Download Traits and probability

Traits and probability
6.5
Essential Question: How is a Punnett
square used to predict inheritance
patterns.
A Punnett square is a grid system used to predict all
possible genotypes resulting from a cross.
Probability – the likelihood that a particular event will
occur.
Monohybrid cross – a cross that examines the
inheritance of only ONE specific trait.
T is a dominant trait for tallness.
t is a recessive trait for shortness.
Homozygous Dominant = Same letters = TT
Homorzygous Recessive = Same letters = tt
Heterozygous = different letters = Tt.
TT = will be a tall tree.
tt = will be a short tree.
Tt = will ALSO by a tall tree! Why? Because it has the
dominate (T) allele present.
Dihybrid Cross – a cross that examines the
inheritance of two different traits.
Dihybrid crosses tend to result in a 9:3:3:1 ratio.
Parental Group = P
First generation of offspring = F1
Second generation of offspring = F2
Mendel’s Law of Independent Assortment – Different
traits appear to be inherited separately.
Bacteria and other microorganisms reproduce by
binary fission – asexual reproduction by the
separation of a cell into 2 new cells.
There is no sex involved.
Multicellular organisms reproduce sexually, which
means that the resulting offspring has genetic
material from both parent organisms.
Yes…plants can reproduce
sexually…
Let’s get it off so we can get it on…
The advantage of sexual reproduction is that the
resulting offspring is more likely to have a traits that
will facilitate survival.
Crossing over – the exchange of chromosome
segments (DNA) between homologous chromosomes
in prophase I, prophase I, PROPHASE I.
Crossing over is what makes each individual human
different.
Crossing over is also referred to as genetic
recombination.
Inheritance Patterns
EQ: What does it mean to have one
allele that is dominant to another
allele? 7.1
A carrier does not show symptoms of a disease but
can pass on the allele that can cause disease to
offspring.
Genes that are located on the sex chromosomes (the
X or Y chromosomes) are called sex-linked genes.
All other genes are autosomal genes (located on
autosomes).
This is where it gets tricky…
For sex-linked traits, males only need one copy of the
allele. Females need two copies for the trait to be
expressed. This is NOT good for us males…
What does that mean?
It means, if you’re male, you’re more likely to inherit a
sex-linked trait.
Incomplete Dominance – the heterozygous
phenotype is in-between the homozygous phenotype
(A blending of the traits).
Codominance – neither allele is dominant or
recessive.
Pedigree charts are used to trace the genotypes and
phenotypes of a family.
A blue betta fish mates with another betta fish that is
light green in color. Their offspring appear to have a
bluish green color. What type of inheritance has taken
place here?
A karyotype is a picture of all of the chromosomes
within a cell.
Whenever a problem asks for the probability or
chance of having some allele (gene), JUST go
ahead and create yourself a Punnett Square.
Set the square up first using the mother and
father genotype. Father is usually at the top of
the square. A Genotype of Hh is known as …
A) Homozygous dominant
B) Homozygous Recessive
C) Heterozygous (carrier)
Now, begin to distribute your letters DOWN each
column. The letter above a square MUST go
inside all of the squares below.
Then, begin to distribute your letters ACROSS
each row. The letter to the left of a square MUST
go inside all of the squares to the right of that
letter.
4 out of 4 squares have at least one capital H; all
of the offspring will therefore have hairy bellies.
4/4 = 1.0 and 1.0 x 100 = 100%
¾ = .75 and .75 x 100 = 75%
If a kangaroo is a carrier for large pouches, which
is a dominant trait (P) and it copulates with a
kangaroo that is homozygous recessive with a
small pouch (p), what percentage of the
offspring will have small pouches? Use a Punnett
square…take 90 seconds to discuss with your
group…
Now…work with your group on
the assignment given…
Remember, NO ONE sits in the
back lab area unless you have an
assigned seat there. YES…that
means YOU.