Meiosis Flashcards
All living organisms must __________________ (or generate offspring) via one of ______ types of reproduction.
All living organisms must reproduce (or generate offspring) via one of two types of reproduction.
___________________ Reproduction: no sexual activity (only _______ parent involved). 1
□ Only one source of DNA = Genetically _______________ offspring.
Asexual Reproduction: no sexual activity (only one parent involved).
□ Only one source of DNA = Genetically identical offspring.
_________________ Reproduction: sexual activity (_________ parents involved).
□ Two sources of DNA = Genetically _______________ offspring.
Sexual Reproduction: sexual activity (two parents involved).
□ Two sources of DNA = Genetically unique offspring.
Asexual reproduction differs from sexual reproduction in that:
a) Asexual reproduction produces genetically diverse offspring.
b) Asexual reproduction occurs only in bacteria.
c) Asexual reproduction produces genetically identical offspring.
d) Asexual reproduction does not occur in animals.
c) Asexual reproduction produces genetically identical offspring.
Cell Division is an important process for reproduction (making more life), fetal development (growth), & tissue repair.
●Before any cell can divide, it must first _______________ its DNA, so each daughter cell can get a copy of the DNA.
replicate
Eukaryotes are capable of going through two types of cell reproduction processes:
Mitosis, Meiosis
a type of cell division that reduces the chromosome number by half, producing cells that are used for sexual reproduction. It occurs only in reproductive cells (gametes: sperm and egg cells in animals, pollen and ovules in plants).
Meiosis
_____ happens in all kinds of places in our body(somatic cells), but _____ will only happen in cells that are going to lead to the production of either sperm or eggs.
mitosis happens in all kinds of places in our body, but meiosis will only happen in cells that are going to lead to the production of either sperm or eggs.
small segments of DNA encoding proteins that could lead to expression of a trait (ex. gene for eye color).
Genes
different versions of a specific gene (ex. gene for blue eyes vs. gene for brown eyes).
Alleles
Alleles are typically represented using capital/lower-case letters (ex. B = Blue eyes; b = brown eyes).
Alternate forms of the same gene are called:
Alleles
_____ can be dominant or recessive, and they determine the variation of a trait that an individual might express. For example, the gene for flower color might have a purple allele and a white allele.
Alleles
What is a Haploid:
Things like Gametes (sperm and egg cells)
-1 copy of each gene/chromosome
What is a diploid:
Most body (somatic) cells
-(2n): 2 copies of each gene/chromosome; one copy inherited from each parent.
2 copies of each gene/chromosome; one copy inherited from each parent.
Diploid (2n)
1 copy of each gene/chromosome.
Haploid (n)
Which of the following statements is true of a species that has a chromosome number of 2n = 16?
a) The species is diploid with 32 chromosomes per cell.
b) Each haploid cell of this species has 16 chromosomes.
c) Each diploid cell of this species has 16 chromosomes from the father and 16 chromosomes from the mother.
d) Each diploid cell of this species has 8 chromosomes from the father and 8 chromosomes from the mother.
d) Each diploid cell of this species has 8 chromosomes from the father and 8 chromosomes from the mother.
A cell that has 2 copies of each chromosome is called a __________ cell:
a) Sperm.
b) Diploid.
c) Haploid.
d) Gamete.
b) Diploid.
All human cells, except sex cells, are diploid and have 23 pairs of chromosomes. Human sex cells, such as egg and sperm, are haploid and have _______ chromosomes.
a) 23
b) 12
c) 11.5
d) 46
a) 23
an ordered display of all chromosomes in a cell.
Karyotype
___ pairs of autosomes: non-sex chromosomes that are found in both males & females.
22
Human somatic cells contain__ pairs of chromosomes (for a total of __).
23, 46
_ pair (X & Y chromosomes) are __chromosomes that determine the sex of the organism.
