Transcript
Growth and Development (B5)
B5.1How does an organism produce new cells?
DNA has a double helix structure
The cell cycle• Cell cycle: the main processes
1. Cell growth during which– The number of organelles increase– The chromosomes are copied when the
two strands of each DNA molecule separate and new strands form alongside them
2. Mitosis during which– Copies of the chromosomes separate– The cell divides
1. Cell growth during which– The number of organelles increase– The chromosomes are copied when the two strands of each DNA molecule separate and new strands form alongside them
• Cell Division by Mitosis: this produces two new cells identical to each other and to the parent cell
2. Mitosis during which
–Copies of the chromosomes separate
–The cell divides
There are two types of cell division:
M_______
M_______
How does an organism produce new cells?
Mitosis
Meiosis
Meiosis
• A type of cell division that produces gametes
• It is important in meiosis that the cells produced only contain half the chromosome number of the parent cell.
• A zygote contains a set of chromosomes from each parent
Meiosis
Zygote
Gametes
Questions• What happens in the normal cell cycle?
• What happens during cell growth?
• What happens during Mitosis?
–Cell growth–Mitosis
–Number of organelles increase–Chromosomes are copied by separating DNA strands and forming new strands
–Copies of the chromosomes separate–The cell divides
More questions
• In which organs do cells divide by Meiosis?
• How many chromosomes are in the gamete if the parent cell has 46?
• How many chromosomes does the zygote have? Where are they from?
– Ovaries and Testes
– 23
– 46– A set from each gamete. (from each parent)
Growth and Development (B5)
B5.2How do genes control growth and
development within the cell?
DNA - the genetic code
• The genetic code is in the cell nucleus BUT proteins are produced in the cell cytoplasm
Nucleus
Cytoplasm
Genes do not leave the nucleus but a copy of the gene is produced to carry the genetic code to the cytoplasm
In the nucleus
Travels to thecytoplasm
In the cytoplasm
Both strands of DNA are made up of four different
bases.
The bases always pair up in the same wayA -T C - G
The Genetic Code
The order of the bases in a gene is the code for building up amino acids in the correct order to make a particular protein
Protein made of amino acids
Chromosome made of DNA
mRNA copyof gene
U (not T)
In mRNA
Questions
Where is the genetic code found?
Where are proteins made in cells?
How does the code get into the cytoplasm?
How many different bases are in DNA?
How is the order of the amino acids in proteins determined?
In the cytoplasm
In the nucleus of every cell
A copy of the gene carries the code (RNA)
Four different bases, always pairing the same way
The order of bases in a gene is the code
Growth and Development (B5)
B5.3How do new organisms develop from a single
cell?
The zygote divides by mitosis to form an embryo
In a human embryo, up to the eight cell stage, all the cells are identical and could produce any sort of cell required by the organism (embryonic stem cells)
After this point the cells become specialised and form different types of tissue. Some of the genes are switched off.
Early embryos
After this point the cells become specialised and form different types of tissue
Specialised Cells
Although body cells in an organism contain the same genes, many genes in a particular cell are not active because it only produces the specific proteins it needs
gametes
zygote
mitosis
Specialised cell types in tissues
One cell type becomes many!
Gene switches•Gene for insulin is on in the pancreas but off in the kidney
•Gene for ADH is on in the pituitary gland but off in the salivary gland
Cloning• In carefully controlled conditions of
mammalian cloning, it is possible to reactivate inactive genes in the nucleus of a body cell to form cells of all tissue
types.
• Adult and embryonic stem cells have the potential to produce cells needed to replace damaged tissues.
Plants from from single cells• New cells in plants specialise into cells
of roots, leaves or flowers.
Unlike animal cells some plant cells remain unspecialised and can develop into any type of plant cell.
These unspecialised cells allow the production of clones of plants with desirable features, from cuttings.
Plant meristems
• Plant meristems divide to produce cells that result in increased height, length of roots and girth of the plant.
If the hormonal conditions in their environment are changed, unspecialised plant cells can develop into a range of other tissues (eg xylem and phloem) or organs (eg leaves, roots, flowers)
Cut stems from a plant can develop roots in the presence of plant hormones (auxins) and grow into a complete plant which is a clone of the parent
Phototropism is the plant’s response to light. It increases the plant’s chance of survival
Light causes auxin to move to the opposite side of the shoot tip. The cells on the side with more auxin grow bigger.
Phototropism
REVISEREVISE
Check your knowledgeCheck your knowledge
Growth and Development (B5)
B5.1
How does an organism produce new cells?
