Sexual and Asexual Reproduction

• Key Point

  Gardeners use asexual reproduction to produce large numbers of identical plants.
• Asexual Reproduction

  . Asexual reproduction involves:

  - only one parent

  - no fusion of gametes (sex cells), so no mixing of genetic information

  - the production of genetically identical offspring (clones)

  - mitosis

  . Many plants reproduce asexually and in different ways, e.g.

  - strawberry plants send out long shoots called runners, which touch the ground and grow a new plant

  - daffodils produce lots of smaller bulbs, which can grow into new plants

  . Many fungi reproduce asexually by spores

  . Malarial protists reproduce asexually when they are in the human host
• What is sexual reproduction?

  Fusion of male and female gametes
• What are the male and female gametes in animals?

  Sperm and egg cell
• What are the male and female gametes in flowering plants?

  Pollen and egg cell
• What is the result of the fusion of gametes?

  It produces variation in the offspring
• What process leads to the formation of gametes?

  Meiosis
• What happens during meiosis when a cell divides?

  Copies of genetic information are made
• How many times does a cell divide during meiosis?

  Twice
• How many gametes are formed from one cell during meiosis?

  Four gametes
• What is unique about the gametes produced by meiosis?

  All gametes are genetically different
• Why is meiosis important for gametes?

  It halves the number of chromosomes
• What happens during fertilization regarding chromosome numbers?

  It restores the full number of chromosomes
• How many chromosomes are in a normal adult body cell?

  46 chromosomes
• How many chromosomes does a fertilized egg cell have?

  46 chromosomes
• How are the chromosomes in a fertilized egg cell divided between parents?

  Half from mother and half from father
• What is the equation representing the chromosome contribution from sperm and egg?

  23 chromosomes + 23 chromosomes = 46 chromosomes
• What is the relationship between sperm and egg in fertilization?

  Sperm + egg = fertilized egg cell
• What is the process of meiosis?

  . Cell with two pairs of chromosomes (diploid cell)

  . Each chromosome replicates itself

  . Chromosomes part company and move to opposite poles

  . Cell divides for the first time

  . Copies now separate and the second cell division takes place

  . Four haploid cells (gametes) each with half the number of chromosomes of the parent cell
• Key Point

  A person now has the choice to have their genome tested to see how likely it is that they may get certain disorders. This may be a difficult decision to take. Just because you carry a gene for a disorder, it does not guarantee that you get it.
• What is the genetic material in the nucleus of a cell?

  DNA
• What structures contain DNA in a cell?

  Chromosomes
• What is a gene?

  A small section of DNA on a chromosome
• What does each gene code for?

  A particular sequence of amino acids
• What is the genome of an organism?

  The entire genetic material of that organism
• What are some important uses of studying the human genome?

  • Search for genes linked to disorders
  • Understand causes of inherited disorders
  • Investigate human evolution over time
• How can studying the human genome help doctors?

  By searching for genes linked to disorders
• How can scientists use the human genome to understand inherited disorders?

  By understanding their causes and treatments
• What can scientists investigate by studying the human genome?

  How humans may have changed over time