
• The result is that females will have two copies
of the gene while males would only have one.
Sex linked traits cont.
• If the gene is recessive, then males only
need one such recessive gene to have
the sex linked trait rather than the
normal two recessive genes for non sex
linked traits.
• This is why males exhibit some traits
more frequently than females.
Examples of Sex linked
traits
•
•
•
•
Red-green colorblindness
Male Pattern baldness
Hemophilia
Duchenne Muscular Dystrophy
Red-green colorblindness
genotypes
•
•
•
•
•
Normal vision male-XCYo
Colorblind male-XcYo
Normal vision female-XCXC
Normal vision female (carrier)-XCXc
Colorblind female-XcXc
Normal Vision father X
Colorblind Mother
• Dad genotype:
• Mom genotype:
Normal vision father x normal vision mother
(no colorblindness in her family)
• Dad genotype:
• Mom genotype:
Human Genome Project
• Completed in 2003, the Human Genome
Project (HGP) was a 13-year project
coordinated by the U.S. Department of
Energy and the National Institutes of Health
Some of the project goals were:
• identify all the approximately 20,000-25,000
genes in human DNA
• determine the sequences of the 3 billion
chemical base pairs that make up human
DNA
• store this information in databases
Ethical Issues
• Discussion:
What is the line between medical
treatment and enhancement?