Mitosis & Meiosis (Review) Flashcards
Define genes
Units of hereditary information in the form of a linear sequence of DNA nucleotides
Define chromosomes
A structure that consists of one very long DNA molecule and associated proteins
Define DNA
A nucleic acid molecule composed of hundreds to thousands of nucleotides in the form of a double-stranded helix
What is the relationship between genes, chromosomes, and DNA?
A gene is a linear sequence of DNA nucleotides
DNA molecules are packaged into chromosomes
T or F: eukaryotic chromosomes can contain 100s-1000s of genes?
True
Describe prokaryotic chromosomes
Prokaryotes have a single, circular chromosome
Define genome
one complete set of chromosomes
How many chromosomes are in the human genome?
2 copies of 23 chromosomes
n=23
How many chromosomes are in the fruit fly (Drosophila melanogaster) genome?
2 copies of 4 chromosomes
n=4
T or F: typically DNA is condensed
False. Typically DNA is not condensed
DNA condenses before cell division
When can DNA be seen in a microscope? When it is condensed or uncondensed?
Condensed
Define diploid cells
2 copies of every chromosome
Define haploid cells
1 copy of every chromosome
Define homologous chromosomes/homologues
a pair of chromosomes that have the same length, centromere, and genes (though they might have different alleles for those genes)
Where does each of the chromosome originate from in a homologous pair?
1 from mother
1 from father
Define sister chromatids
identical copies of chromosomes
Describe mitosis
Cell division that occurs in the body/somatic cells to create identical copies of the parent cell
What are the 3 functions of mitosis?
asexual reproduction
growth in multicellular organisms
cell replacement in multicellular organisms
Can mitosis occur in a) haploid cells, b) diploid cells, or c) both
Both
Describe meiosis
Cell division that occurs in the sex cells (gametes) to produce genetically unique cells
What are the functions of meiosis?
sexual reproduction
increase genetic diversity
reduce number of chromosomes by half
What are the four phases of mitosis?
Prophase
Metaphase
Anaphase
Telophase & Cytokinesis
What major events happen during prophase of mitosis?
chromosomes condense
duplicated chromosomes appear as sister chromatids joined at centromeres
spindle forms
centrosomes move apart
What major events happen during metaphase of mitosis?
centrosomes at opposite spindle poles
sister chromatids line up along metaphase plate, each with an individual kinetochore microtubule that is attached to the spindle pole on its side
What major events happen during anaphase of mitosis?
Sister chromatids are pulled to opposite poles by spindle fibres
What major events happen during telophase & cytokinesis of mitosis?
cells cleave and 2 identical daughter cells are created
What happens during the G1 phase of the cell cycle?
Gene expression and cell activity
preparation for DNA synthesis
What happens during the S phase of the cell cycle?
DNA is replicated and chromosomes are duplicated
What happens during the G2 phase of the cell cycle?
Prep for cell division
What happens during the G0 phase of the cell cycle?
Cell differentiation is terminated and division stops
This could lead to either final specialization and no more division or cell death (apoptosis)
What happens during the G0 phase of the cell cycle?
Cell differentiation is terminated and division stops
This could lead to either final specialization and no more division or cell death (apoptosis)
What major events happen during prophase I of meiosis?
sister chromatid pairs form homologous pairs
centrosomes and spindles form
What major events happen during metaphase I of meiosis?
Homologous pairs of sister chromatids align along metaphase plate with a homologous pair facing either pole and spindle fibres attach to each homologue
What major events happen during anaphase I of meiosis?
Homologous pairs are pulled to opposite poles by spindle fibres
What major events happen during telophase I and cytokinesis of meiosis?
cytoplasm is divided as the cell cleaves creating two genetically unique cells with sister chromatids
What is the difference between meiosis I and meiosis II?
Meiosis II follows meiosis I and will divide the sister chromatids apart.
Difference is that meiosis I separates homologous pairs and meiosis II separates sister chromatids
What are the major differences between mitosis and meiosis?
- Meiosis only occurs in diploid germ-line cells (gametes), whereas mitosis occurs in diploid or haploid somatic cells
- Meiosis includes 2 cell divisions, whereas mitosis only includes 1 cell division
- Mitosis produces 2 genetically identical cells that are also genetically identical to the parent cell
- Meiosis produces 4 genetically unique daughter cells that have half the number of chromosomes (haploid)
- Mitosis is involved in asexual reproduction, cell replacement, and growth of multicellular organisms. Whereas meiosis functions in sexual reproduction to create genetic diversity by halving the number of chromosomes in each daughter cell.
