Genetics

VocabularyPunnett Squares

Special Cases

Basic Vocabulary

• Traits are passed from parents to offspring through DNA.

• Your DNA is wrapped up into “X” shaped chromosomes.

• Sections of a chromosome that match a trait are called genes.

• Different forms of a gene are called alleles.

Vocab to solve problems

• Everyone has 2 alleles (1 from mom; 1 from dad)• Dominant Alleles – Alleles that “mask” others or show whenever 1 or more

allele is there. Use capital letter.

• Recessive Alleles– Alleles that “hide” when dominant allele is there. You

only see it if there are two lowercase letters.

Vocab to solve problems• Genotype – What two alleles someone has (Ex. “AA” , “aa” or “Aa”)

• Homozygous– Both alleles are the same (Ex. “AA” or “aa”)

• Heterozygous– One of each allele (Ex. “Aa” – will look like “A” trait

because it is dominant)

• Phenotype– What the trait actually looks like (Ex. “brown eyes” or

“tall” etc.)

Punnett Squares

• Punnett Squares organize the parents’ genotypes and all possible offspring (children) they could have.

• Complete the one in your study guide.• They are the best way to check any genetics

problem to make sure it is correct!!!– And sometimes the only way to solve it!!!

Special Cases to watch for

• Sex linked – some genes are on the X and Y “sex” chromosomes. They are more common in men.

• Co-Dominant – Rather than one dominant allele, two both are shown. (Ex. Black X White = Black AND White babies)

• Incomplete Dominance – two dominant alleles are blended, (Red X White = Pink)

• Polygenic – Controlled by many genes (not just 1)

In mussels, the allele for brown coloring (B) is dominant, and the allele for blue coloring (b) is recessive. For which parental genotypes are 100% of the offspring expected to be blue?

A. Bb × Bb

B. BB × bb C. bb × bb D. BB × BB

In mussels, the allele for brown coloring (B) is dominant, and the allele for blue coloring (b) is recessive. For which parental genotypes are 100% of the offspring expected to be blue?

C. bb × bb

Since brown B is dominant, and blue (b) is recessive, a

blue mussel would have genotype “bb”. The only way to guarantee 100% of offspring have this is to have no “B” in either parent.

In guinea pigs, the allele for black hair (B) is dominant to the allele for brown hair (b). Two black-haired guinea pigs are crossed. One of the guinea pigs is homozygous for black hair and one is heterozygous.

What percentage of the offspring are expected to have black hair?

A.25% B. 50% C. 75% D. 100%

In guinea pigs, the allele for black hair (B) is dominant to the allele for brown hair (b). Two black-haired guinea pigs are crossed. One of the guinea pigs is homozygous for black hair and one is heterozygous.

What percentage of the offspring are expected to have black hair?

D. 100%

(B) Black hair is dominant. One parent is homozygous (BB). No matter what this parent will pass a “B” to all offspring. 100% will be black. (try to build the punnett square to prove it!!)

The table below shows the genotypes that result in four different blood types in humans.

Genotype Blood TypeIA IA, IA i AIB IB, IB i B

IA IB ABi i O

Based on the information in the table, which of the following describes alleles IA and IB?

A. The IA and IB alleles show sex linkage.

B. The IA allele is recessive to the IB allele. C. The IA allele is dominant to the IB allele. D. The IA and IB alleles show co-dominance.

The table below shows the genotypes that result in four different blood types in humans.

Genotype Blood TypeIA IA, IA i AIB IB, IB i B

IA IB ABi i O

Based on the information in the table, which of the following describes alleles IA and IB?

D. The IA and IB alleles show co-dominance.When IA and IB are together, both are in the blood

type. Neither one is stronger than the other.

In garden pea plants, the tall allele (T) is dominant to the short allele (t), and the round seed allele (R) is dominant to the wrinkled seed allele (r).

Which of the following crosses could produce short pea plants with wrinkled seeds?

A. TtRr x TTRR

B. TTRr x TTRr C. TtRr x Ttrr D. TtRR x ttRR

In garden pea plants, the tall allele (T) is dominant to the short allele (t), and the round seed allele (R) is dominant to the wrinkled seed allele (r).

