Week 5: Meiosis Flashcards
The gametes during meiosis must contain precisely?
one member of each homologous pair of chromosomes
During a phase called _________, there is genetic exchange between members of each homologous pair of chromosome. This creates intact chromosomes that are mosaics of the maternal and paternal homologs.
crossing over
To achieve haploidy, two divisions (Meiosis I and II) are required that results in the formation of _____ gametes, each genetically different from each other.
four
As in mitosis, the process of meiosis begins with a diploid cell duplicating its genetic material in the interphase stage (forming a __________ joined at the centromere).
duplex of two sister chromatids
The second nuclear division in meiosis loosely resembles a mitotic division, but there is no?
DNA replication
The net effect of two divisions is the creation of ___________, each containing the equivalent of a single sister chromatid from each pair of homologous chromosomes.
four haploid daughter cells
The first meiotic division is also called the __________ because it divides the chromosome number in half.
reductional division
The first meiotic division is also called the reductional division because?
it divides the chromosome number in half
Prophase I is subdivided into five stages?
leptotene, zygotene, pachytene, diplotene and diakinesis
Leptotene means?
“thin thread”
At this stage during prophase I, the chromosomes first become visible as long, thread-like structures. Numerous dense granules appear at irregular intervals along their length.
Leptotene
The localized contractions (numerous dense granules) during leptotene are called?
chromomeres
Zygotene means?
paired thread
It is marked by lateral pairing (synapsis) of homologous chromosomes, beginning at the chromosome tips. It results in a precise chromomere by chromomere association.
Zygotene
The lateral pairing during zygotene is called?
synapsis
Synapsis is accompanied by the synthesis of _______, a protein structure that helps to hold the homologous chromosomes together.
synaptonemal complex
Each pair of synapsed homologous chromosomes is referred to as?
bivalent
Pachytene means?
thick thread
Condensation of chromosome continues. During this period, the chromosomes shorten and thicken.
Pachytene
Genetic exchange, or _______ takes place during pachytene.
crossing over
What process takes place during pachytene?
genetic exchange or crossing over
Diplotene means?
double thread
During this stage of prophase I, the synaptonemal complex breaks down and the synapsed chromosomes begin to separate.
Diplotene
True or false: During diplotene, the homologous chromosomes remain held together at the intervals along their lengths by cross-connections resulting from crossing-over.
True
The cross-connection, called a __________, is formed by a breakage and rejoining between non-sister chromatids.
chiasma (pl. chiasmata)
Diakenesis means?
moving apart
In this stage of prophase I, the homologous chromosomes seem to repel each other, and the segments not connected by chiasmata move apart.
Diakenesis
It is at this substage that the chromosomes attain their maximum condensation.
Diakenesis
Near the end of diakinesis, the formation of a ______ is initiated, and the __________ breaks down.
spindle; nuclear envelope
In metaphase I, as each bivalent moves onto the metaphase plate, its centromeres are oriented at ______ with respect to the poles of the spindle.
random
During __________ , the homologous chromosomes separate from one another and move to opposite poles of the spindle.
Anaphase I
At _________ , a haploid set of chromosomes consisting of one homolog from each bivalent is located near each pole of the spindle.
Telophase I
The second meiotic division is also called ________________ because the chromosome number remains the same in each cell before and after the second division.
equational division
The second meiotic division is also called equational division because?
the chromosome number remains the same in each cell before and after the second division
True or false: Chromosome replication never takes place between the two meiotic divisions.
True
In __________, the centromeres divide longitudinally and the chromatids of each chromosome move to opposite poles of the spindle.
anaphase II
In anaphase II, the centromeres divide ____________ and the chromatids of each chromosome move to opposite poles of the spindle.
longitudinally
Once the centromere has split at anaphase II, each chromatid is considered a?
separate chromosome
It is marked by transition to the interphase condition of the chromosomes in the four haploid nuclei, accompanied by the division of the cytoplasm.
Telophase II
Association type: One division.
Mitosis
Association type: 2 daughter cells per cycle.
Mitosis
Association type: Daughter cells genetically identical.
Mitosis
Association type: Chromosome number of daughter cells same as that of parent cell (2n).
Mitosis
Association type: Occurs in somatic cells.
Mitosis
Association type: Occurs throughout life cycle.
Mitosis
Association type: Used for growth, repair, asexual reproduction.
Mitosis
Association type: Two divisions.
Meiosis
Association type: 4 daughter cells per cycle.
Meiosis
Association type: Daughter cells genetically different.
Meiosis
Association type: Chromosome number of daughter cells half that of parent cell (1n).
Meiosis
Association type: Occurs in germline cells.
Meiosis
Association type: In humans, completes after sexual maturity.
Meiosis
Association type: Used for sexual reproduction, producing new gene combinations.
Meiosis
This process takes place in the testes.
Spermatogenesis
Spermatogenesis begins with the enlargement of the germ cell?
spermatogonium
Spermatogonium grows to become a ____________, which undergoes the first meiotic division.
primary spermatocyte
The products of the first meiotic division during Spermatogenesis are called __________, which then undergo meiosis II that produces the ___________.
secondary spermatocytes; spermatids
The spermatids go through developmental changes to become?
spermatozoa (sperm)
Occurs in the ovaries.
Oogenesis
The daughter cells resulting from the two meiotic division during oogenesis receive equal amounts of genetic material, but do not receive equal amounts of?
cytoplasm
The daughter cell with very little surrounding cytoplasm is called?
polar body
The other daughter cell produced by the first meiotic division and contain most of the cytoplasm is called the?
secondary oocyte
The __________ will be produced from the secondary oocyte during the second meiotic division.
mature ovum
The mature ovum will be produced from the __________ during the second meiotic division.
secondary oocyte
The cytoplasm of the secondary oocyte again divides unequally, producing an?
ootid and a second polar body
The ootid then differentiates into a?
mature ovum
Humans have ___ chromosomes consisting of ____ pairs.
46 ; 23
One member of each chromosome pair is derived from?
each parent
Twenty-two pairs of chromosomes are known as __________ and appear as homologs of each other (they are indistinguishable from each other).
autosomes
The first 22 pairs of chromosomes are numbered 1-22 in _________ order of length.
descending
The twenty-third pair includes the?
sex chromosomes (X and Y chromosomes)
The chromosomes contains a constricted region called the _________, whose location establishes the general appearance of each chromosome.
centromere
