Meio sis
Cells, Nucleus, Chromosomes
Chromosomes
Made up of a DNA wrapped around histone proteins
Each organism has 2 sets of chromosomes,
this is known as the diploid condition (2n).
The gamete each only had one set of chromosomes and are called haploid (n).
Gametes are produced during meiosis of diploid cells.
During meiosis the number of chromosomes is halved.
Meiosis only takes place in the ovaries and testes of animals and in the ovaries and
anthers of plants.
In humans there are 22 pairs of chromosomes (autosomes) plus one pair of sex
chromosomes.
There are two types of sex chromosomes (gonosomes): X and Y.
Females have two X chromosomes (XX)
Males have an X and Y chromosome (XY).
Pairs of chromosomes, one form each parent are called
= homologous chromosomes because they both carry genes that control the same
characteristics.
Chromatin network The chromatin is the network of the cell nucleus, which contains
all the DNA of the nucleus of the cell.
Chromatid One of two identical halves of a replicated chromosome
Chromosome Thread-like structure of DNA (nucleic acids and proteins) that carries
genes
Gene Unit of hereditary information that occupies a fixed position on a
chromosome
Karyotyping
A karyotype represents a set of chromosomes in an organism, usually in a picture/
diagram form.
It shows the number, size and shape of the
chromosomes during metaphase of mitosis.
, How is a karyotype produced?
• A high-magnification print of a complete set of chromosomes is made as early on in
mitosis as possible. A set with minimum overlap is best to avoid confusion.
• Late prophase & metaphase will provide clearest view as the chromosomes are in a
replicated & condensed state. Nuclear membrane is not visible so chromosomes have
been ‘released’ into cytoplasm & will be spread out, not tangled up together.
• Chromosomes and cut out & arranged in order of decreasing order of length from left -
right on paper.
• The chromosomes are arranged in identical pairs (a diploid cell) according to their
length & position of centromere (while crossing over in adult is random, position of
centromere in any given individual is not). Short arm of chromosome is uppermost &
centromeres kept in line.
• Chromosomes are pasted onto paper
• Chromosome pairs are numbered, and the karyotype headed.
• Once done, sex and chromosomal abnormalities of the child can be determined.
Recap of Mitosis + How is it different to Meiosis
Meiosis is different because its purpose is to
create sex cells/gametes, also known as
sperm and egg (ova) cells.
The importance with this kind of division is
we need half the number of chromosomes
in the cells that are produced.
During sexual reproduction the sperm and
ova fuse to form a zygote, this process is
known as fertilisation.
The zygote will become a new organism.
The zygote will contain a full set of
chromosomes, half from mom and half from
dad.
Basically, in a pair of homologous
chromosomes the zygote will receive one of
the pair from mom and the other from dad.
Meiosis is important - it ensures all organisms
produced via sexual reproduction contain correct Occurs during the formation of the
number of chromosomes. Meiosis also produces reproductive cells, or gametes, of
genetic variation by process of recombination. sexually reproducing organisms
Cells, Nucleus, Chromosomes
Chromosomes
Made up of a DNA wrapped around histone proteins
Each organism has 2 sets of chromosomes,
this is known as the diploid condition (2n).
The gamete each only had one set of chromosomes and are called haploid (n).
Gametes are produced during meiosis of diploid cells.
During meiosis the number of chromosomes is halved.
Meiosis only takes place in the ovaries and testes of animals and in the ovaries and
anthers of plants.
In humans there are 22 pairs of chromosomes (autosomes) plus one pair of sex
chromosomes.
There are two types of sex chromosomes (gonosomes): X and Y.
Females have two X chromosomes (XX)
Males have an X and Y chromosome (XY).
Pairs of chromosomes, one form each parent are called
= homologous chromosomes because they both carry genes that control the same
characteristics.
Chromatin network The chromatin is the network of the cell nucleus, which contains
all the DNA of the nucleus of the cell.
Chromatid One of two identical halves of a replicated chromosome
Chromosome Thread-like structure of DNA (nucleic acids and proteins) that carries
genes
Gene Unit of hereditary information that occupies a fixed position on a
chromosome
Karyotyping
A karyotype represents a set of chromosomes in an organism, usually in a picture/
diagram form.
It shows the number, size and shape of the
chromosomes during metaphase of mitosis.
, How is a karyotype produced?
• A high-magnification print of a complete set of chromosomes is made as early on in
mitosis as possible. A set with minimum overlap is best to avoid confusion.
• Late prophase & metaphase will provide clearest view as the chromosomes are in a
replicated & condensed state. Nuclear membrane is not visible so chromosomes have
been ‘released’ into cytoplasm & will be spread out, not tangled up together.
• Chromosomes and cut out & arranged in order of decreasing order of length from left -
right on paper.
• The chromosomes are arranged in identical pairs (a diploid cell) according to their
length & position of centromere (while crossing over in adult is random, position of
centromere in any given individual is not). Short arm of chromosome is uppermost &
centromeres kept in line.
• Chromosomes are pasted onto paper
• Chromosome pairs are numbered, and the karyotype headed.
• Once done, sex and chromosomal abnormalities of the child can be determined.
Recap of Mitosis + How is it different to Meiosis
Meiosis is different because its purpose is to
create sex cells/gametes, also known as
sperm and egg (ova) cells.
The importance with this kind of division is
we need half the number of chromosomes
in the cells that are produced.
During sexual reproduction the sperm and
ova fuse to form a zygote, this process is
known as fertilisation.
The zygote will become a new organism.
The zygote will contain a full set of
chromosomes, half from mom and half from
dad.
Basically, in a pair of homologous
chromosomes the zygote will receive one of
the pair from mom and the other from dad.
Meiosis is important - it ensures all organisms
produced via sexual reproduction contain correct Occurs during the formation of the
number of chromosomes. Meiosis also produces reproductive cells, or gametes, of
genetic variation by process of recombination. sexually reproducing organisms
