Savology Chapter 9 :33

Which statement best represents the theory of pangenesis developed by Hippocrates?

Particles called pangenes, which originate in each part of an organism's body, collect in the sperm or eggs and are passed on to the next generation

If A is dominant to a and B is dominant to b, what is the expected phenotypic ratio of the cross AaBb × AaBb?

9:3:3:1

Mendel's law of independent assortment states that

the allele that a gamete receives for one gene does not influence the allele the gamete receives for another gene

Imagine that we mate two black Labrador dogs with normal vision and find that three of the puppies are like the parents, but one puppy is chocolate with normal vision and another is black with PRA (progressive retinal atrophy, a serious disease of vision). We can conclude that

the alleles for color and vision segregate independently during gamete formation

A testcross is

a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest.

Using a six-sided die, what is the probability of rolling either a 5 or a 6?

1/6 + 1/6 = 1/3

Assuming that the probability of having a female child is 50% and the probability of having a male child is also 50%, what is the probability that a couple's first-born child will be female and that their second-born child will be male?

25%

Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes?

Dd and Dd

A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring.

heterozygous for the trait and able

Most genetic disorders of humans are caused by

recessive alleles

Most people afflicted with recessive disorders are born to parents who were

not affected at all by the disease

Mendel conducted his most memorable experiments on

peas

Explain why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders?

Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce.

Amniocentesis and chorionic villus sampling allow for ________ and ________ of the fetus so that it can be tested for abnormalities.

karyotyping; biochemical testing

(true or false) Chorionic villus sampling is typically performed later in the pregnancy than amniocentesis.

false

For most sexually reproducing organisms, Mendel's laws

cannot strictly account for the patterns of inheritance of many traits.

All the offspring of a cross between a red-flowered plant and a whiteflowered plant have pink flowers. This means that the allele for red flowers is ________ to the allele for white flowers.

incompletely dominant

Imagine that beak color in a finch species is controlled by a single gene. You mate a finch homozygous for orange (pigmented) beak with a finch homozygous for ivory (unpigmented) beak and get numerous offspring, all of which have a pale, ivory-orange beak. This pattern of color expression is most likely to be an example of

incomplete dominance

Which trait is an example of incomplete dominance in humans?

hypercholesterolemia

The expression of both alleles for a trait in a heterozygous individual illustrates

codominance

The presence of AB blood type illustrates the principle of

codominance

Which statement regarding sickle-cell disease is false?

Sickle-cell disease causes white blood cells to be sickle-shaped

Varieties of plants in which self-fertilization produces offspring that are identical to the parents are referred to as

true-breeding

Sickle-cell disease is an example of

pleiotropy

Which term refers to a situation where a single phenotypic character is determined by the additive effects of two or more genes?

polygenic inheritance

The individual features of all organisms are the result of

both the interaction between genetics and the environment

The chromosome theory of inheritance states that

the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance

Genes located close together on the same chromosomes are referred to as ________ genes and generally ________.

linked; do not sort independently during meiosis

Linked genes generally

do not follow the laws of independent assortment.

You conduct a dihybrid cross. A ________ ratio would make you suspect that the genes are linked.

12:1:1:4

The mechanism that "breaks" the linkage between linked genes is

crossing over

Which of the following kinds of data could be used to map the relative position of three genes on a chromosome?

the frequencies with which the corresponding traits occur together in offspring

What is the usual complement of sex chromosomes in a human male?

one X chromosome and one Y chromosome

(true or false) The hybrid offspring of a cross are the P1 generation.

false

The usual sex chromosome complement of a human female is

XX.

How many sex chromosomes are normally in a human gamete?

one

Any gene located on a sex chromosome

is called a sex-linked gene

Recessive X-linked traits are more likely to be expressed in a male than a female because

the male's phenotype results entirely from his single X-linked gene.

A colorblind woman marries a man who is not colorblind. All of their sons, but none of their daughters, are colorblind. Which of the following statements correctly explains these results?

The gene for color vision is found on the X chromosome.

Sex-linked conditions are more common in men than in women because

men need to inherit only one copy of the recessive allele for the condition to be fully expressed.

According to scientists, about what percentage of men currently living in Central Asia may be descended from the Mongolian ruler Genghis Khan?

8%

Maternal inheritance patterns from generation to generation cannot be analyzed by simply studying the X chromosome in the way that paternal inheritance patterns can follow the Y chromosome because

the X chromosome is obtained from both the father and the mother.

Blood samples are taken from the heel of newborn babies to test for a mutation in the PKU gene, which, if left untreated and in severe cases, can lead to mental retardation, reduced skin pigmentation, and seizures. Which concept is being illustrated by this example?

pleiotropy

In giraffes, long necks (N), long legs (L), dark spots (D), and the ability to digest maize (M) are all dominant traits. What possible genotype could a long-necked, short-legged, light-spotted, maize-digesting giraffe have?

