Test 4 Review Flashcards
1- The reduction of number of chromosomes occurs in-
Meiosis I
The first cycle of meiosis is also known as the reductional phase because it reduces the number of chromosomes, whereas meiosis II is almost exactly the same as mitosis
2- Which of the following does not contribute to genetic variation
The pairing of homologous chromosomes in prophase I
Homologous chromosomes simply pairing with themselves won’t result in genetic variation. The random alignment (which happens in prophase but are still paired in metaphase)
3- Children often look like grandparents because
None of the above
Independent assortment and crossing over does not allow us to determine how much of the grandfathers or grandmothers genetic information will be passed onto the child
4- During meiosis cell division a non-disjunction occurs during meiosis I, How many gamete cells will be affected and how many chromosomes will each have
Four cells;
two being with an extra homologue, two missing a chromosome
Just draw it out. It just is
5- One of the primary advantages of sexual reproduction is?
The creation of genetic variation within the population
Sexual reproduction primarily evolved not as a primary means of reproduction because mitosis already does that, but instead as a means of creating diversity.
6- After meiosis how many cells are created?
4
After Meiosis 4 cells are created each with ½ the genetic information as a normal somatic cell
7- Which of the following best describes random fertilization
The many possible combinations of a variety of different possible sperm and egg cells
Because each organism can create an enormous number of different possible gametes, the number of possible zygotes created by two different organisms is the number of different possible gametes produced by each organism multiplied.
8- What process would not contribute to genetic variation if crossing over did not occur?
Meiosis II
If crossing over did not occur then each chromatid would always be exactly alike so that during meiosis II when the sister chromatids separated each resulting cell would still be the same as the mother cell (remember that meiosis II is like mitosis)
9- Which of the following best describes crossing over in Meiosis II
None of these (Crossing over does not occur in Meiosis II)
Crossing over only occurs in prophase of Meiosis I
An organism has 42 pairs of chromosomes, how many different possible gametes could be produced assuming no crossing over occurs?
2^42
Remember that the formula for different possible combinations of chromosomes randomly assorting is 2n where n is the Pairs of chromosomes
11- Meiosis increases the number of chromosomes in a cell.
False
Meiosis decreases the number of chromosomes in a cell
12- A zygote always has twice the haploid number of chromosomes in an organism.
True
Unless a non-disjunction occurs an organism will generally have twice the number of chromosomes as its haploid number
13- Sexual reproduction _____.
All of the above
Sexual reproduction creates haploid organisms, and creates organisms that are genetically different from the parents
14- Sexual reproduction decreases the genetic variability of the next generation.
False
Sexual reproduction evolved to increase genetic variation
15- Homologous chromosomes are found in _____
Diploid body cells
Homologous chromosomes are chromosomes that could pair during prophase I, in an egg, sperm or haploid cell homologous chromosomes have been separated
16- Homologous chromosomes _____
All of the above
Homologous chromosomes are the same size, have the same genes in the same location on the chromosome and have the centromere located in the same place too
17- Although homologous chromosomes have genes for the same traits such as hair color, one homologue may have a gene for brown hair and the other homologue may have a gene for blonde hair.
True
Homologous chromosomes contain the same gene at the same location, but not necessarily the same allele
18- Gametes _____
contain only one chromosome of each kind
Gametes have only one chromosome of the 23 pairs
19- Gametes
Contain half the genetic information of the organism- but can be any mixture from the mother and father
Again due to random assortment and crossing over the
20- An organism that reproduces sexually passes on genetic information that did not belong to either of the parents of that organism, it can be concluded that-
A mutation has occurred
A mutation is the only possible explanation that could create new genetic material (remember crossing over, independent assortment, and random fertilization are all just ways of shuffling the deck of genes. The only way to put new cards (genes) in the deck is mutation
21- Once duplicated, a chromosome is composed of two identical parts called _____
Duplication of a chromosome creates two identical sister chromatids
22- Replication of the DNA occurs _____
Prior to meiosis I
Replication of DNA occurs before any division process occurs
23- Homologous chromosomes separate during _____
Meiosis I
Meiosis I also known as the reductional phase
24- Replication of DNA is necessary between meiosis I and meiosis II
False
The cell does not stop and undergo a new G1, S, or G2 phase. It either pauses in part of the phase (as in humans) or goes straight on to meiosis II
25- At the completion of meiosis II, there are _____ daughter cells.
Four haploid
Mitosis produced 2 diploid daughter cells, Meiosis produces 4 haploid cells
26- At the completion of meiosis I, there are ______ daughter cells
Two haploid
Again remember meiosis I is the reductional phase. We are reducing the number of chromosomes.
27- The diploid number of chromosomes is restored after _____ so that an animal’s body cells contain the diploid number of chromosomes.
Fertilization
Through fertilization the number of chromosomes in an organism doubles hence the reason why meiosis must undergo a phase to make it haploid
28- Synapsis are strongest associated with-
Prophase I
A synapse is one bond between homologous chromosomes. All of the synapses holding homologous chromosomes together are known as the synaptonemal complex
29- During meiosis II, sister chromatids separate from one another.
True
Meiosis II is exactly like mitosis in that sister chromatids separate
30- After synapsis are completely formed during meiosis I, the homologous chromosomes _____
Separate
If homologous chromosomes are already joined by the synaptonemal complex then if they were to try to join any more they would be fusing together. The only process that makes sense is saying that they separate in anaphase, which occurs after the synapsis has formed.
31- Sexual reproduction contributes greatly to the process of _____
: Evolution
Evolution selects for an organism that can best fit an environment. Nature will thus select to creating a wide range of diverse organisms, as well as organisms that can easily change to fit new environments.