Which of the following crosses could produce short pea plants with wrinkled seeds?

C. TtRr x Ttrr

To make short it must have (tt). To be wrinkled it must be (rr). Each parent must have the recessive alleles for both “t” and “r” to make such a offspring possible.

In mice with black agouti coats, each hair is black and yellow. Two mice with black agouti coats are crossed. Among the offspring, most of the mice have black agouti coats, and the rest of the mice have non-agouti coats with solid black hairs.

Based on the results of the cross, which of the following statements describes the most likely genetics of the coat color in the mice?

A. The agouti allele is recessive to the non-agouti allele. B. The agouti allele is dominant to the non-agouti

allele. C. The agouti allele and non-agouti allele are sex-

linked.D. The agouti allele and non-agouti allele are codominant.

In mice with black agouti coats, each hair is black and yellow. Two mice with black agouti coats are crossed. Among the offspring, most of the mice have black agouti coats, and the rest of the mice have non-agouti coats with solid black hairs.

Based on the results of the cross, which of the following statements describes the most likely genetics of the coat color in the mice?

B. The agouti allele is dominant to the non-agouti

allele.Tough reading question, but this is the only answer

that makes sense.

In snapdragons, the allele for red flower color (CR) is incompletely dominant to the allele for white flower color (CW). Snapdragons that are heterozygous for flower color have a pink phenotype.

Which of the following crosses could yield all three flower color phenotypes (red, white, and pink) among the offspring?

A.

B.

C.

D.

In snapdragons, the allele for red flower color (CR) is incompletely dominant to the allele for white flower color (CW). Snapdragons that are heterozygous for flower color have a pink phenotype.

Which of the following crosses could yield all three flower color phenotypes (red, white, and pink) among the offspring?

C.

To make red you need (CRCR ); for for white (CWCW)and for pink (CR CW). This cross makes all 3. (try to draw the punnett to prove it!!!)

Polycystic kidney disease (PKD) can result in kidney failure. In most cases, PKD is caused by a dominant allele.

What is the chance that a child will have PKD if the father is unaffected and the mother is heterozygous for PKD?

A. 0%

B. 25% C. 50% D. 75%

Polycystic kidney disease (PKD) can result in kidney failure. In most cases, PKD is caused by a dominant allele.

What is the chance that a child will have PKD if the father is unaffected and the mother is heterozygous for PKD?

C. 50%

Having PKD is Dominant (D). Since dad is unaffected,

he must have (dd). Mom is heterozygous (Dd). (try the punnett!!!)

Female cattle that have white coats are crossed with male cattle that have red coats. Both male and female offspring have roan coats, which are coats with both red hairs and white hairs.

Which of the following best describes the genetics of coat color in the cattle?

A. The red and white alleles are sex-linked.B. The red and white alleles are co-dominant.

C. The red allele is recessive to the white allele. D. The red allele is dominant to the white allele.

Female cattle that have white coats are crossed with male cattle that have red coats. Both male and female offspring have roan coats, which are coats with both red hairs and white hairs.

Which of the following best describes the genetics of coat color in the cattle?

B. The red and white alleles are co-dominant. Co-dominant means neither is dominant. Both colors

are seen.

In tomato plants, the tall vine allele (T) is dominant to the short vine allele (t). Two tomato plants are crossed. Among the offspring plants grown from seed, 45% have tall vines and 55% have short vines.

What are the most likely genotypes of the parent plants?

A. TT and tt B. Tt and TT C. Tt and tt D. tt and tt

In tomato plants, the tall vine allele (T) is dominant to the short vine allele (t). Two tomato plants are crossed. Among the offspring plants grown from seed, 45% have tall vines and 55% have short vines.

What are the most likely genotypes of the parent plants?

C. Tt and tt The results are about 50/50. Make punnett squares to

see which crosses would give these results.

In fish of the species Perissodus microlepis, some individuals have mouths that open to the right and some individuals have mouths that open to the left. The direction of the mouth opening is a genetic trait controlled by a single gene. The allele for a right-opening mouth (R) is dominant to the allele for a left-opening mouth (r).

