meiosis quiz 9 Flashcards
In a multi-cellular organism, what type of cell would undergo meiosis?
Meiocytes, Oocytes, Spermatocytes
What is ploidy?
The number of sets of chromosomes within a cell
What is the difference between a diploid and haploid cell?
Haploid - one copy/set of each chromosome I (1n)
Diploid - two copies/sets of each chromosomes II (2n)
What is a homologous pair of chromosomes?
A homologous pair of chromosomes is two chromosomes in a pair
What are sister chromatids?
One of two identical halves that make up a chromosome
How many strands of DNA are in a typical replicated chromosome? (G2 Phase)
2
What are non-sister chromatids?
Non-sister chromatids are chromatids that are on opposite homologs in a homologous pair, they are not identical.
What is a dyad?
A dyad is a pair of sister chromatids (homolog) X
What is a tetrad?
A tetrad is two pairs of sister chromatids (homologous pairs) XX
A diploid cell that will undergo meiosis has 4 chromosomes. Fill in the blanks referring to chromosome number, DNA amount, and ploidy.
G1: Chromosome # :
DNA amount :
Ploidy :
G2: Chromosome # :
DNA amount :
Ploidy :
G1: 4
1x
2n
G2: 4
2x
2n
What is happening to the chromosomes in Prophase I of Meiosis?
- Chromatin condenses
- Nuclear membrane dissolves
- Crossing over between non-sister chromatids
-> As chromatin condenses, homologous pairs of chromosomes pair up, finding one another and aligning. After crossing over, each homolog is now made of portions of the paternal and maternal chromosomes from the previous generations.
Explain what “crossing over” refers to during prophase I of meiosis
The matching, pairing, alignment of homologous chromosomes and the cross of DNA between the non-sister chromatids
What is happening during Mid-Meiotic Interphase of Meiosis? For just one of the cells:
Chromosome #:
DNA Amount:
Ploidy:
ASK CAHOON
What is happening during Telophase II and Cytokinesis II of Meiosis? For one of the cells:
Chromosome #:
DNA Amount:
Ploidy:
HAPLOID 1n=2/1n=10
What is a gamete?
a matured male or female haploid cell
What is non-disjunction?
When chromosomes do not separate properly
Since Meiosis is the source of _____ cells, incorrect chromosome separation during this process is the source of ______ that result from _____ or ____ chromosomes
sex; genetic disorders; extra; missing
Since Meiosis is the source of _____ cells, incorrect chromosome separation during this process is the source of ______ that result from _____ or ____ chromosomes
sex; genetic disorders; extra; missing
What is the correlation between non-disjunction and human maternal age? Why is there a correlation?
Chances of non-disjunction increase as age increases - ASK CAHOON, SOMETHING WITH THE CELLS STICKING TOGETHER?
What is the most common outcome of aneuploidy - when a human zygote receives an extra chromosome (trisomy) or one less chromosome (monosomy?)
Trisomy
In terms of aneuploidy, what are Patau’s, Edward’s and Down’s syndromes?
Trisomy 13, Trisomy 18, and Trisomy 21
Why can an extra X chromosome tolerated during human development?
Cells have the ability to shut down extra X-chromosomes in a process called X-inactivation
In terms of aneuploidy, what are XXX, Klinefelters, XYY, and Turners syndromes?
XXX - extra X for females
Klinefelters - extra X for males
XYY - extra Y chromosome for males
Define Aneuploidy
abnormal amount of chromosomes
Define monoploidy
missing chromosome (1n-1)
On a recent expedition to Monster Island, you collect tissue samples from gigantic Godzilla-like creatures. Upon examining their chromosomes, you discover they are diploid with 12 homologous pairs. (2n=24).
Draw out the ploidy and total # of chromosomes you would expect in G1, Metaphase I, Metaphase II, in a sperm cell, and in a skin cell
PLOIDY STAYS THE SAME FROM G1 TO G2. DNA AMOUNT IS DOUBLED
2n - > 2n -> 1n + 1n -> 1n + 1n + 1n + 1n
Bonus Q: How did you get the tissue samples from the giant godzilla-like creatures?
Biopsy
What stage of meiosis would this event occur? Individual dyad chromosomes align along a single plane
Metaphase II
What stage of meiosis would this event occur? Homologous pairs of chromosomes (tetrads) separate into dyads
Anaphase I
What stage of meiosis would this event occur? Dyads separate into individual chromosomes
Anaphase II
What stage of meiosis would this event occur? Homologous pairs of chromosomes condense
Prophase I
What stage of meiosis would this event occur? Homologous pairs of chromosomes cross over
Prophase I