15: Meiosis Flashcards
Module 3, Lesson 4
For organisms that perform sexual reproduction, genetic information can be passed on via cycles of ____ and ____.
Meiosis and fertilization
Meiosis often involves transitions between ____ and ____ states.
Diploid and haploid
Most animal cells are…
Diploid
Diploid ____ cells perform meiosis.
Germline
The end product of meiosis is ____.
Gametes
Are gametes haploid or diploid?
Haploid
During sexual reproduction, gametes fuse to produce…
A zygote
Are zygotes haploid or diploid?
Diploid
A zygote contains both a ____ homologue and a ____ homologue.
Maternal ; paternal
A zygote becomes a multicellular organism through the process of…
Mitosis
List three ways in which mitosis and meiosis are similar.
- Both use a microtubule-based spindle machine
- Both segregate condensed DNA molecules into two daughter cells
- Both include prophase, metaphase, anaphase, and telophase
List the four phases of division that are common to both mitosis and meiosis.
- Prophase
- Metaphase
- Anaphase
- Telophase
List three features of meiosis that are distinct from mitosis.
- Two rounds of division, but only one round of DNA replication
- Synapsis
- Crossing over
List the three main phases of meiosis.
- DNA replication
- Meiosis I (first division)
- Meiosis II (second division)
Through the process of meiosis I, a diploid germ cell splits into…
Two haploid daughter cells
The cells produced in meiosis I have ____ copy(ies) of each chromosome.
2
True or false:
The daughter cells replicate their DNA before entering meiosis II.
False
These cells suppress their DNA replication.
The daughter cells produced in meiosis II have ____ copy(ies) of each chromosome.
1
A tight association between homologous pairs is called…
Synapsis
The process by which homologues can exchange segments of their DNA is called…
Crossing over
During which phase of meiosis does synapsis occur?
Early prophase 1
(in meiosis I)
During synapsis, the homologous chromosomes form a structure called the…
Synaptonemal complex
The synaptonemal complex is also called…
A tetrad or a bivalent
How does the synaptonemal complex associate chromosomes?
It pairs them along their length using a matrix of connecting proteins
Crossing over is possible due to…
Synapsis
True or false:
Crossing over can only occur between sister chromatids.
False
It allows genetic recombination between non-sister chromatids
True or false
Because of crossing-over, alleles of genes that were on separate homologues can end up on the same homologue.
True
The site where crossing over takes place is called…
Chiasmata
Crossing over generally occus during…
Prophase 1
Chromosomes remain connected due to synapsis until…
Anaphase 1
True or false:
Meiotic cells do not go through interphase.
False
Meiotic cells do have an interphase (G1, S, and G2) period.
What occurs during prophase 1?
(three)
- Homologous chromosomes associate (synapsis)
- Cross-over events occur
- Microtubules from opposite poles attach to each homologue
What occurs during metaphase 1?
(one)
Bivalents congress to the metaphase plate
The orientation of homologues on the metaphase plate is random, so…
Different combinations of maternal and paternal homologues can be attached to each spindle pole
What happens during anaphase 1?
(one)
Homologues of each pair separate
During anaphase 1, what happens to the sister chromatids?
They remain connected
What happens during telophase 1?
The homologues move to opposite poles
After the completion of meiosis I, the two haploid cells formed have…
Different combinations of maternal and paternal homologues
The varied genetic makeup of the daughter cells produced in meiosis I is known as…
Independent assortment
True or false:
After meiosis I, the sister chromatids are identical.
False
Due to cross-over events, they may no longer be identical.
Meiosis I is often called…
“Reduction division”
Meiosis results in a ____ of chromosomes for each daughter cell.
Loss
How long after meiosis I ends does meiois II begin?
It varies
Meiosis II closely resembles ____ division.
Mitotic
During meiosis II, the ____ are separated.
Sister chromatids
Each daughter cell produced in meiosis II has one random chromosome from…
Each homologous pair
True or false:
The daughter cells produced in meiosis II are genetically identical.
False
Each cell contains a different set of parental genes.
True or false:
In animal cells, daughter cells develop into gametes immediately after the completion of meiosis II.
True
True or false:
In plants, fungi, and protists; daughter cells develop into gametes immediately after the completion of meiosis II.
False
These cells reproduce mitotically to increase their numbers before developing into gametes.
____ occurs when chromosomes fail to move to opposite poles during either meiosis I or meiosis II.
Nondisjunction
Nondisjunction results in ____ gametes, which have missing or extra chromosomes.
Aneuploid
____ is the most common cause of spontaneous abortion in humans.
Note: spontaneous abortion is when the embryo just dies without any external influence. This is what causes miscarriages.
Nondisjunction
This is because having the wrong number of chromosomes is usually fatal to the cell. Exceptions would be things like Down Syndrome.
From a species viewpoint, the benefit of increased genetic variation ____ the chance and impact of negative errors.
Far outweighs
After meiosis is complete, a single parent cell has split into ____ daughter cells.
Four
