Chapter 11 Flashcards
Incomplete Dominance
the dominant allele is not completely expressed when the recessive allele is around
Polygenic Traits
many genes coding for one trait
Sickle Cell Anemia Affects
hemoglobin
How does Sickle Cell Anemia affect the body?
some blood cells become sickle shapes and the elongated cells get stuck in certain blood vessels and parts of the body don’t get the oxygen they need
How does Sickle Cell Anemia happen?
it is caused by a single code letter change in DNA and that alters an amino acid in the hemoglobin protein
-Valine sits where glutamic acid should be in the hemoglobin protein
-Valine makes the hemoglobin molecules stick together forming long fibers that distort the shape of the red blood cells and that brings on an attack
According to Mendel’s law of segregation, __________.
allele pairs separate in gamete formation
Pea plants are tall if they have the genotype TT or Tt, and they are short if they have genotype tt. A tall plant is mated with a short plant. Which outcome below would indicate that the tall parent plant was heterozygous?
A 1:1 ratio of tall offspring to short offspring
A single genetic locus that controls more than one trait is said to be __________.
pleiotropic
When two average-height parents give birth to a child exhibiting achondroplasia, it is most likely due to a new mutation. This is because __________.
achondroplasia is caused by an allele that is always expressed; therefore, the parents must not have the allele
Flower color in snapdragons is an example of incomplete dominance. When 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 progeny plants will be __________.
25% red, 50% pink, and 25% white
Huntington’s disease is an example of a genetic disorder caused by __________.
a lethal dominant allele that afflicts an individual later in life
If an organism that is homozygous dominant is crossed with a heterozygote for that trait, the offspring will be __________.
all of the dominant phenotype
After obtaining two heads from two tosses of a coin, the probability of obtaining a head on the next toss is __________.
1/2
Which of the following human diseases is inherited as a simple recessive trait?
Cystic fibrosis
Tom’s brother suffers from phenylketonuria (PKU), a recessive disorder. The brothers’ parents do not have PKU. What is the chance that Tom, who is normal for this trait, is a carrier of PKU?
2/3
Tail length in a certain species of armadillo falls along a continuum, following a normal distribution. Assuming that environmental factors do not play an important role in determining tail length, this type of variation probably reflects __________.
polygenic inheritance
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%
If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?
1/2
Which of the following describes the expression of the Tay-Sachs allele in humans at the biochemical level?
Incompletely dominant
The probability of tossing three coins simultaneously and obtaining two heads and one tail is __________.
3/8
Heart disease, diabetes, cancer, alcoholism, and many mental illnesses can best be described as __________.
multifactorial disorders with a possible polygenic component
In Mendel’s monohybrid cross of purple-flowered and white-flowered peas, all members of the F1 generation had the __________ phenotype because their genotype was __________ at the flower-color locus.
purple-flowered; heterozygous
A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of alleles that are __________.
codominant
Assume that in guinea pigs, the brown coat color allele (B) is dominant over red (b), and the solid color allele (S) is dominant over spotted (s). The F1 offspring of a cross between true-breeding brown, solid-colored guinea pigs and red, spotted guinea pigs are crossed. What proportion of their offspring (F2 generation) would be expected to be red and solid-colored?
3/16
In a certain plant, the alleles A, B, and C are completely dominant to the alleles a, b, and c. A plant with the genotype AABbcc will have the same phenotype as a plant with the genotype __________.
AaBBcc
How does codominance at the molecular level help to explain why evolutionary processes haven’t resulted in the elimination of the sickle-cell allele among people of African descent?
Heterozygous individuals have both normal and sickle-cell hemoglobin in their red blood cells and reduced vulnerability to malaria.
Which of the following is a basic difference between Mendel’s particulate hypothesis and the hypothesis of blending inheritance?
The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring and that these contributions cannot then be separated.
Mendel’s theory of particulate inheritance __________.
can explain inheritance patterns for virtually every sexually reproducing organism but does not explain multifactorial characters
In the F2 of a dihybrid cross involving two independently assorting genes, what proportion of the offspring will be true-breeding?