DNA has a ____________ structure
double helix
The Cell Cycle• Cell cycle: the main processes
1. Cell growth during which
- ______________________________ ___________________________ when the two strands of each DNA molecule separate and new strands form alongside them
2. Mitosis during which– ____________________________– ____________________________
- The number of organelles increase
- The chromosomes are copied
Copies of the chromosomes separateThe cell divides
1. Cell growth during which– _______________________________ – ____________________________ when the two
strands of each DNA molecule separate and new strands form alongside them
The number of organelles increase
The chromosomes are copied
• Cell Division by Mitosis: this produces ____ new cells identical to each other and to the parent cell
2. Mitosis during which
____________________________
_______________________
two
—Copies of the chromosomes separate— The cell divides
There are two types of cell division:
M_______
M_______
How does an organism produce new cells?
Mitosis
Meiosis
Meiosis
• A type of cell division that produces
• It is important in meiosis that the cells produced only contain the chromosome number of the parent cell.
• A contains a set of chromosomes from each parent
gametes
half
zygote
Meiosis
Zygote
Gametes
Questions• What happens in the normal cell cycle?
• What happens during cell growth?
• What happens during Mitosis?
–Cell growth–Mitosis
–Number of organelles increase–Chromosomes are copied by separating DNA strands and forming new strands
–Copies of the chromosomes separate–The cell divides
More questions
• In which organs do cells divide by Meiosis?
• How many chromosomes are in the gamete if the parent cell has 46?
• How many chromosomes does the zygote have? Where are they from?
– Ovaries and Testes
– 23
– 46– A set from each gamete. (from each parent)
Growth and Development (B5)
B5.2How do genes control growth and
development within the cell?
DNA - the genetic code
• The genetic code is in the ________ BUT proteins are produced in the cell __________.
Nucleus
Cytoplasm
cell nucleus
cytoplasm
Genes do not leave the nucleus but a _______________ is produced to carry the genetic code to the cytoplasm
In the nucleus
Travels to thecytoplasm
In the cytoplasm
copy of the gene
Both strands of DNA are made up of ____ different
bases.
The bases always pair up _______________
A - ? C - ?
four
in the same wayT G
The Genetic Code
The _____________________ in a gene is the code for building up amino acids in the correct order to make a particular ________.
Protein made of __________.
Chromosome made of ____
mRNA ______________
order of the bases
protein
DNA
copyof gene
amino acids
__ (not T)
In mRNA
U
Questions
Where is the genetic code found?
Where are proteins made in cells?
How does the code get into the cytoplasm?
How many different bases are in DNA?
How is the order of the amino acids in proteins determined?
In the cytoplasm
In the nucleus of every cell
A copy of the gene carries the code (RNA)
Four different bases, always pairing the same way
The order of bases in a gene is the code
Growth and Development (B5)
B5.3How do new organisms develop from a single
cell?
The zygote divides by ________ to form an embryo
In a human embryo, up to the __________ stage, all the cells are identical and could produce any sort of cell required by the organism (embryonic stem cells)
After this point the cells become __________ and form different types of_________.
Early embryos
mitosis
eight cell
specialised
tissue
After this point the cells become ________ and form different types of________.
Specialised Cells
Although body cells in an organism contain the same genes, many genes in a particular cell are _________ because it only produces the specific _________ it needs
specialised
tissue
not active
proteins
gametes
zygote
mitosis
Specialised cell types in tissues
One cell type becomes many!
Gene switches•Gene for insulin is on in the _________ but off in the kidney
•Gene for ADH is on in the ____________ but off in the salivary gland
pancreas
pituitary gland
Cloning• In carefully controlled conditions of
mammalian cloning, it is possible to __________ inactive genes in the nucleus of a body cell to form cells of all tissue
types.
• Adult and embryonic _________ have the potential to produce cells needed to replace damaged tissues.
reactivate
stem cells
Plants from from single cells• New cells in plants specialise into cells
of roots, leaves or ________.flowers
Unlike animal cells some plant cells remain ____________ and can
develop into any type of plant cell.These unspecialised cells allow the production of _______ of plants with desirable features, from _______.
unspecialised
clones
cuttings
Plant meristems
• Plant meristems divide to produce cells that result in increased ___________________ and ______ of the plant.height, length of roots
girth
If the hormonal conditions in their environment are changed, unspecialised plant cells can develop into a range of other tissues (eg _____________________) or organs (eg ____________________)
xylem and phloemleaves, roots, flowers
Cut stems from a plant can develop _______ in the presence of plant hormones (________) and grow into a complete plant which is a _______ of the parent
rootsauxins
clone
Plant Hormones
Phototropism is _________________________. It increases the plant’s chance of _________.
Light causes ______ to move to the opposite side of the shoot tip. The cells on the side with more auxin grow ______.
Phototropismthe plant’s response to light
survival
auxin
bigger
QuestionsDivision of a cell by mitosis creates ____ cells.
When do mammalian embryonic cells become specialised?
How do cells control which proteins they produce?
If animal stem cells can produce cells to replace damaged tissues, what can plant stem cells do?
They can inactivate genes or reactivate inactivated genes.
Develop into any type of plant cell
two
The eight cell stage
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