If two fish heterozygous for the mouth trait are crossed, what is the expected ratio of phenotypes in the offspring?

A. 1 right-opening mouth : 3 left-opening mouth B. 2 right-opening mouth : 2 left-opening mouth C. 3 right-opening mouth : 1 left-opening mouth D. 4 right-opening mouth : 0 left-opening mouth

In fish of the species Perissodus microlepis, some individuals have mouths that open to the right and some individuals have mouths that open to the left. The direction of the mouth opening is a genetic trait controlled by a single gene. The allele for a right-opening mouth (R) is dominant to the allele for a left-opening mouth (r).

If two fish heterozygous for the mouth trait are crossed, what is the expected ratio of phenotypes in the offspring?

C. 3 right-opening mouth : 1 left-opening mouth

Make a Punnett of 2 heterozygous parents to confirm

Garden pea plants can have yellow seeds or green seeds. In a pea plant that is heterozygous for seed color, the allele for yellow seeds masks the effects of the allele for green seeds.

Which of the following terms best describes the allele for yellow seeds?

A. co-dominant B. dominant C. recessive D. sex-linked

Garden pea plants can have yellow seeds or green seeds. In a pea plant that is heterozygous for seed color, the allele for yellow seeds masks the effects of the allele for green seeds.

Which of the following terms best describes the allele for yellow seeds?

B. dominant Dominant “masks” or covers the other allele.

Which of the following crosses does not follow Mendel’s law of segregation?

A. Two tall pea plants (Tt × Tt) are expected to produce some tall offspring plants.

B. Two tall pea plants (Tt × Tt) are expected to produce some short offspring plants.

C. A tall pea plant and a short pea plant (Tt × tt) are expected to produce all tall offspring plants.

D. A tall pea plant and a short pea plant (TT × tt) are expected to produce all tall offspring plants.

Which of the following crosses does not follow Mendel’s law of segregation?

C. A tall pea plant and a short pea plant (Tt × tt) are expected to produce all tall offspring plants.

In this cross only 50% will be tall. (prove it with a punnett square)

In humans, freckles are encoded by a dominant allele. An individual woman is heterozygous for freckles.

According to the law of segregation, which of the following would apply to a child of this woman?

A. The child must inherit the dominant allele for freckles.

B. The child must inherit the recessive allele for freckles.

C. The child has an equal chance of inheriting the dominant allele or the recessive allele for freckles from her mother.

D. The child has a greater chance of inheriting the dominant allele than the recessive allele for freckles from her mother.

In humans, freckles are encoded by a dominant allele. An individual woman is heterozygous for freckles.

According to the law of segregation, which of the following would apply to a child of this woman?

C.The child has an equal chance of inheriting the

dominant allele or the recessive allele for freckles from her mother.

She is heterozygous (F f). She has a 50% chance to

pass either one (F) or (f).

The illustration below shows two adult rabbits and their offspring.

In rabbits, the allele for spots (R) is dominant to the allele for solid color (r). What is the most likely genotype of the parent rabbits in the illustration?

A. rr x rr B. Rr x rr C. Rr x Rr D. RR x rr

The illustration below shows two adult rabbits and their offspring.

In rabbits, the allele for spots (R) is dominant to the allele for solid color (r). What is the most likely genotype of the parent rabbits in the illustration?

B. Rr x rr The babies are 3 spotted and 3 solid or 50% each. This

cross gives those results (prove it with a Punnett!!)

In pea plants, the allele for purple flowers (P) is dominant to the allele for white flowers (p).

A plant that is heterozygous for purple flowers is crossed with a plant with white flowers. What percentage of the offspring plants are expected to have purple flowers?

A. 25% B. 50% C. 75% D. 100%

In pea plants, the allele for purple flowers (P) is dominant to the allele for white flowers (p).

A plant that is heterozygous for purple flowers is crossed with a plant with white flowers. What percentage of the offspring plants are expected to have purple flowers?

B. 50% One parent is (P p) heterozygous, the other is white

so must be (p p ). Now make the punnett to prove answer!

