Chapter 23 - Patterns of Gene Inheritance

Mendel carried out most of his research with

pea plants.

Unattached earlobes (EE or Ee) are dominant over attached earlobes (ee). A couple both have unattached earlobes. Both notice that one of their parents on both sides have attached earlobes (ee). Therefore, they correctly assume that they are carriers for attached earlobes (Ee). If the couple proceeds to have four children, then

two heterozygous, one homozygous dominant, and one homozygous recessive is a likely outcome, but all heterozygous, or two, three or all four homozygous is also possible.

To try and discover if the environment has an effect on a particular characteristic scientists often examine

Monozygotic human twins that were separated at birth.

Which of the following would be considered a heterozygous dihybrid genotype? ( ) Ww ( ) sS ( ) WWSs ( ) WWss ( ) WwSs

WwSs

Two parents with widow's peak and short fingers have a child with a continuous hairline and long fingers. What are the genotypes of the two parents? (W = widow's peak; S = short fingers) ( ) WWSS x wwss ( ) wwss x WWSS ( ) WWss x WWss ( ) WwSs x WwSs ( ) WwSs x wwss

WwSs x WwSs

A man with widow's peak (dominant) who can curl his tongue (dominant) has a child who has a continuous hairline and cannot curl the tongue. What is the genotype of the father? ( ) WWTT ( ) wwtt ( ) WwTt ( ) Wwtt ( ) WT

WwTt

Humans can have any of several eye colors, this is because we possess a variety of

alleles.

What are alleles?

alternative forms of a gene for a single trait, such as blue eyes or brown eyes

The _____ indicates the gene combination of an individual.

genotype

a dihybrid can form [ ] different gametes.

4

A woman who can roll her tongue (presumably dominant) is married to a man who cannot. Two of their four children can roll their tongues and two cannot. If A = roll tongue and a = cannot roll tongue, then what is the genotype of the parents? ( ) woman Aa; man Aa ( ) woman AA; man aa ( ) woman Aa; man AA ( ) woman Aa; man aa ( ) woman aa; man aa

woman Aa; man aa

Any chromosomes other than sex chromosomes are called [ ]

autosomes

In which kind of cross would you expect to find a phenotypic ratio of 3:1 among the F2 offspring?

monohybrid cross

The inheritance of blood types in humans can be explained by

multiple alleles.

Since each child of two heterozygous parents has a 1/4 chance of receiving a recessive trait from each parent,

no matter what the first child's phenotype, the next child will have a 1/4 chance of being phenotypically recessive.

For Mendel's law of segregation to occur, the alleles must be

on a homologous pair of chromosomes.

If an organism shows a recessive phenotype, such as short pea plants, its genotype can be ( ) either TT or Tt. ( ) either Tt or tt. ( ) only TT. ( ) only tt. ( ) TT, Tt, or tt.

only tt.

the idea developed by Mendel that proposed that inheritance involves the reshuffling of the same genes from generation to generation is called the [ ] theory of inheritance

particulate

Cold weather can change the ______ of a Himalayan rabbit.

phenotype

Traits that are controlled by several sets or pairs of alleles, such as skin color and height in humans, are the result of what form of inheritance?

polygenic

When two or more sets of alleles affect the same trait in an additive fashion, it is termed

polygenic inheritance.

Tay-Sachs is a recessive genetic disease in humans. If one parent is homozygous normal and the other is a carrier (heterozygous), what are the chances that their child will have this disease?

0%

a normal GAMETE (sperm and eggs) has [ ] allele(s) for each trait.

1

In guinea pigs, B = black, b = brown, S = short hair, s = long hair. A heterozygous black, shorthaired animal reproduces with a brown, longhaired animal. What is the expected phenotypic ratio of the offspring?

1 black short hair, 1 black long hair, 1 brown short hair, 1 brown long hair

A cross is made between two parents with genotypes AaBB and aabb. If there are 32 offspring, how many of them would be expected to exhibit both dominant characteristics?

16

How many alleles are required to express a monohybrid trait?