NnllddMM

(true or false) An organism with two different alleles for a single trait is said to be homozygous for that trait.

false

In some cats, black coat color (B) is dominant over brown (b) and a striped fur pattern (S) is dominant over a marbled fur pattern (s). You rescued a black striped cat from an animal shelter but could not determine its exact genotype. To do so, you mated the cat with a brown marbled cat. The mating produced 3 brown marbled, 2 brown striped, 2 black marbled, and 3 black striped. Immediately, you concluded the genotype of your rescued cat was

BbSs

You prepare a human karyotype. Upon analysis, you find 22 pairs of chromosomes that are each of approximately equal length and also a single pair that has one chromosome longer than the other. What can you conclude from this information?

The organism that this cell came from is likely a male

Suppose that an elephant with the genotype EEFfggHh reproduces with an elephant with the genotype eeFFGgHh. What is the probability that a baby elephant (called a calf) would have the genotype EeFFGghh?

1/16

You are trying to determine the linkage map of a series of genes, X, Y, and Z, from Caenorhabditis elegans, a nematode worm commonly used in scientific research. From doing several crossover experiments, you know that the recombination frequency between X and Y is 11.5%, between Y and Z is 13%, and between X and Z is 25%. What is a possible sequence of these genes?

X-Y-Z

Justin has type A blood and his wife Brittany has type B blood. Justin's parents both have type AB blood, and Brittany's parents also both have type AB blood. What are the chances that Justin and Brittany's son Theodore has type A blood?

0%

You are trying to determine if a newborn boy has an X-linked genetic disorder by analyzing a family pedigree. Which of these findings would rule out the X-linked hypothesis?

Both brothers and sisters have the disorder though neither parent does

DNA kits do not provide information on

the likely sex ratio of one's offspring.

(true or false) Height is determined by variations in more than a hundred genes as well as environmental conditions.

true

(true or false) In some animals, sex chromosomes determine sex and, in some animals, environmental factors such as temperature determine sex.

true

(true or false) An individual may have some genes producing proteins for maleness and other genes producing proteins for femaleness.

true

Research since Mendel's time has established that the law of segregation of genes during gamete formation applies to all ___

sexually reproducing organisms

Blood samples are taken from the heel of newborn babies to test for a mutation in the PKU gene. Why is this so important?

PKU can be completely treated with dietary management of the amino acid phenylalanine, preventing any negative outcomes in the child, but the diet needs to be started immediately

All the offspring of a cross between a black-eyed Mendelian and an orange-eyed Mendelian have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed Mendelians?

0 black-eyed:1 orange-eyed

The alleles of a gene are found at ________ chromosomes.

the same locus on homologous

The phenotypic ratio resulting from a dihybrid cross of two heterozygote individuals showing independent assortment is expected to be

9:3:3:1

Which plants in this figure must all be heterozygous?

purple-flowered plants in the F1 generation

According to this figure, heterozygotes for this form of hypercholesterolemia suffer from the disease because they

don't produce enough LDL receptors

What type of inheritance fits the data in this pedigree?

autosomal recessive

What is the most likely explanation for the occurrence of an X-linked genetic disorder in the boy at the bottom of the pedigree shown?

The boy has a new mutation for the disorder

Shown here is a representation of a portion of a pair of homologous chromosomes.

hair and legs

A man and his wife are having trouble having a baby. Using modern technologies, the woman's eggs are removed, fertilized with her husband's sperm, and implanted into her uterus. The procedure is successful, and the woman gives birth to a healthy baby boy. After a while, though, they discover that their son is colorblind and has blood type O. The woman claims that the child can't be theirs since she has blood type A and her husband has type B. Also, neither parent is colorblind, although one grandparent (the woman's father) is also colorblind.

As a genetic counselor, you would explain to the parents that:

each parent could have contributed one recessive allele, resulting in type O blood.

A man and his wife are having trouble having a baby. Using modern technologies, the woman's eggs are removed, fertilized with her husband's sperm, and implanted into her uterus. The procedure is successful, and the woman gives birth to a healthy baby boy. After a while, though, they discover that their son is colorblind and has blood type O. The woman claims that the child can't be theirs since she has blood type A and her husband has type B. Also, neither parent is colorblind, although one grandparent (the woman's father) is also colorblind.

In regard to the baby's color blindness, a sex-linked recessive trait, you explain that

since color blindness is sex-linked, a son can inherit color blindness if his mother has the recessive color blindness allele

During a summer study abroad program, you traveled to Austria to study genetics at the University of Vienna. While you were there, a momentous discovery was made: Some of Gregor Mendel's original lab books and notes were found to be buried outside of the abbey where he lived. It just so happened that the professor you were working with obtained copies of these notes and enlisted your help to decipher them.

You hired a translator to translate Mendel's notes from Czech to English, and using your knowledge of modern genetics (which Mendel did not have!) you were able to construct a partial Punnett square for crosses with peas (shown here). Because the notebook was damaged from being buried for so long, this is the only information that you have regarding a cross that Mendel must have performed. Your professor has tasked you with figuring out more about this experiment.

In pea plants, round peas are dominant (R) and shriveled peas are recessive (r), and yellow peas (shown as light gray in the Punnett square) are dominant (Y) and green peas (dark gray) are recessive (y). Using this information and the partial Punnett square shown, what were the phenotypes of the parental plants that were used in this cross by Mendel?

