Summary by: Kaylin Teneal
Chromosomes
Are long, thread-like structures that form part of the chromatin network in the nuclei of cells. Made up of a
strand of DNA wound around proteins.
In somatic (body) cells of diploid organism:
→ Number of chromosomes is the same
→ Diploid (two sets of chromosomes): mother (maternal chromosome) and father (paternal
chromosome)
→ Paternal chromosome & maternal chromosome = homologous pair
→ DNA of each chromosome replicates to from two identical threads or chromatids joined by a
centromere.
Meiosis
DEFINITIONS:
Is cell division in the reproductive organs to produce gametes (sex cells)
DIPLOID – two sets of
chromosomes in a cell
→ Number of chromosomes is reduced from two sets (2n) to one set (n)
→ Gametes/spores formed are called haploid (one set of chromosomes)
HAPLOID – one set of
chromosomes in a cell
Male haploid gamete & female haploid gamete fuse during fertilization and form
a diploid zygote.
SPERMATOGENESIS – formation of sperm cells in testis
OOGENESIS – formation of egg cells / ova in the ovaries
MICROSPORANGIA – pollen sacs in the male anthers
MEGASPORANGIA – ovules in the female ovaries
Importance:
1. Form gametes
2. Chromosome number is kept constant from generation to generation
3. Creates variation through crossing over and random arrangement of chromosomes
, Summary by: Kaylin Teneal
PROCESS OF MEIOSIS
Prophase
Metaphase
Anaphase
Telophase
Meiosis 1 results in two cells
Meiosis 2 results in four cells
MEIOSIS 1 – a reduction division
Prophase 1:
1. Nuclear membrane disappears
2. Chromatin network unwinds and forms chromosomes in homologous pairs
3. Crossing-over takes place (results in the exchange of genetic material)
4. Centrosome splits into two centrioles
Metaphase 1: PROPHASE 1
1. Spindle threads form between centrioles
2. Chromosomes move to the equator in homologous pairs and are attached to
spindle threads
Anaphase 1: METAPHASE 1
1. Spindle threads contract
Chromosomes
Are long, thread-like structures that form part of the chromatin network in the nuclei of cells. Made up of a
strand of DNA wound around proteins.
In somatic (body) cells of diploid organism:
→ Number of chromosomes is the same
→ Diploid (two sets of chromosomes): mother (maternal chromosome) and father (paternal
chromosome)
→ Paternal chromosome & maternal chromosome = homologous pair
→ DNA of each chromosome replicates to from two identical threads or chromatids joined by a
centromere.
Meiosis
DEFINITIONS:
Is cell division in the reproductive organs to produce gametes (sex cells)
DIPLOID – two sets of
chromosomes in a cell
→ Number of chromosomes is reduced from two sets (2n) to one set (n)
→ Gametes/spores formed are called haploid (one set of chromosomes)
HAPLOID – one set of
chromosomes in a cell
Male haploid gamete & female haploid gamete fuse during fertilization and form
a diploid zygote.
SPERMATOGENESIS – formation of sperm cells in testis
OOGENESIS – formation of egg cells / ova in the ovaries
MICROSPORANGIA – pollen sacs in the male anthers
MEGASPORANGIA – ovules in the female ovaries
Importance:
1. Form gametes
2. Chromosome number is kept constant from generation to generation
3. Creates variation through crossing over and random arrangement of chromosomes
, Summary by: Kaylin Teneal
PROCESS OF MEIOSIS
Prophase
Metaphase
Anaphase
Telophase
Meiosis 1 results in two cells
Meiosis 2 results in four cells
MEIOSIS 1 – a reduction division
Prophase 1:
1. Nuclear membrane disappears
2. Chromatin network unwinds and forms chromosomes in homologous pairs
3. Crossing-over takes place (results in the exchange of genetic material)
4. Centrosome splits into two centrioles
Metaphase 1: PROPHASE 1
1. Spindle threads form between centrioles
2. Chromosomes move to the equator in homologous pairs and are attached to
spindle threads
Anaphase 1: METAPHASE 1
1. Spindle threads contract
