Growth and Development (B5) How does an organism produce new cells?

DNA has a double helix structure

The cell cycle Cell cycle: the main processes 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 Mitosis during which Copies of the chromosomes separate The cell divides

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

Copies of the chromosomes separate The cell divides 2. Mitosis during which Copies of the chromosomes separate The cell divides Cell Division by Mitosis: this produces two new cells identical to each other and to the parent cell

How does an organism produce new cells? There are two types of cell division: M_______ 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 Gametes Zygote

Questions What happens in the normal cell cycle? Cell growth Mitosis What happens during cell growth? Number of organelles increase Chromosomes are copied by separating DNA strands and forming new strands What happens during Mitosis? Copies of the chromosomes separate The cell divides

More questions In which organs do cells divide by Meiosis? Ovaries and Testes How many chromosomes are in the gamete if the parent cell has 46? 23 How many chromosomes does the zygote have? Where are they from? 46 A set from each gamete. (from each parent)

Growth and Development (B5) How 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 the cytoplasm In the cytoplasm

Both strands of DNA are made up of four different bases. The bases always pair up in the same way A -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 Chromosome made of DNA U (not T) In mRNA mRNA copy of gene Protein made of amino acids

Where is the genetic code found? Questions Where are proteins made in cells? In the cytoplasm Where is the genetic code found? In the nucleus of every cell How does the code get into the cytoplasm? A copy of the gene carries the code (RNA) How many different bases are in DNA? How is the order of the amino acids in proteins determined? Four different bases, always pairing the same way The order of bases in a gene is the code

Growth and Development (B5) How do new organisms develop from a single cell?

Early embryos 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.

Specialised Cells After this point the cells become specialised and form different types of tissue 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

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 gametes zygote mitosis Specialised cell types in tissues

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 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.

REVISE Check your knowledge

Growth and Development (B5) How does an organism produce new cells?

DNA has a ____________ structure double helix

The Cell Cycle Cell cycle: the main processes Cell growth during which - ______________________________ ___________________________ when the two strands of each DNA molecule separate and new strands form alongside them Mitosis during which ____________________________ - The number of organelles increase - The chromosomes are copied Copies of the chromosomes separate The cell divides

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

____________________________ _______________________ 2. Mitosis during which ____________________________ _______________________ Copies of the chromosomes separate The cell divides Cell Division by Mitosis: this produces ____ new cells identical to each other and to the parent cell two

How does an organism produce new cells? There are two types of cell division: M_______ 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 Gametes Zygote

Questions What happens in the normal cell cycle? Cell growth Mitosis What happens during cell growth? Number of organelles increase Chromosomes are copied by separating DNA strands and forming new strands What happens during Mitosis? Copies of the chromosomes separate The cell divides

More questions In which organs do cells divide by Meiosis? Ovaries and Testes How many chromosomes are in the gamete if the parent cell has 46? 23 How many chromosomes does the zygote have? Where are they from? 46 A set from each gamete. (from each parent)

Growth and Development (B5) How do genes control growth and development within the cell?

DNA - the genetic code cell nucleus The genetic code is in the ________ BUT proteins are produced in the cell __________. cytoplasm Nucleus Cytoplasm

copy of the gene Genes do not leave the nucleus but a _______________ is produced to carry the genetic code to the cytoplasm In the nucleus Travels to the cytoplasm In the cytoplasm

Both strands of DNA are made up of ____ different bases. four The bases always pair up _______________ A - ? C - ? in the same way T G

The Genetic Code order of the bases The _____________________ in a gene is the code for building up amino acids in the correct order to make a particular ________. protein Chromosome made of ____ DNA __ (not T) In mRNA mRNA ____ __________ copy of gene U Protein made of __________. amino acids

Where is the genetic code found? Questions Where are proteins made in cells? In the cytoplasm Where is the genetic code found? In the nucleus of every cell How does the code get into the cytoplasm? A copy of the gene carries the code (RNA) How many different bases are in DNA? How is the order of the amino acids in proteins determined? Four different bases, always pairing the same way The order of bases in a gene is the code

Growth and Development (B5) How do new organisms develop from a single cell?

Early embryos The zygote divides by ________ to form an embryo mitosis 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) eight cell After this point the cells become __________ and form different types of _________. specialised tissue

Specialised Cells After this point the cells become ________ and form different types of ________. specialised 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 tissue not active proteins

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 gametes pancreas zygote mitosis Specialised cell types in tissues 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. unspecialised These unspecialised cells allow the production of _______ of plants with desirable features, from _______. 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 phloem leaves, roots, flowers

Plant Hormones 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 roots auxins clone

Phototropism the plant’s response to light Phototropism is _________________________. It increases the plant’s chance of _________. survival Light causes ______ to move to the opposite side of the shoot tip. The cells on the side with more auxin grow ______. auxin bigger

Questions Division 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? two The eight cell stage They can inactivate genes or reactivate inactivated genes. Develop into any type of plant cell