Genetics: Chapter 2 Homework
Humans autosomal cells have two copies each of 23 unique chromosomes. Match each cell division event and cell type according to the number of chromatids present.
- 23 chromatids: spermatozoa, ootid - 46 chromatids: G1 prior to meiosis - 92 chromatids: anaphase of mitosis
Match the checkpoint to its function.
- G1/s checkpoint: maintains cell until necessary enzymes for replication are synthesized - G2/M checkpoint: detection of DNA damage after replication - Spindle-assembly checkpoint: ensures that each chromosome is attached to spindle fibers from opposite poles
An autotriploid (3𝑛) has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals (2𝑛). How would meiosis be different in an autotriploid?
Gametes have a varying number of chromosomes from each set
What happens during prophase I of meiosis?
Homologous chromosomes form and crossing over occurs between them.
What happens during anaphase I of meiosis?
Homologous chromosomes separate, but sister chromatids remain joined at their centromeres
What are checkpoints?
transition points during the cell cycle that ensure all cellular components are functioning properly
Cell division by mitosis is a mechanism of asexual cell replication. Some single‑celled organisms reproduce by cell division, and cell division enables multicellular organisms to grow and to repair damaged cells. Which is a product of cell division by mitosis?
two cells genetically identical to the original cell
Meiosis and mitosis are both forms of cell division. However, the outcomes of these processes differ. Consider a diploid organism with two sexes. Select the reasons why meiosis typically produces genetic variation, wheras mitosis does not.
- genetic material is exchanged between homologous chromosomes in meiosis during crossing over. - gametic chromosomes have a different combination of alleles than parental chromosomes as a result of independent assortment - meiosis produces four genetically different haploid cells
Classify each cell as haploid or diploid.
- haploid: microspore, first polar body, spermatid, megaspore, ovum, secondary oocyte - diploid: primary spermatocyte, microsporocyte, oogonium, spermatogonium
An autotriploid has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals. Calculate the number of chromosomes in an autotriploid cell, given an 𝑛=18.
- number of chromosomes: 3 x 18 = 54
Cells are categorized as either prokaryotic or eukaryotic. Classify the characteristics as being unique to prokaryotic cells, common to both cell types, or unique to eukaryotic cells. Move each description into the correct category.
- prokaryotic cells: relatively small, typically less than 10 micrometers in size, lacks a true cytoskeleton - both cell types: contain DNA, use ribosomes to synthesize proteins - eukaryotic cells: nuclear membrane surrounds DNA
A cell has a circular chromosome and histone proteins associated with its DNA, but lacks a nuclear membrane.
The cell belongs to Archaea because it has histone proteins, which are present in Archaea and eukaryote but absent in Eubacteria
The cells shown in the image are from a rare species of plant and illustrate different stages of mitosis or meiosis. Determine the diploid number of chromosomes (2n) in this species of plant.
diploid number of chromosomes: 6
The fruit fly Drosophila melanogaster has four pairs of chromosomes, whereas the housefly Musca domestica has six pairs of chromosomes. How many different combinations of chromosomes are possible in the gametes of the fruit fly? How many different combinations of chromosomes are possible in the gametes of the house fly? Based on chromosome number, in which species would you expect to see more genetic variation among the progeny?
- chromosome combinations in fruit flies: 2^4 = 16 - chromosome combinations in house flies: 2^6 = 64 - more genetic variation: house fly
The somatic cell of a rat contains 42 chromosomes (2𝑛=42). How many chromosomes and how many DNA molecules would the primary oocyte of this rat have?
- chromosomes: 42 - DNA molecules: 84
On average, what fraction of the genome in the pairs of humans would be exactly the same if no crossing over took place? For the purposes of this question only, ignore the special case of the X and Y sex chromosomes and assume that all genes are located on nonsex chromosomes. Also, assume that the uncle and niece are related by a sibling and not by marriage alone.
- father and child: 1/2 - mother and child: 1/2 - full siblings: 1/2 - half-siblings: 1/4 - uncle and niece: 1/4 - grandparent and grandchild: 1/4
An autotriploid has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals. Calculate the number of chromosomes in a diploid cell, given an 𝑛=16.
- number of chromosomes: 2 x 16 = 32
Place the steps of the prokaryotic cell cycle in order.
1. prokaryotic chromosome attaches to the plasma membrane 2. prokaryote chromosome replicates 3. cell elongates, pulling each chromosome to a different end of the cell 4. plasma membrane and cell wall grow inward and divide the cell 5. two genetically identical daughter cells are produced
Suppose a diploid European wild raspberry is completely heterozygous at all 14 of its chromosomes (2𝑛=14). How many different combinations of gametes can be produced by this European wild raspberry, assuming no homologous recombination between chromosomes?
2^7 = 128
Consider two cells, where one cell is haploid and the other is diploid. Which of the following differences between the two cells is observed during prophase of mitosis?
In the haploid cell, only one pair of sister chromatids are present, whereas in the diploid cell, two pairs of sister chromatids are present
An autotriploid (3𝑛) has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals (2𝑛). How would mitosis be different in an autotriploid?
There are more chromosomes that line up on the metaphase plate
What are the functions of mitotic cell division?
asexual reproduction, cell regeneration, organism growth
Female honey bees are diploid and male honey bees are haploid. The haploid males produce sperm and can successfully mate with diploid females. Fertilized eggs develop into females and unfertilized eggs develop into males. How does the process of sperm production in male honey bees differ from sperm production in other animals?
Male honey bees use mitosis, whereas other animals use meiosis
Use the mitosis and meiosis interactive to answer the question. Use the word bank to complete the passage describing mitosis and meiosis. All words will be used at least once and most words will be used more than once. A male giant panda has 42 chromosomes in its skin cells. This represents the ________ chromosome number. As the animal's old skin cells die and slough off, cells nearby divide through ________ to produce more skin cells. Germ cells within the animal's testicles undergo _______ to replicate themselves and _________ to produce sperm. The cells produced by mitosis in this panda have a _____ chromosome number and are produced after _____ are pulled apart into separate daughter cells. The cells produced by meiosis 1 in this panda have a _____ chromosome number and are produced after _____ are pulled apart into separate daughter cells. The cells produced by meiosis 2 in this panda have a _____ chromosome number and are produced after _____ are pulled apart into separate daughter cells.
A male giant panda has 42 chromosomes in its skin cells. This represents the DIPLOID chromosome number. As the animal's old skin cells die and slough off, cells nearby divide through MITOSIS to produce more skin cells. Germ cells within the animal's testicles undergo MITOSIS to replicate themselves and MEIOSIS to produce sperm. The cells produced by mitosis in this panda have a DIPLOID chromosome number and are produced after SISTER CHROMATIDS are pulled apart into separate daughter cells. The cells produced by meiosis 1 in this panda have a HAPLOID chromosome number and are produced after HOMOLOGOUS CHROMOSOMES are pulled apart into separate daughter cells. The cells produced by meiosis 2 in this panda have a HAPLOID chromosome number and are produced after SISTER CHROMATIDS are pulled apart into separate daughter cells.
