Chapter 13 and 14 Study Guide-Bellringers Flashcards
What is a genome?
The complete complement of an organism’s genes
Which of the following statements about genes is incorrect?
One gene type only is used in a specific cell type
Asexual reproduction and sexual reproduction are different in that
Asexual reproduction is utilized only by fungi and protists, whereas sexual reproduction is utilized only by plants and animals
heredity
Is the transmission of traits from one generation to the next
variation
Shows that offspring differ somewhat in appearance from parents and siblings
genetics
Is the scientific study of heredity and hereditary variation
asexual reproduction
One parent produces genetically identical offspring by mitosis
clone
any individual that is genetically identical to its parents is a clone
sexual reproduction
Two parents give rise to offspring that have unique combinations of genes inherited from the two parents.
What is a karyotype?
A karyotype is an ordered, visual representation of the chromosomes in a cell
By examining a karyotype, it is possible to determine:
A) which of two related plant forms is a gametophyte, and which is a sporophyte.
B) the sex of an animal.
D) A and B only
D)
The human X and Y chromosomes are
called sex chromosomes because they determine the sex of the offspring
If the liver cells of an animal have 24 chromosomes, how many chromosomes do its sperm cells have?
12
Which of the following is true of a species that has a chromosome number of 2n = 16?
There are 8 homologous pairs.
Which of the following is the term for a human cell that contains 22 pairs of autosomes and two X chromosomes?
A female somatic cell
Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life cycles have in common? alternation of generations meiosis fertilization gametes spores
meiosis, fertilization, and gametes
In animals, meiosis results in gametes, and fertilization results in
a zygote
Which of the following is an example of alternation of generations?
B) A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
After telophase I of meiosis, the chromosomal makeup of each daughter cell is
D) haploid, and the chromosomes are composed of two chromatids
When does the synaptonemal complex disappear?
late prophase of meiosis I
Tetrads of chromosomes are aligned at the center of the cell; independent assortment soon follows.
B) II
Synapsis of homologous pairs occurs; crossing over may occur.
A) I
Centromeres of sister chromatids uncouple and chromatids separate.
VII
Which of the following happens at the conclusion of meiosis I?
Homologous chromosomes are separated.
Which of the following is true of the process of meiosis?
Four haploid cells result
Crossing over occurs…
during Prophase I of meiosis
How do cells at the completion of meiosis compare with cells that have replicated their DNA and are just about to begin meiosis?
They have half the number of chromosomes and one-fourth the DNA
Which of the following terms belongs with the words synapsis, tetrads, and chiasmata?
Crossing over!
A cell divides to produce two daughter cells that are genetically identical.
Only true for MITOSIS
Homologous chromosomes synapse and crossing over occurs.
True for MEIOSIS 1 only
Centromeres uncouple and chromatids are separated from each other.
True for both Meiosis II and Mitosis
Independent assortment of chromosomes occurs.
Meiosis 1 only
The process is preceded by replication of the DNA.
Mitosis and Meiosis 1
You have in your possession a microscope slide with meiotic cells on it and a light microscope. What would you look for if you wanted to identify metaphase I cells on the slide?
Tetrads lined up in the middle of the cell
When comparing prophase I of meiosis with prophase of mitosis, which of the following occurs only in meiosis?
Synapsis of chromosomes, crossing over
How does the sexual life cycle increase the genetic variation in a species?
Allows for independent assortment of chromosomes, random fertilization, and crossing over
Independent assotment of chromosomes is a result of
the random and independent way that each pair of homologous chromosoms lines up on the metaphase plate during meiosis 1
When pairs of homologous chromosomes separate during anaphase I,
sister chromatids remain attached
Which of the following statements about crossing over is incorrect?
Crossing over takes a role in both asexual and sexual reproduction.
Pea plants were particularly well suited for use in Mendel’s breeding experiments for all of the following reasons except that
A) peas show easily observed variations in a number of characters, such as pea shape and flower color.
B) it is possible to completely control matings between different pea plants
C) it is possible to obtain large numbers of progeny from any given cross
D) peas have an unusually long generation time
E) many of the observable characters that vary in pea plants are controlled by single genes
Which of the following statements about Mendel’s breeding experiments is correct?
D)
Which of the following statements about Mendel’s breeding experiments is correct?
A) None of the parental (P)plants were true-breeding.
B) All of the F2 progeny showed a phenotype that was intermediate between the two parental (P)phenotypes.
C) Half of the F1 progeny had the same phenotype as one of the parental (P) plants, and the other half had the same
phenotype as the other parent.
D) All of the F1 progeny resembled one of the parental (P) plants, but only some of the F2 progeny did.
E) none of the above
D)
A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates
complete dominance
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
Traits are inherited in discrete units and are not a result of blending.
