genetics

A cross occurs between a black homozygous mouse and a white homozygous mouse. They produce gray offspring. Use this scenario to respond to the next three questions:

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A man who is a carrier for cystic fibrosis marries a woman who is a carrier for cystic fibrosis. Respond to the next three questions based upon this scenario.

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The probability of an event, such as inheriting a recessive allele, is 1⁄2. The probability of inheriting a second recessive allele is 1⁄2 . What, then, is the probability of inheriting two recessive alleles?

1/4

What are the percentage probabilities for the genotype and phenotype of the offspring?

100% gray; 100% Bb

What is the percentage probability that this couple will have a child with cystic fibrosis?

25%

Referring to the mouse scenario noted above, what is the percentage phenotypic probability if we cross two gray mice from the F1 generation?

25% black; 50% gray; 25% white

Mendel observed patterns of inheritance for all of the traits he tested. The F1 generation all had a phenotype identical to one of the parents in the P generation. What results did he find for the F2 phenotypes?

3⁄4 had the phenotype of the F1 generation and 1⁄4 had the phenotype of one of the P generation parents.

What is the percentage probability that they will have a child who is a carrier?

50%

Consider a dihybrid cross between two rabbits LlBb x LlBb. What are the phenotypic ratios of the offspring? (L = long ears l = short ears; B = black b = white)

9 Long Black; 3 Long white: 3 short Black: 1 short white

What determines "maleness" in humans?

A single Y chromosome, regardless of number of X chromosomes.

How does inbreeding increase the probabilities of recessive disorders?

Carriers have an increased chance of reproducing together to produce a homozygous recessive condition.

Blood type in humans is the result of multiple alleles. Blood type is also an example of which type of inheritance pattern?

Co-dominance

What is true about the majority of sex-linked disorders in humans?

Males have a higher probability of inheriting sex linked disorders

Jean-Baptiste Lamarck introduced a theory about inheritance in the early 1800s. Which of the following accurately describes his Theory of Acquired Characteristics?

Offspring traits are the result of parent individuals modifying their traits due to use or non-use.

Which of the following accurately describes the relationship between a dominant and a recessive allele?

The dominant allele is expressed however the recessive allele is unaltered.

Which of the following statements best describes one aspect of the chromosomal theory of inheritance, posited after Mendel's time?

The hereditary factors from Mendel's experiments are actually genes located on chromosomes.

What does the term autosomal refer to?

The non XY chromosomes found in an organism

Mendel crossed two plants, called the P generation. The offspring of this cross are known as hybrids. What are hybrids?

The result of crossing two true breeding plants; they contain two genes, one of each allele.

Which of the following is accurate about an X-linked trait?

There is 0% chance that a son inherits an X-linked trait from his father

Mendel used dihybrid crosses in an effort to uncover more information about inheritance patterns. From this he developed two laws of inheritance. Which of the following accurately described the law of segregation?

This law states that gametes each carry only one allele for a trait, to be combined when fertilization occurs.

A female who is AO (iA, iO) mates with a male who is BO (iB, iO). What possible blood types can their children inherit?

Types, A, AB, B and O

What is meant by the term pleiotropy?

When a single allele affects multiple phenotypes

Polygenic inheritance refers to which of the following conditions of inheritance?

When multiple alleles affect one trait.

What is considered to be incomplete dominance?

When the phenotype of the hybrid shows an in-between phenotype of the two parents.

Before having children, a couple prepares a pedigree of their family for one particular autosomal dominant disorder. They chart all of their relatives back three generations. From this information, can they determine whether or not they will have a child with the disorder?

Yes, they can know with certainty.

A group of individuals have lived for generations on an island. Their average height is 5 feet 2 inches. Eventually, ships stop by the islands bringing more fruits, vegetables and meats to their diet and more food overall. While the islanders continue to marry islanders and produce children, over generations the average height of the islander population reaches 5 feet 6 inches. What was most likely the main factor in this change?

changes in nutrition that affected the phenotype, fully expressing the genotype

A cross occurs between a chicken with white feathers and a chicken with black feathers. This results in offspring with some black feathers and some white feathers. What type of inheritance is this?

codominance

What type of dominance is reflected in the scenario above?

incomplete dominance

The couple in the above scenario has four children. How many of their children will have cystic fibrosis?

it could be none to all of their children

Prenatal or fetal tests can be performed that can provide information about the genetic make-up. Which of the following is based upon family history to estimate probabilities of genetic disorders?

pedigrees

Gregor Mendel was a critical contributor to our understanding of inheritance today. In his experiments he tracked seven visual traits of pea plants and ensured that they produced offspring identical to themselves. What are the terms that we used to identify two separate factors?

phenotype; true breeding

Sickle cell disease is the result of one gene abnormality. When two recessive alleles occur, sickle cell disease is inherited. The disease results in mis- shaped hemoglobin. What type of molecule is hemoglobin?

protein

Issues with inbreeding often occur with dog breeds, such as German shepherds. How can we best describe inbreeding?

successive breeding with individuals from within one population