1 ,sex chromosomes
______Chromosomes: pairs similar in size/shape & carry the same genes but can have different alleles.
Homologous Chromosomes
□ Within each homologous chromosome pair, one is ______inherited & the other is _____ inherited.
□ Within each homologous chromosome pair, one is paternally inherited & the other is maternally inherited.
How might the two members of a pair of homologous chromosomes differ from each other?
a) In the sequence of the DNA making up each of the chromosomes.
b) In the relative position of the genes present on each of the chromosomes.
c) They cannot differ if they are homologous.
d) In the kinds of genes present on each of the chromosomes
a) In the sequence of the DNA making up each of the chromosomes.
Human life cycle:
*Two adults (2n), Diploid individuals with 46 chromosomes each.
*_____,Specialized cell division that produces:
*____ (sperm n and egg n) , Haploid cells with 23 chromosomes.
*Fertilization: The sperm and egg fuse to form:
*___ (2n) — A diploid cell with 46 chromosomes.
*_____ — The zygote undergoes many rounds of cell division.
*Baby (2n) — A new ____ organism that grows and develops.
Two adults (2n) — Diploid individuals with 46 chromosomes each.
Meiosis — Specialized cell division that produces:
Gametes (sperm n and egg n) — Haploid cells with 23 chromosomes.
Fertilization — The sperm and egg fuse to form:
Zygote (2n) — A diploid cell with 46 chromosomes.
Mitosis — The zygote undergoes many rounds of cell division.
Baby (2n) — A new diploid organism that grows and develops.
Gene: Small segment of __________ that encodes a protein.
DNA
Alleles: Alternate versions of a __________.
gene
Cell ploidy refers to the number of __________ of chromosomes in a cell.
sets, pairs
A cell with one set of chromosomes is called __________.
haploid (n)
A cell with two sets of chromosomes is called __________.
diploid (2n)
The 22 pairs of chromosomes that are not sex chromosomes are called __________.
autosomes
Homologous chromosomes carry the same __________ but may have different __________.
genes; alleles
Meiosis produces __________ cells, also called gametes.
haploid
Fertilization restores the chromosome number to __________ in the zygote.
diploid (2n)
The zygote is the first __________ cell of a developing organism.
diploid
Mitosis results in ___ genetically __________ cells.
2; identical
Meiosis results in ___ genetically __________ cells.
4; unique
Mitosis is used for __________, __________, and asexual reproduction.
growth; repair
Meiosis is used for producing __________ for sexual reproduction.
gametes
Cells produced by mitosis are __________
diploid (2n)
Cells produced by meiosis are __________
haploid (n)
Meiosis introduces genetic variation through __________ and __________.
crossing over; independent assortment
Mitosis has how many cell divisions? ___
1
Meiosis has how many cell divisions? ___
2
In meiosis, homologous chromosomes separate during Meiosis ___.
I (Meiosis I)
In meiosis, sister chromatids separate during Meiosis ___.
II (Meiosis II)
Crossing over occurs during __________ of meiosis.
Prophase I
The resulting cells of meiosis are genetically __________ from the parent and each other.
different
Mitosis occurs in __________ cells.
somatic (body)
Meiosis occurs in __________ cells.
germ (sex)
All eukaryotic sexual life cycles include:
a) Mitosis, gamete formation, and fertilization.
b) Mitosis, meiosis, gamete formation, and fertilization.
c) Mitosis, meiosis, and gamete formation.
d) Mitosis, fertilization, and meiosis.
e) Mitosis, meiosis, apoptosis.
f) Gamete formation, meiosis, mitosis.
A: b) Mitosis, meiosis, gamete formation, and fertilization.