What is genetic cross between an individual showing a dominant phenotype (but of unknown genotype) and a homozygous recessive individual called?
a testcross(unknown)
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests
That the parents were both heterozygous
A 9:3:3:1 phenotypic ratio is characteristic of which of the following?
Each of the characters is controlled by a single gene,
The genes controlling the characters obey the law of independent assortment,
Each of the genes controlling the characters has two alleles
It was important that Mendel examined not just the F1 generation in his breeding experiments, but the F2 generation as well, because
Parental traits that were not observed in the F1 reappeared in the F2, suggesting that the traits did not truly disappear in the F1
P = purple, pp = white. The offspring of a cross between two heterozygous purple-flowering plants (Pp × Pp) results in
Purple and white-flowered plants
What are Punnett squares used for?
Predicting the result of genetic crosses between organisms of known genotypes
the ability of a single gene to have multiple phenotypic effects
Pleiotropy
the ABO blood group system demonstrates
multiple alleles
the phenotype of the heterozygote differs from the phenotypes of both homozygotes
incomplete dominance
Which of the following is an example of polygenic inheritance?
skin color/height
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
The relationship between genes S and N is an example of
epistasis
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce
all sharp spined progeny
If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?
9 sharp spined: 3 dull-spined: 4 spineless
Skin color in a fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system?
4
A woman and her spouse both show the normal phenotype for pigmentation, but both had one parent who was an albino. Albinism is an autosomal recessive trait.
What is the probability that their first child will be an albino?
1/4
Explain how the phenotypic expression of the heterozygote is affected by complete dominance, incomplete dominance, and codominance.
In complete dominance, the dominant trait shows in the organism’s phenotype. As seen in Mendel’s experiment with purple pea plants and white pea plants, one can see that only the dominant trait is expressed in heterozygotes , and the recessive trait is only expressed when an organism is a recessive homozygote. In incomplete dominance, none of the original traits from the parent are shown, because of individual segregation of alleles within each cell. An example of this is the crossing of red and white snapdragons. Instead of the dominant allele being expressed throughout, each cell individually chooses what color it will be. From far away, this gives the snapdragon a pink appearance, a color that did not come from either parent, but rather a combination of the two. Finally, in codominance, both traits show in the phenotype, and are equally dominant. This is evident in the ABO blood system, where O is a recessive allele. In this system, type A blood and type B blood are codominant. This means that if a person inherits these two blood types, not only one will be expressed, but both will be expressed.
Explain how epistasis affects the phenotypic ratio for a dihybrid cross.
In epistasis, one allele(the first allele) affects another allele. In normal dihybrid crossing, the ratio is 9:3:3:1, but in epistasis, the ratio is 9:3:4. Because the first allele affects the second allele, the characteristics of the second allele can only be expressed when one dominant gene from the first trait is present. If it is not present, then it does not matter what the second allele coded for.
Describe how environmental conditions can influence the phenotypic expression of a character.
Environmental conditions can influence phenotypic expression of a character by stunting growth or changing color. If a person or a plant do not get the nutrients they need to grow, then they will be shorter than their genotype says. In hydrangea plants, pH can determine what color the petals are. In basic soil, the hydrangeas will turn purple and in acidic environments, hydrangeas will turn a pinkish color
Distinguish among the life cycle patterns of animals, fungi, and plants.
In animals, two gametes combine to form a viable offspring. When meiosis happens, the gametes cannot survive on their own. However, this is not the case with fungi and plants. Plants can have viable haploid offspring, and fungi are actually fully developed when they are haploid. This is called alternation of generation. In plants and fungi, the haploid stage can survive on its own, but later reproduces to form diploid offspring. From the diploid stage, meiosis takes place, and the plants and fungi fully develop as haploids.
List the phases of meiosis I and meiosis II and describe the events characteristic of each phase.
The phases of meiosis I and II are Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis. In prophase I, chromosomes condense, and homologous chromosomes pair up. Crossing over takes place in this stage, as well as synapsis. Crossing over is the rearranging of DNA between nonsister chromatids. Through synapsis, the synaptonemal complex holds the homologues together. This complex disassembles in later prophase I, and the centrosomes begin to move to opposite ends of the cell. In metaphase I, pairs of homologous chromosomes line up at the metaphase plate, arranged in tetrads. In anaphase I, the pairs are pulled apart, and sister chromatids move together to one side of the cell. During telophase I, each half of the cell has a complete haploid set of chromosomes, but the sister chromatids are still attached. Cytokinesis just separated the cytoplasm by a cleavage furrow(in animals) or a cell plate(in plants). Then prophase II occurs. The spindle forms, and chromosomes move towards opposite ends of the cell. In metaphase II, the sister chromatids are pulled apart. Anaphase II is when the chromatids come apart, and go to the opposite ends of the cell. Finally in telophase II and cytokinesis, the nuclei are reformed and four daughter cells are produced.
