Genetics

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Genetics

• Unit 6

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What is genetics?

• Genetics Is the science of heredity
• Genetics began with Mendel
• Mendel is considered the Father of Genetics
• Mendel was a monk who experimented with pea
  plants to study heredity

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What is a trait?

• Trait Is a notable feature or characteristic in
  an organism
• Physical traits
• Examples - Hair color, eye color, height
• Behavioral traits
• Example Sheepdog has herding instincts
• Medical conditions
• Examples Cancer, Sickle cell, cystic fibrosis

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Why did Mendel study peas?

• Peas reproduce and grow quickly
• They had easy to observe traits
• Can reproduce using 2 different plants or using 1
  plant
• True-Breeding Can produce offspring with only
  1 parent
• Cross Pollination 2 parents
  self-fertilizing/true-breeding

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What are alleles?

• Allele Alternative form that a single gene may
  have for a particular trait. (huh?)

A gene in a particular place on a particular
chromosome will express a particular trait.like
flower color
Purple is an Allele coming from mom
But what color will the offspring show?
Chromosome from MOM
Chromosome from DAD
White is an Allele coming from dad
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How do alleles determine what traits will show?

• Some alleles are dominant and others are
  recessive

Do you have to remember which traits are dominant
and which are recessive?...
Dominant A trait that will appear (show)
Represented with a CAPITAL letter Example Tall
(T), Black (B), Brown (B)
NO Punnett Square questions will give you clues
or will tell you in the question! You HAVE TO
READ!
Recessive A trait that is masked (hidden) if a
dominant allele is present, but will show if
both alleles are recessive Represented
with a lower case letter Example short
(t), blond (b), blue (b)
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How do you know if a trait will show or not?

• Rule 1 If there is a dominant trait present,
  it will always show that trait.

Tall is dominant over short
Capital T bosses the little t
T T
T t
Dominant
Dominant
Dominant
Recessive
Shows Tall
Shows Tall
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I do you know a trait will show or not?

• Rule 2 If there is NOT a dominant trait
  present, then the recessive trait will always
  show.

Tall is dominant over short
t t
Recessive
Recessive
Shows Short
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Clicker Question 1

• Who is considered the
• Father of Genetics?
• Darwin
• Hooke
• Mendel
• Paquin

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Clicker Question 2

• These plants were used in Mendels experiments
  because they grow reproduce quickly
• Peas
• Corn
• Wheat
• Roses

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Clicker Question 3

• What is true-breeding?
• 2 parents reproduce offspring
• 2 offspring with three parents
• Self fertilizing plants
• Cross pollinating plants

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Clicker Question 4

• If a girl has Tt, she will show
• Short
• Tall
• Both (a) (b)
• None of the above

Tall is dominant over short
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Before we start Punnett Squares, we have a few
more things to learn
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What are some terms that will help with
understanding Punnett Squares?

• Homozygous Organism with 2 of the same alleles
  for a particular trait. Also called pure.

Examples TT tt DD
dd
Same sized letters!
Same sized letters!
Same sized letters!
Same sized letters!
Same
Homo means ________
Think Same SIZED letters
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What are some terms that will help with
understanding Punnett Squares?

• Heterozygous Organism with 2 different alleles
  for a particular trait. Also called hybrid.

Examples Tt Dd Gg
Bb
Different sized letters!
Different sized letters!
Different sized letters!
Different sized letters!
Different
Hetero means __________
Think Different SIZED letters
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What are some terms that will help with
understanding Punnett Squares?

• Phenotype The observable characteristic or
  outward expression of an allele pair

Characteristics you can see with your eyes!
Think Phenotype -- Physical
Black Hair
Blond Hair
Red Hair
Brown Hair
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What are some terms that will help with
understanding Punnett Squares?

• Phenotype

Characteristics you can see with your eyes!
Multi color Butterfly
Blue Butterfly
White Butterfly
Orange Butterfly
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What are some terms that will help with
understanding Punnett Squares?

• Genotype The organisms allele pairs

Characteristics you can NOT see with your eyes!
Think Genotype Genetic Code
HH
GG
bb
Gg
Hh
Bb
hh
gg
BB
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Clicker Question 5

• Another term for heterozygous is
• Allele
• Same
• Hybrid
• Pure

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Clicker Question 6

• tt is an example of
• homozygous
• heterozygous
• hybrid
• all of the above

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Clicker Question 7

• tt is an example of
• phenotype
• heterozygous
• hybrid
• genotype

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Clicker Question 8

• If a boy has tt, he will show
• tall
• short
• both (a) (b)
• none of the above

Tall is dominant over short
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Clicker Question 9

• Tall is an example of
• phenotype
• Heterozygous
• pure
• genotype

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What is Mendels Law of Segregation?

• Law of Segregation States that the two alleles
  for each trait separate during meiosis.

During meiosis, the alleles separate
During fertilization, the alleles unite into a
pair again
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Whats the difference between monohybrid ?
dihybrid crosses?
Punnett Square A diagram used to predict the
possible outcomes (offspring) of a particular
cross or breeding.

• Monohybrid Cross The use of Punnett Square for
  1 trait
• (will have 4 boxes)

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Punnett Square Video
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Whats the difference between monohybrid ?
dihybrid crosses?
Dihybrid Cross The use of Punnett Square for 2
traits (will have 16 boxes)
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Whats the difference between monohybrid ?
dihybrid crosses?
Law of Independent Assortment Mendelian law
stating that two alleles for each trait separate
during meiosis
During Dihybrid crosses The random assortment
of alleles results in four possible gameteseach
of which is equally likely to occur
I will show you this when I show dihybrid crosses
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Sometimes two traits can be dominant at the same
time
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Whats the difference between incomplete
dominance and co-dominance?
Incomplete Dominance Complex inheritance
pattern in which the heterozygous phenotype is
intermediate between those of the two homozygous
parent organismshuh?
Mixes like paint!
R
R
W
RW
RW
W
RW
RW
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Whats the difference between incomplete
dominance and co-dominance?
Co-Dominance Complex inheritance pattern that
occurs when neither allele is dominant and both
alleles are expressed.
B
B
BW
BW
W
BW
BW
W
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Clicker Question 10

• Each gamete has only one allele for a trait
  because of
• recessive
• Law of segregation
• dominance
• phenotype

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Clicker Question 11

• When a white flower a red flower have pink
  offspring, this is because of
• Co-dominance
• Law of segregation
• Law of Independent assortment
• Incomplete dominance

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Clicker Question 12

• In speckled chickens, both alleles are express
  because of
• Co-dominance
• Law of segregation
• Law of Independent assortment
• Incomplete dominance

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Clicker Question 13

• The cross with one trait is called
• Dihybrid
• Trihybrid
• Monohybrid
• All of the above

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Clicker Question 14

• A dihybrid cross will have how many squares?
• 4
• 16
• 18
• 20

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Lets start Punnett Squares!