Flashcards in Meiosis Deck (36):
What is a homologous pair?
Chromosomes that code for the same trait. They can have different information though. They different versions, or alleles, of the same gene.
What do homologous pairs have that sister chromatids dont?
1. One comes from mom, one from dad
2. Have different versions of the same genes
What do sister chromatids have that homologous pairs dont?
1. Bound together by centromeres
2. Chromatids are identical
3. Product of DNA replication
What is represented by "n"?
The number of pairs or different types of chromosomes(haploids).
What is represented by "2n"?
The total number of chromosomes(diploids)
What is a haploid?
A cell that has 1 copy of each type of chromosome(Human gametes)
What is a diploid?
A cell that has 2 copies of each type of chromosome.(Human somatic cells)
What is the result of meiosis?
4 haploid, gamete, daughter cells with half the number of chromosomes that the parent cell has.
What are gametes?
Cells with only half the "normal" number of chromosomes.
What is fertilization?
The joining of gametes, the result is an individual cell with the same number of chromosomes as the parent.
What happens in the interphase of meiosis 1?
•Cell spends 90% of its life in this phase.
•Cell carries out life processes
•Chromosome(DNA) replication takes place
What is synapsis?
The process of homologous chromosomes coming together, and "crossing over" occurs. The result ks the formation of tetrads.
What happens in prophase 1?
•Homologous chromosomes join together(synapsis)
•Tetrads are formed
•Crossing over occurs
•Centrioles move away from each other
•Nuclear membrane disappears
•Spindles and asters appear
What is a tetrad?
A group of 4 chromatids bound together after the homologous pairs have "crossed" over.
What happens in metaphase 1?
•Chromosomes that are now grouped as homologous pairs align on the equator
What happens in anaphase 1?
•Sister chromatids remain attached at centromeres
•Replicated chromosomes move to opposite poles
•Homologous pairs separate
What happens in telophase 1?
•Chromosomes reach poles
•Cells start to cleave
•Two non-identical haploid cells are produced
•New cells may or may not enter a brief interphase
What is chiasma?
The point or space where two homologous pairs cross over.
What happens in prophase 2?
•Replicated chromosomes move towards equator
•Any nuclear membrane that may have formed from meiosis 1 disappears
What happens in metaphase 2?
•Replicated chromosomes line up on equator
What happens in Anaphase 2?
•Sister chromatids move towards opposite poles
What happens in telophase 2?
•Nuclear membranes form at opposite poles
•Cytokinesis occurs(division of cell)
•4 haploid cells are produced
What are the 4 main differences between meiosis and mitosis?
1. In meiosis in prophase 1, homologous chromosomes pair up, unlike in mitosis
2. In meiosis, homolougous pairs align on the equator in metaphase 1
3. In meiosis in anaphase 1, homologous pairs of chromosomes separate, NOT pairs of sister chromatids
4. Meiosis results in 4 haploid daughter cells, and mitosis results in two diploid daughter cells.
What is gametogenesis?
The production of gametes.
What is spermatogenesis?
The production of sperm cells.
What is Oogenesis?
The production of egg cells.
What do gametogenesis, spermatogenesis, and oogenesis have in common?
1. All of meiotic divisions
2. They all result in haploid gametes
What are pros and cons of sexual reproduction?
Pro: Genetic variation
Con: Requires another individual
Why is genetic variation good?
1. Organisms the have variety are less likely to all be invaded by pathogens or parasites
2. Differential reproductive success
3. Able to adapt better
What are the sources of varitation?
1. Crossing over-Exchanges more genetic material
2. Independent assortment-Over 8 million combinations from just two parents for humans
What is the result of fertilization?
A zygote, represented by 2n.
What is darwin evolution?
•The foundation of adaptation
•"Only the strongest survive", best adapted are most likely to survive.
What is artificial insemination?
•Semen is collected from male
•Semen is inserted into female by artificial means
•Pregnency/birth is natural
•The mother is the biological mother and carries her own baby
What is invitro fertilization?
•Sperm and ovum are united outside the female
•Zygote is allowed to develop until 8 cell stage
•"embryo" is implanted into the female, this could be an egg donor or surrogate mother.
•Egg donor is usually treated with fertility drugs to "super" ovulate
•Multiple "embryos" usually implanted
•Extra embryos can be frozen and used later if others arent successful
What is the cloning process?
•Egg cell is enucleated
•2n nucleus from individual to be cloned is inserted
•"Zygote" clone is incubated until the 8-cell stage
•Embryo is implanted into uterus of surrogate mother
•Goes through gestation and birth