1/4
Observable heritable feature
Character
variants for character
Trait
produces offspring identical to parents
True-Breeding
true breeding, homozygous parents of F1 hybrid offspring
P generation
F1 generation
offspring resulting from parental cross
F2 generation
offspring resulting from the interbreeding of the F1 generation
sequence of DNA nucleotides that can be passed from parents to offspring
Gene
location of a gene on a particular chromosome
Locus
alternative versions, or forms, of the same gene, can be 2 or more
Allele
True or False: for each gene, an organism inherits two alleles, one from each parent
True
True or False: two different alleles for the same gene can be found on sister chromatids of a duplicated chromosome
False
The __________ allele is always expressed when present, while the _________ allele is only expressed when two copies are present
dominant
recessive
diagram showing the outcomes of possible fertilization events between the gametes made by the parents
Punnett Square
AA
homozygous dominant
Aa
heterozygous
aa
homozygous recessive
True or False: when phenotype is dominant, the corresponding genotype can only be homozygous dominant
false
True or False: when phenotype is recessive, the corresponding genotype can only be homozygous recessive
true
Principle of Segregation Explains
how alleles are separated during gamete formation
Segregation occurs during which stage of meiosis?
anaphase 1
Segregation Description
each gamete will receive a single copy of each gene singe homologs separate
Independent Assortment Explains
how each pair of alleles assorts independently from any other pair during gamete formation
Independent Assortment happens during which stage of meiosis?
metaphase 1
Independent Assortment Description
orientation of homologs shows that they will assort independently
Exceptions to Mendelian Rules
incomplete dominance
co-dominance
multiple allele
pleiotropic effect
epistasis
polygenic
Intermediate phenotype is expressed in heterozygotes
Incomplete dominance
both phenotypes are expressed in heterozygotes
Co-dominance
in the population, some genes have more than two alleles
Multiple Allele
Example of Incomplete Dominance
Snapdragon Flower
red, purple, and white phenotype color
Example of Co-Dominance
AB Blood type
Example of Multiple Allele
ABO blood group containing 3 different alleles
Pleiotropic Effect
one gene affects multiple phenotypic traits
Epistasis
two genes contribute to one phenotype trait
Polygenic
multiple genes contribute to one phenotypic trait
Example of Pleiotropic Effect
sickle cell disease
Example of Epistasis
Labrador Coat Color
Example of Polygenic
Skin Color
True or False: Pleiotropy and polygenic inheritance are essentially opposite of each other
true
Three Types of Mendelian Crosses
monohybrid
dihybrid
test cross
between individuals that are heterozygous for one character
example: PPxPp
Monohybrid Cross
Monohybrid Cross Ratios
genotypic ratio: 1:2:1
phenotypic ratio: 3:1
between individuals that are heterozygous for two characters
example: YyRrxYyRr
Dihybrid Cross
Dihybrid Cross Ratios
phenotypic ratio: 9:3:3
used to determine if an organism with the dominant phenotype is homozygous dominant or heterozygous
Test Cross
Rule of Multiplication
probability of two independent events occurring simultaneously
Probability is 1x2
Rule of Addition
if an event occurs in two or more different ways, add separate possibilities of these ways
True or False: Dominant and recessive alleles of the same gene interact with each other to affect phenotype
true
The most common phenotype in a population is referred to as the
wild-type
True or False: Dominant alleles are always more common in populations than recessive alleles
False
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.)
Her genotype cannot be determined.
Which of the following genotypes represent the possible gametes produced by an FfGg individual? Assume that the genes are not linked and therefore assort independently.
FG, Fg, fG, fg
Which of the following student-drawn Punnett squares shows a correct setup for a MMHh ×
mmHh cross?
Which of the following student-drawn Punnett squares shows a correct setup for a FfGg ×
FfGg cross?
How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?
Cross the green-pod plant with a yellow-pod plant
What is the difference between heterozygous and homozygous individuals?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.
gametes, progeny
True or false: The same phenotype can be produced by more than one genotype.
true
True or false: In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
false
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
none
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
25
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the “1” in the 9:3:3:1 ratio)?
ttpp
If an individual with type O blood marries an individual with type AB blood, what are the possible blood types of their children?
A and B
An unaffected man whose mother had sickle-cell anemia marries an unaffected woman whose father had sickle-cell anemia. Which of the following statements about their offspring is NOT true?
They must all have the sickle-cell trait.
True or false: In codominance, both phenotypes are expressed in heterozygotes; but in incomplete dominance, the heterozygotes exhibit a phenotype that is intermediate between the two homozygotes.
true
What is tyrosinase?
Tyrosinase is the term used for a person who is afflicted with albinism as well as sickle-cell trait.
Which of the following statements is NOT true for a person who is heterozygous for sickle cell?
A person who is heterozygous for sickle cell tends to die at a younger age than a person with sickle-cell anemia does.
Crossing a plant with white flowers and a plant that is homozygous for purple flowers results in offspring with what color combinations?
All flowers will be purple
