Download Mendel`s Pea Plants

Mendel’s Pea Plants
Life Science Unit 7 Lesson 1
Attendance link: http://goo.gl/forms/bOZWikMCIc
EXPECTATIONS
Required Class Connects
Tuesday, Wednesday, & Thursday
1:30-2:30 pm
Be active and participate in class.
Be respectful to your classmates
Be positive in the chat box and use it correctly.
Have a working microphone!
You will need it during the lessons and break out rooms.
If you have a question, please place it in the chat box and repost it
if I don’t see it.
2
Objectives
• Identify traits as genetically determined characteristics and
give examples of traits (for example, eye color, leaf shape).
• Distinguish between dominant and recessive traits.
• Summarize Mendel's contributions to the field of genetics.
• Describe how genetic information is passed from parents to
offspring.
The study of
characteristics transferred
from both parents
Organisms that produce
sexually, two parents
Genetics
Coded in DNA
Examples:
Hair color, eye color
Things we inherit
Where it all started…
• Over 100 years ago in a monastery.
• A curious Austrian monk named Gregor Mendel started
to wonder why pea plants have different colored
flowers.
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 (1900’s)
Between 1856 and 1863, Mendel cultivated and tested some
28,000 pea plants
He found that the plants' offspring retained traits of the
parents
Called the “Father of Genetics"
Mendel stated that physical traits are inherited
as “particles”
Mendel did not know that the “particles” were
actually Chromosomes & DNA
Mendel kept detail accounts of his observations
and experiments. This helped later scientist
confirm his findings.
Alleles
• Two forms of a gene (dominant &
recessive); you get one allele from each
parent.
Dominant
• Stronger of two alleles expressed in the
hybrid; represented by a capital letter;
only need one copy for it to show.
Recessive
• Allele that show up less often in a cross,
must have two copies for it to show up;
represented by a lowercase letter.
Genotype
Gene combination for a trait
• This is the allele make up of a gene/trait. Must show both alleles.
• Example: RR, Rr, or rr
Phenotype
The physical feature resulting from a genotype
• This is the trait that is expresses. That is the trait that you see.
• Example: Brown hair, blue eyes, two ears, etc.
Genotypes
Homozygous
The gene combination
involving 2 dominant or 2
recessive alleles for a gene.
Label genes as homozygous
recessive or
homozygous dominant
Heterozygous
The gene combination
of one dominant and
one recessive allele
for a gene.
Don’t use recessive or
dominant
Called hybrid
Called Pure or true breeders
Why peas?
Can be grown in a small area
Produce lots of offspring
Produce pure plants when
allowed to self-pollinate several
generations
Can be artificially crosspollinated
Reproduction in Flowering Plants
•Pollen contains sperm
•Produced by the stamen
•Ovary contains eggs
•Found inside the flower
Pollen carries sperm to the eggs for
fertilization
Self-fertilization can occur in the
same flower
Cross-fertilization can occur
between flowers
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12
•
Mendel’s Experimental Methods
•Mendel hand-pollinated flowers using a
paintbrush
•He could snip the stamens to prevent
self-pollination
•Covered each flower with a cloth bag
•He traced traits through the several generations
How Mendel Began
Mendel
produced
pure
strains by
allowing the
plants to
selfpollinate
for several
generations
copyright cmassengale
14
Eight Pea Plant Traits
• Seed shape --- Round (R) or Wrinkled (r)
• Seed Color ---- Yellow (Y) or Green (y)
• Pod Shape --- Smooth (S) or wrinkled (s)
• Pod Color --- Green (G) or Yellow (g)
• Seed Coat Color ---Gray (G) or White (g)
• Flower position---Axial (A) or Terminal (a)
• Plant Height --- Tall (T) or Short (t)
• Flower color --- Purple (P) or white (p)
copyright cmassengale
15
copyright cmassengale
16
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17
Mendel’s Experimental Results
18
Generation “Gap”
• Parental P1 Generation = the parental generation in a breeding
experiment.
• F1 generation = the first-generation offspring in a breeding
experiment. (1st filial generation)
• From breeding individuals from the P1 generation
• F2 generation = the second-generation offspring in a breeding
experiment.
