Download the study of genetics

NAME _______________________________________________________________ PER ______________ DATE _________________________
THE STUDY OF GENETICS
Use your knowledge about Gregor Mendel and genetics to answer the following questions.
1. Your teacher will work through this problem with you. Probability is the likelihood an event will happen
and can be expressed as percentages, fractions, or decimals. The following formula is used to determine
probability.
Probability = number of times an event is expected to occur (part)
number of chances for the event to occur (total)
For Example
In a cage there are 250 mice. Of the 250 mice, 225 are black and 25 are white. You get to buy a mouse
but can’t look in the cage.
What is the probability of getting a white mouse?
What is the ratio of black to white mice?
2. You are running away from a bear in a forest. In the forest there are 23 eucalyptus trees and 77 oak trees.
a) If you are not paying attention, what is the probability of you running into an oak tree?
b) What is the ratio of oak trees to eucalyptus trees?
3. Obtain a sack of beans from your teacher. There are four possible choices that can be pulled from the
sack (green, black, white, and brown) and each is in equal proportion (20 of each). Total number of
beans is 80. Determine the probability of getting a black bean. __________________
4. Pull one bean out and record the selection. Return the bean to the sack, shake it, and select again. Do
this procedure until the table is filled.
1
5
9
13
17
2
6
10
14
18
3
7
11
15
19
4
8
12
16
20
1
5. Based on your data, what percentage of your picks were black beans?
6. Is this the same percentage that was predicted in number 3? Explain why.
7. What is the purpose of meiosis?
8. Where do you get your genetic information from?
9. Who was Gregor Mendel?
10. Why are pea plants good organisms to conduct genetic research on?
11. Match the following terms.
_____ heredity
a) The scientific study of heredity.
_____ genetics
b) Physical characteristics
_____ traits
c) The passing of traits from parent to offspring.
12. Describe the relationship between a gene and an allele.
13. A pea plant can have flowers that are purple or white.
a) What is the gene in the above statement?
b) What are the alleles?
14. A _______________________________ allele is represented by a(n) capital letter.
A recessive allele is represented by a _______________________________ allele.
15. Match the following terms.
_____ phenotype
a) An organism with two identical alleles for a trait
_____ genotype
b) An organism’s physical appearance, or visible traits
_____ homozygous
c) An organism’s genetic make-up, or allele combination
_____ heterozygous
d) An organism that has two different alleles for a trait
2
16. How can you tell what is a dominant trait versus a recessive trait?
17. In plants, the allele T represents “tall” and the allele t represents “short”. A tall plant was mated with
another tall plant. Four offspring resulted with the following genotypes.
a) Which of the two traits, tall or short, is dominant?
b) What is the genotype in box “1”?
c) What is the phenotype of individual “4”?
d) What percentage is tall?
e) How many of the offspring are homozygous?
f) Which plants are heterozygous tall?
18. Mendel crossed rounded pea seed plants with wrinkled pea seed plants (P). The offspring were all
rounded (F1). He allowed the rounded pea seed plants to fertilize. In the generational offspring (F2),
there were 5474 rounded pea seed plants and 1850 wrinkled pea seed plants.
a) Which trait is dominant?
b) What is the ratio of rounded to wrinkled?
3
NAME _______________________________________________________________ PER ______________ DATE _________________________
INTRODUCTION TO PUNNETT SQUARES
QUESTION: What is the likelihood two heterozygous red-throated birds will have a baby white-throated
bird?
Let's say that for the red-throated bird, red throat is the dominant trait and white throat is recessive.
Since the "red-throat code" and the" white-throat code" are alleles (two forms of the same gene), we
abbreviate them with two forms of the same letter. So we use "R" for the dominant allele/trait (red throat)
and "r" for the recessive allele/trait (white throat).
 Determine the genotypes of the parent organisms
 Write down your "cross" (mating)
 Draw a p-square
 "Split" the letters of the genotype for each parent & put them "outside" the p-square.
 Determine the possible genotypes of the offspring by filling in the p-square.
 Summarize results (genotypes & phenotypes of offspring).
 Answer the question in a complete sentence.
Scientists at Bikini Bottoms have been investigating the genetic makeup of the organisms in this community.
Use the information provided and your knowledge of genetics to answer each question.
1. For each genotype below, indicate whether it is a heterozygous (Het) OR homozygous (Hom).
TT ________ Bb ________ DD ________Ff ________ tt ________ dd ________
Dd ________ ff ________ Tt ________ bb ________ BB ________FF ________
4
2. Determine the phenotype for each genotype using the information provided about SpongeBob.
Yellow body color is dominant to blue.
YY ________________ Yy ________________ yy ________________
Square shape is dominant to round.
SS ________________ Ss ________________ ss ________________
3. For each phenotype, give the genotypes that are possible for Patrick.
A tall head (T) is dominant to short (t).
Tall = _______________ Short = _______________
Pink body color (P) is dominant to yellow (p).
Pink body = _____________ Yellow body = _________________
4. SpongeBob SquarePants recently met SpongeSusie Roundpants at a dance. SpongeBob is heterozygous for
his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities that would
result if SpongeBob and SpongeSusie had children. HINT: Read question #2!