Hemophilia is an X-linked recessive condition in which blood does not clot properly. Queen Victoria of England had one allele for hemophilia.

Which of the following statements describes the most likely pattern for the occurrence of hemophilia in Queen Victoria’s descendants?

A. All of Queen Victoria’s children had hemophilia. B. All of Queen Victoria’s children were carriers for

hemophilia. C. Female descendants of Queen Victoria could not

pass on the gene for hemophilia. D. More male descendants than female

descendants of Queen Victoria had hemophilia.

Hemophilia is an X-linked recessive condition in which blood does not clot properly. Queen Victoria of England had one allele for hemophilia.

Which of the following statements describes the most likely pattern for the occurrence of hemophilia in Queen Victoria’s descendants?

D. More male descendants than female

descendants of Queen Victoria had hemophilia.

X linked or Sex linked traits are more common in men!

An inherited metabolic disorder called phenylketonuria (PKU) can result in serious problems in infancy. The chance that two parents who are heterozygous will have a child with PKU is 25 %.

Which of the following terms best applies to the inheritance pattern for PKU?

A. codominant B. dominant C. recessive D. sex-linked

An inherited metabolic disorder called phenylketonuria (PKU) can result in serious problems in infancy. The chance that two parents who are heterozygous will have a child with PKU is 25 %.

Which of the following terms best applies to the inheritance pattern for PKU?

C. recessive Make a punnett of 2 heterozygotes. Which condition

comes up 25% of the time? The recessive!!!

In fruit flies, the gene for eye color is located on the X chromosome, and the red eye allele (R) is dominant to the white eye allele (r). A female fly with genotype XRXr is mated with a male fly with genotype XrY.

Which of the following statements best describes the expected outcome of the cross?

A. The chance of an offspring having red eyes is 75% . B. The chance of an offspring having white eyes is 50% C. The chance that a male offspring will have white

eyes is 0%. D. The chance that a female offspring will have red

eyes is 100%.

In fruit flies, the gene for eye color is located on the X chromosome, and the red eye allele (R) is dominant to the white eye allele (r). A female fly with genotype XRXr is mated with a male fly with genotype XrY.

Which of the following statements best describes the expected outcome of the cross?

B. The chance of an offspring having white eyes is 50%

Easiest way to see this is through making a punnett!!

In mussels, brown (B) coloring is dominant, and blue (b) coloring is recessive. If a blue mussel has two brown parents, what percentage of the total offspring of these brown parents are expected to be blue?

A. 100% B. 75%

C. 50% D. 25%

In mussels, brown (B) coloring is dominant, and blue (b) coloring is recessive. If a blue mussel has two brown parents, what percentage of the total offspring of these brown parents are expected to be blue?

D. 25%

We know blue baby has (b b). Made by two parents who are brown (each has at least 1 “B”). The parents must be heterozygotes (B b) to make a blue baby. (as would 25% of their babies)

Two chromosome pairs from a diploid organism are shown below.

Assuming meiosis and fertilization occur normally, which of the following pairs of alleles can an offspring receive from this parent?A. A and A

B. A and a C. A and f D. F and F

Two chromosome pairs from a diploid organism are shown below.

Assuming meiosis and fertilization occur normally, which of the following pairs of alleles can an offspring receive from this parent?

C. A and f

One of each allele is passed to offspring

In rabbits, a single gene controlling coat color has four alleles. The inheritance pattern for coat color in rabbits is therefore best described as which of the following?

A. multiple allele

B. polygenic C. recessive D. sex-linked

In rabbits, a single gene controlling coat color has four alleles. The inheritance pattern for coat color in rabbits is therefore best described as which of the following?

A. multiple allele

Multiple (4) alleles!!!

Height is a polygenic trait in humans. Which of the following statements best explains the genetics of this trait?

A. Height is controlled by more than one gene. B. Height is controlled by a single dominant gene. C. The gene for height is located on the X

chromosome. D. The gene for height is located on the Y

chromosome.

Height is a polygenic trait in humans. Which of the following statements best explains the genetics of this trait?

