BIOL 150 Test 3 Flashcards
Characteristics of Homologous Chromosomes
- Maternal and paternal pairs
- 23 pairs in humans
- Numbered in a karyotype
Characteristics of Sister Chromatids
- Replica of single chromosome
- Formed during interphase
- Separated during mitosis
- Attached to each other by cohesin
The longest phase of the cell cycle for most cells
G1
During this phase, the cell replicates its genome
S
A growth phase for the cell that happens after DNA synthesis has occurred
G2
The process by which cellular chromosomes are divided and separated from each other is called
mitosis
During this phase, the cytoplasm divides
cytokinesis
The resting phase of the cell cycle is called
G0 (zero)
Characteristics in anaphase
- Centromeres split and move apart
- Sister chromatids separate
Characteristics in telophase
- Chromosomes at poles
- Nucleus reformation
Characteristics in Cytokinesis
- Cleavage furrow or plate forms
- Cells divide
Primary checkpoint of the cell cycle that is influenced by external signals
G1/S checkpoint
Checkpoint that ensures all of the chromosomes are attached to microtubules
spindle checkpoint
Checkpoint that assesses whether DNA is damaged and whether DNA replication has completed
G2/M checkpoint
Passage through checkpoints is controlled by ______ enzymes.
Cdk (Cyclin-Dependent Kinases)
In bacterial cell division, the cell divides into two nearly equal halves. This process is referred to as:
Binary fission
The point of constriction on chromosomes that contains certain repeated DNA sequences that bind specific proteins is called:
The centromere
Eukaryotic chromosome complexes are composed of 60% protein and 40% DNA. This complex is referred to as:
chromatin
The number of chromosomes in diploid eukaryotic cells:
varies considerably from 2 to over 1000 in different species
A scientist wants to study histones. Histones are:
proteins that double-stranded DNA molecules wrap around in eukaryotes
The two copies of each type of chromosome found in normal somatic (body) cells in an organism, throughout the cell cycle, are called:
Homologous chromosomes
These structures are held together by cohesin:
sister chromatids
If there are 32 sister chromatids in a normal somatic cell, how many chromosomes are there?
16
A somatic cell from a garden pea plant normally contains 14 chromosomes. How many sister chromatids would that cell contain during G1 of the cell cycle?
0
A somatic cell from a garden pea plant normally contains 14 chromosomes. How many sister chromatids would that cell contain during G1 of the cell cycle?
G1 to S to G2 to mitosis to cytokinesis
A duplicate copy of all of the hereditary information contained in the nucleus of eukaryotic cells is made during what stage of the cell cycle?
S
If a cell has 32 chromosomes prior to S and undergoes mitosis followed by cytokinesis, each new daughter cell will have how many chromosomes?
32
In what portion of the cell cycle do the chromosomes appear invisible under a light microscope because they are not yet condensed?
Interphase
If a chromosome contains a mutation such that it cannot bind to the kinetochore complex, what would be the consequence?
That chromosome would not be able to bind to the mitotic spindle.
This is the stage of mitosis characterized by the alignment of the chromosomes in a ring along the inner circumference of the cell:
Metaphase
This is the stage of mitosis characterized by the alignment of the chromosomes in a ring along the inner circumference of the cell:
Prophase
What stage of mitosis is essentially the reverse of prophase?
Telophase
The drug Taxol, or Paclitaxel, is used to treat patients with a variety of cancers, including breast, lung and ovarian cancers. The drug works by stabilizing microtubules, and preventing their disassembly. The goal of this drug is to prevent dividing cells from completing mitosis. As a result, cancerous cells can no longer divide. In a cell treated with Taxol, at what stage of mitosis will the cells arrest?
Prior to metaphase
Animal cells typically achieve cytokinesis by:
forming a cleavage furrow that pinches the cell into two
The progress of the eukaryotic cell cycle is regulated primarily by what proteins?
Cyclins
You are studying cell cycle progression in an early frog embryo. If you were to inject a protein synthesis inhibitor into this cell during S phase, where do you predict the cell would arrest?
