revision of b5

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)


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


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


B5.1


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_______


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)


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


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

revision of b5

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