Chapter 11 - Meiosis And Sexual Reproduction Flashcards
Haploid cells are produced by a type of cell division called what?
Meiosis
Gametes unit to form what? Which has two sets of chromosomes (one from each gamete)
A zygote
Cells with two sets of chromosomes are called what? While one set is called what?
2 sets - diploid (2n)
1 set - haploid (n)
Sexual reproduction requires diploid cells to do what with their chromosome count?
Reduce their chromosome number by half and produce haploid cells, otherwise it would double the chromosomes every generation
Meiosis always starts with what type of cells and the daughter cells being what type?
Starts with diploid ends with haploid
How does meiosis achieve the reduction in chromosome number?
By undergoing one round of nuclear replication immediately followed by 2 rounds of nuclear reduction
What is the difference in named stages from mitosis to meiosis?
Meiosis has the same name but 2 stages of each. Pro/meta/ana/telophase 1 and 2 instead of just 1.
Are G1, S, and G2 similar to mitosis in meiosis?
Yes, virtually identical
What happens in prophase 1? (Be very specific) include as much details as possible.
-Homologous (in form of sister chromatids) are brought together forming a synaptonemal complex of four chromatids
-a dense lattice of proteins tightly pairs the homologous called synapsis, during synapsis the genes of the sister chromatids align precisely with each other
-the precise alignment of homologous non-sister chromatids allows for crossing over (exchange of the ends of the homologous non sister chromatids, visible as chiasmata)
-a short area of homology attaches the X and Y chromatids in males
What is crossing over and what does it do?
Crossing over is a form of genetic recombination between nonsister chromatids (mothers and fathers homologues)
-it mixes mother and father genes producing recombinant chromosomes (red and blue)
What does recombination nodules do? And what are they?
They are large proteins complexes that mark the location of chiasmata in the process of crossing over
-an enzyme cuts the double strand of DNA and makes new connections between nonsister chromatids
When the synaptonemal complex breaks down, the homologous chromosomes are attached only at what point?
The chiasmata and centromers
The groups of four chromatids when visible are called…
Tetrads
In terms of DNA exchange what does crossing over do in simple terms?
It leads to one chromosome having both maternal and paternal DNA
What happens in prometaphase 1?
-Spindle fiber microtubules attach to kinetochore proteins at the centromeres
-each member of the homologous pair attaches to the opposite pole assuring that the homologous pairs are pulled apart at metaphase 1
-homologous chromosomes are still held together at the chiasmata
-nuclear membrane breaks down completely