Before meiosis, a diploid cell must replicate its DNA & make proteins in:
Interphase
Meiosis starts with a diploid ______ cell and ends with _____ genetically diverse ______ gametes.
germ; 4; haploid
Specialized cells that are the precursor for making gametes.
germ cell
In Meiosis I, cytokinesis after telophase I produces:
Two haploid cells
In Meiosis II, ________ cells are divided into 4 ___________ daughter cells.
haploid, haploid
In Meiosis I, cytokinesis usually occurs after telophase I and produces:
two haploid daughter cells
the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.
cytokinesis
●Meiosis I
□ In Metaphase I, homologous chromosomes are paired & aligned in ______ rows in the middle of the cell.
□ In Anaphase I, ____________________ chromosomes are separated while sister chromatids remain connected.
□ After Telophase I, cytokinesis produces _____ haploid (n) daughter cells that can then begin _____.
●Meiosis I
□ In Metaphase I, homologous chromosomes are paired & aligned in two rows in the middle of the cell.
□ In Anaphase I, homologous chromosomes are separated while sister chromatids remain connected.
□ After Telophase I, cytokinesis produces 2 haploid (n) daughter cells that can then begin Meiosis II.
A daughter cell is created by meiosis I and the first round of cytokinesis. This daughter cell is just beginning meiosis II. Which of the following is an appropriate description of this daughter cell’s genetic contents?
a) It has half the amount of DNA as the parent cell.
b) It has half the chromosomes but twice the DNA of the parent cell.
c) It has one-fourth the DNA and one-half the chromosomes as the parent cell.
d) It is genetically identical to the parent cell.
a) It has half the amount of DNA as the parent cell.
In Meiosis II, each haploid cell produced in Meiosis I divides, forming 4 genetically ____, haploid gametes.
diverse
Meiosis II is almost exactly the same as _____.
□ Similar to ____, chromosomes align in 1 row in Metaphase II.
□ Also, similar to _____, sister chromatids are divided in Anaphase II.
Mitosis
A major difference between meiosis II and mitosis in a diploid animal is:
Meiosis II occurs in a ____ cell, while mitosis occurs in ____ cells.
haploid, diploid
During which of the following stages of meiosis do homologous chromosomes pair up and align along the metaphase plate of the cell?
Metaphase I of meiosis
What separates during Anaphase II?
Sister chromatids
Which of the following statements describes a difference between mitosis and meiosis I in a diploid organism?
a) Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.
b) Sister chromatids separate in mitosis and in meiosis I.
c) DNA replication takes place prior to mitosis, but not before meiosis I.
d) Only meiosis I results in daughter cells that contain identical genetic information.
a) Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.
During which of the following processes do sister chromatids separate from each other?
a) During meiosis I only.
b) During meiosis II only.
c) During both mitosis and meiosis I.
d) During both mitosis and meiosis II.
d) During both mitosis and meiosis II.
Which of the following statements describes a difference between meiosis II and mitosis in a diploid organism?
a) Sister chromatids align along the metaphase plate in mitosis while homologous chromosomes align in meiosis II.
b) Sister chromatids separate in mitosis and homologous chromosomes separate in meiosis II.
c) Meiosis II occurs in a haploid cell, while mitosis occurs in a diploid cell.
d) Crossing over of chromosomes takes place in meiosis II and does not take place in mitosis.
c) Meiosis II occurs in a haploid cell, while mitosis occurs in a diploid cell.
Which of the following processes occurs in meiosis but not in mitosis?
a) Chromosome replication during interphase.
b) Synapsis of chromosomes during prophase.
c) Alignment of chromosomes at the center of the cell.
d) Condensation of chromosomes during prophase.
e) None of the above.
b) Synapsis of chromosomes during prophase.
What does it mean when we say that mitosis and meiosis II are forms of “equational division” while meiosis I is
a form a) b) c)
d) e) f)
of “reductional division”?
Daughter cells of mitosis and meiosis II are both diploid while the daughter cells of meiosis I are haploid.
The number of chromosomes in daughter cells of meiosis I is half the number of chromosomes of the parent cell. The number of chromosomes in daughter cells of mitosis and meiosis II is equal to the number of chromosomes in the parent cells.
