Homeroom Warm Up
3-4-15
List the 4 major layers of the Earth from the
hottest to the coolest. Also list at least one
fact about each layer.
© Fall 2005, Pflugerville ISD, 7th Grade
Science Warm Up 3-4-15
Scientist theorize that the Atlantic Ocean is
slowly increasing in width. Which is the best
approximation of the rate at which
lithospheric plates beneath the Atlantic
Ocean are moving?
A. 2 millimeters per year
B. 2 centimeters per year
C. 2 meters per year
D. 2 kilometers per year
© Fall 2005, Pflugerville ISD, 7th Grade
Vocabulary Words
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
You should be able to define all of the following words
Genes
Genotype
Phenotype
Chromosome
Inherited Trait
Recessive Trait
Dominant Trait
Heredity
Homozygous
Heterozygous
© Fall 2005, Pflugerville ISD, 7th Grade
GLEs
• GLE 0707.4.3 Explain the relationship among
genes, chromosomes, and inherited traits.
• GLE 0707.4.4 Predict the probable
appearance of offspring based on the genetic
characteristics of the parents.
Unit A : Chapter 1 : Section 1
© Fall 2005, Pflugerville ISD, 7th Grade
What is genetics?
• The scientific
study of heredity
© Fall 2005, Pflugerville ISD, 7th Grade
Gregor Mendel
(1822-1884)
The Father of
Genetics
copyright cmassengale
© Fall 2005, Pflugerville ISD, 7th Grade
6
Gregor Johann Mendel
Austrian monk
Studied the
inheritance of traits in
pea plants
Developed the laws of
inheritance
Mendel's work was
not recognized until
the turn of the 20th
century
7
© Fall 2005, Pflugerville ISD, 7th Grade
Gregor Johann Mendel
Between 1856 and
1863, Mendel
cultivated and tested
thousands of pea plants
He found that the
plants' offspring
retained traits of the
parents
copyright cmassengale
© Fall 2005, Pflugerville ISD, 7th Grade
8
Particulate Inheritance
Mendel stated that
physical traits are
inherited as “particles”
Mendel did not know
that the “particles” were
actually Chromosomes &
DNA
copyright cmassengale
© Fall 2005, Pflugerville ISD, 7th Grade
9
Why peas?
Can be grown in a
small area
Produce lots of
offspring
Produce pure plants
when allowed to selfpollinate several
generations
Can be artificially
cross-pollinated
copyright cmassengale
© Fall 2005, Pflugerville ISD, 7th Grade
10
Mendel and His Peas
• Mendel tested 7 traits:
1.
2.
3.
4.
5.
6.
7.
Flower color
Flower position
Seed color
Seed shape
Pod shape
Pod color
Plant height
http://www.fieldmuseum.org/exhibits/traveling_mendel.htm
© Fall 2005, Pflugerville ISD, 7th Grade
Mendel and His Peas
• Mendel crossed flowers that were truebreeding for each characteristic.
• He crossed a purple (PP) flowered plant
with a white (pp) flowered plant.
(Parent Generation)
http://biology.kenyon.edu/courses/biol114/KH_lecture_images/Mendel/Mendel.html
© Fall 2005, Pflugerville ISD, 7th Grade
Mendel and His Peas
• Where did the
white color go??
© Fall 2005, Pflugerville ISD, 7th Grade
White Parent
• The first
generation (F1) of
plants all had
purple flowers.
(pp)
Purple Parent (PP)
(Pp)
(Pp)
(Pp)
(Pp)
Mendel and His Peas
• In the second
generation (F2) he had
3 purple flowered
plants, and 1 white
flowered plant.
© Fall 2005, Pflugerville ISD, 7th Grade
Purple Parent (Pp)
Purple Parent (Pp)
• Mendel took two of his
first generation (F1 x F1)
purple flowered plants
and crossed them
together.
(PP)
(Pp)
(Pp)
(pp)
Mendel and His Peas
• Mendel noticed in the first generation, all
of the white flowers seemed to
disappear.
• He called this a recessive trait.
• The white color faded into the
background at first.
