Reproduction Introduction

View mindmap
  • Reproduction Introduction
    • Genes
      • A gene is a small section of DNA.
      • DNA is coiled into separate chromosomes
      • Can exist in different versions, each codes for a different characteristic, these different versions of the same genes are called alleles
    • Sexual and Asexual
      • Sexual reproduction is animals and plants, offspring contain a mixture of genes from both parents, produces offspring (cells) that are genetically different from their parents
        • Advantages     - Variation in offspring        - Natural      selection
        • Disadvantage  - Needs 2 parents           - Takes a long time, requires a lot of energy
      • Asexual reproduction is plants, bacteria and yeast. Only one parent so genes come from one place, this makes them genetically identical so they are called clones.
        • Advantages     - 1 parent needed           - Many offspring produced        - Faster
        • Disadvantage  - Clones vulnerable to change in environment    - Faulty DNA passed on
    • Nervous and Endocrine System
      • Thyroxine is made in the thyroid gland (neck), it regulates the basal metabolic rate (chemical reactions), It stimulates protein synthesis for growth and development.
      • Adrenaline is made in the adrenal gland, its released in response to stressful or scary situations. Produces the fight or flight response (increase oxygen and glucose levels available to cells and  muscles.
        • How it works    - Brain detects fear, sends nervous impulses to the adrenal gland               - Adrenaline secreted into blood               - This triggers mechanisms that get the body ready for fight or flight.
      • Nervous system
        • Response speed? Signals travel along an alpha motor neuron in the spinal chord
          • Long acting?    short lived, fast acting
            • Precision?        rapid and precise responses
              • Example?         The nervous system is a responsible for movement of voluntary muscles and the process known as a reflex arc. This system carries nerve impulses back and fourth between the central nervous system, which is the brain and the spinal chord, and the skeletal muscles, skin and sensory organs.
      • Endocrine (hormones)
        • Response speed?            The endocrine system responds to stimulation by secreting hormones into the circulatory system that travel to the target tissue- slow
          • Long acting?    slow reacting, long lasting
            • Precision?        Maintains homeostasis and long term control using chemical signals
              • Example?         The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep and moods.
      • Glands
        • Pituitary gland produces many hormones that regulate body conditions by acting on other glands and directing them to release hormones to bring about change
        • thyroid produces thyroxine
        • Adrenal gland produces adrenaline
        • pancreas produces insulin
        • ovaries produce oestrogen
        • testes produce testosterone
    • Meiosis
      • Body cells are diploid, have 2 sets of chromosomes 1 of each pair comes from parent
      • Gametes are Haploid and have 1 set of chromosomes
      • produces new genetic combinations, cell division by reduction, forms gametes (sex cells), can adapt, 4 daughter cells are made,
      • Method: before the cell divided it duplicates its genetic info,arranged into pairs, in the first division the pairs line up in the center of the cell. they are then pulled apart  so each cell has one copy of the chromosomes, in the second division the cells line up again in the center of the cell, the arms are pulled apart, You end up with 4 gametes with a single set of chromosomes they are all genetically different.
    • Structure of DNA
      • chromosomes are made from DNA, double helix structure.
      • A section of DNA is called a gene. A gene codes for a sequence of amino acids that form a particular protein.
      • Complementary base pairing is when each base in a DNA strand links to a base on the opposite strand in the helix. A is always with T and c is always with G
      • Non coding parts of DNA   There are parts of DNA that dont code for proteins. some of these non coding parts switch genes on and off so they control whether or not a gene is expressed (used to make a protein)
    • Protein synthesis
      • Step 1              The strands of the DNA molecule are separated, A copy of a selection of the DNA is made using base pairing rules, this copy is called messenger  RNA.
      • Step 2              The mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm, carrier molecules attach to the mRNA using base pairing rules. Each one carries a specific amino acid, has a triplet code that matches the mRNA code.
      • Step 3              As the ribosome moves along the mRNA molecule, the amino acids form a chain, this chain of amino acids falls off the carrier molecule, the completed chain of amino acids is the protein, the protein folds into a useful shape
      • Protein functions
        • Enzymes act as biological catalysts to speed up chemical reactions in the body.
        • Hormones are used to carry messages around the body
        • structural proteins are physically strong
    • Inherritance
      • Females have 2 'x' chromosomes Males have 1 'x' and 1 'y' chromosome
      • Ways to predict the sex of a child include using punnets square
      • Inherrated disorders
        • Polydactycy is caused by a defective dominant gene, results in more fingers or toes
        • Cystic Fibrosis is caused by a defective recessive gene, results in mucus building up in the airways and pancreas
    • Genetics
      • Genotype, the combination of alleles you have
        • phenotype what characteristics you have that are shown.
      • Allele, different forms of the same gene.
      • Heterozygous, if an organism has 2 alleles of a gene that are different then its heterozygous
        • Homozygous, if an organism has 2 alleles for that gene that are the same then its homozygous
      • dominant, ovextules the recessive allele shown with a capital letter
        • recessive, overwhelmed by the dominant allele shown with a lower case letter, only if both allele are recessive.
    • Embryonic screening
      • Pre implantation genetic diagnosis: during IVF embryos are fertilissed, a cell is taken out from the embryo to analyse the genes
      • chorionic villus sampling: carried out between 10-13 weeks of pregnancy, takes sample cells out of the placenta and analysing the genes, can look for disorders
      • Arguments for: stops people suffering, treating disorders costs alot of money so screening could reduce healthcare costs, during IVF embryos are destroyed anyway, gives parents the choice
        • Arguments against: everyone might  want to screen their baby to get the perfect one,  increase prejudice, unethical because humans are killed, causes miscarriage, expensive
    • Cloning plants
      • Method 1: Taking cuttings
        • Reason: keep desired characteristics of plant faster method than growing from a seed
          • Method: cut small section of plant stem, remove leaves each with a bud, dip end of branch into rooting hormone (auxin), plant in damp compost, keep warm until fully formed
      • Method 2: Tissue culture
        • Method: cut small sections of plant stem, sterilize it, put in agar jelly plate containing nutrients and auxins, grow plants in pots
          • Advantages: free of disease, keep desired characteristics, high number of clones, grown all year
            • Disadvantages: several steps involved , lab access needed, more workers, disease will kill all of the plants
    • Cloning animals
      • Method 1: Embryo transplants
        • Reason: produce many ideal offspring per year, all offspring will have the desired traits
          • Method: prize cow and prize bull have the sperm and the egg produced and put together, fertilization, egg starts to divide producing embryo, embryo is split into 4, these are then put into surrogate mothers and 4 calves are born
      • Method 2: Adult cell cloning
        • Reason: produce exact copies of animals, all offspring will be identical
          • Method: skin cell is taken from a white donor sheep , unfertilized egg is taken from a black female ewe  donor sheep, donor eggs nucleus is removed and placed inside empty egg cell, an electric shock stimulates the division of cells, then put into a dish with nutrients where it divides and grows, then put into a surrogate sheep and a lamb is born 9 months later
      • Ethical issues of animal cloning
        • For: could be used to stop animals from going extinct, could be used to grow new organs and help treat diseases
          • Against: could be used to clone humans or replace children who have died, it takes many attempts before it actually works, clones often have many health problems and could die younger.

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Variation and reproduction resources »