32- The only method of creating genetic variation is sexual reproduction.
False
Mutation is the ultimate source of genetic variation
33- Meiosis prevents the number of chromosomes from increasing in the next generation.
True
If a cell did not undergo meiosis and simply fused with another cell of the same species, the number of chromosomes would double each time.
34- Regions where non-sister chromatids are attached due to crossing over are called _____?
Chiasmata
The location where crossing over occurs in known as a chiasmata, (or chiasma s)
35- Mitosis always creates cells with the exact same genetic information as the parental cell
True
Assuming a non-disjunction or some other mutation does not occur, the cells in mitosis are genetically identical
36- After crossing over, the sister chromatids _____
All of the above
After crossing over the genes and chromosomes from the mother are mixed with the genes on the chromosome that are from the father
37- Genetic recombination during meiosis occurs by _____
Crossing over
Recombinant DNA is DNA that has been broken and relegated to another segment of DNA. We will learn more about this when we study biotechnology
38- When genetic information is exchanged between non-sister chromatids, _____ has occurred.
Crossing over
Crossing over is when homologous chromosomes cross over
39- The combining of chromosomes from genetically different gametes occurs during _____
Fertilization
40- When homologues align at the metaphase plate, the maternal and paternal homologues are oriented towards a specific pole.
False
The organization is randomized
41- After Anaphase I each chromosome still has two chromatids
True
Meiosis one separates homologous chromosomes, not sister chromatids
42- Which of the following occurs during prophase I?
: all of the above
In prophase I the synaptonemal complex forms, the nuclear lamina breaks down, the chromosomes condense, and the spindle apparatus forms and moves to polar ends.
43- During _____ the sister chromatids separate and therefore four daughter cells each have chromosomes.
meiosis II
In mitosis sister chromatids separate, but not into four cells as the problem specifies
44- At the end of telophase II and cytokinesis there are __________ haploid cells.
Four
At the end of meiosis there are four haploid cells
45- Which of the following does not contribute to genetic diversity within a gamete cell?
Random fertilization.
After fertilization the cell is no longer a gamete, but a zygote.
46- Which of the following process leads to less genetic diversity in a gamete in sexual reproduction?
Meiosis I
Because homologous chromosomes (which have different alleles) separate in meiosis I, the total genetic diversity for the cell actually goes down, but will be later replaced with different genetic material after fertilization
47- If a species had several different chromosomes such as chromosome 1, chromosome 2 etc… but all homologous chromosome 1’s were identical and all homologous chromosome 2’s were identical, which processes would no longer lead to genetic diversity
All of the Above
If all homologous chromosomes were exactly identical in a species then it wouldn’t matter how many times you crossed them over, or shuffled them or recombined them you will still only have organisms with the same chromosome 1 and chromosome 2 and etc…
48- During ____ sister chromatids separate and become chromosomes
A & C
Sister chromatids separate during mitosis and meiosis, the only difference is that in meiosis crossing over may mix the chromosomes and the number of chromosomes in each cell has been reduced by half
What was the prevailing notion prior to the time of Lyell and Darwin?
Earth is 6,000 years old, and populations are unchanging.
“Improving the intelligence of an adult through education will result in that adult’s descendants being born with a greater native intelligence.” This statement is an example of
Lamarckism.
Darwin’s mechanism of natural selection required long time spans in order to modify species. From whom did Darwin get the concept of Earth’s ancient age?
Charles Lyell
Charles Darwin was the first to propose
a mechanism for evolution that was supported by evidence.
In evolutionary terms, the more closely related two different organisms are, the
more recently they shared a common ancestor
Both Darwin’s and Lamarck’s ideas regarding evolution suggest which of the following?
The interaction of organisms with their environment is important in the evolutionary process
Which statement about natural selection is most correct?
Well-adapted individuals leave more offspring, and thus contribute more to the gene pool, than poorly adapted individuals.
Given a population that contains genetic variation, what is the correct sequence of the following events, under the influence of natural selection?
- Differential reproduction occurs.
- A new selective pressure arises.
- Allele frequencies within the population change.
- Poorly adapted individuals have decreased survivorship.
2, 4, 1, 3
To observe natural selection’s effects on a population, what must be true?
A and B only (One must observe more than one generation of the population.
The population must contain genetic variation.)
During drought years on the Galapagos, small, easily eaten seeds become rare leaving only large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, what should one expect to result from natural selection?
More small-beaked birds dying than the larger-beaked birds. The offspring produced in subsequent generations have a higher percentage of birds with large beaks.
Which of the following statements is not an inference of natural selection?
An individual organism undergoes evolution over the course of its lifetime.
Which statement best describes how the evolution of pesticide resistance occurs in a population of insects?
that survive pesticide application, and adjust their own behaviors to copy those of the survivors.
A number of genetically resistant pesticide survivors reproduce. The next generation of insects contains more genes from the survivors than it does from susceptible individuals.
Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails just as fish do, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are
B and C only ( examples of convergent evolution.
adaptations to a common environment.)
It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that
island forms and mainland forms descended from common ancestors.
Which of these is a consequence of uniformitarianism?
Earth is old
Which of the following is not an observation or inference on which natural selection is based?
Poorly adapted individuals never produce offspring.
Which of the following observations helped Darwin shape his concept of descent with modification?
South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.
Within a few weeks of treatment with the drug 3TC, a patient’s HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?
A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.
Darwin synthesized information from several sources in developing his theory of evolution by natural selection. Which of the following did not influence his thinking?
observations of molecular homologies
Which definition of evolution would have been most foreign to Charles Darwin during his lifetime?
change in gene frequency in gene pools
