BLG 143 Lecture Notes - Lecture 9: Sister Chromatids, Spindle Apparatus, Nuclear Membrane

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12 Jan 2017

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Meiosis: nuclear division that precedes formation of gametes (egg+sperm) and results in halving of chromosome #. First off: each species has a unique # of chromosomes. Haploid: species with only one set of chromosomes. One set from maternal parent, other set from paternal parent. Autosomes: regular chromosomes, doesn"t carry genes involved in determining sex. Karyotype: # and types of chromosomes present in an organism. Homologous chromosomes: the 2 chromosomes of each type, similar in size, shape and gene content. In diploids, the products of meiosis are halpoid. Early: chromosomes condense, nuclear envelope breaks up, spindle apparatus form. Homologous chromosomes pair together in a process called synapsis, forming a tetrad, consisting of 2 homologous chromosomes. During synapsis, the 2 pairs of sister chromatids are held tightly together by a network of proteins called the synaptonemal complex. Late: crossing over between non-sister chromatids occurs, joined at chiasmata (sing: chiasma). Sister chromatids attach to the spindle fibres at their kinetochores.

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Which statements pertaining to genetic variability are correct? Check all that apply (note that wrong answers will be deducted from right answers)!

Crossing over is defined by the exchange of chromosome pieces during metaphase one of meiosis.

If a germ cell (i.e. parent cell before meiosis) had only two pairs of homologous chromosomes (i.e. 4 chromosomes total) there are 2 possible combinations of maternal and paternal chromosomes in gametes.

Siblings produced by sexual reproduction are different because sperms are different from one another and eggs are different from one another, and the combination of an egg and sperm is basically unique.

Random fertilization means that all possible combinations of eggs and sperm are equally likely, i.e. it is pure chance which sperm fuses with which egg.

Individual chromosomes contain thousands of genes. This means that during each crossing over event, more than one gene is exchanged between paternal and maternal chromosomes.

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13. Meiosis differs from mitosis in that:
a. meiosis results in the production of two new cells, whilemitosis results in the production for four new
cells., b. meiosis is used for growth and repair, while mitosis isused for production of eggs and sperm., c.
cytokinesis can be unequal following meiosis, but is approximatelyequal following mitosis., d. meiosis
involves one cell division, while mitosis involves two celldivisions., e. meiosis results in the production of
diploid cells, while mitosis results in the production of haploidcells.
14. Bits of maternal and paternal chromosomes are exchanged betweenhomologous chromosomes during
synapsis of meiosis I. This process is called:
a. crossing over., b. random mating., c. random fertilization., d.random shuffling of parental
chromosomes.,
e. mutation.
15. The advantage of sexual reproduction over asexual reproductionis that:
a. all young are genetically identical to the parent., b. malesmust evolve a copulatory organ., c. genetic
variability in the population is increased., d. females must evolvea vagina., e. mates are not needed.
16. Many different types of information are used to constructphylogenetic trees. Which of the following types
of information is the most direct measure of evolutionaryrelatedness?
a. physiology, b. gene sequence data, c. the fossil record, d.information about the structure of ribosomes.,
e. information about the structure of enzymes
17. A species is:
a. a group of individuals that can interbreed under naturalconditions and produce fertile offspring., b.
denoted by both a genus and a species name., c. the onlybiologically defined taxon., d. a group of
organisms with a large number of traits in common., e. all of theabove.
18. The process of spermatogenesis results in:
A. 4 diploid sperm; B. 1 diploid sperm and 3 haploid polar bodies;C. 1 haploid sperm and 3 haploid
polar bodies; D. 4 haploid sperm
19. Which cell division process results in an unequal division ofthe cytoplasm?
A. Spermatogenesis; B. Testiculargenesis; C. Oogenesis; D. None ofthe above
20. Meiosis is the process by which:
A. 1 diploid cell becomes 4 haploid cells; B. 1 diploid cellbecomes 1 haploid cell and 3 haploid polar
bodies; C. 1 haploid cell becomes 4 diploid cells; D. Both A andB
21. The phase of mitosis where chromosomes line up at the equator(middle) of the cell is called:
A. Anaphase; B. Telophase; C. Interphase; D. Metaphase
22. Chromosome #6 from Mom and Chromosome #6 from Dad form achromosome pair called:
A. Sister Chromatids; B. Centromeres; C. Homologous Chromosomes; D.Spindle Apparatus

