Download Genetics - Wando High School

Genetics - Chapter 12
Name _______________________________________
Gregor Mendel
•
Gregor Mendel was a monastery priest who carried out the first important studies of _____________
– Heredity – the passing on of characteristics from _____________ to _____________
– _____________ is the branch of biology that studies the _____________ of inheritance and
_____________ in organisms
•
Mendel was the first to succeed in predicting how traits would transfer from one _____________ to
the _____________.
Mendel’s Experiment
• Mendel chose to study _____________
–
They reproduce _____________ – meaning they have two
distinct sex cells (called _____________)
–
•
The female gamete is the _____________ (located on the pistil)
•
The male gamete is in the __________________________
The structure of the pea plants allowed Mendel to _____________ their fertilization
•
The transfer of male pollen grains to the pistil is called _____________
•
Fertilization is when the male and female gametes ___________________
• Mendel studied one trait at a time and analyzed the results __________________________
Monohybrid Crosses
• Mendel crossed __________ pea plants with __________ pea plants
• Mendel called this cross a _____________ – a cross between two
parents that show _____________ forms of a trait
• Mendel’s first experiments were monohybrid since the parents differed
only in _____________ trait.
• The first generation (_____) are the initial cross organisms
–
In this case, a ________ pea plant and a ________ pea plant
• The second generation (_____) includes the offspring from the initial
cross
–
For Mendel, this resulted in all _________ plants
• The third generation (______) is the result of crossing the offspring from
the ______ generation
–
For Mendel, this resulted in _______ tall plants and _______ short
Mendel’s Conclusions
•
•
•
•
Mendel concluded that each organism had ________ factors that controlled each trait.
One factor is passed down from ______________________
The factors are located on the _______________________
The different forms of the genes are called _____________
Rule of Dominance
• Even though the F1 generation plants had a tall allele from one
parent and a short allele from the other, they all appeared _____________
• Mendel concluded that one trait was _____________ over the other trait which he
called _____________
• Plants with two alleles for tallness (TT) were_____________.
• Plants with two alleles for shortness were _____________ (tt)
• Plants with one allele for tallness and one for short (Tt) were __________
Law of Segregation
• If an organism has two _____________ alleles for a trait, that organism can make two
_____________ types of gametes.
–
Tt plant can produce ___ gametes and ___ gametes
• Fertilization from a Tt + Tt cross will result in _____________ pairs of the available gametes
(_____________ possible combinations)
–
T from male + T from female = _______
–
T from male + t from female = _______
–
t from male + T from female = _______
–
t from male + t from female = ________
Describing Offspring
• There are _______ ways to describe the results of a pairing
–
–
An offspring’s _____________
–
An offspring’s _____________
Genotype – the _____________ _____________ of an organism
–
An pea plant with two alleles for tallness has the genotype, _________
–
An pea plant with one allele for tallness and one allele for shortness has the genotype, ______
T
t
• Phenotype – the _____________ _____________ of the organism

–
A pea plant with two alleles for tallness has the phenotype, _________
–
A pea plant with one allele for tallness and one allele for shortness has the phenotype, _______
If an organism has the __________ two alleles for a trait, the organism is _____________
–
_____
–
_____
TT
• If an organism has two _____________ alleles for a trait, the organism is _____________
–
tt
_____
• Recessive traits must be ___________________ (_____) to be expressed
• Dominant traits __________________ if they are homozygous (_____) or heterozygous (____)
Predicting Offspring
•
Mendel devised a way to _____________ the possible outcome of a cross. This method is called a
_____________ Square (or _____________ Chart)
•
•
•
Punnett Square’s take into account that fertilization of gametes is _____________
To use a Punnett Square, you need to know the _____________ of the parent generation.
Punnett Squares can be used to predict offspring from a _____________ or a _____________ cross
Monohybrid Punnett Square
•
Put _____ of each type of possible gamete from _____ parent on top of the square
•
Put _____ of each type of possible gamete from the _________ parent on the side of the square
•
Fill each box with the ______________ of that box’s row and column
•
The _____________ offspring combinations can be seen
•
The ratio of offspring phenotypes after a heterozygous
monohybrid cross is _______________
–
In this case we see 3 _________ and 1 ___________
Monohybrid Crosses
Homozygous tall crosses with
Homozygous short crosses with
heterozygous tall
heterozygous tall
Genotype Ratio:
Genotype Ratio:
Phenotype Ratio:
Phenotype Ratio:
Tt
Incomplete Dominance
• _____________ _____________ is a condition in which one
allele is not _____________ dominant over another.
