Chapter Four Flashcards
What is Mendelian Inheritance pattern?
The common pattern of inheritance observed by Mendel, which involves the transmission of eukaryotic genes that are located on the chromosomes found within the cell nucleus.
What are the two laws the traits of Mendelian inheritance follow?
The law of segregation
The law of independent assortment.
What is simple mendelian inheritance?
An inheritance pattern involving a simple, dominant/recessive relationship that produces observed ratios in the offspring that readily obey Mendel’s laws.
What is incomplete dominance?
Inheritance pattern that occurs when the heterozygote has a phenotype that is intermediate between either corresponding homozygote.
Ex: cross between red and white flower produces a pink flower.
What is overdominance?
Inheritance pattern occurs when the heterozygote has a trait that is more beneficial than either homozygote.
What is codominance?
Inheritance pattern occurs when the heterozygote expresses both alleles simultaneously without forming an intermediate phenotype.
Ex: parents with A blood type and B blood type will produce an offspring with AB blood type
What is sex-influenced inheritance?
Inheritance pattern the refers to the effect of sex on the phenotype of the individual. Some alleles are recessive in one sex and dominant in the opposite sex.
What is sex-limited inheritance?
Inheritance pattern that refers to traits that occur in only one of the two sexes.
What are lethal alleles?
An allele that has the potential of causing the death of an organism.
Which of the following statements is true?
a. Not all inhertance patterns follow a strict dominant/recessive relationship.
b. Geneticists want to understand both inhertiance patterns and the underlying molecular mechanism that cause them to happen.
c. Different inheritance patterns are explained by a variety of different molecular mechanisms
d. all of the above.
d. all of the above.
What are wild-type alleles?
An allele that is fairly prevalent in a natural population, generally greater than 1% of the population. For polymorphic genes, there may be more than one wild-type allele.
What is genetic polymorphism?
When two or more alleles occur in population; each allele is found at a frequency of 1% or higher.
What are mutant alleles?
Alleles that have been created by altering a wild-type allele by mutation.
Does a PP individual produce more of the protein encoded by the P gene than is necessary for the purple flower?
Yes. The PP homozygote probably makes twice as much of the protein that is needed for purple pigment formation.
What are thre three explanations that account for most dominant mutant alleles?
A gain-of-function mutation
A dominant-negative mutation,
Haplo-insufficiency.
What is gain-of-function mutation?
A mutation that causes a gene to be expressed in an additional place where it is not normally expressed or during a stage of development when it is not normally expressed.
What is dominant-negative mutation?
A mutation that produces an altered gene product that acts antagonistically to the normal gene product. Shows a dominant pattern of inheritance.
What is haploinsufficiency?
The phenomenon in which a person has only a single functional copy of a gene, and that single functional copy does not produce a normal phenotype.
What is incomplete penetrance?
A pattern of inheritance in which a dominant allele does not always control the phenotype of the individual.
What is expressivity?
The degree to which a trait is expressed.
For example, flowers with deep red color have a high expressivity of the red allele.
Which of the following is not an example of a wild-type allele?
a. yellow-flowered elderflower orchid
b. Red-flowered elderflower orchid
c. a gray elephant
d. an albino elephant.
d. an albino elephant.
Dominant alleles may results from mutations that cause
a. the overexpression of a gene or its protein product.
b. a protein to inhibit the function of a normal protein
c. a protein to be inactive and 50% of the normal protein is insufficient for a normal phenotype
d. all of the above.
d. all of the above.
Polydactyly is a condition in which a person has extra fingers and/or toes. It is caused by a dominant allele. If a person carries this allel but does not have any extra fingers or toes, this is an example of
a. haploinsufficiency.
b. a dominant negative mutation
c. incomplete penetrance
d. a gain-of-function mutation.
c. incomplete penetrance
What is temperature sensative allele?
An allele in which the resulting phenotype depends on the environment temperature.
What are the two main factors that determines an organisms traits?
Genes and the environment.
What is norm of reaction?
The effects of environmental variation on an individual’s traits.
How do researchers evaluate norm of reaction?
Begin with true-breeding strains that have the same genotype and subject them to different environmental conditions.
The outcome of an individual’s traits is controlled by what?
a. genes
b. the environment
c. genes and the environment
d. neither genes nor the environment
c. genes and the environment
At the moleular level, what is the explanation for why the flowers are pink instead of red?
50% of the functional enzymes is not enough to give a red color.
At which level is incomplete dominance more likely to be observed– at the molecular/cellular level or at the organism level?
Molecular/cellular level.
What is heterozygote advantage?
Or overdominance.
An inheritance pattern in which a heterozygote is more vigorous than either of the corresponding homozygotes.
Why does heterozygote have an advantage for sickle cell anemia?
The heterozygote is resistant to malaria.