(2nd filial generation)
• From breeding individuals from the F1 generation
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Following the Generations
Cross 2
Pure
Plants
TT x tt
Results
in all
Hybrids
Tt
Cross 2 Hybrids
get
3 Tall & 1 Short
TT, Tt, tt
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Mendel’s hybridization experiments…
Monohybrid crosses:
Parental
Generation
F1 generation
True-breeding
purple flower
x
True-breeding
white flower
All purple flowers (the hybrids)
Allowed F1 offspring
to self-fertilize
F2 generation
705 purple
224 white
• Mendel crossed two true breed plants. The first generation of a cross
between a true-breeding plant with yellow seeds and a true-breeding plant
with green seeds, all the offspring had yellow seeds. The yellow-seed trait
was the same trait that only one of the parents had. Where did the green
seeds go?
The parent with yellow seeds must have been homozygous dominant, YY.
The parent with green seed must have been homozygous recessive, yy.
Therefore, with each offspring getting one allele from each parent, their genotype must be Yy. Because
yellow is dominant it only needs one allele for that phenotype to show up.
How can we see if this is true?
• Mendel then crossed the offspring of this cross to each other (remember, they
all have yellow seeds). In the second generation of plants, Mendel noticed an
odd pattern. In each cross, three-fourths of the offspring had yellow seeds, and
about one-fourth had green seeds. The green seeds came back!
• In the second generation, a cross between two plants grown from first-
generation yellow seeds will produce three-fourths yellow seeds and onefourth green seeds.
Breakout rooms: Answer this question in complete sentences.
• The trait for height in pea plants can be expressed as tall or short. Tall is
the dominant expression of the height trait. Short is the recessive
expression. A true-breeding tall plant is crossed with a true-breeding
short plant, and the first-generation plants are crossed with each other.
How will height be expressed in the first- and second-generation plants?
Breakout rooms: Answer this question in complete sentences.
• The trait for height in pea plants can be expressed as tall or short. Tall is
the dominant expression of the height trait. Short is the recessive
expression. A true-breeding tall plant is crossed with a true-breeding
short plant, and the first-generation plants are crossed with each other.
How will height be expressed in the first- and second-generation plants?
• In the first generation, all the plants will be tall, but they
will all carry one dominant and one recessive allele. In the
second generation, three-fourths of the plants will be tall
and one-fourth will be short.
Breakout rooms (if time)
Characteristics
You have red hair
Soccer is your favorite sport
You can roll your tongue
You speak Spanish fluently
You are colorblind
Your hair is dyed brown
You have pierced ears
You have freckles
You prefer sweet food over sour.
You can play the saxophone
Your blood type is O
You have dimples when you
smile
You are tall for your age
Your nails are painted red
You enjoy writing poetry
Genes/ Inherited
Environment
Breakout rooms (if time)
Characteristics
You have red hair
Soccer is your favorite sport
You can roll your tongue
You speak Spanish fluently
You are colorblind
Your hair is dyed brown
You have pierced ears
You have freckles
You prefer sweet food over sour.
You can play the saxophone
Your blood type is O
You have dimples when you
smile
You are tall for your age
Your nails are painted red
You enjoy writing poetry
Genes/ Inherited
Environment
A true-breeding pea plant with greed seeds is crossed
with another true-breeding pea plant with green seeds.
What kind of seeds will the offspring have?
• The offspring will have 100% green seeds.
• Green seed color is recessive so the parent
generation must both be homozygous recessive
and therefore can only pass on the recessive
allele.
Which statement best summarizes Gregor
Mendel’s contribution to science
A. Factors for traits in pea plants cannot be controlled.
B. Wrinkled seeds grow faster than smooth seeds.
C. Garden pea plants can be grown in a variety of colors.
D. Factors for some traits are inherited from parents.
Assignment
• OLS
• Part 1 online – 2 questions
• Part 2 Offline – 3 questions
• Make sure that you are mastering your lessons (80%+). They do not count
as part of your progress if they are not mastered.
• If you have any questions, please let me know.