Bi 112 review Flashcards
During metaphase humans have how many chromosomes?
46
When not actively dividing, what phase are cells arrested in?
G0 phase
What phase are chromosomes most condensed in?
Metaphase
How many homologous chromosomes do humans have?
23
At the end of metaphase how many chromosomes do humans have?
46
_______ & _______ can disturb the cell cycle when they are mutated.
Tumor-suppressors and proto-onco genes.
A human that is XO (missing a sex chromosome) is:
2n-1=46
Down syndrome is “2n+1=47”
Cells that are “2n+1” are called _____ and cause ________.
Trisomic (have an extra chromosome)
And cause Down syndrome
Somic=1 extra chromosome
Cells that are triploid are:
3n (have an extra SET of chromosomes)
Can’t have offspring
Ploid=sets
How does cytokinesis occur in plants?
The cell plate forms between nuclei (by vesicles)
What is the primary checkpoint for external signal influence?
(Double check this one)
G1/S checkpoint
What checkpoint does the cell make a commitment to complete mitosis?
(Double check)
G2/M
Cereal grains have __ sets of chromosomes.
6n
Strawberries have ___ sets of chromosomes.
8n
____ is the point of constriction of chromosomes
Centromere
In what phases of interphase can the nucleolus be seen?
ALL
Sperm and eggs have ___ sets of chromosomes
n (1n)
1/2 the amount of genetic material
In what phase is genetic material duplicated?
S-phase of interphase
How many sets of chromosomes do human cells have?
2n
Uncontrolled checkpoints in the cell cycle can cause ________
CANCER!
On the average chromosome there are ______ crossing over events.
2-5
In what phase of mitosis does the nucleolus disappear?
Prophase
In what phase do chromosomes move to center of the cell through associated protein “motors”?
Pro-metaphase
What is the longest phase (primary growth) in interphase?
G1
In mitosis how Many chromosomes in a human cell after interphase?
(Double check)
46
When does non-disjunction occur?
When nonsister chromatids fail to separate
Failure of chromosomes to move to opposite poles during either meiotic division
Gametes produced from Nondisjunction in meiosis1 and meiosis 2.
Meiosis-1: n+1,n+1,n-1,n-1
Meiosis-2: n+1,n-1,n,n
Homologous chromosomes “zipper together”:
Synapsis (crossing over occurs between nonsister chromatids)
Occurs in prophase 1 in meiosis 1
Microtubules of spindle shorten and (chiasmata break) in ________.
Anaphase 1
Sister chromatids remain attached, homologues separate and move to opposite poles
What is “reductive division” and when does it occur?
In meiosis 1.
It is the “first meiotic division”. Results in daughter cells that contain one homologue from each chromosome pair.
Diploid—>Haploid
What is worse, Nondisjunction at meiosis 1 or meiosis 2?
Meiosis 1, because both daughter cells will be diploid?
(2 will have an extra chromosome, 2 will be missing a chromosome)
all gametes will be affected
The site of chromosome crossover is called _______.
Chiasmata
What happens in anaphase II?
Sister chromatids separate and chromosomes move toward opposite poles.
(Microtubules shorten, centromeres split, sister chromatids pulled to opposite poles)
Why must a cell undergo meiosis?
Sexual reproduction (exchanges genetic material) Producing non-identical haploid cells (diploid–>haploid)
How many chromosomes in humans after metaphase 1?
23
Tetrad:
4 chromatids attached (one unit)
-composed of two nonsister chromatids (4 total)
During meiosis, chromatids remain attached during:
Prophase1 and Metaphase1
Separate in anaphase1
How many microtubules are attached per tetrad?
2 (one for each sister chromatid)
In meiosis, how many chromosomes after anaphase1? (Humans)
46
Aneuploid gametes:
Gametes with missing or extra chromosomes
Conditions caused by Aneuploid gametes include:
Turner Syndrome, Jacob’s Syndrome, Down Syndrome
Difference between mitosis and meiosis:
Mitosis-identical diploids (body cells/somatic)
Meiosis-non-identical haploid cells
How many chromosomes after telophase2?
23 (1/2 the amount of genetic makeup)
How would a women go her entire life without knowing she is XXX?
“Barr Bodies”
-no syndrome present/unable to produce offspring-
How do chromosomes migrate to their respective poles?
By microtubules shortening
How many daughter cells after meiosis2?
4 (4 1n – 1 set of chromosome each)
Why can a 4n cell produce, but not 3n?
Unequal separation of chromosomes. Needs to be even number for pairing.
How many human chromosomes at the end of prophase1?
23
In what phase do tetrads line up at the equator of the cell?
Metaphase1
Operative word= “tetrads”
Only case in which humans can survive w/ less than 46 chromosome:
Down Syndrome