Mastering Biology Chapter 9
An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. If an individual with wavy hair mates with an individual with straight hair, what is the probability that their child will have curly hair?
0%
Assume that having three nostrils is inherited as a sex-linked trait on the Y chromosome. A man with three nostrils has a daughter who has a son with a man who has only two nostrils. What is the probability that the three nostriled man's grandson has three nostrils?
0%
The parents of a child with unusual disease symptoms take the child to a doctor for help. The doctor suspects that the condition might have a genetic basis. She recommends that the child be take to a specialty clinic where physicians and staff members are trained to diagnose genetic diseases and counsel parents. Ultimately, the child is diagnosed with a rare recessively inherited disease. The parents are tested for the gene, and both are found to be heterozygous. The parents what to have another child but are afraid this child will also be affected. What would genetic counselors say is the probability that the second child will have the disease?
1/4
A couple has two female children. What is the probability that their next child will be a male?
50%
Achondroplasia is a form of dwarfism caused by a dominant allele. the homozygous dominant genotype causes death, so individuals who have this condition are all heterozygotes. If a person with achondroplasia mates with a person who does not have achondroplasia, what percentage of their children would be expected to have achondroplasia?
50%
Attached earlobes are recessive to free earlobes. What is the probability of having a child with attached earlobes when an individual with attached earlobes mates with an individual heterozygous for free earlobes?
50%
Which of these crosses will only produce heterozygous offspring?
AA x aa
Hypophosphatemia (vitamin Dresistant rickets is inherited as a sex-linked dominant trait. The relevant gene is found on the X chromosome. What is the expected outcome of a cross between a homozygous recessive woman and a man with hypophosphatemia?
All of their daughters and none of their sons exhibit hypophophatemia.
Chromosomes contain most of the cell's __________ which acts as the molecule of heredity.
DNA
In humans, the presence or absence of dimples is a trait controlled by a single gene. What is the genotype of an individual who is heterozygous for dimples?
Dd
Red-green color blindness is inherited as a sex-linked recessive trait. The gene is found on the X chromosome. Can a man with normal color vision father a daughter who is red-green color-blind?
No, he can't (unless there is a mutation).
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered snapdragon. All of the F1 are pink. What can you say about the alleles for the parental traits?
Red and white show incomplete dominance.
What is the key to the recognition of codominance?
The heterozygote expresses the phenotype of both homozygotes.
What is the key to the recognition of incomplete dominance?
The phenotype of the heterozygote falls between the phenotypes of the homozygotes.
What is key to recognition of a trait whose expression is determined by the effects of two or more genes (polygenic inheritance)?
The trait varies along a continuum in the population.
A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds. The seeds of all of the offspring are yellow. Why?
The yellow allele is dominant to the green allele.
The sex chromosomes in humans that make an individual a male are ___________.
X and Y
Mendel discovered that the allele for green seed pods (G) is dominant to the allele for yellow seed pods (g). He crossed true-breeding (homozygous) parental plants with green (GG) and yellow (gg) seed pods to produce an F1 generation, all of which were heterozygous (Gg) with green seed pods. He then crossed two of these F1 plants to produce an F2 generation. Drag the genotypes and phenotypes from the left to correctly complete the Punnett square for the F2 generation. Drag only blue labels to blue targets and pink labels to pink targets. Labels may be used more than once.
a. GG b. green plant c. Gg d. green plant e. Gg f. green plant g. gg h. yellow plant
Human ABO blood type is determined by a single gene that comes in 3 distinct alleles: IA , IB , and i. The IA and IB alleles are each dominant to the i allele, but are codominant with each other, meaning that both phenotypes are expressed in the heterozygote. The Punnett square below shows a cross between two parents with different blood types. Drag the genotypes and phenotypes from the left to correctly complete the Punnett square.
a. I^AI^B b. Type AB c. I^Ai d. Type A e. I^Bi f. Type B g. ii h. Type O
The disease hemophilia is caused by a single gene that is located on the X chromosome. Because human females have two X chromosomes (XX), they have two copies of this gene. Since hemophilia is recessive (h), a female must have two copies of the recessive allele to have the disease. A human male (XY), on the other hand, has only one X chromosome, and so needs only one copy of the recessive allele to have the disease. Complete the Punnett square below of a cross between a carrier mother (a female who carries one copy of the recessive allele and so appears normal herself) and a non-hemophiliac father.
a. female b. normal c. male d. normal e. female f. carrier g. male h. hemophiliac
Can you label these chromosomes with the correct genetic terms?
a. homologous chromosomes b. gene locus c. recessive allele d. centromere e. sister chromatids f. alleles g. dominant allele
Most human genes come in alternate versions called _________.
alleles
Alleles are described as __________.
alternate versions of a gene
An individual who is homozygous ____________.
carries two copies of the same allele for a gene
A duplicated chromosome remains tightly paired with its partner at a region called the ______________.
centromere
A ___________ is an inherited feature that varies from individual to individual.
character
DNA and protein together form a complex called __________.
chromatin
The DNA of every eukaryotic cell is stored in one or more ____________ located at the __________.
chromosomes... nucleus
If an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the __________ allele.
dominant
The scientific study of heredity is called ___________.
genetics
The ____________ is the genetic makeup of an organism.
genotype
In humans, the inheritance of ____________ is best explained as being polygenic.
height
Mendel crossed purebred purple-flowered plants with purebred white-flowered plants, and all of the resulting offspring produced purple flowers. The offspring are all ___________, and the allele for purple flowers is _____________.
heterozygotes... dominant
An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. What is the relationship between the alleles for hair texture?
incomplete dominance
Many human traits, such as our performance on intelligence tests or our susceptibility to heart disease, are _____________.
influenced by both genes and the environment
To determine the genotype of an individual who expresses a dominant trait, you would cross that individual with an individual who ___________.
is homozygous recessive for that trait
What name is given to the specific location of a gene on a chromosome?
locus
In humans, the ___________ determines the sex of the offspring because _____________.
male... the male can contribute either an X or a Y chromosome
A genetic cross involving parents that differ in a single character is called a _____________.
monohybrid cross
Incomplete dominance is a condition in plants and people where ___________.
offspring have an appearance in between the phenotypes of the two parents
The physical traits of an organism are called its __________.
phenotype
Marfan syndrome is the result of inheriting a single allele. Individuals with Marfan syndrome are tall and long-limbed, and have both cardiovascular and eye defects. Of what type of inheritance is the phenotype of Marfan syndrome an example?
pleiotropy
Which of the following is used to define a phenotypic characteristic resulting from the expression of two or more genes?
polygenic inheritance
If an organism has two non-identical versions of a gene, the one that is not expressed in the organism is called the ____________ allele.
recessive
This genetic disorder causes red blood cells to assume an unusual shape and produce abnormal hemoglobin proteins.
sickle-cell disease
Before a cell divides, it copies all of its chromosomes. While the two copies of a chromosome are attached they are called _____________.
sister chromatids
Why are human males much more likely than human females to inherit the recessive condition hemophilia (a failure of the blood to clot properly)?
the gene for hemophelia is sex-linked
A ___________ is one particular variation of a character.
trait
