Download Genetics: The Science of Heredity

Genetics: The
Science of
Heredity
Chapter 3
VA Standards of Learning
addressed:
LS.1
The student will plan and conduct investigations in which
a) data are organized into tables showing repeated trials and means;
d) sources of experimental error are identified;
e) dependent variables, independent variables, and constants are identified;
g) continuous line graphs are constructed, interpreted, and used to make predictions; and
i) an understanding of the nature of science is developed and reinforced.
LS.2
The student will investigate and understand that all living things are composed of cells.
Key concepts include
d) cell division (mitosis and meiosis).
LS.3
The student will investigate and understand that living things show patterns of cellular
organization. Key concepts include
b) life functions and processes of cells, tissues, organs, and systems (respiration, removal of
wastes, growth, reproduction, digestion, and cellular transport).
LS.13
The student will investigate and understand that organisms reproduce and transmit
genetic information to new generations. Key concepts include
a) the role of DNA;
b) the function of genes and chromosomes;
c) genotypes and phenotypes;
d) factors affecting the expression of traits;
e) characteristics that can and cannot be inherited;
g) historical contributions and significance of discoveries related to genetics.
LS.14
The student will investigate and understand that organisms change over time. Key
concepts include
a) the relationships of mutation, adaptation, natural selection, and extinction;
Chapter 3, Section 1
Mendel’s Work
After completing the lesson, students
will be able to:
1. Describe Mendel’s genetics
experiments;
2. Identify the factors that control the
inheritance of traits in organisms;
3. Explain how genetics use symbols
to represent allels.
Who was Mendel?
• Gregor Mendel was a young _________ from a
monastery in Central Europe in the mid-1800s
• Studied math and science at the University of
Vienna
• Tended the monastery’s garden and became
curious about why some of the plants had
different characteristics, or _______________.
• Mendel experimented with thousands of pea
plants to understand the process of ________,
the passing of ______________ from parents
to offspring.
• His work formed the foundation of _________,
the scientific study of _______________.
Who was Mendel?
• Gregor Mendel was a young priest from a
monastery in Central Europe in the mid-1800s
• Studied math and science at the University of
Vienna
• Tended the monastery’s garden and became
curious about why some of the plants had
different characteristics, or traits.
• Mendel experimented with thousands of pea
plants to understand the process of heredity,
the passing of traits from parents to offspring.
• His work formed the foundation of genetics, the
scientific study of heredity.
Why study PEAS????
• Many ______________ that exist in only
____________ forms
• Pea plant stems are either ___________
or _________________
• Garden peas produce a large number of
__________________ in one generation
making it easy to collect large amounts of
_____________ to analyze
Why study PEAS????
• Many traits that exist in only two
forms
• Pea plant stems are either tall or
short
• Garden peas produce a large number
of offspring in one generation making
it easy to collect large amounts of
data to analyze
More on Peas
• In nature, pea plants
are usually
__________________.
This means that pollen
from one flower lands
on the pistil of the
____________ flower.
• A ________________
plant is one that
always produces
offspring with the
same form of a trait as
the parent.
Stamens
Pistil
More on Peas
• In nature, pea plants
are usually selfpollinating. This
means that pollen from
one flower lands on
the pistil of the same
flower.
• A purebred plant is one
that always produces
offspring with the
same form of a trait as
the parent.
Stamens
Pistil
What are they?
• The __________
produces ______
sex cells, or eggs,
while the
_____________
produce pollen,
which contains
the __________
sex cells.
Stamens
Pistil
What are they?
• The pistil
produces female
sex cells, or eggs,
while the stamens
produce pollen,
which contains
the male sex
cells.
Stamens
Pistil
Self-Pollination
__________
____________
_____________
When Mendel crossed __________________tall and short plants, all
the offspring in the F1 Generation were tall. In the F2 Generation,
three fourths of the plants were tall, while one fourth were short.
P Generation
F1 Generation
F2 Generation
When Mendel crossed purebred tall and short plants, all the offspring
in the F1 Generation were tall. In the F2 Generation, three fourths of
the plants were tall, while one fourth were short.
