[WAHL] Bio Chapter 13 HW

How are sister chromatids and homologous chromosomes different from each other?

Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.

Identify all possible products of meiosis in plant and animal life cycles.

Spores, Gametes (sperm and eggs)

Which of the following occurs during meiosis but not during mitosis?

Synapsis occurs.

What is the best evidence telling you whether this cell is diploid or haploid?

The cell is diploid because it contains two sets of chromosomes.

For what purpose(s) might a karyotype be prepared?

The first three answers are correct.

Which processes lead to most genetic variation in sexually reproducing organisms?

crossing over random fertilization independent assortment of chromosomes in meiosis

Select Figure 2 in the drop-down menu (Figure 2). The graph with labels indicating the different phases of the meiotic cell cycle (MI = meiosis I; MII = meiosis II) is shown. Think carefully about the point on the graph where the line at the highest value begins to slope downward, indicated by the red arrow. What specific point of meiosis does this "corner" represent?

cytokinesis

Can you match these prefixes, suffixes, and word roots with their definitions?

different, other: hetero- change, after: meta- one-half: semi- milk: lact- within: intra- across: trans- enzyme: -ase blood: hem- (or hemato-) three: tri-

Heritable variation is required for which of the following?

evolution

Meiosis II typically produces _____ cells, each of which is _____.

four ... haploid

Drag the labels from the left to their correct locations in the concept map on the right.

https://snag.gy/7nNs1V.jpg

Can you recognize the eight stages of meiosis based on the location and behavior of the chromosomes? Drag the diagrams of the stages of meiosis onto the targets so that the four stages of meiosis I and the four stages of meiosis II are in the proper sequence from left to right. (Note that only one of the two daughter cells is shown for meiosis II.)

https://snag.gy/Bf5GNh.jpg

If you looked through a microscope, and saw chromosomes lined up like this, two by two, what stage of cellular reproduction must you be looking at?

meiosis I

During _____ chromosomes align single file along the equator of a haploid cell.

metaphase II

Of the processes we talked about, which is going on in my hand right now?

mitosis

Which life cycle stage is found in plants but not animals?

multicellular haploid

Imagine that I've taken a snapshot of chromosomes in a hypothetical cell. What stage of the life cycle must the cell be in?

the start of meiosis I

To see patterns in the data from a time-course experiment like this, it is helpful to plot the data on a line graph. But first, you must determine which variable should go on each axis of the graph. What variable did the researchers intentionally vary in the experiment, and what are the units for this variable? (This is the independent variable.)

time after induction, in hours

Meiosis I produces _____ cells, each of which is _____.

two ... haploid

Mitosis results in the formation of how many cells; meiosis results in the formation of how many cells?

two diploid cells ... four haploid cells

If we continued to follow the cell lineage from question 5, then the DNA content of a single cell at metaphase of meiosis II would be

x

Homologous chromosomes move toward opposite poles of a dividing cell during

meiosis I

What is crossing over?

the exchange of homologous portions of nonsister chromatids

A human cell containing 22 autosomes and a Y chromosome is

a sperm

Most of the yeast cells in the culture were in G1 of the cell cycle before being moved to the nutrient-poor medium to induce meiosis. A graphical version of the data (similar to the one you just made) is shown (Figure 1). How many femtograms of DNA are there in a yeast cell in G1? Estimate this value from the data in the graph.

24 fg

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be

2x

Imagine you found a hypothetical organism, you examine one of its gametes, and you see that it contains 5 chromosomes. How many chromosomes will one of its body cells contain just before mitosis begins?

10

Given the fact that 1 fg of DNA = 9.78 × 105 base pairs (on average), you can convert the amount of DNA per cell to the length of DNA in numbers of base pairs. Millions of base pairs (Mb) is the standard unit for expressing genome size. Calculate the approximate number of base pairs of DNA in the haploid yeast genome.

12 Mb (12 x 106 base pairs )

Based on this data, how much DNA is present in a gamete of Saccharomyces cerevisiae?

12 fg

How many femtograms of DNA are present in a cell at the end of meiosis II?

12 fg

Now that you have determined which variable goes on each axis, the graph can be constructed. An effective graph marks off the axes with just enough evenly spaced tick marks to accommodate the full set of data. Assuming that the x-axis tick marks will be separated by 1.0 units (0, 1.0, 2.0, and so on), what is the largest value that should appear on the x-axis?

14.0

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

16

How many different combinations of maternal and paternal chromosomes can be packaged in gametes made by an organism with a diploid number of 8 (2n = 8)?

16

Given the fact that 1 fg of DNA = 9.78 × 105 base pairs (on average), you can estimate the rate of DNA synthesis in Saccharomyces cerevisiae. Approximately how many base pairs per minute were synthesized during the S phase of these yeast cells?

200,000 (2.0 × 105) base pairs per minute

Normal human gametes carry _____ chromosomes.

23

How many femtograms of DNA are present in a cell at the end of meiosis I?

24 fg

What number and types of chromosomes are found in a human somatic cell?

44 autosomes and 2 sex chromosomes

How many femtograms of DNA are present in a cell in G2?

48 fg

Assuming that the y-axis tick marks will be separated by 5 units (0, 5, 10, and so on), what is the largest value that should appear on the y-axis?

55.0

Which of these cells is (are) haploid?