AandB.
BandC.
All of the above.
Answer: A and B.
Daughter cells of mitosis and meiosis II are both diploid, while the daughter cells of meiosis I are haploid. The number of chromosomes in daughter cells of meiosis I is half the number of chromosomes of the parent cell. The number of chromosomes in daughter cells of mitosis and meiosis II is equal to the number of chromosomes in the parent cells.
Which of the following processes occurs when homologous chromosomes cross over in meiosis I?
a) Two sister chromatids get tangled, resulting in one re-sequencing its DNA.
b) Two sister chromatids exchange identical pieces of DNA.
c) Maternal alleles are “corrected” to be like paternal alleles and vice versa.
d) Corresponding segments of non-sister chromatids from homologous chromosomes are exchanged.
d) Corresponding segments of non-sister chromatids from homologous chromosomes are exchanged.
Crossing over involves each of the following EXCEPT:
a) The transfer of DNA between two non-sister chromatids.
b) The transfer of DNA between two sister chromatids.
c) The formation of a synaptonemal complex.
d) The alignment of homologous chromosomes.
e) All of the above are involved in crossing over.
b) The transfer of DNA between two sister chromatids.
Meiosis creates genetic diversity via two events:
Crossing Over & Independent Assortment.
____ _____: process in which pairs of homologous chromosomes exchange genetic material.
□ Forms non-identical sister chromatids during Prophase I of meiosis I.
□ Synapsis: process where homologous pairs align their DNA sequence at similar alleles.
□ Chiasma: sites of crossing over (attachment sites) between homologous chromosomes.
Crossing Over: process in which pairs of homologous chromosomes exchange genetic material.
□ Forms non-identical sister chromatids during Prophase I of meiosis I.
□ Synapsis: process where homologous pairs align their DNA sequence at similar alleles.
□ Chiasma: sites of crossing over (attachment sites) between homologous chromosomes.
a process where homologous pairs align their DNA sequence at similar alleles. (part of crossing over)
Synapsis
sites of crossing over (attachment sites) between homologous chromosomes.
Chiasma
process in which pairs of homologous chromosomes exchange genetic material.
Crossing Over
Which of the following processes occurs when homologous chromosomes cross over in meiosis I?
a) Two sister chromatids get tangled, resulting in one re-sequencing its DNA.
b) Two sister chromatids exchange identical pieces of DNA.
c) Maternal alleles are “corrected” to be like paternal alleles and vice versa.
d) Corresponding segments of non-sister chromatids from homologous chromosomes are exchanged.
d) Corresponding segments of non-sister chromatids from homologous chromosomes are exchanged.
Crossing over involves each of the following EXCEPT:
a) The transfer of DNA between two non-sister chromatids.
b) The transfer of DNA between two sister chromatids.
c) The formation of a synaptonemal complex.
d) The alignment of homologous chromosomes.
e) All of the above are involved in crossing over.
b) The transfer of DNA between two sister chromatids.
Independent Assortment
●During _________________ I, pairs of homologous chromosomes are independently & _______________ aligned.
□ Results in an ENORMOUS amount of possible genetic _______________________ during meiosis. □ To calculate # of combinations, use the equation ______ (n = haploid # of chromosomes).
During Metaphase I, pairs of homologous chromosomes are independently & randomly aligned.
□ Results in an ENORMOUS amount of possible genetic combinations during meiosis.
□ To calculate # of combinations, use the equation 2ⁿ (n = haploid # of chromosomes).
For a species with a haploid number of 23 chromosomes, how many combinations of maternal and paternal chromosomes are possible for the gametes based on the independent assortment of chromosomes during meiosis?
a) 23.
b) 46.
c) About 1,000.
d) About 8 million.
✅ d) About 8 million. (because 2²³ ≈ 8.4 million)
How many genetically unique gametes can be created in an organism with 4 chromosomes?
a) 256.
b) 23.
c) 16.
d) 1 million.
e) 4.