Other Traits
• Mendel studied seven traits in garden
peas: seed shape, _________
__________, seed coat color,
________ ________, pod color,
_________ _________, and stem
height.
• The results in each experiment were
___________ to those observed with
stem height.
Other Traits
• Mendel studied seven traits in garden
peas: seed shape, seed color, seed
coat color, pod shape, pod color,
flower position, and stem height.
• The results in each experiment were
similar to those observed with stem
height.
Book Work
• Turn to page 89 in your text book.
• Complete the chart on the Genetics
of Pea Plants handout.
• When it is complete - place it in your
binder.
Dominant and Recessive
Alleles
• Mendel reasoned that _______________
factors must control the _____________
of traits in peas. The ___________ that
control in each trait exist in __________.
One factor from the female parent and
one factor from the male parent.
• Mendel went on to reason that one factor
in a pair can __________, or _________,
the other factor. Tallness ____________
the shortness factor.
Dominant and Recessive
Alleles
• Mendel reasoned that individual factors
must control the inheritance of traits in
peas. The factors that control in each
trait exist in pairs. One factor from the
female parent and one factor from the
male parent.
• Mendel went on to reason that one factor
in a pair can mask, or hide, the other
factor. Tallness masked the shortness
factor.
Alleles Cont’d
• Scientists call the factors that control
traits _________. They call the different
forms of a gene ____________.
• Individual _____________ control
the inheritance of traits. Some
alleles are __________, while other
alleles are ___________.
• ____________ allele is one whose trait
always shows up in the organism when
the allele is present. A _____________
allele, on the other hand, is masked or
covered up, whenever the dominant allele
is present.
Alleles Cont’d
• Scientists call the factors that control
traits genes. They call the different
forms of a gene alleles.
• Individual alleles control the
inheritance of traits. Some alleles
are dominant, while other alleles are
recessive.
• Dominant allele is one whose trait always
shows up in the organism when the allele
is present. A recessive allele, on the
other hand, is masked or covered up,
whenever the dominant allele is present.
Understanding Mendel’s
Crosses
• Understanding Mendel’s Crosses –
Definition:
• Hybrid – An organism that has two
different alleles for a trait;
Mendel
• Today known as the
________ ___ _____
• However, his work
had been forgotten
for ____ _________
before being
rediscovered in
_________ by three
different scientists
who recognized his
the importance of his
work.
Mendel
• Today known as the
Father of Genetics
• However, his work
had been forgotten
for 34 years before
being rediscovered in
1900 by three
different scientists
who recognized his
the importance of his
work.
Chapter 3 Section 2
Probability and Genetics
After completing the lesson, students will be
able to:
1. Describe the principles of probability and
how Mendel applied them to inheritance;
2. State how geneticists use Punnett
squares;
3. Explain the meanings of the terms
phenotype, genotype, homozygous,
heterozygous, and cocominance.
Mini Lab Mini Lab Mini Lab
What is the Chance
• In your lab notebook:
1. Suppose you were to toss a coin 20
times. Predicts how many times the
coin would land “heads up” and how
many times it would land “tails up.”
2. Now test your prediction by tossing a
coin 20 times. Record the number of
times the coin lands heads up and the
number of times it land tails up.
3. How did steps 1 and 2 compare?
________________
• ________________ is the ___________
that a particular event will occur.
• The laws of _________________ predict
what is likely to occur, not necessarily
what will occur. However, the more
tosses you make, the closer your actual
results will be to the results predicted by
probability.
Probability
• Probability is the likelihood that a
particular event will occur.
• The laws of probability predict what
is likely to occur, not necessarily
what will occur. However, the more
tosses you make, the closer your
actual results will be to the results
predicted by probability.
__________ and Probability
• ___________ was
the first scientist to
_______________
that the principles
of probability can
be used to predict
the results of
genetic crosses.
