Bio Mastering- Patterns of Inheritance
Vitamin D - resistant rickets is an X-linked dominant bone disorder. A man with this form of rickets marries a normal woman. What proportion of the couple's daughters is expected to have vitamin D - resistant rickets?
100%
You cross two fruit trees. One tree produces lemons with spiky leaves and bumpy fruit. The other produces lemons with smooth leaves and smooth fruit. Your F1 generation produces lemons with smooth leaves and spiky leaves and bumpy fruit. What are the genotypes of the parents? L = lemons with bumpy fruit; l = lemons with smooth fruit; S = smooth leaf; s = spiky leaf.
LLss and llSs
Akin to urban legends, there are curious genetics legends - things like eye color being determined by one gene, with a brown eye allele being completely dominant to blue. The problem comes when simple myth meets the complex reality of how eye color and many other traits are transmitted. Why is the inheritance of so many traits difficult to explain using only Mendel's view of genetics?
Mendel was correct for the traits he investigated, but his principles must be extended (not discarded) to explain many more complex patterns of inheritance
The Y chromosomes of mammals contain genes that code for _____.
"maleness' and a few other characteristics
In fruit flies, a particular sex-linked recessive allele can lead to abnormal wing formation. A cross is performed between two normal-winged fruit flies with the genotypes XRY and XR Xr. What percentage of the offspring are expected to be female with abnormal wing development?
0%
If one parent is blood type AB and the other is type O, what fraction of their offspring is expected to have blood type A?
0.5
In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?
1 AB : 1 aB
parent with orange eyes and white skin. Carole is a MendAlien with orange eyes and white skin. If Sam and Carole wereto mate, the predicted phenotypic ratio of their offspring would be _____.
1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin
Pea flowers may be purple (P) or white (p). Pea seeds may be round (R) or wrinkled (r). What proportion of the offspring from the cross PpRr × PpRr are expected to have white flowers and wrinkled seeds?
1/16
In a standard monohybrid cross between purple-flowered and white-flowered peas, in which purple flowers are dominant, what fraction of the purple-flowered peas in the F2 generation would you expect to be true-breeding?
1/3 (1/3 would be homozygous, while 2/3 would be heterozygous)
Assume that in cattle a spotted coat is dominant to an even coat, short horns are dominant to long horns, and the traits for coat type and horn length assort independently. In a cross between cattle that are each heterozygous for both traits, what proportion of their offspring are expected to have long horns?
1/4
Hypercholesterolemia is a disorder in which blood cholesterol levels are elevated. The H allele is incompletely dominant to the h allele, with hh homozygotes having extremely high levels of blood cholesterol. A husband and wife are both Hh heterozygotes. What is the chance that their first child will have normal levels of blood cholesterol?
1/4
There are over 100 alleles known for the gene associated with cystic fibrosis. With current technology, it is possible to determine exactly which allele or alleles is/are carried by a person. What is the maximum number of different alleles that any person can carry?
2
Flower color in snapdragons is an example of incomplete dominance. If a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the expected progeny plants will be __________.
25% red 50% pink 25% white
A woman with type O blood is expecting a child. Her husband is type A. Both the woman's father and her husband's father had type B blood. What is the probability that the child will have type O blood?
50%
Snapdragons show incomplete dominance in their flowers. A pink snapdragon is crossed with a red snapdragon. What color(s) are the offspring?
50% red 50% pink
A woman who is a carrier of hemophilia marries a man affected with hemophilia. What percentage of their sons and daughters is expected to have hemophilia?
50% sons and 50% daughters
You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half the offspring trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents? A = big apples; a = small apples; R = red apples; r = yellow apples.
AArr and aaRr
In lentils, the C gene has two different alleles. CSCS homozygotes have spotted seeds, CDCD homozygotes have dotted seeds, and CSCD heterozygotes have seeds with both spots and dots. This indicates that __________.
CS & CD are co-dominant
An insect that has the genotype EeGGcc will have the same phenotype as an insect with the genotype __________.
EEGgcc (EE & Ee have same phenotype; GG & Gg have same phenotype)
Two individuals decide to have children. The expected blood group genotypes are 50% of blood type A, and 25% each of blood types AB and B. What genotypes are the parents?
IAi x IAIB
In breeding pure-breeding large and small strains of mice, you cross individuals of each strain and note that their offspring are intermediate in size. Two models (explanations) to account for this result are (1) that body size in these strains is due to one gene with alleles that show incomplete dominance and (2) that body size is a polygenic trait. How could you distinguish between these models?
Intercross the F1 and see if the F2 contains three size classes (consistent with the incomplete dominance model) or if there is a range of sizes (consistent with the polygenic model).
Why are lethal dominant alleles so much more rare than lethal recessive alleles?
Lethal dominant alleles are harmful whether they are carried in homozygous or heterozygous form, so there is always strong selection against these alleles.
Suppose we have a pea plant with purple flowers, determined by the dominant allele P. How might you determine whether the plant is homozygous (PP) or heterozygous (Pp)?
Perform a testcross: Cross the plant with a white one, which must be homozygous recessive (pp).
he existence of rare XY individuals who are phenotypically normal women was instrumental in learning about human sex determination. Maleness is determined by the SRY gene found on the Y chromosome. How is it possible to be an XY woman?
