Heredity
Heredity
• the passing of physical characteristics from
parents to offspring
Trait
• a characteristic that an organism can pass on
to its offspring through its genes.
Offspring
• The product of reproduction; a new organism
produced by one or more parents (ex. Human
baby)
Chromosome
• DNA tightly coiled and rod shaped ~ location
of genes
Gene
A segment of DNA located on a chromosome
that controls some aspect of how cell or living
things grow and develop
Allele
• alternate form of a gene for a trait; two or
more forms of the same gene, they may be
dominant or recessive.
• For example, brown and blue eyes are two
different alleles for eye color. We have 2
alleles for any, one trait, one from our mother
and one from our father. They may be the
same form of the gene (homozygous) or two
different forms (heterozygous).
Dominant
• stronger trait; overrides or covers up the
recessive trait. Ina gene pair (Rr) the dominant
allele overrides the effects of the recessive
allele
Dominantly Inherited Disorders
• Achondroplasia, a form of
dwarfism with an incidence
of one case among every
10,000 people.
Heterozygous individuals
have the dwarf phenotype
• Huntington’s disease, a
degenerative disease of the
nervous system, is caused
by a lethal dominant allele
that has no obvious
phenotypic effect until the
individual is about 35 to 45
years old.
Recessive
• weaker trait; covered up or hidden by the
dominant trait, In a gene pair (rr) the effects
of a recessive allele will be hidden if a
dominant allele is present
• Ex: sickle cell anemia
Disorders Inherited as Recessive Traits
• Over a thousand human
genetic disorders are
known to have
Mendelian inheritance
patterns. Each of these
disorders is inherited as
a dominant or recessive
trait controlled by a
single gene. Most
human genetic
disorders are recessive.
Disorders Inherited as Recessive Traits
• Sickle-cell disease,
which affects one out of
400 African Americans.
Sickle-cell disease is
caused by the
substitution of a single
amino acid in the
hemoglobin protein of
red blood cells
Homozygous
• an organism that has 2 identical alleles for a
trait. An individual may be homozygous
dominant (AA) or homozygous recessive
(aa). Individuals who are homozygous for a
trait are also referred to as homozygotes.
Heterozygous
• a genotype consisting of two different alleles
of a gene for a particular trait. An individual
that is heterozygous (Aa) is also referred to as
hybrids.
Punnett Square
• a tool to predict the chances of a trait by using
the allele combinations.
How Punnett squares work
Now you try….
Gregor Mendel~ Father of Genetics
• Austrian Monk.
• Experimented with “pea plants”.
• Used pea plants because:
– They were available
– They reproduced quickly
– They showed obvious differences in the traits
Understood that there was something that
carried traits from one generation to the
next- “FACTOR”.
Gregor Mendel
•
Mendel's Plant Breeding
Experiments
•
Gregor Mendel was one of the first to
apply an experimental approach to
the question of inheritance.
•
For seven years, Mendel bred pea
plants and recorded inheritance
patterns in the offspring.
•
•
Particulate Hypothesis of Inheritance
Parents pass on to their offspring
separate and distinct factors (today
called genes) that are responsible for
inherited traits.
Mendel was fortunate he chose the Garden Pea
• Mendel probably chose to
work with peas because
they are available in many
varieties.
• The use of peas also gave
Mendel strict control over
which plants mated.
• Fortunately, the pea traits
are distinct and were
clearly contrasting.
To test the particulate hypothesis, Mendel crossed true-breeding plants that
had two distinct and contrasting traits—for example, purple or white
flowers.
Mendel cross-fertilized his plants by hand. Why is it important to control
which plants would serve as the parents?
Pea Generations
For each monohybrid cross, Mendel cross-fertilized truebreeding plants that were different in just one character—in
this case, flower color. He then allowed the hybrids (the F1
generation) to self-fertilize.
Typical breeding experiment
• P generation (parental
generation)
• F1 generation (first filial
generation, the word filial from
the Latin word for "son") are the
hybrid offspring.
• Allowing these F1 hybrids to selfpollinate produces:
• F2 generation (second filial
generation).
• It is the analysis of this that lead
to an understanding of genetic
crosses.
Mendel studies seven characteristics in the
garden pea
Statistics indicated a pattern.
What is Genetics
• The study of how traits are inherited and
passed down from parents to offspring
How is it possible to maintain such genetic
continuity?
Martin Sheen
Charlie Sheen
Emilio
Estevez
How is it possible to maintain such
genetic continuity?
How are Genes passed down?
• In sexual reproduction both parents pass the
genes for specific traits to their offspring. Each
parent donates 23 chromosomes for a total of
46. The father giving 50% and mother giving
50%. Genes that both parents have will code
dominant in offspring. Ex. Both parents
carrying the dominant trait for black hair will
result in a black haired offspring.
What is a genetic trait?
A genetic trait is a characteristic controlled by
genes that result in specific characteristics such
as eye color and hair color.
Where are genes located?
Centromere
The centromere is the structure formed when
two chromatids join
Chromatids
Are two identical parts of a chromosome when
two join it becomes a tetrad (meaning 4parts)
Tetrad
A four-part structure that forms during the prophase of meiosis
and consists of two homologous chromosomes, each composed
of two sister chromatids
What is a genotype?
A genotype is an organisms make up ~ all the
alleles inherited for specific traits
Example:
Bb, DD, Rr, Aa
What is a phenotype?
The phenotype is the outward appearance and
behavior of an organism resulting from genes
passed down from both parents.
Hair and eye color
freckles
What is an acquired trait?
~An acquired trait is a trait that can NOT be
passed down genetically.
Examples include:
• Temper
• Behavior
• Attitude
• Habbits
What is an inherited trait?
An inherited trait is a trait that is passed down
to offspring from one generation to the next.
You have no control over the outcome.
Example:
Eye color
Hair color
Height
The ability to roll your tongue
What is a generation?
A generation is the average length of time
between the birth of parents and the birth of
their children
Example:
• You all your siblings and cousins born to your
aunts and uncles equate one generation. Your
parents , your aunts and uncles and their
cousins equate one generation
What is DNA ?
• genetic material of an organism,
Deoxyribonucleic Acid, chemical that contains
the instructions for cells to make the
necessary protein. It has a structure like a
twisted ladder made up of nucleotides.
DNA
• DNA is often called
the blueprint of life.
• In simple terms,
DNA contains the
instructions for
making proteins
within the cell.