Inheritance, variation and evolution

Question 1

Reproduction, the genome and gene expression

Answer 1

Reproduction occurs in all organisms. DNA is important, as it allows new proteins to be synthesised. Mutations in the DNA can have serious implications.

Question 2

Asexual Reproduction

Answer 2

Only one parent is needed in asexual reproduction. There is no fusion of gametes so genetic material does not mix, which means that the offspring produced through this process are genetically identical clones to the parent.

Examples of organisms that use asexual reproduction include:
○ bacteria
○ production of spores by fungi
○ some plants, such as strawberries, use runners
○ formation of tubers in potatoes and bulbs in daffodils

Question 3

Mitosis

Answer 3

Asexual reproduction uses the process of mitosis to create the identical copies (clones) of the parent cell.

Mitosis is part of the cell cycle, which involves:
○ cell growth, and the increase of the number of structures in the cell (mitochondria, ribosomes)
○ genetic material is copied
○ mitosis occurs leading to chromosomes separation and cell division

Mitosis is also used for:
○ growth
○ repair to damaged tissue
○ replacement of worn-out cells

Question 4

Sexual Reproduction

Answer 4

Two parents are needed in sexual reproduction. During this process the nuclei of the male and female gametes are fused in order to create a zygote. This process is known as fertilisation. The gametes contain half the number of chromosomes in each (haploid). When the male and female gametes combine they create the full complement of chromosomes (diploid) in order to create a human embryo.

The gametes in:
○ animals are sperm and eggs
○ flowering plants are pollen and eggs

The offspring produced in sexual reproduction are genetically different to each other and the parents. This process results in variation as it involves the mixing of genetic information.

Question 5

Meiosis

Answer 5

Sexual reproduction uses the process of meiosis, which creates gametes. The process of meiosis happens in the male and female reproductive organs. As a cell divides to form gametes:
○ copies of the genetic information is made
○ the cell divides twice to form four gametes, each with a single set of chromosomes
○ all gametes are genetically different from each other