2

Both parents are heterozygous for Tay-Sachs disease (an autosomal recessive disorder). Three children in a row were born with Tay-Sachs disease. What is the chance that a fourth child will have Tay-Sachs disease?

25%

In humans, assume red hair is recessive to dark hair. What are the chances of a dark-haired couple having a red-haired child if each had a red-haired parent?

25%

What are the chances that two individuals with wavy hair (an incomplete trait) will have a curly-haired child? Curly hair and straight hair exhibit incomplete dominance.

25%

If the probability of event A is 3/4 and the probability of event B is 1/4, then the probability of both A and B occurring at the same time is ( ) 3/4. ( ) 1/4. ( ) 1 or absolute certainty. ( ) 1/2. ( ) 3/16.

3/16.

In humans, widow's peak (W) is dominant over straight hairline (w). If a heterozygous male marries a female with a straight hairline, what percent of their children can be expected to have widow's peak?

50%

The four o'clock flower is an example of incomplete dominance: R = red, r = white, and Rr = pink. If two hybrids are crossed, what are the chances that an offspring will have pink flowers?

50%

In guinea pigs, B = black, b = brown, S = short hair, s = long hair. Two heterozygous individuals reproduce. The expected results are

9 black short hair, 3 black long hair, 3 brown short hair, 1 brown long hair.

In humans, aniridia, a type of blindness, is due to a dominant allele A. Migraine headaches are due to another dominant allele M. If a man who suffers from both conditions (AaMm) marries a woman who suffers from both (AaMm), what are the chances of an offspring having both traits?

9/16

Indicate the genotypic and phenotypic ratios that you could expect if an individual who is heterozygous for Huntington disease has children with a normal individual. (type in answer)

<correct answer not given in long answer questions> Feedback says: The individual who is heterozygous for Huntington disease would be Hh since it is a dominant disorder. The normal individual would be hh. Hh x hh would produce a genotypic ratio of 50% Hh and 50 hh. The phenotypic ratio would be 50% Huntington disease and 50% normal.

Which of the following represents the physical characteristics of the individual? A) phenotype B) genotype C) alleles D) homozygous E) dominance

A) phenotype

If one parent has type B blood and the other has type AB, what type might the child have? ( ) A or O only ( ) B or O only ( ) A or B only ( ) A, B, AB only ( ) A, B, O, or AB

A, B, AB only

Which of the following is an autosomal dominant disorder? A) Marfan syndrome B) Tay-Sachs C) Sickle cell disease D) Cystic fibrosis (CF) E) Phenylketonuria (PKU)

A) Marfan syndrome

In peas, yellow is dominant over green in seeds. With which of these is it best to cross a yellow-seeded pea plant to determine whether it is homozygous or heterozygous? A) a green-seeded plant B) a heterozygous yellow-seeded plant C) a pure yellow-seeded plant D) a heterozygous yellow-seeded plant or a pure yellow-seeded plant E) There is no way to determine if the plant is pure or hybrid

A) a green-seeded plant

A pheasant breeder starts with two birds in the P generation, one of which is AA and the other is aa. If he takes two of the birds from the F1 generation and breeds them together, what can he expect in his F2 offspring? ( ) AA and Aa ( ) Aa and aa ( ) AA, Aa, and aa ( ) AA only ( ) Aa only

AA, Aa, and aa

If an individual with a dominant phenotype is crossed with an individual with a recessive phenotype, 4 of their 9 offspring show the recessive phenotype. What is the genotype of the dominant parent? ( ) AA ( ) Aa ( ) aa ( ) either AA or Aa ( ) either Aa or aa

Aa

Some plants fail to produce chlorophyll, and this trait appears to be recessive. Many plants also self-pollinate. If we locate a pea plant that is heterozygous for this trait, self-pollinate it and harvest seeds, what are the likely phenotypes of these seeds when they germinate?

About 1/4 will be white and three-fourths green since it is similar to a monohybrid cross.