Mendel and Probability
• Mendel was the
first scientist to
recognize that the
principles of
probability can be
used to predict the
results of genetic
crosses.
_____________ Squares
• A ____________
Square is a chart
that shows all the
possible
combinations of
___________ that
can result from a
_________ _____.
• Geneticists use
_____________
Squares to show all
the possible
outcomes of a
genetic cross and
to determine the
probability of a
particular outcome.
Punnett Squares
• A Punnett Square
is a chart that
shows all the
possible
combinations of
alleles that can
result from a
genetic cross.
• Geneticists use
Punnett Squares to
show all the
possible outcomes
of a genetic cross
and to determine
the probability of a
particular outcome.
Punnett Square
T
t
t
T
(25%)
(25 %)
Tt
Tt
(25%)
(25%)
Tt
Tt
Punnett Square
T
T
t
t
(25%)
(25%)
TT
Tt
(25%)
(25%)
Tt
tt
Now you try…..
B
B
b
B
Now you try…..
B
B
B
BB
BB
b
Bb
Bb
Terms
• An organism’s
_________________
is its physical
appearance, or its
visible traits. (Ex. tall
or short stems)
• An organism’s
_________________
is its genetic makeup.
__________ ______
______________
_________ _________
________ TT
Tall
________
________ tt
Terms
• An organism’s
phenotype is its
physical appearance,
or its visible traits.
(Ex. tall or short
stems)
• An organism’s
genotype is its
genetic makeup.
Phenotype and Genotype
Phenotype
Genotype
Tall
TT
Tall
Tt
Short
tt
More Terms
Phenotype Genotype
• An organism that
has two identical
alleles for a trait is
Tall
TT
said to be
_______________.
Tall
Tt
• An organism that
has two different
alleles for a trait is Short tt
said to be
_______________.
• ______________ used the
term _______________ to
describe ______________.
___________
Or
___________
___________
___________
___________
More Terms
Phenotype Genotype
• An organism that
has two identical
alleles for a trait is
Tall
TT
said to be
homozygous.
Tall
Tt
• An organism that
has two different
alleles for a trait is Short tt
said to be
heterozygous.
• Mendel used the term
hybrid to describe
heterozygous.
Homozygous
Or
Heterozygous
Homozygous
Heterozygous
Homozygous
One More Term
• In ___________________, the alleles are
neither dominant nor recessive. As a
result, both alleles are expressed in the
offspring.
One More Term
• In codominance, the alleles are neither
dominant nor recessive. As a result, both
alleles are expressed in the offspring.
If Erminette chickens
reproduced….
What is this an example of?
• _____________________
What is this an example of?
• CODOMINANCE – Roan Cattle are an
example of codominance
Chapter 3, Section 3
The Cell and Inheritance
After completing the lesson, students
will be able to:
• Describe chromosomes and their role
in inheritance;
• Identify and describe the events that
occur during meiosis.
Walter Sutton
In 1903, Walter Sutton, an ________
geneticist, added an important piece of
information to the understanding of
genetics. Sutton was studying the cells
of __________________. He was trying
to understand how sex cells form.
• ___________ – the male sex cell
• ___________ – the female sex cell
Walter Sutton
In 1903, Walter Sutton, an American
geneticist, added an important piece of
information to the understanding of
genetics. Sutton was studying the cells
of grasshoppers. He was trying to
understand how sex cells form.
• Sperm – the male sex cell
• Egg – the female sex cell
Sperm and Egg
More on Sutton
• Sutton became particularly
interested in the movement of
_____________ during the
________________ of sex cells.
• Sutton hypothesized that
______________ were the _______
to understanding how offspring come
to have _______________ similar to
those of their parents.
More on Sutton
• Sutton became particularly
interested in the movement of
chromosomes during the formation
of sex cells.
• Sutton hypothesized that
chromosomes were the key to
understanding how offspring come to
have traits similar to those of their
parents.
Chromosomes and
Inheritance
• Sutton knew that structures inside
cells must be responsible for the
inheritance of ______________. He
needed evidence to support his
__________________________ that
_________________________ were
those structures.