C and D

Meiosis guarantees that in a sexual life cycle, offspring will inherit one complete set of chromosomes (and their associated genes and traits) from each parent. The transmission of traits from parents to offspring is called heredity. Another important aspect of meiosis and the sexual life cycle is the role these processes play in contributing to genetic variation. Although offspring often resemble their parents, they are genetically different from both of their parents and from one another. The degree of variation may be tremendous. The following processes are associated with meiosis and the sexual life cycle: DNA replication before meiosis crossing over chromosome alignment in metaphase I and separation in anaphase I chromosome alignment in metaphase II and separation in anaphase II fertilization

All of them are both

What name is given to this process?

Asexual reproduction

Which of these gametes contains one or more recombinant chromosomes?

B and C

Two sister chromatids are joined at the centromere prior to meiosis. Which statement is correct?

Barring mutation, the two sister chromatids must be identical.

The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid. Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.

This chromosome has two chromatids, joined at the centromere. What process led to the formation of the two chromatids?

The two chromatids were formed by duplication of a chromosome.

Assume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of meiosis. If crossing over did not occur, which of the following statements about meiosis would be true? Select all that apply.

There would be less genetic variation among gametes.

Look at the cell in the figure. Based on this figure, which of the following statements is true?

This cell is diploid.

Can you match these prefixes, suffixes, and word roots with their definitions?

against: anti- change, turn, move: trop- (or -tropic) of neither gender or type: neutr- to love: -phil (or philo-) from, out of, remove: de- difficult, painful: dys- to: ad- with or together with: co- many: poly- not: non-

Homologous chromosomes migrate to opposite poles during _____.

anaphase I

During _____ sister chromatids separate.

anaphase II

What variable's response to the independent variable was measured by the researchers, and what are the units for this variable?

average amount of DNA per cell, in femtograms

You may remember this shot from the video podcast, here I am representing a duplicated chromosome. What structure is represented by my waist, where I am joined to my twin?

centromere

Consider a diploid cell where 2n = 6. During metaphase I of meiosis, as the pairs of homologous chromosomes line up on the metaphase plate, each pair may orient with its maternal or paternal homolog closer to a given pole. There are four equally probable arrangements of the homologous pairs at metaphase I. (Note that this problem assumes that no crossing over has occurred.) Four diagrams showing four equally probable arrangements of three homologous pairs at metaphase 1. In arrangement 1, the pairs are from top to bottom: red-blue, red-blue, red-blue. In arrangement 2, the pairs are from top to bottom: red-blue, blue-red, blue-red. In arrangement 3, the pairs are from top to bottom: red-blue, blue-red, red-blue. In arrangement 4, the pairs are from top to bottom: red-blue, red-blue, blue-red. The cells below show the eight possible combinations of chromosomes that the daughter cells of meiosis II can receive. Sort each daughter cell into the appropriate bin depending on which arrangement at metaphase I would create it.

https://snag.gy/Bh5QS9.jpg

Crossing over plays a critical role in increasing the genetic variation among offspring of sexual reproduction. It is important to understand how crossing over occurs and its consequences in meiosis. Look carefully at the diagrams depicting different stages in meiosis in a cell where 2n = 6. Assume that the red chromosomes are of maternal origin and the blue chromosomes are of paternal origin. Drag the labels to fill in the targets beneath each diagram of a cell. Note that the diagrams are in no particular order. Drag the blue labels to the blue targets to identify the stage of meiosis depicted in each diagram. Drag the pink labels to the pink targets to identify whether the configuration of the chromosomes related to crossing over is possible or not.

https://snag.gy/M29kDV.jpg

In the life cycle of an organism, meiosis is paired with the process of fertilization. Understanding the life cycle of an organism is the key to understanding how sexual reproduction ensures the inheritance of traits from both parents and also introduces genetic variation. Complete the diagram to show the life cycle of a typical animal. Follow these steps: First, drag blue labels onto blue targets only to identify each stage of the life cycle. Next, drag pink labels onto pink targets only to identify the process by which each stage occurs. Then, drag white labels onto white targets only to identify the ploidy level at each stage. Labels can be used once, more than once, or not at all.

https://snag.gy/mIEMUN.jpg

Use the data at left to make a line graph. To create the graph, first click on "add graph" and select the label "Amount of DNA per Cell Over Time." (For more help using the graphing tool, open the hint.)

https://snag.gy/tVkmTJ.jpg

This diagram shows a diploid nucleus (2n=8) in which chromosome replication has occurred in preparation for mitosis (top) and meiosis (bottom). The nucleus at top right is now in prophase of mitosis; the nucleus at bottom right is now in prophase I of meiosis. Drag the labels to their appropriate targets to correctly identify the various chromosome structures. Labels can be used more than once.

https://snag.gy/uWr8hI.jpg

Human gametes are produced by _____.

meiosis

The shuffling of chromosomes that occurs during both fertilization and _____ can lead to genetic variation.

meiosis

Asexual reproduction _____.

produces offspring genetically identical to the parent

Synapsis occurs during _____.

prophase I

During _____ a spindle forms in a haploid cell.

prophase II

Meiosis II is similar to mitosis in that

sister chromatids separate during anaphase

In alternation of generations, what is the diploid stage of a plant that follows fertilization called?

sporophyte

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

telophase I

At the end of _____ and cytokinesis there are four haploid cells.

telophase II