✅ c) 16. (because 2⁴ = 16)
During which of the following processes does independent assortment of chromosomes occur?
a) In meiosis I only.
b) In meiosis II only.
c) In mitosis and meiosis I.
d) In mitosis and meiosis II.
e) In meiosis I and meiosis II.
✅ a) In meiosis I only.
Independent assortment occurs during Metaphase I when homologous chromosome pairs line up randomly at the metaphase plate. It does not occur in meiosis II or mitosis because those involve separation of sister chromatids, not homologous pairs.
Independent assortment of chromosomes is a result of which of the following processes?
a) The random way each pair of homologous chromosomes lines up at the metaphase plate.
b) The random combinations of eggs and sperm during fertilization.
c) The random distribution of the sister chromatids into the two daughter cells.
d) The diverse combination of alleles that may be found within any given chromosome.
a) The random way each pair of homologous chromosomes lines up at the metaphase plate.
This random alignment leads to different combinations of maternal and paternal chromosomes in gametes — the basis of independent assortment.
Nondisjunction
●An ERROR during meiosis I or II when chromosomes ___________ to separate, resulting in aneuploid cells. □ _____________________ Cells: cells containing either too many or too few chromosomes.
□ Can lead to genetic disorders (ex. trisomy-21/Down-Syndrome) or even cell death.
● An ERROR during meiosis I or II when chromosomes fail to separate, resulting in aneuploid cells.
□ Aneuploid Cells: cells containing either too many or too few chromosomes.
□ Can lead to genetic disorders (ex. trisomy-21/Down syndrome) or even cell death.
Non-disjunction means that chromosomes:
d) Do not separate correctly from one another during anaphase.
the chromosomes fail to separate properly during anaphase of meiosis I or II.
________ cells have an extra or missing chromosomes after meiosis due to nondisjunction during Meiosis I.
d) Aneuploid Cells.
“Aneuploid” describes any cell with an abnormal number of chromosomes, often caused by nondisjunction
The location of a gene on a chromosome
locus
A specific sequence of DNA (A, T, C, G) that codes for a protein or trait.
gene
How many alleles for each gene does a diploid organism have?
Two—one from each parent.
What is the purpose of crossing over?
To exchange DNA between homologous chromosomes and increase genetic variation.
During which phase does crossing over occur?
Prophase I of Meiosis.
How does asexual reproduction differ from sexual reproduction in terms of genetic variation?
Asexual creates identical offspring (no variation), sexual creates genetically unique offspring.
What is the overall goal of meiosis?
To produce four non-identical haploid (n) cells from one diploid (2n) parent.
Where does meiosis occur?
In reproductive cells (e.g., testes and ovaries).
___________ occurs during Prophase I of meiosis and mixes alleles between homologous chromosomes.
crossing over
Asexual reproduction involves ______ parent and produces genetically __________ offspring.
One; identical
Sexual reproduction involves ______ parents and produces genetically __________ offspring.
Two; unique/non-identical
The purpose of meiosis is to reduce chromosome number from _____ to _____.
→ 2n to 1n
What happens during Interphase before Meiosis I?
DNA replicates and the cell prepares for division.
What forms during Prophase I as homologous chromosomes pair up?
Tetrads (bivalents).
What process increases genetic diversity during Prophase I?
Crossing over during the pachytene substage.
What aligns during Metaphase I?
Homologous chromosomes (tetrads) at the metaphase plate.
What is pulled apart during Anaphase I?
Homologous chromosomes (sister chromatids stay attached).
What is the result of Telophase I and Cytokinesis?
Two haploid cells, each with duplicated chromosomes (sister chromatids).
What happens in Prophase II?
Chromosomes begin to align again—no crossing over.
What aligns during Metaphase II?
Chromosomes made of sister chromatids.
What separates during Anaphase II?
Sister chromatids (now considered individual chromosomes).
