Transcript how to succeed in genetics problem-solving

Genetics is the study of inheritance
Parents send information about traits
(characteristics) to their offspring.
This information is what we refer to as genes.
Genes are located on chromosomes which are made
of DNA.
Each individual has two copies of a gene, one from
each parent.(one from egg, one from sperm).
The two copies of each gene may or may not have
the same information (or ALLELES) for each trait
For example both of your parents gave you an
ALLELE for tongue rolling.
Allele = form of a trait
Your mom might have given you the gene that says
you can roll your tongue. While your dad might
have given you the gene that says you cannot roll
your tongue.
Dominant - represented by capital
letters it is the overpowering trait
Recessive - represented by lowercase
letters it is the trait that is
sometimes hidden by the dominant
trait
The ability to roll your tongue is a dominant trait,
so it would be represented with a T
Not being able to roll your tongue would be a
recessive trait represented with a t
If they are the same genes the individual is
said to be homozygous for that trait. DD or
dd
If they have different information the
individual is said to be heterozygous for
that trait. Dd
Remember homo means the same
And
Hetero means different
Let’s Practice!
Determine if each is Homozygous or
Heterozygous.
AA
Aa
aa
Phenotype of an organism is its physical
appearance (what it is going to look like)
Example: Acne or No Acne, Big Eyes or
Small Eyes
The genotype of an organism is the genes or
letters that organism has for a trait.
Ex. AA, Aa, or aa
Hybrid vs. Purebred?
If you have a Hybrid dog breed vs. a
Purebred Dog breed, what does that mean?
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
The ability to roll your tongue is a dominant trait,
so it would be represented with a T
Not being able to roll your tongue would be a
recessive trait represented with a t
If the dad cannot roll his tongue his
genotype is tt
If the mom can roll her tongue her genotype
is either TT or Tt
Let’s say the mom is heterozygous for the
tongue rolling trait which would make her
genotype Tt
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
T= Tongue
roller
t = non
roller
PARENTS
CROSS IT
RESULTS
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
T= Tongue
roller
t = non
roller
PARENTS
tt x Tt
CROSS IT
RESULTS
In flowers red petal color is dominant to
white petal color. Cross a heterozygous red
petaled flower with a white petaled flower
Rr x
rr
Phenotype
50% Red
50% White
Genotype
50% Rr
50% rr
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
Rr x Rr
Phenotype
Genotype
75% Red
25% RR
25% White
50% Rr
25% rr
RR x Rr
Phenotype
Genotype
100% Red
50% RR
0% White
50% Rr
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
Polydactylous cats have more than five toes. In fact,
the author, Ernest Hemingway is credited with
establishing a large colony of about 50 feral
polydactylous cats in the Florida Keys. One of his
cats, Princess six-toes appeared in the New York
Times. The polydactyl allele is dominant over the
allele for five toes and fingers. Predict the offspring
of a mating between a heterozygous polydactylous
male and female.
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
More Practice!
Albinism is the absence of skin pigmentation and is a recessive
trait found in humans and other animals. In the human
population about 1/20,000 individuals is an albino. Normal
pigmentation (A) is dominant to albinism (a). If an albino
woman marries a homozygous normal man, what is the
likelihood that one of their children will display albinism?
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
Test Cross
• A common squash in Texas is the Yellow
crooked-neck squash. This fruit is a source of
vitamin A, B, and C. It also contains calcium
and iron. Yellow colored squash (y) is recessive
to white-colored squash (Y). If a yellow male
squash is crossed with a female white-squash
and 5 of the offspring are yellow, and 5 are
white, what is the genotype of the female white
squash?
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
Test Cross
BONUS: A woman with normal pigmentation
marries an albino man and their first child is an
albino. What are the genotypes of the couple?
HOW TO SUCCEED IN
GENETICS PROBLEMSOLVING
LEGEND
PARENTS
CROSS IT
RESULTS
DIY Monohybrid Cross Practice
Problems
• You will be responsible for creating a practice
problem for your classmates to perform. Do a
quick google search of real world dominant and
recessive traits, and then create a document or
presentation to share with your classmates.
• Example on next slide!
In Quaker Parrots, green feathers (F) are
dominant to blue feathers (f). If a homozygous
dominant male mates with a homozygous
recessive female, what are the chances that they
would have a blue feathered offspring?
Legend
Parents
F = Green feathers
f = blue feathers
FF x ff
Cross
Results
F
f
f
F
Ff
Ff
Ff
Ff
Phenotype:
Green : blue
4: 0
Genotype
FF: Ff: ff
0 : 4: 0
Or make it a little fun….
• Bieber hair (H) is dominant over clown fro hair
(h). Vernon has bieber hair, If Vernon married a
clown fro chicka what is the possibility of them
having clown fro babies?
•
Vernon
+
Clown Fro
Chicka
Dihybrid Cross
• Monohybrid = 1 trait
• Dihybrid = 2 traits
RrYy x RrYy
Phenoype:
9:3:3:1
9 round & yellow, 3 round & green,
3
wrinkled & yellow, 1 wrinkled & green
Incomplete Dominance
Sometimes the dominant and the recessive trait
blend together. This is called incomplete
dominance.
For example in some flowers petal color is
incompletely dominant. If you cross a red flower
RR with a white flower rr, you would get pink
flowers Rr
Phenotypic Ratio: 25% red, 50% pink, 25% white
Genotypic Ratio: 25% RR, 50% Rr, 25% rr
Your 23rd pair of chromosomes are called your “sex
chromosomes”
These chromosomes have the genes that determine if you
are male XY or female XX.
Who determines the sex of the child the mom or the dad?
The dad is the only one that can give a Y chromosome so
he is the one that determines the sex of the child.
Some traits are sex linked traits like: colorblindness,
hemophilia (a blood disorder), and certain types of
baldness.
Sex linked traits are traits that are on the X chromosome
Cross a male who does not have hemophilia with a female
carries hemophilia, but does not have it.
Some traits are controlled by genes that have more
than two alleles this is called a multiple allele.
An example of multiple alleles is blood types.
Blood Type
Genotype
(Phenotype)
A
IAIA or IAi
B
IBIB or IBi
AB
I AI B
O
ii
Phenotypic Ratio
25% AB
25% A
25% B
25% O
Phenotypic Ratio
50% A
50% O
Polygenic Traits
Poly – many
Genic – genes
Polygenic Traits are traits that are controlled by
many genes.
Skin, hair, and eye color are all influenced by the
effects from three to six genes.
Each of these genes control the amount of a
pigment called melanin. The more of the genes
that are expressed, the darker the color
produced.
http://www.howe.k12.ok.us/~jimaskew/bio/bktype.htm