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• what is the differences between sexual and asexual reproduction

  • in mitosis they have paired chromosomes
  • in meiosis they aren’t paired
  • gametes made by meiosis
  • meiosis produces no identical cells
• how many chromosomes does a human gamete contain

  23
• how do cells divide to form gametes

  • it only takes place in reproductive organs of humans
  • all of the chromosomes are copied
  • the cell divides into 2
  • both of there cells divide one more time forming the gametes
  • original chromosomes were paired but they are now single
  • meiosis has halved the number of chromosomes
  • all gametes are genetically different from eachother
• are gametes chromosomes paired

  no
• what is it called when male and female gametes join together

  fertalisation
• how many chromosomes does egg cells have

  23
• how many chromosomes does egg cells have

  23
• what happens to the new cell after fertilisation

  • the new cell divides by mitosis producing a clump of identical cells this is called an embryo
  • as the embryo develops the cells differentiate forming different cell types
• why is asexual reproduction

  • involves only one parent and no fusion of gametes
  • there is no mixing of genetic information
  • this leads to genetically identical offspring
  • only mitosis is involved
• describe the structure of dna

  • dna consists of two strands
  • each strand is a polymer made up of two strands forming a double helix
  • dna is contained in structures called chromosomes
• what is a gene

  a small section of dna on a chromosome
• what is a genome

  an genome is the entire genetic material of that organism
• what are the benefits of scientists studying the the whole human genome

  • help to search for genes linked to a disease
  • understanding and treatment of genetic disorders
  • use in tracing human migration patterns from the past
• what are alleles

  versions of a gene
• what is a genotype

  the genotype of a person tells us the alleles present
• what is homozygous

  two types of the same allele
• what is heterozygous

  when two different alleles are present
• what is dominant

  only one big letter is needed for the genotype to be present
• what is recessive

  when two small letters are needed for the genotype to be present
• what is a phenotype

  a physical atribute
• what allele is polydactyl formed by

  dominant
• what allele is cystic fibrosis formed by

  recessive
• what are the issues around embryo screening

  • it’s expensive and people think it should be used elsewhere in the health service
  • a large number of embryos made but only a few implanted os some healthy embryos are destroyed and people think thats unethical
  • in the future we may be able to produce offspring with more desirable features many people find this unethical
• how many chromosomes does the human body contain

  46 or 23 pairs
• what do the different chromosomes control

  • 22 control characteristics
  • one carries the genes that determine sex
• model answer genetic variation

  • variation occur
  • mutations occur
  • reproduction to offspring
  • more likely to survive
  • more reproduction
  • evolution over many years
• what are fossils

  fossils are the remains of organisms from millions of years ago which are found in rocks