Transcript Genetics - TeacherWeb

Genetics
Who do you look like????
Vocab
 Homozygous dominant/ homozygous
recessive
 Heterozygous
 Genotype/ phenotype
 Gamete
 Hybrid
 Gene
 Segregation
 P/ F1 generation/ F2 generation
Gregor Mendel
 Austrian Monk crossed some pea plants
 Laws of ____________
 There are alternative forms of genes, the
units determining heritable characteristics.
This is now known as an ____________

An organism inherits one allele from each
parent.
Segregation


A sperm or egg carries only one allele for each
characteristic which pair upon fertilization.
When the alleles are different, one is fully
expressed and the other is masked, now
known as ____________ and recessive
genes.
Genes and Dominance
 Dominance - the ability of one allele to
express its ____________ at the expense of
an alternate allele;
 Generally the dominant allele will make a
gene product that the recessive can not;
therefore the dominant allele will
____________ itself whenever it is present
Lets Practice:
 What do you get for F1 when your P
generation is Homozygous dominant Yellow
and green?
 What if you cross two of the offspring from
that cross? What is the F2 generation?
 What if I said to cross a Tall with a Tall? What
are the possible outcomes?
Test Cross
 When you
are not
sure of the
genotype
of the
dominant
phenotype
you do a
test cross
More Practice…
 What if I wanted to know if a flower was likely
to be tall/ short and purple/ white?
 How would I do that?
Dihybrid
Cross
 In any case
where the
parents are
heterozygous for
both traits (AaBb
x AaBb) you will
get a 9:3:3:1
ratio
Independent Assortment
 This law states that allele pairs separate
independently during the formation of
____________ Therefore, traits are
transmitted to offspring independently of one
another.
Dihybrid Cross
A cross (or mating)
between two
organisms where two
genes are studied is
called a DIHYBRID
cross.
The genes are located
on separate
chromosomes, so the
traits themselves are
unrelated.
BB = black
Bb = black
bb = white
LL = short hair
Ll = short hair
ll = long hair
Also in rabbits, black eyes are dominant to red eyes.
These letters represent the genotypes of the rabbits:
GG = gray hair
Gg = gray
hair
gg = white
hair
BB = black
eyes
Bb =
black
eyes
bb = red
eyes
1. What are the phenotypes (descriptions) of rabbits that have the
following genotypes:
Ggbb ____________________ ggBB ________________________
ggbb ____________________ GgBb _________________________
 A male rabbit with the genotype GGbb is
crossed with a female rabbit with the genotype
ggBb The square is set up below. Fill it out and
determine the phenotypes and proportions in the
offspring.
How many out of 16 have grey fur and
black eyes? ________
How many out of 16 have grey fur and
red eyes? ________
How many out of 16 have white fur and
black eyes? ________
How many out of 16 have white fur and
red eyes?
Incomplete Dominance
 When there is no
dominant or recessive,
the heterozygous
condition results in a
"blending" of the two
traits. Example:
Snapdragons can be
red, white, or pink
(heterozygous)
 neither allele is
dominant, red x white =
pink
Codominance
 Both are expressed in some way, red x white
= white/red spots
 Use all capital letters - Red (RR) x White
(WW) = Red and white (RW)
The old way still works, though.
Sex linked Traits
 The genes for these traits are on the _____
chromosome
 because boys only receive one X
chromosome they are more likely to inherit
disorders passed to them from their
____________ who would be a carrier.
 Hemophilia and Colorblindness are sex linked
traits, the punnet square below shows how a
woman who is a carrier passes the trait to her
son, but not her daughters.
Pedigree Chart
Muliple Allele Traits
 Traits that are controlled by more than two
alleles. Blood type in humans is controlled by
three alleles: A, B, and O
 Blood can only be transferred to a body of a
person who's immune system will "recognize"
the blood. A and B are antigens on the blood
that will be recognized. If the antigen is
unfamiliar to the body, your body will attack and
destroy the transfused blood as if it were a
hostile invader (which can cause death).
 O is like a blank, it has no antigens. O is
called the universal donor because a person
can receive a transfusion from O blood
without having an immune response
 AB is the universal acceptor, because a
person with AB blood has both the A and B
antigens already in the body, A and B blood
can be transfused to the person (as well as
O) and the body will recognize it and not
attack.
Environmentally Influenced Traits
 Siamese cats have dark ears and feet due to
the temperature. Height in humans is
influenced by the environment (diet)
 Traits are influenced by the environment.
Pattern baldness affects men because
testosterone activates the genes.
 THE ENVIRONMENT EFFECTS THE
EXPRESSION OF GENES!!!!!!