chapter 19 study
"In humans, the ability to roll the tongue is a dominant trait;the inability to roll the tongue is a recessive trait. If two individuals homozygous dominant for this trait have a child, what is the chance that the child will not be able to roll their tongue?
0%
"In humans, the ability to roll the tongue is a dominant trait;the inability to roll the tongue is a recessive trait. If an individual homozygous dominant for this trait has a child with an individual who cannot roll their tongue, what is the chance that the child will have a heterozygous genotype?
100%
In human gamete production there is an average of _____ crossover events per chromosome pair.
2-3
"In humans, the ability to roll the tongue is a dominant trait;the inability to roll the tongue is a recessive trait. If two individuals heterozygous for this trait have a child, what is the chance that the child will not be able to roll their tongue?
25%
Cystic fibrosis is a genetic disorder that results from the inheritance of two recessive alleles. What is the chance that a child will inherit the disorder if one parent is heterozygous for this gene and one parent has cystic fibrosis?
50%
a useful method for predicting the ratios of possible offspring genotypes from a particular mating.
A Punnett square
If an individual with type O blood marries an individual with type AB blood, what are the possible blood types of their children? A. A, B, and O B. A and B C. AB, A, B, and O D. AB and O
A and B *The type AB individual must pass on either the gene for the A polysaccharide or the gene for the B polysaccharide. It would not be possible for this person to have a type O child. The type O individual cannot pass on either an A or a B allele. All children would be either type A or type B and could not be type AB or type O.
Which of the following statements is NOT true for a person who is heterozygous for sickle cell? A. A person who is heterozygous for sickle cell tends to die at a younger age than a person with sickle-cell anemia does. B. Cells generally sickle when oxygen is low. C. The red blood cells of the heterozygous person generally have both normal and abnormal hemoglobin. D. The heterozygous person is generally healthy under normal circumstances. E. The heterozygous person has a greater tendency for hemoglobin polymerization than does a person without the HbS allele.
A. A person who is heterozygous for sickle cell tends to die at a younger age than a person with sickle-cell anemia does.
All of the following statements about homologous chromosomes are true, EXCEPT that __________. A. The alleles on homologous chromosomes are identical to each other. B. One of each pair of homologous chromosomes comes from each parent. C. Homologous chromosomes physically pair up and may exchange parts during meiosis. D. They have genes for the same traits at the same loci.
A. The alleles on homologous chromosomes are identical to each other.
Which of the following results in the separation (or unlinking) of linked genes? A. crossing-over during meiosis I B. separation of sister chromatids during mitosis C. independent assortment during mitosis D. segregation during meiosis
A. crossing-over during meiosis I
two identical or nearly identical copies of a gene
Alleles
In humans, the allele for a widow's peak (W) is dominant and the allele for a straight hairline (w) is recessive. This trait shows complete dominance. Which of the following represents the possible phenotypes in the offspring of two parents, both with a straight hairline? A. Most of the offspring will have a straight hairline, but it is possible for an offspring to have a widow's peak. B. Each offspring will show both phenotypes. C. All offspring will have a straight hairline. D. All offspring will have a widow's peak.
C. All offspring will have a straight hairline.
A homozygous trait can be ________. A. recessive only B. heterozygous under certain circumstances C. either dominant or recessive D. dominant only
C. either dominant or recessive *Homozygous means that both alleles are the same. These alleles may be dominant or recessive.
Which of the following statements correctly expresses the relationship between dominant and recessive alleles? A. A dominant allele is always the most numerous allele in the population. B. A dominant allele is always the preferred or most beneficial allele. C. A dominant allele is expressed only when it is homozygous. D. A dominant allele masks the expression of a recessive allele in a heterozygote.
D. A dominant allele masks the expression of a recessive allele in a heterozygote.
What is the basis for the tremendous genetic diversity resulting from sexual reproduction? A. crossing-over and shuffling of linked genes during meiosis B. independent assortment during gamete production C. random fertilization D. all of these choices
D. all of these choices
Genetics is the study of
DNA and genes and their transmission from one generation to the next
Male and females have which chromosomes?
Females have two X chromosomes and males have an X and a Y chromosome.
The basic laws of genetic inheritance were described by ________. A. Barbara McClintock B. Gregor Mendel C. Watson and Crick D. Charles Darwin
Gregor Mendel
Based on what you know about two-trait inheritance, what can you say about the gametes produced by a female with the genotype AaDd that could NOT be possible?
One of her gametes might be AaDd.
