B12- reproduction

• What is sexual reproduction

  The sperm gamete fertilises the egg gamete and forms a zygote which develops into an offspring
• Adaptations of a sperm cell

  Lots of mitochondria to release energy for swimming

  Enzymes in the tip to break down eggs cell membrane

  Haploid nucleus
• Adaptations of an egg cell

  Lipids in cytoplasm to support embryo

  Haploid nucleus

  Outer layer that hardens after fertilisation
• Advantages of sexual reproduction

  Produces variation

  passes Genetic info from both offspring’s

  Enables evolution to take place
• Disadvantages of sexual reproduction

  Energy and time intensive

  Reproduction is uncertain

  desirable genes may not be passed in
• Advantages of asexual reproduction

  Is more time and energy efficient

  population can rapidly increase in favourable conditions

  Faster than sexual reproduction
• Disadvantages of asexual reproduction

  No variation in a population

  Species may only be suited to one habitat

  Disease could wipe out a population
• Mitosis stages

  Parent cell replicates to form 2 copies of each chromosome

  one set of chromosomes is pulled to each half of the cell

  The cytoplasm and mitochondria divide to form 2 identical diploid daughter cells are formed
• Purpose of mitosis

  Growth and repair
• Stages of meiosis

  The parent cells dna replicates so their are four sets of each chromosome

  each chromosome forms a pair of chromatids

  the cell divides twice in quick succession to form four gamete’s each with a single set of chromosomes
• Differences of mitosis and meiosis

  Where - body cells (mitosis) reproductive organs (meiosis)

  Variation- no (mitosis) yes (meiosis)

  Genetically identical cells- yes (mitosis) no (meiosis)

  Number of cell divisions- 1 (Mitosis) 2 (meiosis)
• What are genes

  Sections of dna that code for proteins that combine with other molecules to make up structures within your body
• What is a genome

  All the genetic material that makes up an organism
• What is the human genome project

  when scientists mapped the human Genome
• Advantages of human genome project

  Enables us to see evolution links between species

  Allows us to see how humans have evolved and migrates

  Helps us understand more about genetic disorders (cystic fibrosis)

  Helped us begin to create personalised medicine
• Disadvantages of human genome project

  Could be used to discriminate against certain people

  Health insurance companies may increase costs or refuse services based of unseen genetic disorders
• What is a genotype

  The chromosomes inherited from parents contain genes

  the combination of genes you get passed is your genotype
• What is a phenotype

  The genes from your parents code for proteins which determine what you look like
• What is homozygous and heterozygous

  Homozygous- 2 of the same alleles (2 recessive or 2 dominant)

  Heterozygous- 2 different alleles (1 recessive and 1 dominant)
• what Is polydactyly

  Condition where individuals have more than usual number of fingers or toes

  Caused by dominant allele using letters P or p
• what is cystic fibrosis

  Thick sticky mucus in lungs, digestive system and reproductive system causing lung infections, difficulty breathing, being underweight due to digestive enzymes breaking down and infertility

  No cure

  Carried by 1/25 people in the UK

  Currently 8500 sufferers in the UK

  Caused by recessive allele
• What are the 2 methods of harvesting embryo cells for screening before being implanted in IVF

  amniocentesis- carried out in 15th week of pregnancy, fluid containing fetal cells if taken from the foetus

  Chronic villus sampling - between 10th and 12th week of pregnancy, small sample of tissue taken from placenta
• Concerns with embryo testing

  Risk of miscarriage

  Can give false results

  Ethical dilemmas

  Economic considerations

  Could lead to rise of “designer babies”