Bell Work 2/5/14
Explain your answer in a complete sentence!
A parent and its offspring have several genes that are
different causing them to have different traits. How was
this organism reproduced?
A. budding
B. asexual reproduction
C. sexual reproduction
D. spurring
Objectives
• Describe the relationship among genes,
chromosomes, and inherited traits. (SPI 0707.4.3)
• Interpret a Punnett square to predict possible
genetic combinations passed from parents to
offspring during sexual reproduction. (SPI0707.4.4)
Word Wall Word of the Day
glucose: a type of sugar that is found in plants and fruits
Heredity
• Why don’t you look like a rhinoceros?
• The answer to this question seems simple: Neither of
your parents is a rhinoceros.
• But there is more to this answer than meets the eye.
• As it turns out, heredity, or the passing of traits from
parents to offspring, is more complicated than you might
think.
• For example, you may have curly hair, while both of your
parents have straight hair. You might have blue eyes
while both of your parents have brown eyes.
• How does this happen?
Who was Gregor Mendel?
• Read pg. 100
• “Who Was Gregor Mendel?”
• “Unraveling the Mystery”
• Gregor Mendel discovered the principles of heredity while
studying the characteristics and traits of pea plants.
• A characteristic is a feature that has different forms in a
population.
• For example, hair color is a characteristic of humans.
• The different forms, such as brown or red hair is called a trait.
With your elbow partner,
name two
characteristics in our
class and two different
traits of those
characteristics.
Mendel’s First Experiments
• One trait was always present in the
first generation, and the other trait
seemed to disappear.
• Mendel chose to call the trait that
appeared the dominant trait.
• Because the other trait seemed to
fade into the background, Mendel
called it the recessive trait.
• The recessive trait for the white
flower reappeared in the second
generation.
Review: Talk with your group…
1. What is heredity?
•
The passing of genetic traits from parent to offspring
2. Who was Gregor Mendel?
•
Discovered the principles, or ideas, of heredity
3. Which trait is present in the first generation?
•
Dominant trait
4. Which trait is present in the second generation?
•
Recessive trait
Challenge Question
So how is it that both of my parents are short, but
I am tall?
The Family Connections
• You and your partner
will help each other
determine the variation
of each characteristic
(trait) that each of you
possess. Record your
traits in the chart
labeled “My
Characteristics” on the
back of the sheet.
Traits and Inheritance
• Mendel knew from his experiment with pea plants that
there must be two sets of instructions for each
characteristic.
• These instructions for an inherited trait are called genes.
• Each parent gives one set of genes to the offspring.
• The offspring then has two forms of the same gene for
every characteristic- one from each parent.
• The two forms (often dominant and recessive) of a gene
are known as alleles.
• Dominant alleles are shown with a capital letter (P for
dominant purple flowers).
• Recessive alleles are shown with a lowercase letter (p for
recessive white flowers).
Just a side note…
Phenotype & Genotype
• Genes affect the traits of an offspring.
• An organism’s appearance (the way they look) is
known as its phenotype.
• In pea plants, possible phenotypes for the
characteristic of flower color would be purple flowers
or white flowers.
• The genotype of an organism is the entire genetic
makeup of an organism; the combination of genes for
a specific trait.
• An organism with two dominant or two recessive alleles is
homozygous (same size letters- PP or pp).
• An organism with one of each (Pp) is heterozygous.
Inherited Disorders
• Albinism is an inherited
disorder that affects a
person’s phenotype in many
ways.
• The boy in the picture has
inherited a condition called
albinism.
• Albinism prevents hair, skin,
and eyes from having normal
coloring because that
person’s gene for producing
melanin is mutated.
Punnett Square
• A Punnett square is used to
organize all possible combinations
of offspring from particular
parents.
• Genotype PP is a purebred.
• What is the genotype for the
offspring to the right?
• The dominant allele P ensures that
the offspring will have purple
flowers.
• The recessive allele p may get
passed to the next generation.
• Why?
Quick Lab
pg. 107
R= round seeds
r= wrinkled seeds
• Work with your group
to complete the
Punnett square.
• What would be the
phenotypes for these
offspring?
• RR= round seeds
• Rr= round seeds
• rr= wrinkled seeds
R
r
R
r
RR
Rr
(genotype- two
dominant
alleles)
(genotype- one
dominant
allele,one
recessive allele)
Rr
rr
(genotype- one
dominant
allele,one
recessive allele)
(genotype- two
recessive alleles)
Probability
• The mathematical chance that something will happen is known as
probability.
• Genotype probability:
• Pp x Pp cross has a 50% chance of receiving either allele from either parent.
• The probability of inheriting two p alleles is ½x½, which equals ¼, or 25%.
Monohybrid vs. Dihybrid Punnett Square
• A monohybrid Punnett
• A dihybrid Punnett square is
square is one where only one one where two traits are
trait is crossed.
crossed.
• Example: A tall pea plant • Example: a tall, green
TT is crosses with a short
flowered plant TtGg is
pea plant tt.
crossed with a short, yellow
flowered plant ttgg.
T
t
t
Tt
Tt
T
Tt
Tt
TG
Tg
tG
tg
tg
TtGg
Ttgg
ttGg
Ttgg
tg
TtGg
Ttgg
ttGg
Ttgg
tg
TtGg
Ttgg
ttGg
Ttgg
tg
TtGg
Ttgg
ttGg
Ttgg
R= round seeds
r= wrinkled seeds
Rr x rr
R= round seeds
r= wrinkled seeds
Y= yellow seeds
y= green seeds
RrYy x rryy
Frankenfish Genetics explanation
Exit Ticket
Create your own monohybrid Punnett Square
cross.
Use the examples in your notes for ideas.