• What he discovered:
Chromosomes and
Inheritance
• Sutton knew that structures inside
cells must be responsible for the
inheritance of genes. He needed
evidence to support his hypothesis
that chromosomes were those
structures.
• What he discovered:
Sutton Discovered
• Grasshoppers have
____ chromosomes in
each of their body
cells.
• Grasshopper’s sex
cells have only _____
chromosomes.
• The fertilized egg that
forms has _______
chromosomes.
Sutton Discovered
• Grasshoppers have
24 chromosomes in
each of their body
cells.
• Grasshopper’s sex
cells have only 12
chromosomes.
• The fertilized egg
that forms has 24
chromosomes.
Sutton’s Conclusion
• Sutton concluded that the ___________
carried Mendel’s heredity factors, or
__________ from one generation to the
next. In other words, _____________
_______________________________.
• Sutton’s idea became known as the
__________ _________ ___ ________
that states: genes are carried from
parents to their offspring on
chromosomes.
Sutton’s Conclusion
• Sutton concluded that the chromosomes
carried Mendel’s heredity factors, or genes
from one generation to the next. In other
words, genes are located on
chromosomes.
• Sutton’s idea became known as the
chromosome theory of inheritance that
states: genes are carried from parents to
their offspring on chromosomes.
Meiosis
• Meiosis is the process by
which the number of
chromosomes is _______
by half to form sex cells
– ______ _____ ______.
• During meiosis, the
chromosome pairs
_____________ and are
__________________ to
two different cells. The
resulting sex cells have
only half as many
chromosomes as the
other cells in the
organism.
Meiosis
• Meiosis is the process by
which the number of
chromosomes is reduced
by half to form sex cells
– sperm and eggs.
• During meiosis, the
chromosome pairs
separate and are
distributed to two
different cells. The
resulting sex cells have
only half as many
chromosomes as the
other cells in the
organism.
Mini Lab Mini Lab Mini Lab
• Turn to page 105 in your text book.
• Draw the stages of Meiosis.
• Label and write a description (your
own or what is in the book) of the
four stages.
Meiosis and Punnett
Squares
• The Punnett square
shows how ________ Parent Cells
separate when sex
cells form during
meiosis. It also
shows the possible
__________
Tt
combinations that can
result after
fertilization occurs.
Tt
Possible Sperm Cells
Possible egg cells
Meiosis and Punnett
Squares
• The Punnett square
shows how alleles
separate when sex
cells form during
meiosis. It also
shows the possible
allele combinations
that can result after
fertilization occurs.
Tt
Parent Cells
Possible Sperm Cells
Tt
TT
Tt
Possible egg cells
Tt
tt
Chromosomes
• ____________ of the
organism doesn’t
determine the
number of
chromosomes:
• _____________ have
46 chromosomes
• _____________ have
78 chromosomes
• _____________ have
56 chromosomes
• Chromosomes are
made up of many
____________ joined
together like beads
on a string.
• Your body has _____
pairs of chromosomes
that contain more
than _____________
genes. Each gene
controls a _________
____________.
Chromosomes
• Size of the organism
doesn’t determine the
number of
chromosomes:
• Humans have 46
chromosomes
• Dogs have 78
chromosomes
• Silkworms have 56
chromosomes
• Chromosomes are
made up of many
genes joined together
like beads on a
string.
• Your body has 23
pairs of chromosomes
that contain more
than 60,000 genes.
Each gene controls a
particular trait.
Chromosomes
-
• Genes are located on
_________________.
• They may have
different __________
for some genes and
the same for others.
Chromosomes
-
• Genes are located
on chromosomes.
• They may have
different alleles for
some genes and
the same for
others.
Chapter 3, Section 4
The DNA Connection
After completing the lesson, students
will be able to:
• Explain the term “genetic code”;
• Describe the process by which a cell
produces proteins;
• Describe different types of mutations
and how they affect organisms.
The Genetic Code
• The main function of genes is to control
the __________ of ______________ in
the organism’s cells.