A. List the possible genotypes and phenotypes for their children.
B. What are the chances of a child with a square shape? ____ out of ____ or ____%
C. What are the chances of a child with a round shape? ____ out of ____ or ____%
5. Patrick met Patti at the dance. Both of them are heterozygous for their pink body color, which is dominant
over a yellow body color. Create a Punnett square to show the possibilities that would result if Patrick and
Patti had children. HINT: Read question #3!
A. List the possible genotypes and phenotypes for their children.
B. What are the chances of a child with a pink body? ____ out of ____ or ____%
C. What are the chances of a child with a yellow body? ____ out of ____ or ____%
5
6. Everyone in Squidward’s family has light blue skin, which is the dominant trait for body color in his
hometown of Squid Valley. His family brags that they are a “purebred” line. He recently married a nice girl
who has light green skin, which is a recessive trait. Create a Punnett square to show the possibilities that
would result if Squidward and his new bride had children. Use B to represent the dominant gene and b to
represent the recessive gene.
A. List the possible genotypes and phenotypes for their children.
B. What are the chances of a child with light blue skin? ____%
C. What are the chances of a child with light green skin? ____%
7. Mr. Krabbs and his wife recently had a Lil’ Krabby, but it has not been a happy occasion for them. Mrs.
Krabbs has been upset since she first saw her new baby who had short eyeballs. She claims that the
hospital goofed and mixed up her baby with someone else’s baby. Mr. Krabbs is homozygous for his tall
eyeballs, while his wife is heterozygous for her tall eyeballs. Some members of her family have short eyes,
which is the recessive trait. Create a Punnett square using T for the dominant gene and t for the recessive
one.
A. List the possible genotypes and phenotypes for their
children.
B. Did the hospital make a mistake? Explain your
answer.
8. You can use a test cross to determine whether a plant with purple flowers is heterozygous (Pp) or
homozygous dominant. Fill in each Punnett square below then answer the questions that follow.
a) What do the letters at the top and on the sides of the box represent?
b) What do the letters in the boxes represent?
c) Calculate the genotype and phenotype ratios if the parent of the unknown genotype were
homozygous for the trait (Figure B).
d) If half of the offspring have white flowers, what is the genotype of the parent plant? Explain.
6
9. In rabbits, the allele B for black hair is dominant over the allele b for brown hair. You can practice using
probabilities to predict the outcome of genetic crosses by completing the genetic problems below. Draw
Punnett squares for each problem.
a) Calculate the probability of homozygous dominant (BB) offspring resulting from a cross between two
heterozygous (Bb) parents.
b) Calculate the probability of heterozygous offspring resulting from a cross between a heterozygous
parent and a homozygous recessive (bb) parent.
c) Calculate the probability of heterozygous offspring resulting from a cross between a homozygous
dominant parent and a homozygous recessive parent.
d) Calculate the probability of homozygous dominant offspring resulting from a cross between a
heterozygous parent and a homozygous recessive parent.
7
NAME _______________________________________________________________ PER ______________ DATE _________________________
DOMINANCE PRACTICE PROBLEMS
For all of the following problems make sure to show: 1)Key for the alleles, 2)Cross, 3)Punnett square with
genotypes, and 4)Punnett square with flowers colored. Be sure to complete the genotypic and phenotypic
ratios.
1. In wildflowers the flower color blue is completely dominant over the flower color purple. Use this
information to complete the following problems.
a) Determine all the possible genotypes and phenotype for this scenario.
b) Cross a homozygous blue flower with a heterozygous blue flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
c) Cross a heterozygous blue flower with a homozygous purple flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
d) Cross a heterozygous blue flower with a heterozygous blue flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
8
2. In wildflowers the flower color red is incompletely dominant over the flower color ivory (white). The
heterozygous phenotype, thus takes on a pink color (a mix in-between red and white). Use this
information to complete the following problems.
a) Determine all the possible genotypes and phenotype for this scenario.
b) Cross a red flower with an ivory flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
c) Cross a pink flower with a pink flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
d) Cross a red flower with a pink flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
9
3. In wildflowers the flower color yellow is codominant with the flower color orange. The heterozygous
phenotype produces a “roan” flower (speckled with both yellow and orange dots). Use this information
to complete the following problems.
a) Determine all the possible genotypes and phenotype for this scenario.
b) Cross a yellow flower with an orange flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
c) Cross an Orange flower with a Roan flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
d) Cross a Roan flower with a Roan flower.
Cross:
Genotypic ratio:
Phenotypic ratio:
10
4. Now complete the following table by putting the word YES or NO in each box.
Normal
Incomplete
Dominance
Dominance
There is a definite dominant trait
Co-dominance
There is a definite recessive trait
The heterozygous is a mixture of the
two traits
The heterozygous shows both traits
at the same time
The genotypic and phenotypic ratios
are always the same
5. In certain varieties of chicken, the allele for black feathers is codominant with the allele for white
feathers. Heterozygous chickens have a color described as “erminette ” speckled with black and white
feathers. If you cross two erminette chickens, what will the genotypic and phenotypic ratios of the
offspring be? Be sure to start with a Punnett square.
