Lecture 2: Mitosis and Meiosis Flashcards
What is evolution
A change in genetic frequency in a population over time
Prokaryotic cell characteristics
No nucleus Unicellular One circular DNA molecule (usually) Small amount of DNA No membrane bound organelles
Eukaryotic cell characteristics
Nucleus present Larger (Unicellular or multicellular) Multiple linear DNA molecules w/histones Large amount of DNA Membrane bound organelles present
Virus
Neither prokaryotic or eukaryotic
Outer protein coat surrounding nucleic acids
Homologous chromosomes
Similar but not identical
Each homolog carries same genes, but the alleles for each trait may not be the same
Diploid cells vs haploid cells
Two sets of genetic information vs one set
Diploids have two sets of chromosomes organized in homologous pairs
Centromere
Attachment point on chromosome for spindle microtubules
Submetacentric centromere
Centromere situated so that one set of arms is shorter than the other
Metacentric centromere
Centromere in the middle
Telocentric centromere
Centromere at the end with no short arm visible
Acrocentric centromere
Centromere near the end producing a very short arm
What happens in G1
Cell grows, proteins necessary for cell division produced
What happens in G0
Non-dividing phase before G1/S checkpoint (cell may or may not have this)
What happens after G1/S checkpoint
Cell is committed to dividing
What happens in G2
Cell prepares for mitosis
G2/M checkpoint and after?
Only passed if DNA is completely replicated and undamaged.
Cell can then divide
Prophase
Chromosomes condense
Each chromosome has two sister chromatids
Mitotic spindle forms
Prometaphase
Nuclear membrane disintegrates
Spindle microtubules attach to chromosomes
Metaphase
Chromosomes line up on metaphase plate
Anaphase
Sister chromatids separate and move toward opposite poles
Telophase
Chromosomes arrive at spindle poles and nuclear membranes reform
Chromosomes decondense
Meiosis is
The production of haploid gametes
Fertilization
Fusion of haploid gametes
A consequence of meiosis is
Genetic variation
Tetrad
Closely associated four sister chromatids of two homologous chromosomes
What is the first mechanism that produces genetic variation in newly formed gametes
Crossing over
What is the second mechanism of generating genetic variation in newly formed gametes
Random distribution of chromosomes into newly divided cells during anaphase I
Chiasmata is formed
During late prophase I, which means crossing over occurs during late prophase I
Prophase II
Chromosomes recondense
Metaphase II
Individual chromosomes line up on metaphase plate
Anaphase II
Sister chromatids separate
T or F: Prophase II occurs in all cells
False. It only occurs in cells in which the spindle has broken down, chromosomes relaxed and nuclear envelope reformed
Negative result of crossing over
Unequal exchange of genetic material producing chromosomes with deleted or duplicated regions
Positives of crossing over
Essential for normal segregation of chromosomes
Adds additional genetic variation
Consequences of meiosis (cells produced, chromosome number, variance, epigenetics)
Four cells produced from each original cell
Chromosome number in each new cell is half (haploid)
Newly formed cells are genetically different from one another and from parent cell
Epigenetic modifications are erased and parent specific modifications are added
Sporophyte and gametophyte
Sporophyte is 2n, undergoes meiosis and becomes a 1n gametophyte (spore)
