PRELIM LEC 4: MEIOSIS Flashcards
first cells that leads the development
of a new individual
GAMETES
FUNCTIONS OF REPRODUCTIVE SYSTEM
- Production of gametes
- Fertilization
- Development and nourishment of individual
- Production of reproductive hormones
- Two divisions
- Four daughter cells per cycle
- Daughter cells genetically different
- Chromosome number of daughter cells half that of parent cell (1n)
- Occurs in germline cells
- In humans, completes after sexual maturity
- Used for sexual reproduction, producing new gene combinations
MITOSIS OR MEIOSIS?
MEIOSIS
- One division
- Two daughter cells per cycle
- Daughter cells genetically identical
- Chromosome number of daughter cells same as that of parent cell (2n)
- Occurs in somatic cells
- Occurs throughout life cycle
- Used for growth, repair, and asexual reproduction
MITOSIS OR MEIOSIS?
MITOSIS
- Reproductive cell division that occurs in the gonads
-produces gametes in which the number of chromosomes is reduced by half
-Gametes contain 23 different chromosomes - Without _____, the sperm and oocyte would each contain 46 chromosomes, and the fertilized ovum would have twice the normal number of chromosomes
- Produces gametes and mixes up trait combination
MEIOSIS
In meiosis, gametes contain ______ different chromosomes
23
Without meiosis, the sperm and oocyte would each
contain ___ chromosomes, and the fertilized ovum would have twice the normal number of chromosome
46
- Such a genetically overloaded cell
- Usually undergoes only a few cell divisions before stopping.
POLYPLOID
In addition to producing gametes, meiosis mixes up
trait combinations.
T OR F?
TRUE
Meiosis explains why siblings differ genetically from each other and from their parents
T OR F?
TRUE
- reduces the number of replicated chromosomes from 46 to 23.
A Meiosis I: reduction division
B Meiosis II: equational division
A Meiosis I: reduction division
- produces four cells from the two cells formed in the first division by splitting the replicated chromosomes
A Meiosis I: reduction division
B Meiosis II: equational division
B Meiosis II: equational division
MEIOSIS 1 STAGES
PROPHASE I
METAPHASE I
ANAPHASE I
TELOPHASE I
CYTOKINESIS
begins as the replicated chromosomes condense and become visible when stained
A Metaphase I
B Anaphase I
C Prophase I
D Telophase I
C Prophase I
5 STAGES OF PROPHASE 1
-chromosomes condense
-homologous chromosomes START TO PAIR UP
-nuclear envelope begins to break down
A Leptotene (Leptonema)
B Zygotene (Zygonema)
C Pachytene (Pachynema)
D Diplotene (Diplonema)
E Diakinesis
A Leptotene (Leptonema)
5 STAGES OF PROPHASE 1
- homologous chromosomes CONTINUE TO PAIR UP
- forming synaptonemal complexes (synapsis)
A Leptotene (Leptonema) Diakinesis
B Zygotene (Zygonema)
C Pachytene (Pachynema)
D Diplotene (Diplonema)
E Diakinesis
B Zygotene (Zygonema)
5 STAGES OF PROPHASE 1
-homologous chromosomes become FULLY PAIRED
-genetic recombination occurs
-crossing over occurs
-each homologs bear genes from each parent
A Leptotene (Leptonema) Diakinesis
B Zygotene (Zygonema)
C Pachytene (Pachynema)
D Diplotene (Diplonema)
E Diakinesis
C Pachytene (Pachynema)
5 STAGES OF PROPHASE 1
- synaptonemal complexes start to dissolve
- but homologous chromosomes remain attached to
points called chiasmata
- chromosomes continue to condense
A Leptotene (Leptonema) Diakinesis
B Zygotene (Zygonema)
C Pachytene (Pachynema)
D Diplotene (Diplonema)
E Diakinesis
D Diplotene (Diplonema)
5 STAGES OF PROPHASE 1
-chromosomes further condense
-nuclear envelope breaks down completely
-spindle apparatus starts to form
A Leptotene (Leptonema) Diakinesis
B Zygotene (Zygonema)
C Pachytene (Pachynema)
D Diplotene (Diplonema)
E Diakinesis
E Diakinesis
Homologous chromosome pairs align along the equatorial plane (metaphase plate) of the cell
The spindle fibers from opposite poles
attach to each homologous chromosome, specifically to the protein structures (kinetochores)
Random alignment of chromosomes causes independent assortment of the genes that they carry
A Metaphase I
B Anaphase I
C Prophase I
D Telophase I
A Metaphase I
(The greater the number of chromosomes, the greater the genetic diversity is generated)
T OR F?
TRUE
Homologous chromosomes separate and migrate toward opposite poles of the cell (disjunction)
Sister chromatids remain attached to each other.
A Metaphase I
B Anaphase I
C Prophase I
D Telophase I
B Anaphase I
Chromosomes reach their respective poles
Nuclear envelope starts to form around each set of chromosomes
A Metaphase I
B Anaphase I
C Prophase I
D Telophase I
D Telophase I
cell divides into 2 daughter cells
CYTOKINESIS
