2. Heredity
• Gregor Mendel
• Austrian Monk
• studied garden pea plants to unveil
patterns of heredity
• Developed the Laws of Inheritance
• Mendel noticed that traits from the
pea plant parents didn’t always
show up in their offspring
3. Heredity
• 2 types of traits were identified:
– Dominant trait – trait that appears in the
offspring, offspring only needs one
dominant allele from the parent to show up
– Recessive trait – trait that fades in the
background or may not show up in the
offspring, only shows up if the offspring
gets two recessive alleles from their
parents
– Mendel noticed that certain traits would
reappear in later generations
4. Genes
Mendel discovered that each
individual carries 2 sets of
characteristics (genes)
Each offspring has two forms
of a gene (one from each
parent)
Genes - carry information that
determines your traits.
5. GenesGenes
Where are They?
• Genes hang out all lined up on thread-like things
called Chromosomes.
– The chromosomes and genes are made of
DNA which is short for deoxyribonucleic acid.
• Chromosomes are found inside cells
–Specifically in the nucleus of the cell. (the
nucleus is sort of like the brain of the cell)
Where are They?
• Genes hang out all lined up on thread-like things
called Chromosomes.
– The chromosomes and genes are made of
DNA which is short for deoxyribonucleic acid.
• Chromosomes are found inside cells
–Specifically in the nucleus of the cell. (the
nucleus is sort of like the brain of the cell)
7. Alleles
Allele - different form(s) of a gene,
responsible for hereditary variation.
– Dominant trait – appears if it inherits the gene
for that trait from either parent; will always be
expressed and will “mask” a recessive trait.
Shown by capital letter(s).
– Recessive trait – appears only if it inherits that
trait from both parents and can only be
expressed if there are no dominant alleles
present; shown by lower case letters.
8. Alleles
• Genotype –The alleles present in an organism.
inherits from its parents, the actual gene makeup
represented by letters.
• (Example: BB, Bb, or bb)
“Purebred”, also called Homozygous consists of gene
pairs with genes that are the same.
(Example: “RR” -or- “rr”)
“Hybrid”, also called Heterozygous and consists of
gene pairs that are different. (Example: “Rr”)
• Note: The capital letter always is written first.
This is the "internally coded, inheritable information" carried by
all living organisms.is
BB Bb bb
9. • Phenotype – is the physical appearance of a trait.
What it looks like…
– Example: blue eyes or brown hair
• These are the physical parts, anything that is part of the observable
structure, function or behavior of a living organism.
Alleles
Red Red WhitePhenotype---------
10. Punnett SquarePunnett Square
Punnett Square - a diagram used to predict
outcomes of genetic combinations. The Punnett
square is a summary of every possible combination of
one maternal allele with one paternal allele for each
gene being studied in the cross.
Steps for Using the Punnett square:
– One parent’s alleles (genotype)(genotype) go along the top
– The other parent’s alleles go down the side.
– You fill in the squares like doing the communicative
property of multiplication.
Punnett Square - a diagram used to predict
outcomes of genetic combinations. The Punnett
square is a summary of every possible combination of
one maternal allele with one paternal allele for each
gene being studied in the cross.
Steps for Using the Punnett square:
– One parent’s alleles (genotype)(genotype) go along the top
– The other parent’s alleles go down the side.
– You fill in the squares like doing the communicative
property of multiplication.
11. Punnett SquarePunnett Square
Practice:
Both parents have the same genotype (Bb)
B= brown hair color b= blond hair color
Fill out the Punnett square on the right to help
answer the following questions.
This organism has ________% or
__________chance of receiving brown hair.
This organism has ________% or
____________ chance of receiving blonde hair.
The possible genotypes are:
The possible phenotypes are:
F
M
12. ReproductionReproduction
• Asexual Reproduction – only need one
parent to produce an offspring, offspring
are exact copies of the parent. The genetic
information passed to offspring is identical
to that of the parent.
– Produces uniform offspring
– Most single-celled organisms reproduce this way
13. ReproductionReproduction
• Sexual Reproduction – requires 2 parents
to reproduce, offspring share
characteristics from both parents and are
not exactly like either parent
– Produces more diverse offspring
14. Survival and Reproduction
Charles Darwin first presented his theory of
evolution by natural selection in his book
called On the Origin of Species in 1859.
Natural Selection – organisms with
favorable hereditary traits are more likely
to survive and reproduce than other
organisms; these organisms gradually
increase their proportion of a species.
Charles Darwin first presented his theory of
evolution by natural selection in his book
called On the Origin of Species in 1859.
Natural Selection – organisms with
favorable hereditary traits are more likely
to survive and reproduce than other
organisms; these organisms gradually
increase their proportion of a species.
15. Survival and Reproduction
Natural Selection in 4 Steps:
– Overproduction – more individuals are born
than will survive to adulthood
– Genetic variation – each individual in the
species has different traits, some traits make
an individual more likely to survive and
reproduce.
– Struggle to survive – only some of the
individuals in a population become adults and
reproduce.
– Successful reproduction – individuals have
traits that make them better adapted to their
environment are more likely to reproduce.