A. Height is controlled by more than one gene. “Poly” means “many”. Polygenic means more than

one gene

In cats, the allele for short hair (H) is dominant to the allele for long hair (h). If a heterozygous short-hair cat is crossed with a long-hair cat, what percentage of the offspring is expected to be heterozygous for hair length?

A. 0%B. 25%C. 50%D. 75%

In cats, the allele for short hair (H) is dominant to the allele for long hair (h). If a heterozygous short-hair cat is crossed with a long-hair cat, what percentage of the offspring is expected to be heterozygous for hair length?

C. 50%

• H=short hair h= long hair mom = Hh X dad = hh• Make the punnett square to prove it!!!

Hawaiian happy face spiders from the island of Maui can have different markings, as shown below. A single gene determines the markings on the spiders.

A plain spider is crossed with a patterned spider. The patterned spider is homozygous. The pattern allele is dominant to the plain allele.

What percentage of the offspring from this cross are expected to be patterned instead of plain?

A. 0% B. 25% C. 50% D. 100%

Hawaiian happy face spiders from the island of Maui can have different markings, as shown below. A single gene determines the markings on the spiders.

A plain spider is crossed with a patterned spider. The patterned spider is homozygous. The pattern allele is dominant to the plain allele.

What percentage of the offspring from this cross are expected to be patterned instead of plain?

D. 100%

A partial Punnett square is shown below.AA AAAa Aa

Which of the following statements describes the parental genotypes that would result in this Punnett square?

A. Both parents are heterozygous. B. Both parents are homozygous dominant. C. One parent is homozygous recessive and the

other parent is heterozygous.D. One parent is homozygous dominant and the other parent is heterozygous.

A partial Punnett square is shown below.AA AAAa Aa

Which of the following statements describes the parental genotypes that would result in this Punnett square?

D. One parent is homozygous dominant and the other parent is heterozygous.

Build the punnett square in reverse to fill in theb parents’ genotypes.

According to Mendel’s law of segregation, which of the following statements describes what happens to the alleles of a gene pair?

A. The alleles are moved to different chromosomes B. The alleles are mutated in the process of mitosis C. The alleles are separated during fertilization. D. The alleles are separated during gamete

formation

According to Mendel’s law of segregation, which of the following statements describes what happens to the alleles of a gene pair?

D. The alleles are separated during gamete formation

Law of segregation says only one allele is passed from the two a parent has. This happens during meiosis.

In a certain variety of chicken, some offspring have a feather pattern that is black-and-white checkered. Chickens with this checkered feather pattern result from the cross of a black chicken with a white chicken.

Which of the following types of inheritance is most likely responsible for the checkered feather pattern?

A. co-dominant B. dominant C. polygenic D. sex-linked

In a certain variety of chicken, some offspring have a feather pattern that is black-and-white checkered. Chickens with this checkered feather pattern result from the cross of a black chicken with a white chicken.

Which of the following types of inheritance is most likely responsible for the checkered feather pattern?

A. co-dominant When mixed Both are seen, not one or the other!

In fruit flies, a single gene controls wing phenotype. The diagram below shows the phenotypes for long wings and vestigial wings in fruit flies.

Two fruit flies that have long wings are crossed. Of the 95 offspring produced, 73 have long wings. The other 22 have vestigial wings.

Which of the following conclusions about the inheritance of long wings and vestigial wings is best supported by the

results of this experiment?

A. The alleles for long wings and vestigial wings are sex-linked. B. The alleles for long wings and vestigial wings are co-dominant. C. The allele for long wings is dominant and the allele for vestigial

wings is recessive. D. The allele for long wings is recessiveand the allele for vestigial

wings is dominant.

2 fruit flies that have long wings are crossed.Of the 95 offspring produced, 73 have long wings. The other 22 have vestigial wings.

Which of the following conclusions about the inheritance of long wings and vestigial wings is best

supported by the results of this experiment?

C. The allele for long wings is dominant and the allele for vestigial wings is recessive.

Results are about 3:1, Long wing is dominant

In sheep, the allele for white wool (W) is dominant, and the allele for black wool (w) is recessive. A farmer has mated two Suffolk sheep for a few years. These matings have resulted in six offspring, four with white wool and two with black wool. One parent has white wool and the other has black wool.

