Meiosis Flashcards
What type of organs are the cells that enter meiosis 1
Sex organs (ovaries and testes)
What event must take place during interphase before a cell proceeds to division
DNA replication
What two structures make up a single replicated chromosome
Sister chromatids
How many replicated chromosomes does the cell contain during prophase
4
At which stage in meiosis 1 do the pairs of homologous chromosomes come together
Late prophase 1
Once chromosomes have formed a pair, what are they called?
Tetrads
At the end of meiosis 1 two cells have been produced. How many replicated chromosomes are in each of these cells
Two
Diploid
Full set of chromosomes
Haploid
Half the chromosomes
Which stage of meiosis 1 are the cells diploid and haploid
Diploid- prophase, metaphase, and anaphase
Haploid- telophase after the cell has split
What is the relationship between the cells at the end of telophase 1 and the original cell?
The new cells have two copies of half of the genetic information in the original cell
Will the cells at the end of telophase 1 be genetically identical to each other?
No because the homologous pairs are separated and the alleles on each homologous pair are not necessarily identical
In meiosis 1 during anaphase 1, which structures separated
Homologous chromosomes
In meiosis 2 during anaphase 2 which structures seperared
Sister chromatids
At the end of meiosis 2 are four daughter cells. Are they haploid or diploid
The cells are haploid. They each contain one chromosome (sister chromatids) from each homologous pair. Each chromosome contains a complete set of genes
What is the relationship between the cells at the end of meiosis 2 and the original cell
The new cells have one copy of half of the genetic information in the original cell
What is the name given to the cells produced at the end of meiosis 1 in males
Secondary spermatocyte
What is the name given to the cells produced at the end of meiosis 1 in females
Secondary oocyte
At the end of meiosis 2 in males, what cells are produced
Spermatids
What do spermatids eventually become
Mature sperm
Before fertilization what happens to the secondary oocyte
Proceed to meiosis 2
During fertilization which two cells come together
Mature sperm and secondary oocyte
During meiosis 2 the secondary oocyte divides unevenly with one cell (the ovum) receiving half of the chromosomes and nearly all the cytoplasm and organelles while the other cell, the polar body, is much smaller and eventually degenerates. Why does the secondary oocyte divide this way?
The ovum will receive more organelles, such as mitochondria for making energy, which will provide the zygote with all of its cytoplasm and organelles( Sperm contains only scant cytoplasm, a few mitochondria and haploid chromosomes) but nuclear division is necessary to produce the correct number of chromosomes in the oocyte
What is the ploidy of the zygote produced by fertilization haploid or diploid
Diploid
What would the Ploidy of the zygote be if egg and sperm were produced by mitosis rather than meiosis. How would this affect the ploidy of each successive generations
The egg and sperm would Each would be diploid. So the zygote would be tetraploid. If the tetraploid organisms produced tetraploid eggs the next generation would be octoploid This doubling would Continue
What is the origin of the chromosomes found in the zygote
The homologous pair of chromosomes found in the zygote have come from each parent. One half of each pair is maternal and the other half is paternal
What are the points where the sister chromatids cross over
Chiasma
What happens to the chromatids during crossover
Sections of the homologous pair switch places on the chromatids
What phrase is used to describe the chromatids after crossing over takes place and the homologous chromosomes separate
Recombinant chromatids
Are the genes of the recombinant chromatid the same as the original chromatids
Yes each chromosome in the homologous pair contains the same genes in the same spot
Are the alleles on a recombinant chromatid the same as the original
No the homologous pair can have a different alleles for each gene
Is either arrangement egually likely during the formations of tetrads in late prophase 1
DNA replication occurs randomly within the nucleus of the cell. When the homologous chromosomes come together as tetrads they are equally likely to line up on one side
If there was 3 sets of homologous chromosomes. How many possible arrangements would there be for the tetrads in late prophase 1
2•2•2=8
What is the possible genetic combination due to independent assortment
2^23= 8,388,608
Meiosis and sexual reproduction each lead to variation in the genetic makeup of every person. With your group, explain how meiotic event as well as random fertilization of eggs and sorry together lead to this genetic variation
Independent assortment leads to multiple different maternal and paternal gene combinations being produced in the cells at the end of meiosis 1. Chiasma formation between homologous pairs of chromosomes leads to blocks of genes being swapped between nonsister chromatids during separation at anaphase 1. This leads to alleles combinations on the chromosomes being shuffled and further varies the chromosomes that end up in Egg and Sperm after meiosis 2 random fertilization of eggs and sperm means that when zygote are formed the gene combination will be different each time, even if they come from the same two parents
When homologous chromosomes pairs align on the spindle during metaphase 1 the orientation of one pair is independent of the orientation of any pair
independent assortment