• It showed up in the next generation
when he pollinated the flowers.
© Fall 2005, Pflugerville ISD, 7th Grade
Mendel and His Peas
• The color (purple) that seemed to mask
over the recessive color was named the
dominant trait.
© Fall 2005, Pflugerville ISD, 7th Grade
Mendel and His Peas
• Mendel was responsible for figuring out
that each plant carried two sets of
instructions for each characteristic (one
from the “mom” and one from the
“dad”).
• Like many scientists, his work was not
accepted until after his death.
© Fall 2005, Pflugerville ISD, 7th Grade
Let’s Review
1. If you crossed a true-breeding black
rabbit with a true-breeding white
rabbit, all of the offspring would be
black. Which trait is dominant in
rabbits: black fur or white fur?
2. Which trait is recessive?
© Fall 2005, Pflugerville ISD, 7th Grade
Answer
White Rabbit (bb)
• The trait for black
fur is dominant
over the trait for
white fur. The
white fur trait is
recessive.
Black Rabbit (BB)
(Bb)
(Bb)
(Bb)
(Bb)
http://www.buckeyevalleyfarms.freeservers.com/photo.html
© Fall 2005, Pflugerville ISD, 7th Grade
Mendel and His Peas
Vocabulary
1. Heredity- the passing of traits from
parent to offspring.
2. Dominant trait- the trait observed when
at least one dominant allele for a
characteristic is inherited
3. Recessive trait- a trait that is apparent
only when two recessive alleles for the
same characteristic are inherited
© Fall 2005, Pflugerville ISD, 7th Grade
Mendel and His Peas
4. Genes- a segment of DNA that carries
hereditary instructions and is passed
from parent to offspring. Genes are
located on chromosomes.
5. Alleles- multiple forms of the same gene
6. Genotype- an organisms inherited
combination of alleles
7. Phenotype- an organisms inherited
appearance
© Fall 2005, Pflugerville ISD, 7th Grade
Probability
• The likelihood of a
particular event
occurring. Chance
• Can be expressed as a
fraction or a percent.
• Example: coin flip.
© Fall 2005, Pflugerville ISD, 7th Grade
Punnett Square
• Developed by Reginald
Punnett.
• A diagram used to show
the probability or chances
of a certain trait being
passed from one
generation to another.
© Fall 2005, Pflugerville ISD, 7th Grade
Reading Punnett squares
• Gametes are placed above and to the left of
the square
• Offspring are placed in the square.
• Capital letters (Y) represent dominant alleles.
• Lower case letters (y) represent recessive
alleles.
© Fall 2005, Pflugerville ISD, 7th Grade
• Homozygous = when an organism possesses
two identical alleles. ex.
– YY or yy
• Heterozygous = when an organism possesses
different alleles. ex.
– Yy
© Fall 2005, Pflugerville ISD, 7th Grade
Phenotype vs genotype
• Genotype
 The genetic makeup
 Symbolized with letters
 Tt or TT
© Fall 2005, Pflugerville ISD, 7th Grade
• Phenotype
• Physical appearance of
the organism
• Expression of the trait
• Short, tall, yellow,
smooth, etc.
Punnett square example
© Fall 2005, Pflugerville ISD, 7th Grade
More Practice
Unit A : Chapter 1 : Section 1
© Fall 2005, Pflugerville ISD, 7th Grade
Punnett square review:
© Fall 2005, Pflugerville ISD, 7th Grade
Science Closure
3-4-15
The image shows a chromosome.
What is located on the
chromosome?
•
•
•
•
A cells
B genes
C enzymes
D organelles
© Fall 2005, Pflugerville ISD, 7th Grade
Science Closure
2-28-14
In a certain breed of dog, short hair (H) is dominant to long
hair (h). A short-haired dog (Hh) is crossed with a longhaired dog (hh). A Punnett square of this cross is shown
below. What is the probability that one of the puppies
produced by these parents will have short hair?
A. 0%
B. 25%
C. 50%
D.100%
Unit A : Chapter 1 : Section 1
© Fall 2005, Pflugerville ISD, 7th Grade