Genetics- Ch.3
The arrangement of homologous during metaphase of meiosis I is a random process. In your own words, explain what this means.
Maternal and Paternal derived chromosomes are randomly aligned along the metaphase plate
Which of the following statements regarding plants is false?
Meiosis directly produces sperm and egg cells in plants
With regard to sister chromatids, which phase of mitosis is the organization phase, and which is the separation phase?
Metaphase is the organization phase and anaphase is the separation phase
List several ways in which telophase appears to be the reverse of prophase and prometaphase?
Prophase/prometaphase: nuclear membrane dissociates, mitotic spindle forms, chromosomes condense, chromosomes attach to spindle telophase: nuclear membrane reforms, mitotic spindle disassembles, chromosomes de-condense, chromosomes detach from the spindle.
How many sets of chromosomes are found in a human somatic cell, and how many chromosomes are within one set?
2 sets with 23 in each set
Eukaryotic cells must sort their chromosomes during mitosis so that each daughter cell receives the correct number of chromosomes. Why don't bacteria need to sort their chromosomes?
Bacteria do not need to sort their chromosomes because they only have one type of chromosome
Three genes (A,B, and C) are found on three different chromosomes. For the following diploid genotypes, describe all of the possible gamete combinations. A. Aa Bb Cc B. AA Bb CC C. Aa BB Cc D. Aa bb cc
A. A B C, A B c, A b C, A b c, a B C, a b C, a B c, a b c B. A B C, A b C C. A B C, A B c, a B C, a B c D. A b c, a b c
For the following events, specify whether they occur during mitosis, meiosis I, or meiosis II: A. Separation of conjoined chromatids within a pair of sister chromatids B. Pairing of homologous chromosomes C. Alignment of chromatids along the metaphase plate D. Attachment of sister chromatids to both poles
A. During mitosis and meiosis II B. During meiosis I C. During mitosis, meiosis I, and meiosis II D. During mitosis and meiosis II
What would be the sex of a human with the following numbers of sex chromosomes? A. XXX B. X (also described as X0) C. XYY D. XXY
A. Female B. Female C. Male D. Infertile male
What is a homolog? With regard to genes and alleles, how are homologs similar to and different from each other?
Are chromosome pairs. They are the same size and carry the same types and order of genes. May differ in genes known as alleles.
Which of the following is not found in a prokaryotic cell?
Cell nucleus
The period between meiosis I and meiosis II is called interphase II. Does DNA replication take place during interphase II? Explain your answer
DNA replication does not take place during interphase II. The chromosomes at the end of telophase I have already replicated (i.e., they are found in pairs of sister chromatids). During meiosis II, the sister chromatids separate from each other, yielding individual chromosomes
What critical event occurs during the S phase of the eukaryotic cell cycle?
DNA replication produces pairs of sister chromatids
Why is it necessary that the chromosomes condense during mitosis and meiosis? What do you think might happen if the chromosomes were not condensed?
During interphase, the chromosomes are greatly extended. In this conformation, they might get tangled up with each other and not sort properly during meiosis and mitosis. The condensation process probably occurs so that the chromosomes easily align along the equatorial plate during metaphase without getting tangled up
Which of the following is the correct order of phases of the cell cycle?
G1,S,G2,M
What is a sister chromatid? Are sister chromatids genetically similar or identical?
Identical copies replicated from the same parental chromosome. Attached by centromere, genetically identical
How does the attachment of kinetochore microtubules to the kinetochore differ in metaphase of meiosis 1 from metaphase of mitosis?
In metaphase I of meiosis, each pair of chromatids is attached to only one pole via the kinetochore microtubules. In metaphase of mitosis, there are two attachments (i.e., to both poles). If the attachment was lost, a chromosome would not migrate to a pole and may not become enclosed in a nuclear membrane after telophase. If left out in the cytoplasm, it would eventually be degraded.
A eukaryotic cell is diploid containing 10 chromosomes (5 in each set). For mitosis and meiosis, how many daughter cells would be produced, and how many chromosomes would each one contain?
Mitosis: Two diploid cells, 10 chromosomes (2 complete sets) Meiosis: Four haploid cells, 5 Chromosomes (one complete set)
The process of binary fission begins with a single mother cell and ends with two daughter cells. Would you expect the mother and daughter cells to be genetically identical?