6. The alleles for curly hair and straight hair are examples of alleles for a trait that are examples of
incomplete dominance. Individuals with curly hair are homozygous for curly hair alleles. Individuals
with straight hair are homozygous for straight hair alleles. Individuals who are heterozygous, with one of
each allele have wavy hair, which is a blend of the expressions of the curly and straight hair alleles. Your
teacher has slightly curly hair. Her dad has curly hair and her mom has straight hair. Use a Punnett
Square to show how your teacher inherited her hair.
11
NAME _______________________________________________________________ PER ______________ DATE _________________________
SEX-LINKED
In fruit flies, eye color is a sex linked trait. Red (XR) is dominant to white (Xr).
1. What are the a) sexes (M/F) and b) eye colors (Red/White) of flies with the
following genotypes?
X R X r Sex = _________
Eye color = ____________
XRY
Sex = _________
Eye color = ____________
X r X r Sex = _________
Eye color = ____________
X R X R Sex = _________
Eye color = ____________
XrY
Eye color = ____________
Sex = _________
2. What are the genotypes of these flies:
white eyed, male ____________
red eyed female (heterozygous) ________
white eyed, female ___________
red eyed, male ___________
3. A woman that is a carrier for colorblindness wants to have children with a man who has normal vision.
Below is a Punnett square that predicts their possible children. Answer the questions based on the cross
already done for you.
a) What are the parental genotypes?
Mom=
Dad=
b) What are the possible genotypes of the daughters?
c) What are the possible genotypes of the sons?
d) Is it possible for the daughters to show the disorder? Explain.
12
4. Show the cross of a white eyed female XrXr with a red-eyed male XRY.
5. A pure red eyed female and a white eyed male mate.
a) What are the genotypes of the parents:
___________ and _______________
b) Show the cross.
c) What percent are:
white eyed, male ______ white eyed, female ______ red eyed, male ______ red eyed, female ______
6. In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the disease. Males
will either have the disease or not (but they won’t ever be carriers).
a) Show the cross of a man who has hemophilia with a woman who is a carrier.
Parent genotypes
Mom =
Dad=
What is the probability that any of their children will have the disease? __________
b) Show the cross of a woman who has hemophilia that marries a normal man.
Parent genotypes
Mom =
Dad=
How many of their children will have hemophilia, and what is their sex?
13
7. In cats, the gene for calico (multicolored) cats is codominant and sex-linked.
Females that receive a B and an R gene have black and orange splotches on white
coats. Males can only be black or orange, but never calico.
Here’s what a calico female’s genotype would look like: XBXR
Show the cross of a female calico cat with a black male?
Parent genotypes
Mom =
Dad=
What percentage of the kittens will be black and male? _________
What percentage of the kittens will be calico and male? _________
What percentage of the kittens will be calico and female? _________
8. Browse pages 184-185, 236-237, and 241-245. Match the pattern on inheritance with the correct
example of that pattern. Your notes will be helpful as well.
_______ Single allele
a. Skin or eye color
_______ codominance
b. ABO blood typing
_______ incomplete dominance
c. Colorblindness
_______ multiple allele
d. Coat color in dogs
_______ epistasis
e. Four o’clock flower color
_______ polygenic
f.
_______ environmental impact
g. Tay-Sachs disease
_______ seX-linked
h. Pea traits
Hydrangea flower color in different pH
14
NAME _______________________________________________________________ PER ______________ DATE _________________________
BLOOD TYPING
1. List the three alleles used in determining blood type.
2. What do the (genes) alleles produce that determines what blood type an individual will have?
3. Blood type is an example of a trait that is considered both codominant as well as multiple allele.
Explain.
4. List (all) genotypes for each of the four blood types.
Type O: _____________
Type B: _____________ and _____________
Type A: _____________ and _____________
Type AB: _____________
5. A man that has type AB blood marries a woman that has type B blood. A Punnett square has been
completed for you. Answer the questions.
a) Give the parental genotypes used in this cross.
b) Is the woman homozygous or heterozygous for her blood type?
c) What are the possible blood types of their offspring?
d) Can the parents have any children with blood type O? Explain.
6. A man who has type B blood (IBIB) is married to a woman with type O (ii) blood. What blood type will
their children have? Support your answer by doing Punnett squares.
Parent genotypes
Mom =
Dad=
15
7. A woman with type A blood is claiming that a man with type AB blood is the father of her child, who is
also type AB. Could this man be the father? Remember the woman can be either homozygous or
heterozygous for the blood type. Support your answer by doing Punnett squares.
Parent genotypes
Mom =
Dad=
8. A man with type AB blood is married to a woman with type O blood. They have two natural children,
and one adopted child. The children's blood types are: A, B, and O. Which child was adopted? Support
your answer by doing Punnett squares.
Parent genotypes
Mom =
Dad=
9. A man has type B blood. What are ALL the possible blood types of his parents. Show the crosses to
prove your answer.
16