Which is NOT true according to Mendel's law of segregation? A) Each individual contains two factors for each trait. B) One factor must be dominant and one factor recessive in each individual. C) Factors separate from each other during gamete formation. D) Each gamete contains one copy of each factor. E) Fertilization restores the presence of two factors.

B) One factor must be dominant and one factor recessive in each individual.

In 1940, two researchers named Weiner and Landsteiner discovered that about 85 percent of the human population sampled possessed a blood cell protein called the Rh factor. The presence of Rh factor was labeled Rh positive (Rh+) and was found to be dominant over the absence of the blood factor (Rh-). Under normal Mendelian inheritance, which of the following statements is FALSE? A) Two Rh+ parents could have an Rh- child. B) Two Rh- parents could have an Rh+ child. C) An Rh- child would require that both parents be carriers of at least one Rh- allele. D) It is possible with just one pair of parents to have children where some siblings are Rh- and some are Rh+. E) Two Rh+ parents can have Rh- or Rh + children.

B) Two Rh- parents could have an Rh+ child.

In which kind of cross would you expect to find a ratio of 9:3:3:1 among the F2 offspring? A) monohybrid cross B) dihybrid cross C) test cross D) homozygous recessive x homozygous dominant E) homozygous dominant x heterozygous

B) dihybrid cross

In humans, brown eyes (B) is a simple dominant trait over blue eyes (b). A brown-eyed woman whose child is blue-eyed would have the genotype ( ) bb. ( ) Bb. ( ) BB. ( ) BBB. ( ) BbBb.

Bb.

Consider skin color to be regulated by three genes A, B and C. All recessive alleles would be 0 or white on the color scale. All dominant alleles would be 6 or black on the color scale. What color is a person with AAbbCc genotype? A) 6 or black B) 5 or dark C) 3 or medium brown D) 2 or light E) 0 or white

C) 3 or medium brown

In a testcross, an organism with a dominant phenotype, but unknown genotype is crossed with which of the following to establish its genotype? A) homozygous dominant B) heterozygous C) homozygous recessive D) heterozygous dominant E) monohybrid dominant

C) homozygous recessive

O1 and O2 are different alleles of a single gene and are both completely expressed in a heterozygous individual,. This type of inheritance is termed [ ]

Codominance

You have two true-breeding rose bushes, one with red flowers and one with white flowers, a cross between these two roses yields a bush with white flowers that have red splotches. What condition does this demonstrate?

Codominance

What will the genotypic ratio be of a monohybrid cross of two individuals who are heterozygous for a trait? A) 100% homozygous dominant B) 100% homozygous recessive C) 50% homozygous dominant, 50% homozygous recessive D) 25% homozygous dominant, 50% heterozygous, 25% homozygous recessive E) 50% homozygous dominant, 50% heterozygous

D) 25% homozygous dominant, 50% heterozygous, 25% homozygous recessive

All but one of the following experiments would allow a scientist to discover if the phenotype of an organism would be affected by environmental changes; choose the experiment that would NOT show environmental effects. A) Cuttings are taken from an English Ivy plant and are then grown in soils with different pH levels. B) A Siamese cat has patches of fur removed from its hips and an ice pack is secured over the area. C) A mouse with the genetic disorder phenylketonuria (PKU) is fed a diet low in phenylalanine for a year and then changed to a diet rich in the same molecule. D) A group of mice that show the same dominant trait are fed a variety of diets to determine if they show different body types. E) A hydrangea is grown for one year in aluminum poor soil and then grown for one year in aluminum rich soil.

D) A group of mice that show the same dominant trait are fed a variety of diets to determine if they show different body types.

Huntington disease is an autosomal dominant disorder that leads to progressive degeneration of brain cells. There is no effective treatment for the disorder and individuals usually die 10 to 15 years after the onset of symptoms. Which of these statements about Huntington disease is TRUE? A) As an autosomal dominant disease, Huntington disease is expressed only if both parents carry the trait. B) Huntington disease usually skips a generation. C) Huntington disease can only be inherited when a parent is showing the trait. D) Huntington disease usually appears during middle age. E) Huntington disease is caused by a defect in the elastic connective tissue protein.