Yes
Explain why the products of meiosis may not be genetically identi-cal whereas the products of mitosis are.
The products of meiosis have only one copy of each type of chromosome. For example, one human gamete may contain the paternally derived copy of chromosome 11,whereas a different gamete may contain the maternally derived copy of chromosome 11. These two homologs may carry different alleles of the same genes and therefore are not identical. In contrast, mitosis produces genetically identical daughter cells that have both copies of all the pairs of homologous chromosomes.
Describe the key events during meiosis that result in a 50% reduction in the amount of genetic material per cell?
The reduction occurs b/c there is a single DNA replication event but two cell divisions. b/c of the nature of separation during anaphase I, each cell receives one copy of each type of chromosome
An abnormal fruit fly has two sets of autosomes and is XXY. Such a fly would be
a female
Let's suppose that a gene affecting pigmentation is found on the X chromosome or the Z chromosome but not the Y or W chromosome. It is found on an autosome in bees. this gene is found in two alleles D (dark), which is dominant to d (light). WHat would the phenotypic results of crosses between true breeding dark female and true breeding light male, and the reciprocal cross in the following species? a. birds, b.drosophilia, c. bees, d. humans
a. dark males and light females; reciprocal all dark offspring b. all dark offspring; reciprocal-dark females, light males c. all dark offspring; reciprocal- dark females and light males d. all dark offspring; reciprocal-dark females and light males
What is the function of microtubules during mitosis?
aster microtubles are important for the positioning of the spindle apparatus within an animal cell and in the process of cell division
Which of the following is not one of the tenets of the chromosome theory of inheritance?
chromosome replication occurs during the S phase of the cell cycle
Describe the timing of meiosis I and II during human oogenesis.
during oogenesis in humans, the cells are arrested in prophase I of meiosis for many years until selected primary oocytes progress through the rest of meiosis I and begin meiosis II. If fertilization occurs, meiosis II is completed
Binary fission
is a form of asexual reproduction, is a way for bacteria to reproduce, begins with a single mother cell and produces two genetically identical daughter cells
When does crossing over usually occur, and what is the end result?
it occurs during prophase of meiosis 1, and the end result is the exchange of pieces between homologous chromosomes
A pea plant has the genotype TtRr. The independent assortment of these two genes occurs at ______ because chromosomes carrying the _______ alleles line up independently of the chromosomes carrying the _____ alleles.
metaphase of meiosis, T and t, R and r
In animals, a key difference between spermatogenesis and oogenesis is that
spermatogenesis produces 4 sperm whereas oogenesis produces only 1 egg
In mammals, sex is determined by
the Sry gene on the Y chromosome
The arctic fox has 50 chromosomes (25 per set), and the common red fox has 38 chromosomes (19 per set). these species can interbreed to produce viable but infertile offspring. How many chromosomes would the offspring have? what problems do you think may occur during meiosis that would explain the offspring's infertility?
the hybrid offspring would have 44 chromosomes (25 +19). the reason for infertility is because each chromosome does not have a homologous partner. Therefore, the chromosomes cannot properly pair during metaphase I, and the gametes do not receive one copy of each homolog. gametes will be missing certain chromosomes, which makes them infertile
Nine-banded armadillos almost always give birth to four offspring that are genetically identical quadruplets.
to produce identical quadruplets, fertilization begins with one sperm and one egg cell. This fertilized egg could then divide twice by mitosis to produce four genetically identical cells. There four cells could then separate from each other to begin the lives of four distinct individuals. Another possibility is that mitosis could produce two cells that separate from each other . these two cells could then divide by mitosis to produce two pairs of cells, which could also separate to produce four individual cells.
At puberty the testes contain a finite number of cells and produce an enormous number of sperm cells during the life span of a male. Explain why testes do not run out of spermatogonial cells?
to produce sperm, a spermatogonial cell first goes through mitosis to produce two cells. one of these remains a spermatogonial cell and the other progresses through meiosis. in this way, the testes continue to maintain a population of spermatogonial cells.
When preparing a karyotype, which of the following steps is conducted?
treat the cells with drugs that cause them to begin cell division, treat the cells with a hypotonic solution that causes them to swell, expose the cells to chemical dyes that bind to the chromosomes and stain them