Reproduction

• Exp,ain how sexual reproduction leads to genetically varied offspring?

  sexual reproduction joins male and female gametes by meiosis to increase genetic variation and there is a mix of genetic variation
• What is a gamete?

  a sex cell formed by meiosis
• Explain how asexual reproduction leads to genetically identical offspring?

  involves one parent, no fusion of gametes so no mixing of genetic information and cell division occurs via mitosis so identical
• Are gametes involved in asexual or sexual repro?

  sexual
• Is fertilisation involved in asexual or sexual repro?

  sexual
• is mixing or genetic information involved in asexual or sexual repro?

  sexual
• does genetic variation occur in asexual or sexual repro?

  sexual
• Is asexual meiosis or mitosis?

  mitosis
• Is sexual meiosis or mitosis?

  meiosis
• Explain the importance of meiosis?

  halves number of chromosomes so when gametes fuse at fertilisation full number of chromosomes is restored
• Describe the process of meiosis?

  DNA replicates, cell divides twice, forms 4 cells each with a single set of chromosomes which are genetically different
• What happens at fertilisation?

  fertilised cell divides by mitosis to increase number, genetically identical cells make embryo, cells differentiate into specialised cells as embryo develops
• Explain the advantages of sexual reproduction?

  genetic variation, if environment changes variation increases survival chance by natural selection, speed up selective breeding to increase food production
• Explain the advantages of asexual reproduction?

  only one parent, more time and energy efficient as no mate, faster, many genetically identical offspring
• Give examples of organisms that reproduce by both asexually and sexually?

  malarial parasites, fungi, flowering plants
• Describe asexual and sexual production in malarial parasites?

  asexually in human host but sexually in mosquito
• Describe asexual and sexual reproduction in fungi?

  asexually by releasing spores but sexually to give variation
• Describe asexual and sexual reproduction in flowering plants?

  sexually to produce seeds, asexually to produce runners
• What is DNA?

  chemical that genetic material in nucleus is composed of
• What is DNA contained in?

  structures called chromosomes
• Describe the basis structure of DNA?

  a polymer made of 2 strands which twist around each other to form a double helix
• Define gene?

  a small section of DNA on a chromosome which codes for a particular sequence of amino acids to make a specific protein
• Define genome?

  entire genetic material of an organism
• Explain the importance of understanding the human genome?

  identifies genes linked to different diseases so better prevention and treatment, improve understanding for inherited disorders, trace human migration patterns so understand ancient history of humans
• Explain how a change in gene causes a different protein to be produced?

  different genes means difference in DNA so different codes for making proteins of different amino acids
• Two parents do not have any alleles for polydactyly (inherited disorder) in their ordinary body cells, but parents produced a child with polydactyly. Explain how polydactyly suddenly occurred in this family. (4)?

  caused my mutation during meiosis causing a change in amino acid sequence causing a different protein to be produced
• How do genes code for proteins?

  each sequence of 3 bases codes for a particular amino acid so order of bases controls order amino acids are assembled to produce a particular protein
• What happens in protein synthesis?

  proteins are synthesised on ribosomes
• Why is the unique shape of proteins important?

  enables them to do their job as enzymes, hormones or forming structure in the body
• What is a mutation?


  random change in DNA base sequence which occur continously
• What does mutation produce?


  a genetic variant
• What is non coding DNA and what is the impact of mutations here?

  parts of DNA that don't code proteins can switch genes on and off, variations in these areas of DNA may affect how genes are expressed
• Why is the unique shape of proteins important?

  enables them to do their jobs
• Explain the effects of mutations on proteins?

  most do not alter the protein, a few code for an altered protein with a different shape as sequence of bases change so sequence of amino acids change
• How many bases are needed to code for one amino acid?

  3
• Explain how a change in one amino acid in an enzyme molecule could stop the enzyme working. (3)?

  different protein made so active site changed and substrate doesn't fit so no more enzyme substrate complexes
• What are chromosomes?

  thread like structure of DNA in nucleus that carries many genes normally found in pairs in body cells
• In a pair of chromosomes, both carry the same genes but they may have different alleles
• What is a gamete?


  a sex cell formed by meiosis so has half number of chromosomes
• What is a gene?

  small section of DNA on a chromosome that codes for a particular sequence of amino acid to make specific protein