• The phenotype expressed is somewhere _____________ the two
possible _____________ phenotypes.
• In snapdragons, flower color is controlled by incomplete
dominance. The two alleles are red (R) and white (r). The
_____________ genotype (Rr) is expressed as_____________.
Dihybrid Crosses
• Mendel also performed dihybrid crosses – involving
__________ traits
• He wondered if the two traits would be inherited
_____________.
• His P1 generation crossed round yellow peas (__________)
with wrinkled green peas (__________)
• The F1 generation was _________ round and yellow
• The F2 generation had ___ round yellow, ___ round green, __ wrinkled yellow and __ wrinkled green
Law of Independent Assortment
•
The fact that traits for the color of the pea and the shape of the pea were passed on independently of
each other led to the Law of _______________________________________
•
When a pea plant with the genotype RrYy produces gamete, the alleles R and r will _____________
from each other (Law of_____________) as well as the from the Y and y alleles (Law of Independent
Assortment)
•
Alleles will sort independently unless they are “_____________”.
This usually occurs when they are so _____________ to each
other on the chromosome that they one is rarely passed on
_____________ the other.
Dihybrid Punnett Square
•
Put one of _____________ of possible gamete combination from
one parent on top of the square
•
Put one of _____________ of possible gamete combination from the other parent on the side of the
square
•
Fill each box with the ___________ of that box’s row and column
•
The possible _____________ combinations can be seen
•
The ratio of offspring phenotypes after a heterozygous dihybrid
cross is _____________
–
In this case we see ___ round yellow, __ round green,
___ wrinkled yellow and ___ wrinkled green
Dihybrid Punnett Square
•
Homozygous round and yellow with a heterozygous yellow and round
•
___________ with _____________
•
Offspring are ___________________________________
•
Homozygous wrinkled and green with a heterozygous yellow and round
•
___________ with _______________
•
_____ round yellow, ______ round green, _______ wrinkled yellow, ______ wrinkled, green
Sex Determination
•
•
Remember that humans have 22 pairs of _____________ and 1 pair of ___________ chromosomes
These sex chromosomes determine the _____________ of the offspring
– XX is a _____________
– XY is a _____________
•
•
•
Each offspring gets an ______ from the mother and either an ____ or a _____ from the father
Predicting the sex of the offspring can be done using a _____________ Square
Each time a male gamete fertilizes a female gamete, there is a _________ chance for either sex
Sex-Linked Traits
•
•
•
Traits controlled by genes carried on the X or Y chromosomes are called ______________________
Most of these types of traits are carried on the ________ chromosome
The alleles for different forms of the sex-linked traits are shown as _________________ on the X
–
•
_______
_________ ________
– _______
________
Because the Y _____________ carry an
allele, a male could _______ be
heterozygous for a sex-linked trait
Predicting Sex-Linked Traits
• The chances that an offspring will have
a sex-linked trait can be predicted using
a Punnett Square
Sex-Linked Crosses
Colorblindness is a recessive sex-linked trait. Use _____ for the normal allele and ______ for the
colorblind allele
Colorblind mother and Normal father
Heterozygous Normal mother and Colorblind father
Results:
Results:
Blood Type
• Human blood types demonstrate multiple alleles (more than two alleles of the gene)
–
________________________
• Human blood types also demonstrate_______________________ – where heterozygous alleles can
be expressed _________________
–
A and B are _________________
–
O is _________________
• These alleles are written as _______, _________, and ________
–
IAIA or IAi will have type _____ blood
–
IBIB or IBi will have type _____ blood
–
IAIB will have type _____ blood
–
ii will have type _____ blood
Blood Type Crosses
Type O mother and Type AB father
Homozygous Type A mother and
Homozygous Type B father
Results:
Results:
Polygenic Traits
•
________________ traits are traits that are controlled by __________
or ____________ genes. These traits often show a great variety of
phenotypes, e.g._________________________.
Pedigrees
• A ____________ is a chart constructed to show an inheritance
__________ (trait, disease, disorder) within a family through multiple_____________________.
• Through the use of a pedigree chart and key, the genotype and ______________ of the family
members and the genetic ______________ (dominant/recessive, sex-linked) of the trait can be
tracked.
• An example of a pedigree key:
Pedigrees
Family with a __________________
genetic trait
Family with a ___________________
genetic trait