3.28-3.39 mitosis, meiosis, variation, mutations

What is mitosis and when does it occur

A type of cell division where one cell divides to form two identical daughter cells - during growth, development, replacing damaged cells, cloning, asexual reproduction

What is diploid

A cell containing two complete sets of chromosomes

Describe the process of mitosis

• before mitosis: each chromosome in the nucleus copies itself (forms x shaped chromosomes)

• Chromosomes line up along the centre of the cell where cell fibres pull the apart

• The cell divides into two daughter cells, each new cell has a copy of each chromosome

What is the importance of mitosis

All cells in the body (excluding gametes) are produced by mitosis, allows growth as it replaces cells

What is meiosis and when does it occur

The formation of four non-identical haploid cells from one diploid cell - to produce gametes for sexual reproduction and introduce genetic variation

Describe the process of meiosis

1. The cell makes copies of its chromosomes

2. The cell divides into two cells, each with half the amount of chromosomes, giving the normal amount of 46

3. Each cell divides into two again, each with 23 chromosomes

How does random fertilisation produce genetic variation of offspring

• meiosis creates diverse gametes

• Random fusion of sperm and egg

What is genetic variation?

The difference in DNA sequences of individuals within the same species

What is genetic variation and examples

Phenotypes that are dependent on inheriting alleles from parents

Eg. Eye colour, blood type

What is environmental variation and examples

variation caused by differences in lifestyle, diet, climate which could lead to organisms to adapt

Eg. Scars, dyed hair, freckles (from the sun), tattoos, accents

What are some examples of a mix of genetic and environmental variations

Height, weight, skin colour (sun exposure) , intelligence

What is a mutation

A rare, random change in genetic material that can be inherited

What is evolution?

A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

Process of evolution

• mutations occur which provide variation between organisms

• If a mutation provides a survival advantage, the organism is more likely to survive (survival of the fittest)

• The mutation will then be passed onto offspring

• Over many generations, the frequency of the mutation will increase within the population

How do bacteria become resistant to antibiotics

• bacteria reproduce at a fast rate and advantageous genes like antibiotic resistant can become prominent

• Exposure to antibiotics creates selection pressure so antibiotic resistant gene will survive and ones without will die