D) Huntington disease usually appears during middle age.

Computer simulations are sometimes used to demonstrate the outcome of monohybrid fruit fly crosses, where a student can run generation after generation of fruit flies with 100 offspring produced each generation, half male and half female, and a 3-to-1 phenotype ratio (or 75 to 25) in the F1 generation. Compared to real genetics results, which of the following is NOT true? A) Rarely would exactly 100 fly offspring be produced or survive. B) An exact balance between males and females would be rare. C) A precise 3-to-1 ratio would be uncommon. D) It is usually possible to have exactly 100 offspring, half male and half female, and a 3-to-1 phenotypic outcome in real life. E) Ratios and outcomes will not be exact but will be very close to the expected numbers.

D) It is usually possible to have exactly 100 offspring, half male and half female, and a 3-to-1 phenotypic outcome in real life.

In which kind of cross could you expect to find of ratios of 1:1:1:1 among the offspring? A) monohybrid cross B) dihybrid cross C) one trait test cross D) two trait test cross E) no cross will yield offspring in 1:1:1:1 ratios

D) two trait test cross

The ability to roll the edges of the tongue upward in a U-shape has been considered to be an inherited ability. The standard assumption is that tongue-rolling is a dominant allele at a single gene locus. Which of the following would CAST DOUBT on this assumption? A) Behaviors are not inherited, only structures are inherited. B) A student who cannot roll his tongue has a mother and father, both of whom can. C) A student who can roll his tongue has a mother and father, both of whom cannot. D) With very little effort the non-tongue-rollers can learn to also roll their tongues. E) A student who can roll his tongue has a mother and father, both of whom cannot roll their tongues AND with very little effort the non-tongue-rollers can learn to roll their tongues.

E) A student who can roll his tongue has a mother and father, both of whom cannot roll their tongues AND with very little effort the non-tongue-rollers can learn to roll their tongues.

Which of the following is NOT correct concerning the law of independent assortment? A) It is based upon the process of meiosis. B) Each pair of factors separates independently. C) All possible combinations of factors can occur in the gametes. D) It was the second law of heredity established by Mendel. E) It follows the observation that all maternal chromosomes end up in the egg.

E) It follows the observation that all maternal chromosomes end up in the egg.

In pea plants, the gene for round seed (R) is dominant, and wrinkled seeds (r) are recessive. The endosperm of the pea is also either starchy, a dominant gene (S), or waxy (s). What CANNOT be said of a cross between two parents that are heterozygous for both traits? A) It is possible to secure offspring that are homozygous for both dominant genes. B) It is possible to secure offspring that are homozygous for both recessive genes. C) It is possible to secure offspring that are homozygous for one dominant gene such as round seed and homozygous recessive for the other recessive waxy gene. D) It is possible to secure offspring that are heterozygous for both genes. E) It is impossible to secure offspring that are homozygous for both dominant genes.

E) It is IMPOSSIBLE to secure offspring that are homozygous for both dominant genes.

Which of the following is an example of the blending of phenotypes? A) codominance B) sex-linked inheritance C) polygenic inheritance D) simple Mendelian inheritance E) incomplete dominance

E) incomplete dominance

Hydrangeas are a flowering plant with large showy blooms. When a plant is grown in aluminum rich soil it has blue flowers; if the same plant is transplanted into soil that is lacking aluminum the flowers produced will be pink. This is an example of

Environmental effects

In a Mendelian monohybrid cross involving two homozygous genotypes, the ____ generation is always completely heterozygous.

F1

You have two true-breeding rose bushes, one with red flowers and one with white flowers, a cross between these two roses yields a bush with pink flowers. What condition does this demonstrate?

Incomplete dominance

Which genetic disorder is associated with a defect in the elastic connective tissue protein called fibrillin?

Marfan Syndrome

If you had a black male guinea pig and a brown female guinea pig, but you didn't know which was the dominant characteristic, how would you find out the dominant color?

