Download Genetics

Bellwork (in spiral)
 Imagine
that you are planning to meet
your pen pal but you two have never met
in person.
 What traits (distinguishing quality or
characteristic) would you use to describe
yourself? Make a list.
 Which of these traits do you think you
inherited? Put a check mark next to these
traits on your list.
Genetics
Inheriting the good, the bad,
and the ugly!
The study of heredity and the
variation of inherited
characteristics.
Why don’t you look like a
rhinoceros?
How likely is it that a dog is the
parent of a cat?
Why??





Because your parents do not have the traits
of a rhinoceros!
Dogs and cats have different DNA. They are
genetically different from one another.
Heredity is the passing of traits from parents to
offspring.
A trait is a distinguishing quality or
characteristic.
Offspring is the descendants of a person,
animal, or plant considered as a group.
My Traits Activity
 Complete
the Inventory of My Traits –
Survey independently
 Data Table Results, as a class
 Make a graph of the class results
 Study the data. What trends do you
observe? What heredity traits are more
common among the class?
Inventory Traits Survey Help
Hmmm…
 But,
what if both of your parents have
straight hair, and you have curly?
 What if both of your parents have brown
eyes, but you have blue?
Hypothesize…
 With
your table group, develop 2-3
possible reasons for how this might
happen. Write your hypotheses in your
spiral.
Question
 If
a black dog and a white dog
have puppies, what color will
those puppies be?
 Grey?
 Black?
 White?
 Half
black and half white?
 A different color all together?
Genetics and Heredity
 The
study of genetics and heredity helps
us to answer these puzzling questions.
 How do we study heredity?
Early Ideas
 Early
studies used plants, rather than
animals.
 Why?
 Plants make LOTS of offspring (seeds).
 Easier to have lots of growing plants in a
lab.
 Easier to control who breeds with who.
Early Ideas - Blending
 Prior
to the 1850’s, people believed in the
idea of blending.
 Blending is like mixing two paints together,
you mix black and white, you get…
 Gray!
 But this didn’t make much
sense…eventually everyone would look
the same.
Blending
 With
blending, if you crossed red with
white, you’d always get pink.
Red
X
White
=
Pink
Gregor Mendel
 An
Austrian monk,
Gregor Mendel, also
thought this was quite
odd and questioned the
idea of blending.
 In the mid-1800s, in a
series of experiments,
Gregor Mendel
discovered the rules
underlying patterns of
inheritance.
Gregor Mendel Used
Scientific Method
 Question:
Does blending occur?
 Prediction: No, blending does not
occur.
 Test Hypothesis: Observed
different characteristics in pea
plants…some had wrinkled seeds
and others had round seeds.
wrinkled
round
Bellwork
 In
your spiral…
 Write a 3-4 sentence summary of what
you learned about genetics yesterday.
Experiment




Planted one wrinkled
seed and one round
seed.
Transferred pollen from
the wrinkled plant to
the round plant, called
cross-pollination.
If blending were
occurring what would
you expect to see as a
result of this test?
Answer: slightly
wrinkled seeds
Parent generation
Results
 The
resulting seeds were ALL round.
 Therefore, proving Mendel correct that
blending did not occur.
New Experiment




This led Mendel to a
second experiment, in
which he planted two
of the resulting round
seeds in 2 other pots.
He cross pollinated the
plants again.
This time, the results
were different.
What do you think the
results were?
First Generation
Conclusion


This plant produced
3 round seeds and 1
wrinkled seed.
Mendel tested this
many times and with
different
characteristics of the
plants, and got the
same pattern of
results over and over.
Second Generation
Results of Mendel’s
Experiments
Parent Generation
First Generation
Second Generation
Ratio = 3:1
Cause & Effect Map (part 1)
Causes (left side)
Main Event (middle)
 Gregor
Mendel’s
Experiments
 Include a
description and
drawing of the
results of his
experiments.


Thinking back to
what you learned
yesterday, add the
reasons that led to
Mendel’s
experiments.
Why did he develop
a hypothesis to test?
:
Statistics indicated a
pattern.
Discoveries




One trait was always present in the first
generation, while the other trait seemed to
disappear. Mendel called this trait the dominant
trait.
Dominant Trait – the trait observed in the first
generation when parents that have different traits
are bred. (Stronger trait)
Recessive Trait – the trait that seems to disappear
in the first generation, but reappears in the second
generation. (weaker trait)
Mendel realized that his results could only be
explained if each plant had two sets of instructions
for each characteristic.
Instructions



First generation plants carried instructions for
both the recessive and dominant trait.
Genes are the instructions for an inherited
trait. (wrinkled or round, we often use letters to
represent each instruction)
Alleles are the different forms of a gene
(recessive or dominant) (R or r, use a capital
letter to represent the dominant allele, and
the same letter in lower case to represent the
recessive allele)
Phenotype
 Phenotype
is an organisms physical
appearance or detectable characteristic.
(what you see) For example: round seeds,
flower color, blue eyes, blonde hair,
freckles etc.
 What is the phenotype for the following
pictures?
Genotype
 Genotype
is the combination of
alleles that make up a specific trait.
(example: RR or Rr)
 Homozygous is a genotype that has
two of the same form of the allele.
(example: RR or rr)
 Heterozygous is a genotype that
has two different forms of the allele.
(example: Rr)
Genotype versus phenotype.
How does a
genotype ratio
differ from the
phenotype ratio?
Hornimonster Activity
Female - mother
Male - father
Pedigree
A diagram that shows the occurrence of a genetic trait in several
generations of a family.
Pedigree analysis reveals Mendel’s pattern in human inheritance
Hemophilia is a recessive trait defined by the absence of one or
more of the proteins required for blood clotting.
Probability Activity…
Probability


Probability is a
mathematical
chance that
something will
happen.
The probability
of throwing
heads or tails
on a coin is 50%
(1/2 chances)
PROBABILITY
o
Helps predict the chance that something will
happen
o
Your predictions become more accurate with the
more trials you run!
Punnett Squares
 Punnett
square: a
chart used to
organize all of the
possible
combinations of
offspring from
particular parents.
Make a Punnett Square
 Look
back and Mendel’s first experiment.
 What allele should we use for the seed
type?
 The round seed is dominant over wrinkled,
so use the letters R and r to represent the
allele.
 The genotype for the round seed is RR.
 The genotype for the wrinkled seed is rr.
Make a Punnett Square
 RR
x rr
R
r
r
R