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Mind Map by killthemoment, updated more than 1 year ago
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Created by killthemoment
over 9 years ago
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B2.7 Cell Division And Inheritance
- B2.7.1 Cell Division
- In body cells the chromosomes are normally
found in pairs. Body cells divide by mitosis.
- The chromosomes contain
the genetic information.
- When a body cell divides by
mitosis copies of the genetic
material are made and then
the cell divides once to form
two genetically identical body
cells
- Mitosis occurs during growth or to produce replacement cells.
- Body cells have two sets of chromosomes;
sex cells (gametes) have only one set.
- Cells in reproductive organs – testes and ovaries in humans – divide to form gametes.
- The type of cell division in which
a cell divides to form gametes is
called meiosis.
- When a cell divides to form gametes copies of the genetic information are made and then
the cell divides twice to form four gametes, each with a single set of chromosomes.
- When gametes join at fertilisation, a single body cell with
new pairs of chromosomes is formed. A new individual
then develops by this cell repeatedly dividing by mitosis.
- Most types of animal cells
differentiate at an early stage
whereas many plant cells are
pluripotent and so retain the
ability to differentiate throughout
life. In mature animals, cell
division is mainly restricted to
repair and replacement.
- Cells from human embryos and adult bone marrow, called stem
cells, can be made to differentiate into many different types of cells.
- Human stem cells have the
ability to develop into any
kind of human cell.
- Treatment with stem
cells may be able to
help conditions such
as paralysis.
- The cells of the offspring produced by asexual reproduction
are produced by mitosis from the parental cells. They contain
the same alleles as the parents.
- The cells of the offspring produced by asexual reproduction
are produced by mitosis from the parental cells. They contain
the same alleles as the parents.
- Treatment with stem
cells may be able to
help conditions such
as paralysis.
- Human stem cells have the
ability to develop into any
kind of human cell.
- Cells from human embryos and adult bone marrow, called stem
cells, can be made to differentiate into many different types of cells.
- Most types of animal cells
differentiate at an early stage
whereas many plant cells are
pluripotent and so retain the
ability to differentiate throughout
life. In mature animals, cell
division is mainly restricted to
repair and replacement.
- When gametes join at fertilisation, a single body cell with
new pairs of chromosomes is formed. A new individual
then develops by this cell repeatedly dividing by mitosis.
- When a cell divides to form gametes copies of the genetic information are made and then
the cell divides twice to form four gametes, each with a single set of chromosomes.
- The type of cell division in which
a cell divides to form gametes is
called meiosis.
- Cells in reproductive organs – testes and ovaries in humans – divide to form gametes.
- Body cells have two sets of chromosomes;
sex cells (gametes) have only one set.
- Mitosis occurs during growth or to produce replacement cells.
- When a body cell divides by
mitosis copies of the genetic
material are made and then
the cell divides once to form
two genetically identical body
cells
- The chromosomes contain
the genetic information.
- In body cells the chromosomes are normally
found in pairs. Body cells divide by mitosis.
- B2.7.2 Genetic Variation
- Sexual reproduction gives rise to variation because, when gametes
fuse, one of each pair of alleles comes from each parent.
- In human body cells, one of the 23 pairs of chromosomes carries
the genes that determine sex. In females the sex chromosomes are
the same (XX); in males the sex chromosomes are different (XY).
- Some characteristics are
controlled by a single gene.
Each gene may have
different forms called alleles.
- An allele that controls the
development of a characteristic
when it is present on only one
of the chromosomes is a
dominant allele.
- An allele that controls the
development of
characteristics only if the
dominant allele is not
present is a recessive allele.
- Chromosomes are made up of large
molecules of DNA (deoxyribo nucleic
acid) which has a double helix structure.
- A gene is a small section of DNA.
- Each gene codes for a particular combination of
amino acids which make a specific protein.
- Each person (apart from identical twins) has unique DNA.
This can be used to identify individuals in a process
known as DNA fingerprinting.
- Each person (apart from identical twins) has unique DNA.
This can be used to identify individuals in a process
known as DNA fingerprinting.
- Each gene codes for a particular combination of
amino acids which make a specific protein.
- A gene is a small section of DNA.
- Chromosomes are made up of large
molecules of DNA (deoxyribo nucleic
acid) which has a double helix structure.
- An allele that controls the
development of
characteristics only if the
dominant allele is not
present is a recessive allele.
- An allele that controls the
development of a characteristic
when it is present on only one
of the chromosomes is a
dominant allele.
- Some characteristics are
controlled by a single gene.
Each gene may have
different forms called alleles.
- In human body cells, one of the 23 pairs of chromosomes carries
the genes that determine sex. In females the sex chromosomes are
the same (XX); in males the sex chromosomes are different (XY).
- Sexual reproduction gives rise to variation because, when gametes
fuse, one of each pair of alleles comes from each parent.
- B2.7.3 Genetic Disorders
- Some disorders are inherited.
- Polydactyly – having extra fingers or toes – is caused
by a dominant allele of a gene and can therefore be
passed on by only one parent who has the disorder.
- Cystic fibrosis must be inherited from
both parents. The parents may be
carriers of the disorder without actually
having the disorder themselves. It is
caused by a recessive allele of a gene.
- Embryos can be screened for the alleles that cause these and other genetic disorders.
- Embryos can be screened for the alleles that cause these and other genetic disorders.
- Cystic fibrosis must be inherited from
both parents. The parents may be
carriers of the disorder without actually
having the disorder themselves. It is
caused by a recessive allele of a gene.
- Polydactyly – having extra fingers or toes – is caused
by a dominant allele of a gene and can therefore be
passed on by only one parent who has the disorder.
- Some disorders are inherited.
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