Inheritance, variation and evolution

Question 1

What are the sex cells in plants and animals

Answer 1

Animals - egg cell and sperm cell

Plants - egg cell and pollen

Question 2

How does meiosis form gametes

Answer 2

Before the cell divides, it duplicates its genetic information
In the first division the chromosome pairs line up in the centre of the cell
The pairs are then pulled apart so each new cell only has one copy of each chromosome
In the second division the chromosomes line up again at the centre of the cell, the arms of the chromosomes are pulled apart
You end up with 4 gametes each with only a single set of chromosomes in it
Each of the gametes is genetically different from the others

Question 3

Why do gametes join at fertilisation

Answer 3

To restore the normal number of chromosomes

Question 4

How many pairs of chromosomes are their in an ordinary human body

Answer 4

23 pairs

Question 5

What is a gene

Answer 5

A small section of DNA found on a chromosome

Question 6

How does a cell divide by mitosis

Answer 6

Before the cell divides it grows and increases the amount of subcellular structures eg mitochondria
It then duplicates its DNA so theres one copy for each new cell
Then the chromosomes line up at the centre of the cell and cell fibres pull them apart
Membranes form around each of the sets of chromosomes. This becomes the nuclei of the new cells
The cytoplasm and cell membrane divide
It produces 2 identical daughter cells