Meiosis
1.1 Introduction
Meiosis is the division of a somatic cell in order to form sex cells.
It follows interphase in the cell cycle and occurs during gametogenesis.
Somatic cell- a cell that contains a full set of chromosomes required to create a living organism.
In humans it occurs in testes and ovaries.
1.2 The Chromosome
A chromosome is a unit of inheritance that carries genetic information. It consists of DNA and protein.
An image showing how chromosomes are arranged is known as a karyotype. It shows 23 sets of
chromosomes. The first 22 sets are known as autosomes (non-sex) and the last set are known as
gonosomes (sex chromosomes).
1.3 The process of meiosis
Meiosis is divided into 2 stages; Meiosis 1 and Meiosis 2; both of which are divided into 4 phases,
namely: Prophase, Metaphase, Anaphase and Telophase.
Interphase:
DNA Replication takes place here.
Each chromosome is replicated.
MEIOSIS I
Prophase 1
Chromatin network unwinds.
Chromosomes condense and become more visible.
Chromosomes come together to form bivalent homologous Chromosomes.
Spindle fibres form.
Crossing over takes place between homologous chromosomes.
, Crossing over- the process whereby non sister chromatids overlap and chromatid segments
are exchanged at a point called the chiasma.
Metaphase 1
M for middle of the cell.
Homologous chromosomes align randomly at the cell’s equator.
Spindle fibres attach to the controversial of the chromosomes.
Anaphase 1
A for apart.
Spindle fibres start to shorten.
Homologous chromosomes are separated and pulled towards opposite poles of the cell.
Telophase 1
1.1 Introduction
Meiosis is the division of a somatic cell in order to form sex cells.
It follows interphase in the cell cycle and occurs during gametogenesis.
Somatic cell- a cell that contains a full set of chromosomes required to create a living organism.
In humans it occurs in testes and ovaries.
1.2 The Chromosome
A chromosome is a unit of inheritance that carries genetic information. It consists of DNA and protein.
An image showing how chromosomes are arranged is known as a karyotype. It shows 23 sets of
chromosomes. The first 22 sets are known as autosomes (non-sex) and the last set are known as
gonosomes (sex chromosomes).
1.3 The process of meiosis
Meiosis is divided into 2 stages; Meiosis 1 and Meiosis 2; both of which are divided into 4 phases,
namely: Prophase, Metaphase, Anaphase and Telophase.
Interphase:
DNA Replication takes place here.
Each chromosome is replicated.
MEIOSIS I
Prophase 1
Chromatin network unwinds.
Chromosomes condense and become more visible.
Chromosomes come together to form bivalent homologous Chromosomes.
Spindle fibres form.
Crossing over takes place between homologous chromosomes.
, Crossing over- the process whereby non sister chromatids overlap and chromatid segments
are exchanged at a point called the chiasma.
Metaphase 1
M for middle of the cell.
Homologous chromosomes align randomly at the cell’s equator.
Spindle fibres attach to the controversial of the chromosomes.
Anaphase 1
A for apart.
Spindle fibres start to shorten.
Homologous chromosomes are separated and pulled towards opposite poles of the cell.
Telophase 1
