Transcript Breeding Corn

Breeding Corn
BELL RINGER
If a green pea pod plant is crossed with a yellow
pea pod plant, what will the offspring look like?
X
ALL the offspring will be green!
Is it possible for a man &
woman (each with dark
hair) to have a child with
blond hair?
Introduction
Read the Introduction…Pg. 282
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What is SELECTIVE BREEDING?
the process by which organisms with
desirable traits are mated with the goal of
producing even more desirable offspring.
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What is SEXUAL REPRODUCTION?
reproduction in which two parents
contribute genetic material to the offspring.
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Corn Reproductive Structures
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How do traits get passed from
parent to offspring?
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Through GAMETES: sex
cells
Male gamete is the
SPERM
Female gamete is the
EGG
FERTILIZATION: union of
egg & sperm
ZYGOTE: fertilized egg
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Challenge

How can information about the
genetic makeup of plants help
farmers breed plants for
desirable traits?
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Get
Started
 Answer
the 3 questions on the
“Traits & Heredity” sheet under
“I think…”
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Breeding Corn: First Generation
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Procedure
Read “Basic Genetics” on p. 286
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What are alleles?
A form of a gene…An organism has two copies
of the gene for each of its traits.
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Distinguish between dominant and
recessive traits.
Dominant traits will mask another version of a trait;
only one dominant allele needed to be expressed…
A recessive trait will be hidden by a dominant trait.
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GENES VS. ALLELES
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Segment of DNA that codes
for one protein/trait
Most traits are determined
by TWO genes.
Remember chromosomes
have a homologous
match…two chromosomes
with similar genetic
information
EXAMPLE:
hair color
eye color
height in pea plants
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Each form of a gene is
called an ALLELE
EXAMPLE:
brown or blond
blue, hazel, brown
tall, short
RECESSIVE (allele)
DOMINANT (allele)
Always expressed if
present
Only need ONE
dominant allele to
be expressed
EXAMPLES:
dark hair, brown
eyes,
tall peas
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May be present but will
not be expressed if
paired w/ dominant
allele
Requires TWO recessive
alleles for recessive
trait to be expressed
EXAMPLES:
light hair, blue eyes,
short peas
Procedure
As a group…
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Use the “P” allele cards to demonstrate
what happened to make all corn kernel
babies purple
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Discuss the 3 questions as a group and
fill in under “My group thinks…”
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Procedure
Creating a Punnett Square
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Key
Vocabulary
Genotype vs. Phenotype
All possible combinations using P, p: PP, pp, Pp, pP
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GENOTYPE:
actual genes in the pair;
can’t see…they’re on
chromosomes…but they
determine the individual’s
traits
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PHENOTYPE: the trait
that is expressed; the
‘physical’ appearance
Key
Vocabulary
Describing GENOTYPE…
Use terms:
homozygous: both genes the same
(PP, pp)
*follow with ‘dominant’ or ‘recessive’ to
distinguish upper case or lower case
heterozygous: genes different;
1 dominant, 1 recessive (Pp, pP)
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Procedure
Read the scenario (step 8 on p.286)
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Count the number of purple kernels and the
number of yellow kernels on corn ear A
Record your data
Count the number of purple kernels and the
number of yellow kernels on corn ear B
Record your data
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Which describes the cross that
produced ear A? Ear B?
Punnett Square X
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Punnett Square Y
Punnett Square Z
Procedure
Breeding Corn: Second Generation
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Revisit the
Challenge
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Complete the “now we know” column of
the “traits & Heredity” page
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Answer the ANALYSIS questions p.289
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Follow Up
Analysis 1
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How does a Punnett square show the
possible results of a cross between two
individuals?
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Follow Up
Analysis 2
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Describe how your observations of
offspring (corn kernels) allowed you to
determine the genetic makeup of the two
parents.
Discuss how you used ratios in this
process
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Follow Up
Analysis 3
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What do you predict will happen if a
purple corn plant with the genes Pp is
bred with a corn plant with purple kernels
and the genes PP? Explain your answer,
and include a matching Punnett Square.
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Follow Up
Analysis 4
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How could scientists use selective
breeding to help solve a sustainability
challenge such as breeding a crop that
can survive drought?
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Revisit the
Challenge

How can information about the
genetic makeup of plants help
farmers breed plants for
desirable traits?
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Key
Vocabulary
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allele
dominant
Punnett square
recessive
selective breeding
sexual reproduction
trait
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