A grid used for predicting patterns of inheritance and the probability that a particular genotype will be inherited
Punnett square
provides a simple way to represent patterns of inheritance of alleles and to predict the probability that a particular genotype will be inherited
Punnett square
carry the genes that determine the gender of the individual.
The X and Y chromosomes, also called the sex chromosomes,
Having a chin dimple (cleft chin) is dominant over having no chin dimple. Having long eyelashes is dominant over having short eyelashes. Jack and Jill are both heterozygous for a chin dimple and long eyelashes. What are the chances that their baby will have no chin dimple and short eyelashes? A. There is about a 25% chance that the child of Jack and Jill will have no chin dimple and short eyelashes. B. The chances are about 1 in 16 that their child will have no chin dimple and short eyelashes. C. Because Jack and Jill are both heterozygous for both traits, all of their children will have a 100% chance of having no chin dimple and short eyelashes. D. The chances are about 9 in 16 that their child will have no chin dimple and short eyelashes.
The chances are about 1 in 16 that their child will have no chin dimple and short eyelashes *No chin dimple and short eyelashes are independent recessive traits. The chance of a child inheriting two independent recessive alleles from heterozygous parents is 1 in 16.
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? A. About 75% can be expected to have the sickle-cell allele. B. They must all have the sickle-cell trait. C. They may not have either sickle-cell trait or sickle-cell anemia. D. About 50% can be expected to be heterozygous for the sickle-cell allele.
They must all have the sickle-cell trait. *This statement is false. Because the parents are both heterozygous, there is a 25% chance that a child of theirs will have sickle-cell anemia and a 25% chance that a child of theirs will be homozygous for no sickle-cell gene.
What is tyrosinase?
Tyrosinase is an enzyme that facilitates the conversion of tyrosine to melanin.
what happens if two people heterozygous for both genes mate? (for example with widows peak and free earlobes)
a mating between two heterozygotes for both genes can indeed produce children with both dominant traits and children with both recessive traits, but other combinations are also possible. Some offspring may have the dominant widow's peak and the recessive attached earlobe phenotypes, and others may have the recessive straight hairline and the dominant free earlobe phenotypes
Cystic fibrosis (CF), the most common potentially fatal genetic disease in North America today, is caused by
a recessive allele of a gene on chromosome 7
Which of the following parental genotypes would produce offspring in a 1:1:1:1 phenotypic ratio? A. aaBb x Aabb B. AaBb x AaBb C. aaBb x aabb D. AaBb x Aabb
aaBb x Aabb
Which of the following would provide an EXCEPTION to Mendel's law of independent assortment?
adjacent genes on the same chromosome
Variations of homologous genes that result in differences in structure and function are
alleles
genes coding for the same trait and found at the same locus on homologous chromosomes
alleles
sequence differences may occur within genes, and when they do, they produce alternative versions of genes called
alleles
of the 23 pairs of human chromosomes, 22 are always matched pairs called
autosomes
A recessive phenotype will be expressed when __________.
both alleles present are recessive
Your phenotype is determined not only by the alleles you inherit from your parents (your genotype), but also
by environmental factors and lifestyle choices such as how much you are exposed to the sun, whether you exercise, and how much and what you eat.
your phenotype is determined by?
by the alleles you inherit from your parents (your genotype), environmental factors, lifestyle choices (such as exposure to sunlight, whether you exercise, and how much and what you eat)
The X and Y chromosomes, also called the sex chromosomes
carry the genes that determine the gender of the individual. Females have two X chromosomes and males have an X and a Y chromosome
each chromosome can be identified by its
characteristic size, centromere location, and distinct banding pattern
the structures that contain most of an organism's DNA
chromosomes
pattern of inheritance in which both alleles of a gene are equally expressed even though the phenotypes they specify are different
codominance
the products of both alleles are expressed equally.
codominance
An allele that masks or suppresses the expression of its complementary allele
dominant allele
refers only to how an allele behaves in combination with a recessive allele in a heterozygote
dominant allele
In eukaryotic cells DNA has the appearance of a _____.
double helix
Mendel's law of independent assortment states that genes separate from each other during gamete formation so that each sperm or egg gets only one unit of each pair TRUE FALSE
false
a segment of DNA that carries the code for making one or more proteins.
gene
the unit of heredity. Most genes encode for specific polypeptides, and each gene has a specific location on a particular chromosome.
gene
DNA sequences that code for one or more specific proteins are called
genes
is the study of DNA and genes and their transmission from one generation to the next.
