BIO 202 Study Guide - Midterm Guide: Sister Chromatids, Homologous Chromosome, Genetic Recombination
16 Jun 2018
School
Department
Course
Professor
Chapter 13: Meiosis and Sexual Life Cycles
1. Compare and contrast diploid and haploid cells.
Diploid Cells
two chromosome sets (46 total)
In humans: somatic cells are diploid.
Diploid cells are formed through
mitosis.
Haploid Cells
one chromosome set (23 total)
In humans: sex cells are haploid cells
2. Recognize the phases of meiosis from diagrams or micrographs. Know the details of meiosis figure in the textbook
3. Describe the movements of chromosomes during meiosis. (DIPLOID GERM CELL GENERATES 4 HAPLOID CELLS)
Meiosis I:
→ Prophase I: chromosomes condense, and synapse (homologous chromosomes loosely pair up forming synaptomental
complex), and exchange segments (genetic recombination)
→ Metaphase I: homologous pairs line up at the metaphase plate
→ Anaphase I: each pair of homologous chromosomes separate (mom and dad chromosomes)
→ Telophase I and Cytokinesis: cleavage furrows, two haploid cells are formed, each still consisting of sister chromatids
Meiosis II:
→ Prophase II: sister chromatids move towards metaphase plate
→ Metaphase II: line up at metaphase plate
→ Anaphase II: each chromatic separates
→ Telophase II and Cytokinesis: chromosomes decondense and each of the four daughter cells are all different
4. Define the relationship between homologous chromosomes and sister chromatids.
→ Homologous chromosomes have similar but not identical DNA (mom vs. dad).
Sister chromatids are one chromosome that copied itself and was stapled together
(genetically identical).
5. Compare the timing, location, numbers of cells, chromosome numbers, and
genetic outcomes of mitosis and meiosis.
]
Mitosis
Meiosis
Timing
Location
somatic cells
germ cells
Number of Cells
Made
2
4
Chromosome
Numbers
46 → 46
46 → 23
Genetic
Outcomes
2 genetically identical diploid
cells
4 different haploid cells
find more resources at oneclass.com
find more resources at oneclass.com
6. Describe the molecular details of synapsis and crossing over
→ Synapsis is the connection of two homologous chromosomes to form a tetrad.
→ This process allows crossing over, when the two homologous chromosomes exchange their genetic information at the
loci where they were crossed over.
7. Understand what is meant by independent assortment of chromosomes
- Independent Assortment: the results of alternative arrangements of maternal and paternal homologous chromosome
pairs on the metaphase plate in meiosis I (there is no plan or preset way that the chromosomes are going to line up,
assorting independently).
8. Distinguish human male and female karyotypes.
- Female karyotypes have two X chromosomes. Male have one X and one Y the Y one is significantly smaller.
9. Be able to draw a diagram that illustrates the relationships among the terms: chromosome, DNA, genes, chromatids,
centromeres, homologous chromosomes (homologues), and alleles.
10. Understand how crossing over, independent assortment and random fertilization contribute to heredity
→ -Meiosis can generate genetic diversity due to crossing over. The crossing over provides a million different outcomes
due to the variations of where the gene could have crossed over.
→ Independent assortment shows that there are 223 possible gamete combinations. Because of this, every haploid cell is
very different. (NUMBER OF POSSIBLE GAMETES = 2n where n is the number of chromosome pairs, in humans 23)
→ Random fertilization (when male combines with female gamete) shows that there are (223)2 possible combinations.
11. Describe the evolutionary advantages of sexual reproduction
- This is important because variation increases survival rate for a species in an unpredictable environment.
find more resources at oneclass.com
find more resources at oneclass.com
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chapter 13: meiosis and sexual life cycles: compare and contrast diploid and haploid cells. In humans: sex cells are haploid cells: recognize the phases of meiosis from diagrams or micrographs. Know the details of meiosis figure in the textbook: describe the movements of chromosomes during meiosis. (diploid germ cell generates 4 haploid cells) Prophase i: chromosomes condense, and synapse (homologous chromosomes loosely pair up forming synaptomental complex), and exchange segments (genetic recombination) Metaphase i: homologous pairs line up at the metaphase plate. Anaphase i: each pair of homologous chromosomes separate (mom and dad chromosomes) Telophase i and cytokinesis: cleavage furrows, two haploid cells are formed, each still consisting of sister chromatids. Prophase ii: sister chromatids move towards metaphase plate. Metaphase ii: line up at metaphase plate. Telophase ii and cytokinesis: chromosomes decondense and each of the four daughter cells are all different: define the relationship between homologous chromosomes and sister chromatids.