G2
If you were to think of the cell as a car, and mitosis as a process that drives that car to go, what would be a good analogy for a cell that has a mutation in both copies of a tumor-suppressor gene?
The brake pedal of a car does not work at all.
In life cycles that alternate between haploid and diploid stages, __________ acts to reduce the number of chromosomes per cell from two sets to one set.
meiosis
In life cycles that alternate between haploid and diploid stages, __________ acts to double the number of chromosomes per cell from one set to two sets.
fertilization
In life cycles that alternate between haploid and diploid stages, __________ acts to keep the number of chromosomes per cell the same.
mitosis
In animals, a single diploid cell called a __________ divides by mitosis to give rise to all the cells of the adult body.
zygote
During fertilization, each haploid __________ contains the genetic contribution from one of the two parents.
gamete
Cells that have one set of chromosomes are called __________
haploid
Cells that have two sets of chromosomes are called __________
diploid
In animals, cells that will eventually undergo meiosis to produce the gametes are set aside early in the course of development. These cells are called __________
germ-line cells
Synapsis of homologous chromosomes and crossing-over take place during
prophase 1
Chromosomes line up in pairs along the _______ plate during ________
metaphase 1
The two members of each homologous pair are pulled to opposite poles of the cell while sister chromatids remain attached during
anaphase 1
Nuclear envelopes reform around two separate haploid nuclei during
telophase 1
A new spindle apparatus begins to form in two separate haploid cells during
prophase II
Unpaired chromosomes line up along the metaphase plate during
metaphase II
Sister chromatids separate and are pulled to opposite poles of the cell during
anaphase II
Nuclear envelopes reform around four separate haploid nuclei during
telophase II
The number of chromosomes per cell is reduced from two sets to one set during
meiosis I
Mutations can occur in any cell of the human body that contains DNA. However, only mutations in _________ can be passed on to the next generation.
germ-line cells
A new drug is discovered which disrupts the process of synapsis. This drug is most likely to affect
cell division in germ-line cells
Which of the following is not haploid?
A cell in prophase I
In life cycles that alternate between haploid and diploid stages, fertilization doubles the number of chromosomes per cell while ______ reduces it in half.
meiosis
Homologous chromosomes pair along their length during prophase I of meiosis. While two homologues are paired, genetic exchange may occur between them in a process called ________.
crossing over
Compared to asexual reproduction, the main advantage of sexual reproduction is that it
increases the genetic diversity of the offspring
Diploid organisms use meiosis to produce haploid cells. Meiosis consists of how many rounds of nuclear division?
2
The zygote has
two copies of each chromosome
Crossing over between homologous chromosomes takes place during
prophase I
At the end of meiosis II, each of the four resulting cells contains
one full set of chromosomes, each with 1 molecule of DNA
What immediately follows meiosis I?
prophase II
You are studying meiosis in an organism where 2n = 24. How many chromosomes will each nucleus have after meiosis II is complete?
12
A life cycle that regularly alternates between haploid and diploid stages is found in all of the following EXCEPT
the bacterium e coli
The first detailed and quantitative studies on inheritance were carried out by an Austrian monk named _________
Mendel
In modern terminology, Mendel’s heredity “factors” are called
genes
Alternate forms of the same gene are called
alleles
In Mendel’s experiments on seed color in pea plants, when a dominant yellow seed-bearing plant was crossed with a recessive green seed-bearing plant, what was the approximate phenotypic ratio among the F2 generation?
3 yellow:1 green
A cross where we follow the inheritance of two pairs of alleles is called
dihybrid
Let P = purple flowers and p = white, and T = tall plants and t = short. What are the genotypes of the gametes that are produced by a plant that is heterozygous for both traits?
PT, Pt, pT, and pt
Let P = purple flowers and p = white, and T = tall plants and t = short. Of the 16 possible gamete combinations in the dihybrid cross between two double heterozygotes, how many would produce the phenotype white, tall?