Mate them and see what color the offspring are —THAT will be the dominant color.

What genetic disorder is associated with the lack of an enzyme necessary for the normal metabolism of the amino acid phenylalanine?

Phenylketonuria (PKU)

The skin pigment melanin is expressed differently according to exposure to sunlight, with a greater production of the molecule with greater exposure. However, the degree of production can never exceed the inherited genetic level. What evolutionary advantage would be gained from having this phenotypic range for skin pigmentation?

Production of the molecule would only occur when necessary.

The leaves of a maple tree vary in size depending on the location of the leaves on the tree. Those growing at the outer region of the tree tend to be smaller than those growing closer to the trunk of the tree. This allows leaves that are growing in the shade to have a larger surface area. This show that genes have the ability to

Respond to environmental factors

Which of the following crosses will yield four phenotypes in a ratio of 9:3:3:1? ( ) RRYY x RRYY ( ) RRYY x rryy ( ) RrYy x RrYy ( ) RrYy x rryy ( ) rryy x rryy

RrYy x RrYy

Which of the following crosses will yield 4 phenotypes in the 1:1:1:1 ratio? ( ) RRYY x RRYY ( ) RRYY x rryy ( ) RrYy x RrYy ( ) RrYy x rryy ( ) rryy x rryy

RrYy x rryy

Which genetic disorder is associated with an irregular shape of the red blood cells?

Sickle cell disease

If you were to breed a black male guinea pig to a brown female guinea pig in an attempt to determine which one was homozygous dominant and which one was homozygous recessive, how could you be certain that the guinea pigs are truly homozygous?

The guinea pigs would be homozygous for black (or brown) coat color if each strain could be bred for many generations and only black (or brown) colored offspring were produced.

If the genotype of an organism is YySsTt, then yST would represent

a gamete of the parent.

Which allele combination represents a recessive monohybrid trait? ( ) aa ( ) Aa ( ) AA ( ) ab ( ) Ab

aa

Alternative forms of a gene that influence the same trait and are found at the same location in homologous chromosomes are called

alleles.

The ABO alleles inherited by humans determines the presence of [ ] on their red blood cells.

antigens

Mendel's law of segregation implies that the two members of an allele pair

are distributed to SEPARATE gametes.

In horses, black coat (B) is dominant over brown coat (b), and being a trotter (T) is dominant over being a pacer (t). A black horse who is a pacer is crossed with a brown horse who is a trotter. The offspring is a brown pacer. What is the genotype of the brown trotter parent? ( ) BBTT ( ) BbTt ( ) Bbtt ( ) bbTt ( ) bbtt

bbTt

A man with blood type AB could NOT be the father of a child with

blood type O.

In which kind of cross would you expect to have your actual results match the predicted results 100% of the time the cross is made?

crosses of differing genotypes result in differing answers—no cross will produce expected ratios every time

A cross that involves two traits is called a ______ cross.

dihybrid

Mr. X has been accused by Miss Z of fathering her child. The child's blood type is AB and Miss Z's blood type is A. Mr. X could NOT be the father if his blood type is ( ) only A. ( ) only B. ( ) AB. ( ) only O. ( ) either A or O.

either A or O.

A blue-eyed, left-handed woman marries a brown-eyed, right-handed man who is heterozygous for both of his traits. If blue eyes and left-handedness are recessive, how many different phenotypes are possible in their children?

four

If an albino (recessive) woman is married to a man with normal coloring and they have an albino child, what was the genotype of the man?

heterozygous

In cattle, consider that the lack of horns is dominant to the presence of horns. A bull without horns is crossed with a horned cow. Of four offspring, one is horned and the other three lack horns. The bull is

heterozygous.

If pairs of factors separate independently of other pairs of factors, you are dealing with the

law of independent assortment.

Which of the following crosses will yield only homozygous recessive offspring? ( ) RRYY x RRYY ( ) RRYY x rryy ( ) RrYy x rryy ( ) rryy x rryy ( ) RrYy x RrYy

rryy x rryy