genetics
An individual's particular set of genes
genotype
An individuals particular set of genes
genotype
your complete set of alleles is called your
genotype
A person who has two different alleles of a gene is
heterozygous
Having different alleles at the same location (on a pair of homologous chromosomes)
heterozygous
people with different alleles (Aa) are
heterozygous
If a person with a widow's peak and free earlobes who is homozygous dominant for both genes (EEWW) mates with a person with a straight hairline and attached earlobes who is homozygous recessive for both genes (eeww), all of their children will be
heterozygous for both genes (EeWw), and will have a widow's peak and free earlobs
the 22 pairs of autosomes are called
homologous chromosomes
Having identical alleles at the same location (on a pair of homologous chromosomes)
homozygous
If an individual possesses two identical alleles of a particular gene, the person is said to be
homozygous
If both alleles of a particular gene are identical, the person is said to be
homozygous
People with the same two alleles of a gene (either aa or AA) are
homozygous
Collectively, all the various genes and their alleles in the human population are known as the
human gene pool
all the various genes and their alleles in the human population are known as the
human gene pool
The law of segregation states that __________.
in the formation of gametes, alleles separate from each other so that each gamete receives only one allele
A pattern of genetic inheritance in which the heterozygous genotype results in a phenotype that is intermediate between the two homozygous phenotypes
incomplete dominance
Caucasians people having the trait of straight, wavy or curly hair is an example of
incomplete dominance
characteristics or traits that are transmitted from parents to offspring via genes
inheritance
A composite display of all the chromosomes of an organism is called
karyotype
The diploid chromosomal complement in any species. The human _____ typically is shown as a composite display of the 22 pairs of autosomes arranged from longest to shortest, plus the sex chromosomes X and Y
karyotype
the diploid chromosomal complement in any species. Typically is shown as a composite display of the 22 pairs of autosomes arranged from longest to shortest, plus the sex chromosomes X and Y.
karyotype
All alleles of different genes are distributed to egg and sperm cells independently of each other during meiosis
law of independent assortment
when gametes are formed in the parents, the alleles separate from each other so that each gamete gets only one allele of each gene
law of segregation
Homologous pairs of chromosomes are lined up independently of other such pairs during _____.
metaphase I
where did these different alleles come from?
most likely, resulted from millions of years of mutations or random changes to the DNA sequence, of cells destined to become sperm or eggs
A change in the DNA base pair sequence of a cell
mutation
Crossing over, resulting in an increase in genetic variation, occurs between _____.
nonsister chromatids of homologous chromosomes
Place the following in order from smallest, simplest, least complex, to largest and most inclusive: A. gene, nucleotide, genome, chromosome B. nucleotide, gene, genome, chromosome C. genome, chromosome, gene, nucleotide D. nucleotide, gene, chromosome, genome
nucleotide, gene, chromosome, genome
DNA is composed of building blocks called _____.
nucleotides
chromosomes are identifiable in cells
only just before cell division
The observable physical and functional traits of an organism
phenotype
Your genotype has a profound influence on your
phenotype
the observable physical and functional traits of an organism (such as hair, eyes, skin color, height and body shape) (or traits less observable like blood type and susceptibility to disease)
phenotype
your genotype has a profound influence on your
phenotype or the observable physical and functional traits that characterize you
hair, eye, and skin color; your height and body shape; and your ability (or inability) to curl your tongue are what kinds of traits?
phenotypic traits
some people possess a dominant allele (Pp or PP), and the presence of this allele causes them to have extra fingers and toes on each hand and foot a condition known as
polydactyly
Inheritance of phenotypic traits that depend on many genes is called
polygenetic inheritance
pattern of inheritance in which a phenotypic trait depends on many genes. An example is eye color, controlled by three or more genes
polygenetic inheritance
Punnett squares are used to
predict the outcomes of a particular combination of parental alleles
A grid used for predicting patterns of inheritance and the probability a particular genotype will be inherited
punnett square
An allele that does not manifest itself in the presence of a more dominant allele.
recessive allele
the two chromosomes of the 23rd pair are the
sex chromosomes, X and Y
An inherited disorder in which the red blood cells assume a sickle shape when the oxygen concentration is low
sickle-cell anemia
Mendel's law of segregation holds that when sperm and eggs form
the two alleles of each gene separate from each other so that each sperm or egg receives only one allele of each gene.
chromosomes are identified and paired according to
their size, centromere location, and characteristic banding patterns
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 *In both types of inheritance, the heterozygote shows a phenotype that is distinct from either homozygote.
when two alleles in an individual are different
usually one is dominant and the other is recessive
A trait expressed by a recessive allele will only be present
when there is no dominant allele, that is, when both alleles are recessive
Your complete set of alleles is called
your genotype
your genotype, determines
your particular physical and functional traits, and even your susceptibility to certain diseases