3
If an individual allele has more than one effect on the phenotype, this is called
pleiotropy
ABO blood group determination is an example of
multiple alleles
Prisha knows her blood type is A, but Sebastian does not know his blood type. However, Sebastian knows that his mother and father both had blood type B. Prisha and Sebastian’s first child is a boy with type O blood. Based on this information, Sebastian’s blood type could be
either B or O
A male fruit fly has the genotype PpYYrrTt. In terms of these 4 allele pairs, how many different types of gametes can he form?
4
Let R = red pigment and r = no pigment. In carnations, RR offspring make a lot of red pigment, rr offspring make no pigment and Rr offspring make a small amount of red pigment, thus appearing pink. Pink carnations are therefore an example of
incomplete dominance
A Punnett square is generally used to
predict the genotypic ratio among the offspring
Height is a trait that shows continuous variation in humans. In pea plants, on the other hand, the tall allele is dominant over the short allele and there are no intermediate heights. What is the best explanation for this difference?
Height is a polygenic trait in humans.
During his experiments with pea plants, Mendel referred to the trait that was expressed in the F1 or first filial generation as
dominant
If fertilization involves two gametes that contain different alleles of a given gene, the resulting offspring is
heterozygous
In humans, the sickle-cell trait is caused by a single mutant allele, but sickle-cell disease only occurs in individuals that are homozygous for the sickle-cell allele. A male and female each carry the trait, but do not have sickle-cell disease. What is the probability that their first two children will both have sickle-cell disease?
1/16
Of the 23 pairs of human chromosomes, 22 pairs are homologous and are found in both males and females. These are called _________
autosomes
Suppose you are carrying out a series of crosses with an insect where the mechanism of sex determination is unknown. You discover a mutant male with black wings and decide to cross it with a wild type female that has gray wings. Half of the F1
progeny have black wings but all of these F1
progeny with black wings are females. Based on these results, a valid hypothesis would be
Females are XX, males are XY and wing scales are caused by a dominant allele on the X chromosome.
In Morgan’s experiments, the white eye allele in Drosophila was shown to be
located on the X chromosome
Which of the following best describes the pattern of inheritance for mitochondrial DNA?
It is usually inherited entirely from the mother
Occasionally, chromosomes fail to separate during meiosis, leading to daughter cells that have an atypical number of chromosomes. This phenomenon is called
nondisjunction
How many Barr bodies does a normal human female contain in each diploid cell?
1
Humans who have lost one copy of an autosome is called
monosomic
In humans, individuals with trisomy of the _________ chromosome are most likely to survive until adulthood.
21st
A human female with only one X chromosome is said to have a condition called
Turner Syndrome
In sickle cell anemia, the hemoglobin differs from typical hemoglobin by
a single amino acid substitution
Hemophilia is caused by a
recessive allele on the X chromosome
__________ is a human hereditary disease that is caused by a dominant allele but does not show up in affected individuals until they are in middle age.
Huntington’s disease
Huntington’s disease is caused by a single dominant allele. It is a lethal disease, yet it persists in the human population. Which of the following statements best describes why?
Huntington’s disease presents symptoms in mid-life, after most people have already had offspring.
If a human female has 2 Barr bodies per cell, it is almost certain that
she developed from a fertilized egg with 3 X chromosomes
In humans, if nondisjunction led to an individual with a genotype of XO, that person would
be female because each cell lacks a Y chromosome
In humans, if nondisjunction led to an individual with a genotype of XXY, that person would
be male because each cell has one Y chromosome
In some human populations, the proportion of individuals who are heterozygous for the sickle cell allele is much higher than would be expected by chance alone. Why?
Heterozygous individuals have an advantage over individuals with two normal alleles.
In humans, hemophilia is caused by a recessive allele on the X chromosome. Suppose a man with hemophilia has children with a woman who doesn’t have hemophilia but whose mother had hemophilia. What is the probability that their second child will have hemophilia?
50%
In fruit flies (Drosophila melanogaster) there is a dominant allele for red eyes and a recessive allele for white eyes. These alleles are located on the X chromosome. If a heterozygous red-eyed female is mated with a white-eyed male, what percentage of the offspring are expected to be white-eyed females?
25