Rryy and RrYy

During a summer study abroad program, you traveled to Austria to study genetics at the University of Vienna. While you were there, a momentous discovery was made: Some of Gregor Mendel's original lab books and notes were found to be buried outside of the abbey where he lived. It just so happened that the professor you were working with obtained copies of these notes and enlisted your help to decipher them.

You hired a translator to translate Mendel's notes from Czech to English, and using your knowledge of modern genetics (which Mendel did not have!) you were able to construct a partial Punnett square for crosses with peas (shown here). Because the notebook was damaged from being buried for so long, this is the only information that you have regarding a cross that Mendel must have performed. Your professor has tasked you with figuring out more about this experiment.

In pea plants, round peas are dominant (R) and shriveled peas are recessive (r), and yellow peas (shown as light gray in the Punnett square) are dominant (Y) and green peas (dark gray) are recessive (y). Using this information and the partial Punnett square shown, what genotype should be listed in the square labeled A?

RrYy

During a summer study abroad program, you traveled to Austria to study genetics at the University of Vienna. While you were there, a momentous discovery was made: Some of Gregor Mendel's original lab books and notes were found to be buried outside of the abbey where he lived. It just so happened that the professor you were working with obtained copies of these notes and enlisted your help to decipher them.

You hired a translator to translate Mendel's notes from Czech to English, and using your knowledge of modern genetics (which Mendel did not have!) you were able to construct a partial Punnett square for crosses with peas (shown here). Because the notebook was damaged from being buried for so long, this is the only information that you have regarding a cross that Mendel must have performed. Your professor has tasked you with figuring out more about this experiment.

In pea plants, round peas are dominant (R) and shriveled peas are recessive (r), and yellow peas (shown as light gray in the Punnett square) are dominant (Y) and green peas (dark gray) are recessive (y). Using this information and the partial Punnett square shown, what phenotype should be in the square labeled B?

round and green

During a summer study abroad program, you traveled to Austria to study genetics at the University of Vienna. While you were there, a momentous discovery was made: Some of Gregor Mendel's original lab books and notes were found to be buried outside of the abbey where he lived. It just so happened that the professor you were working with obtained copies of these notes and enlisted your help to decipher them.

You hired a translator to translate Mendel's notes from Czech to English, and using your knowledge of modern genetics (which Mendel did not have!) you were able to construct a partial Punnett square for crosses with peas (shown here). Because the notebook was damaged from being buried for so long, this is the only information that you have regarding a cross that Mendel must have performed. Your professor has tasked you with figuring out more about this experiment.

In pea plants, round peas are dominant (R) and shriveled peas are recessive (r), and yellow peas (shown as light gray in the Punnett square) are dominant (Y) and green peas (dark gray) are recessive (y). Using this information and the partial Punnett square shown, what is the phenotypic ratio of the offspring pea plants in this Punnett square?

3:3:1:1

Cats normally have a total of 18 toes, 5 on each front paw and 4 on each back paw. But some cats express the dominant phenotype for polydactyly, which results in the development of extra toes on one or more paws. Jake, a Canadian tabby cat, has 28 toes and is recognized by the Guinness Book of World Records as the cat with the most toes.

Suppose that Jake mates with a female cat, Lucy, who has 18 total toes. Over several years, they have multiple litters and a total of 16 kittens (10 males and 6 females). The total number of toes on each kitten ranges from 21 to 25.

If we use the letter P to represent the polydactyly gene, what is Jake's genotype?

PP

Cats normally have a total of 18 toes, 5 on each front paw and 4 on each back paw. But some cats express the dominant phenotype for polydactyly, which results in the development of extra toes on one or more paws. Jake, a Canadian tabby cat, has 28 toes and is recognized by the Guinness Book of World Records as the cat with the most toes.

Suppose that Jake mates with a female cat, Lucy, who has 18 total toes. Over several years, they have multiple litters and a total of 16 kittens (10 males and 6 females). The total number of toes on each kitten ranges from 21 to 25.

One of Jake and Lucy's kittens mates with another cat that has 18 total toes. What is the probability that one of their offspring would have 18 total toes?

50%

Cats normally have a total of 18 toes, 5 on each front paw and 4 on each back paw. But some cats express the dominant phenotype for polydactyly, which results in the development of extra toes on one or more paws. Jake, a Canadian tabby cat, has 28 toes and is recognized by the Guinness Book of World Records as the cat with the most toes.

Suppose that Jake mates with a female cat, Lucy, who has 18 total toes. Over several years, they have multiple litters and a total of 16 kittens (10 males and 6 females). The total number of toes on each kitten ranges from 21 to 25.

Along with having a variable number of toes, some kittens from Jake and Lucy's litter had a white spot on their nose. In fact, out of the 16 kittens, all 10 males had the white spot, but none of the 6 females had the white spot. Jake has a white spot on his nose, but Lucy does not. What can you conclude from this information?

A sex-linked gene that controls the expression of the white spot is found on the X chromosome