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What is a genome? What is a genome made of? Describe the bacterial genome. How do bacteria reproduce? What is binary fission? Distinguish between a chromosome and chromatin. Where are chromosomes located in eukaryotic cells? What is the chromosome made of? What is a centromere? What is the centromere's role? What are sister chromatids and how do they arise? Distinguish between somatic cells and germ (gametes) cells. Describe the cell cycle. What are the different phases? What occurs during S phase? What is interphase? How is the cell cycle controlled?

Describe mitosis. What are the phases of mitosis? What occurs in each of the phases of mitosis? What is cytokinesis? How does this differ between plant and animal cells? What is a kinetochore? Where does it form? What is its role? What is the role of microtubules in mitosis? What is a centriole and what is it composed of? What is a centrosome and what is its role in mitosis? What is the metaphase plate and why is this important? What is the mitotic spindle, its role and its makeup? What defines a diploid cell? How many copies of each chromosome is in a diploid cell? What about a haploid cell? Why do the daughter cells of mitosis always have the same complement of chromosomes?

Describe meiosis. What are the phases of meiosis? What occurs in each of the phases of meiosis? Distinguish between meiosis I and meiosis II and describe how each of these processes compare to mitosis. Why do animal cells undergo meiosis? What is a gamete? What is a zygote? What are recombination, crossing-over, and chiasma? When and why does this occur? What is meant by 'homologous pair of chromosomes'? Why don't the daughter cells of meiosis have the same genetic makeup? What controls the segregation of chromosomes into the gametes?

What are genetic characters? What are genetic traits? What is an allele? What is a locus? How many alleles at each locus would a human cell have and why? Distinguish between genotype and phenotype. What is meant by a dominant gene? What is meant by a recessive gene? How do these differ? What is the genotype of a homozygous dominant organism? What is its phenotype? What is the genotype of a homozygous recessive organism? What is its phenotype? What is the genotype of a heterozygous organism? What is its phenotype? What is a genetic cross? Distinguish between the P, F1, and F2 generations. What is a true-breeding line? What is the genotype and phenotype of a cross between homozygous dominant and homozygous recessive parents? If the F1 progeny are crossed, what would be the genotype and phenotype of the F2 generation? What would be the phenotypic ratio? What would be the genotypic ratio? Be ready to generate Punnet square tests or probability analyses of crosses involving more than one genetic locus. Describe a dihybrid cross where two alleles are homozygous dominant in one parent and homozygous recessive in the other. What would be the phenotypic ratio of the F2 generation from this dihybrid cross? What is meant by independent assortment? Be prepared to calculate probabilities resulting from different crosses.

Distinguish between complete and incomplete dominance. How would incomplete dominance alter the results of a hybrid cross? What would the resulting F2 generation phenotype and genotype ratios be? What is codominance? How does this affect the results of crosses? Be prepared to determine likely blood types of parents based on the blood types of their offspring. What is a polygenic trait? What is a carrier state for a genetic disease? What is meant by linked genes? How does this affect expected outcomes of genetic crosses? How is gene linkage used for chromosomal mapping? Distinguish between autosomes and sex chromosomes. What sex chromosomes are found in women? What sex chromosomes are found in men? What are sex-linked traits? Be prepared to give the results of crosses that involve sex-linked recessive traits. What is the process of nondisjunction? What are the likely results? Why is this important? What is a Barr body? Recognize the genetic abnormality of Downs Syndrome, Turner's Syndrome, and Klinefelter's Syndrome.

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BLG 143 Lecture Notes - Lecture 9: Sister Chromatids, Spindle Apparatus, Nuclear Membrane

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