• __________________ help to determine
the __________, _____________, and
many other traits of an organism.
The Genetic Code
• The main function of genes is to
control the production of proteins in
the organism’s cells.
• Proteins help to determine the size,
shape, and many other traits of an
organism.
Keeping it in perspective!
_______________
___________
_______
_______
____
_______
Keeping it in perspective!
Chromosome
Cell
Nitrogen
Bases
DNA
Molecule
Review of Chapter 2
• DNA is a major component of
chromosomes.
• DNA is made up of four different Nitrogen
Bases – adenine (A), thymine (T),
guanine (G), and cytosine (C) – these
bases form the rungs on the DNA ladder.
• A single gene on a chromosome may
contain anywhere from several hundred
to a million or more of these bases that
are arranged in a specific order.
Cracking the Code
• The order of the
_____________
____________
along a gene
forms a _______
___________
that specifies
what type of
___________ will
be produced.
Cracking the Code
• The order of the
nitrogen bases
along a gene
forms a genetic
code that
specifies what
type of protein
will be produced.
Cracking the Code
• In a genetic code, a
group of three bases
codes for the
attachment of a
specific _________
_______. _______
__________ are the
building blocks of
__________. The
order of the bases
determines the
order in which
________ ________
are put together to
form a __________.
Cracking the Code
• In a genetic code, a
group of three bases
codes for the
attachment of a
specific amino acid.
Amino acids are the
building blocks of
proteins. The order
of the bases
determines the
order in which
amino acids are put
together to form a
protein.
How Cells Make Proteins
• _______ ___________ is the production of
proteins
• During _________ __________, the cell uses
information from a gene on a chromosome to
produce a specific protein.
• _________ _____________ takes place on
the ______________ in the cytoplasm outside
the nucleus
• __________________ are inside the nucleus
• HOW does the information needed to produce
proteins get out of the nucleus and into the
cytoplasm???
How Cells Make Proteins
• Protein synthesis is the production of proteins
• During protein synthesis, the cell uses
information from a gene on a chromosome to
produce a specific protein.
• Protein synthesis takes place on the
ribosomes in the cytoplasm outside the
nucleus
• Chromosomes are inside the nucleus
• HOW does the information needed to produce
proteins get out of the nucleus and into the
cytoplasm???
The Role of RNA
• The _______ ___________ is called ribonucleic
acid or RNA – RNA carries the genetic code
from the DNA inside the nucleus into the
cytoplasm.
• RNA and DNA are similar, but DNA looks like
one side of the ladder. RNA contains a different
______________ molecule then DNA. Instead
of thymine, RNA contains __________.
• _______________ ________ copies the coded
message from DNA in the nucleus and carries
the message into the cytoplasm.
• Another type of RNA, called ______________
__________, carries amino acids and adds
them to the growing protein.
The Role of RNA
• The genetic messenger is called ribonucleic acid
or RNA – RNA carries the genetic code from the
DNA inside the nucleus into the cytoplasm.
• RNA and DNA are similar, but DNA looks like
one side of the ladder. RNA contains a different
sugar molecule then DNA. Instead of thymine,
RNA contains uracil.
• Messenger RNA copies the coded message from
DNA in the nucleus and carries the message
into the cytoplasm.
• Another type of RNA, called transfer RNA,
carries amino acids and adds them to the
growing protein.
Handout and Book Work
• Turn to pages 110 and 111 in your
textbook.
• Complete the handout on Protein
Synthesis.
• When the handout is complete read
pages 110-112 in your textbook
about Mutations.
Mutations
• Some of the
changes brought
about by
mutations are
harmful to an
organism.
Other mutations,
however, are
helpful, and still
others are
neither harmful
nor helpful.
Helpful Mutations
• Monarch Butterfly
• Viceroy Butterfly
Birds do not like the taste of monarch butterflies. Many years ago the
viceroy butterflies looked different. Through various mutations in
appearance the viceroy looks like the distasteful monarch butterfly.