Biology GCSE combined science B2: Cell division

DNA

The chemical from which dna is made

Cell

the basic building block of a living organism

Gene

Small packets of DNA controlling a protein (characteristic)

Chromosome

Thread like structures holding genes

Nucleus

The part of the cell containing genetic information

List those 5 parts from largest to smallest

Cell, Nucleus, Chromosome, Genes, DNA, base pairs

What are new cells needed for?

Growth and to REPLACE old cells and to REPAIR tissue

How many pairs of chromosomes do we have?

23 pairs

How many chromosomes in each cell do we have?

46 chromosomes

Why do gametes (sex cells) only have half the number of chromosomes?

When gametes fuse in fertilisation, chromosomes will add up to 23 pairs or 46 chromosomes

What are the two types of cell division?

Mitosis(body/somatic cells) and meiosis(gamete/sex cells)

What are chromosomes made from?

Long strands of DNA

What are sections of DNA called and what are they for?

Sections of DNA are genes which code for a characteristic (protien)

What happens in stage 1 of mitosis and what is it called?

Interphase: Cell growth until parent cell with 4 chromatids is ready to replicate, then DNA replicates so that there are 4 chromoSOMES

What happens in stage 2 of mitosis and what is it called?

Nuclear division/mitosis: Nuclear membrane breaks down, each chromosome lines up at the centre of the cell, Chromosomes split and each 'arm' (chromatid) migrates to opposite ends of the cell, nuclear membrane reforms

What happens in stage 3 of mitosis and what is it called?

Cytokinesis: Cytoplasm and cell membrane divide, 2 identical daughter cells are produced

Explain why a cells genetic material has to be copied before it divides by mitosis

Chromosomes need to replicate to make sure the daughter cell has the same number of chromosomes as the parent

Explain why cells need to divide

to replace worn out/damaged cells, growth, repair tissue and organs

How does mitosis differ in mature animals

Mitosis doesn't take place for growth, slower rate of mitosis to repair and heal wounds

Where does mitosis take place in plants

In the meristems found in the shoot and root tips

When can an animal cells differentiate vs plant cells

Plant cells have the ability to differentiate throughout life, while animal cells differentiate at an early stage of development

Where do specialised sperm cells come from and how do they divide?

The testes, divide by meiosis because there are only 23 chromosomes in the gamete/sex cell

Where do specialised egg cells come from and how do they divide?

The ovaries, divide by meiosis because there are only 23 chromosomes in the gamete/sex cell

What is fertilisation?

fusion of male and female gametes/sex cells to form a zygote

Differentiation

To become 'different' or specialised

Specialisation

To become a specialised cell

Describe stem cells

Undifferentiated, unspecialised, have the potential to specialise to become other types of specialised cell

Where are stem cells found in?

In early human embryos or the bone marrow of adults

What are the purpose of specialised cells

To have different genes switched on to create a different structure and have a different function. It can only make more of the same cell

Where are stem cells found in plants?

Meristems in roots and stems

Why do humans stop growing?

Humans stop differentiating at an early stage of development because we loose many of our stem cells

What is a clone?

a genetically identical copy of a organism/cell

Why are plants cloned?

To produce identical copied of mature plants quickly and economically for reasearch, horticulture, and agriculture

What animal stem cells can be cloned and what for?

Embryonic stem cells(human embryos) and adult stem cells (bone barrow) can be cloned and made to differentiate into many different types of cell

What can treatment with stem cell cloning help?

Paralysis and diabetes

What happens in therapeutic cloning?

An embryo is produced with the same genes as the patient so the stem cells are not rejected and may be used for medical treatment. YOU CANNOT MAKE A HUMAN (illegal) it is only for research and treatment

What animal stem cells are the most useful?

Embryonic stems cells are more useful because they can differentiate into any type of specialised cell in the body, adults can only differentiate into their associated cell type (e.g. bone marrow stem cells -> red blood cells)

Who would benefit from stem cell research

Helps people with suffering diseases from faulty cells, Parkinsons disease: can replace faulty brain cells, Diabetes: replace insulin producing tissue in the pancreas, replace damaged spinal nerves so that limbs can work again, replace organs that no longer work

List pros of stem cells

Used to grow new organs for transplants; We can use stem cells from umbilical cords-no embryo destroyed; Embryonic stem cells offer the best chance of treating serious conditions; Adult stem cells can be manipulated to act like embryonic stem cells-no embryo needed; embryos that are used are spares from IVF

Cons of stem cells

Embryos cannot consent to being experimented on - unethical; Too much money is being spent on stem cell research when we could be developing new & better drug; All embryos have the potential to become babies, unethical to experiment/destroy; Treatment is experimental so risk of side effects such as cancer; Surgery always has risk; May be rejected