The SRY locus of the Y chromosome is deleted
Previously, it was thought that the blending hypothesis explained inheritance. The blending hypothesis maintained that __________
after a mating, genes of the two parents are mixed in the offspring and lose their individual identities
Imagine you're counseling a couple who have undergone carrier screening for Tay-Sachs disease. The man is a carrier, and the woman does not carry the Tay-Sachs allele. How should you advise them?
They should be informed that if they have a child, the child will not have Tay-Sachs disease but will have a 50% chance of being a carrier of the Tay-Sachs allele.
If the gene for seed color that Mendel studied exhibited pleiotropy, how might a green pea be different from a yellow pea?
With pleiotropy, there would be other differences between the peas - for example, green peas may also be larger, ripen earlier, and be more sensitive to frost.
A woman and her male partner have normal color vision. However, her father and her first son are colorblind. What is her genotype? Use C as the gene for colorblindness.
X(C) X(c)
Huntington's disease is an example of a genetic disorder caused by __________.
a late-acting lethal dominant allele
most human genes come in alternate versions called ___
alleles
Human genetic disorders __________.
are most often recessive
A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.
both parents are heterozygous for both genes
a ___ is an inherited feature that varies from individual to individual
character
Imagine that long fins in zebrafish is a dominant trait. A breeder wants to set up a breeding program beginning with homozygous dominant long-finned fish. If she obtains a handful of the long-finned fish, how can she tell which, if any, of these are homozygous for the trait?
cross the long finned fish with short finned fish; if the offspring are all long finned, the long-finned parent is homozygous
A cross between two individuals with black eyes and green skin which results in an individual with orange eyes and white skin is an example of a _____ cross.
dihybrid cross
if an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the ___ allele
dominant
DdEe pea plants can produce _____ type(s) of gametes, but a ddee plant can produce _____ type(s) of gametes.
four; one
the ___ is the genetic makeup of an organism
genotype
Imagine that a deaf male has a child with a hearing female. You know that the male must have the genotype dd, but the female could be either Dd or DD. If the couple's first child has hearing, can you determine the mother's genotype? (Hint: Draw Punnett squares for the two possible crosses.) Use the Punnett square from the introduction and the ones you drew for Part A to select the three statements that are true about the inheritance of this form of deafness. Use the Punnett square from the introduction and the ones you drew for Part A to select the three statements that are true about the inheritance of this form of deafness. The child of a Dd father and Dd mother has a 50% chance of having hearing. If a deaf child is born to hearing parents, both parents must be Dd. If a deaf man and a hearing woman have a deaf child, the mother's genotype must be Dd. If the first two children from Dd parents are deaf, there is no risk that their next child will also be deaf. The child of a deaf man and a DD hearing woman will definitely have hearing
her genotype cannot be determined If a deaf child is born to hearing parents, both parents must be Dd. If a deaf man and a hearing woman have a deaf child, the mother's genotype must be Dd. The child of a deaf man and a DD hearing woman will definitely have hearing
When you cross two heterozygotes (Aa), the offspring will most likely be __________.
in the ratio 1:1 homozygotes to heterozygotes
Mendel's principle of independent assortment applies to the __________.
independent assortment of alleles of one gene relative to the alleles of any other gene
A child with cystic fibrosis can be born to two parents who do not have the disease. This is because the disease _____.
is caused by a recessive allele
A BbGg x bbgg cross yields a phenotypic ratio of approximately 5 black eyes, green skin : 5 orange eyes, white skin : 1 black eyes, white skin : 1 orange eyes, green skin. Which of the following best explains these results?
mendel's law of independent assortment is being violated
a genetic cross involving parents that differ in a single character is called a ___
monohybrid cross
When applied to Mendel's experiments, the term true-breeding means a self-fertilization of two plants that produces __________.
offspring identical to the parent
Several inherited disorders are much more common in close-knit religious communities, such as the Amish, than in the general population. This is at least partly because __________.
people in such communities are more likely to reproduce with relatives
Imagine a particular character (such as flower color) that is determined by a single gene. If this gene is present in two forms, how can you tell which allele is dominant and which is recessive?
perform a cross between the two true breeding individuals and observe the trait expressed by the F1 individuals
the physical traits of an organism are called its ___
phenotype
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
The cross-fertilization of two different, but true-breeding, varieties of pea plants will _____.
result in hybrid plants
Hemophilia appears rarely in females. This is because __________.
the female must possess the hemophilia allele on both x chromosomes
In people with sickle-cell disease, red blood cells break down, clump, and clog blood vessels. Blood vessels and broken cells accumulate in the spleen. Among other symptoms, this leads to physical weakness, heart failure, pain, and brain damage. Such a suite of symptoms can be explained by __________.
the pleiotropic effects of the sickle-cell allele
Two parents of mixed ethnicity have twins, one of which is born with very light skin and one of which is born with very dark skin. This is because of __________.
the polygenic nature of skin color genes
In a monohybrid cross, F2 refers to _________
the second filial generation, or the "grandchildren" of the original mating pair
a ___ is one particular variation of a character
trait
Mendel's view of the mechanism of heredity was radically different from the prevailing view of the time because he saw heredity working through __________.
unchanging (immutable) heritable factors that were contributed by each parent and never altered by mixing