Which of the following could be the genotypes of the parent sheep?

A. WW and Ww B. WW and ww C. Ww and Ww D. Ww and ww

In sheep, the allele for white wool (W) is dominant, and the allele for black wool (w) is recessive. A farmer has mated two Suffolk sheep for a few years. These matings have resulted in six offspring, four with white wool and two with black wool. One parent has white wool and the other has black wool.

Which of the following could be the genotypes of the parent sheep?

D. Ww and wwBlack parent must be (ww). They have some black

offspring so other must be (Ww).

In pea plants, the genes for seed color and seed shape are on different chromosomes. Which of the following explains why the genes for these traits are not inherited together?

A. natural selection B. artificial selection C. the law of segregation D. the law of independent assortment

In pea plants, the genes for seed color and seed shape are on different chromosomes. Which of the following explains why the genes for these traits are not inherited together?

D. the law of independent assortment

Each gene is separated without any connection to the others. They are assorted (spread out) independently.

The pedigree below shows the occurrence of Becker muscular dystrophy in a family. Becker muscular dystrophy causes muscle weakness.

Based on this pedigree, it is most reasonable to conclude that Becker muscular dystrophy is which of the following?A. a polygenic trait

B. a codominant trait C. a sex-linked recessive trait D. an autosomal dominant trait

The pedigree below shows the occurrence of Becker muscular dystrophy in a family. Becker muscular dystrophy causes muscle weakness.

Based on this pedigree, it is most reasonable to conclude that Becker muscular dystrophy is which of the following? C. a sex-linked recessive trait

Notice its only in Men. Must be sex linked.

Human blood types are genetically determined. The table below shows the symbols used to represent two of the alleles for blood types and gives a description of each allele.

In homozygous individuals, two IAalleles result in blood type A andtwo IB alleles result in blood type B.The IA and IB alleles are co-dominant, resulting in blood type AB in individuals heterozygous for the two alleles.

A male and a female both have blood type AB. If they have a child, what is the probability that the child will also have blood type AB?

A. 1/4 B. 1/2 C. 3/4 D. 1/1

Human blood types are genetically determined. The table below shows the symbols used to represent two of the alleles for blood types and gives a description of each allele.

In homozygous individuals, two IAalleles result in blood type A andtwo IB alleles result in blood type B.The IA and IB alleles are co-dominant, resulting in blood type AB in individuals heterozygous for the two alleles.

A male and a female both have blood type AB. If they have a child, what is the probability that the child will also have blood type AB?

B. 1/2 Easiest way to see this is to make a punnett !!!

The diagram below shows the positions of the genes for flower color and stem length in a pea plant. The chromosomes represented below will replicate before meiosis.

For these two genes, what is the maximum number of different allele combinations that can be formed normally in gametesproduced from this cell?

A. 2 B. 4 C. 6 D. 8

The diagram below shows the positions of the genes for flower color and stem length in a pea plant. The chromosomes represented below will replicate before meiosis.

For these two genes, what is the maximum number of different allele combinations that can be formed normally in gametesproduced from this cell?

B. 4 One allele of each is passed. There is PT, Pt, pT, pt

Which of the following terms applies to traits, such as human eye color, that are controlled by more than one gene?

A. codominant B. polygenic C. recessive D. sex-linked

Which of the following terms applies to traits, such as human eye color, that are controlled by more than one gene?

B. polygenic Remember “poly” = many

In pigeons, the allele B produces ash-red feathers. The allele b produces blue feathers. The B allele is dominant to the b allele.

A pigeon with genotype Bb is crossed with a pigeon with genotype bb. What percent of the offspring are expected to have ash-red feathers?

A. 0% B. 25% C. 50% D. 100%

In pigeons, the allele B produces ash-red feathers. The allele b produces blue feathers. The B allele is dominant to the b allele.

A pigeon with genotype Bb is crossed with a pigeon with genotype bb. What percent of the offspring are expected to have ash-red feathers?

C. 50%