B2.5 Simple Inheritance in Animals and Plants

Cell Division and Growth
1. Cells
  1. New cells are needed to replace old ones, repair damaged tissue, grow, etc, but they much have the same genetic material
  2. They have a nucleus containing genes (some DNA). Different forms of genes are alleles. Genes are grouped in chromosomes.
    1. 46 chromosomes in a nucleus. 23 pairs. One from a pair is inherited from father and one from mother. Gametes have only one of each pair
2. Mitosis
  1. two identical cells
  2. Same chromosomes
  3. asexual
  4. no genetic variation
  5. Produces copies of chromosomes then cell divides
  6. eg, skin
3. Differentiation
  1. In embryos cells are unspecialised (stem cells)
  2. Some genes are switched on to specialise certain cells and differentiate them
  3. In adult animal cells differentiation has already occured so mitosis is common yet plants can still differentiate making them easy to clone
Cell Division in Sexual Reproduction
1. Meiosis
  1. ova made in ovaries. Sperm in testes
  2. Chromosomes are copied, cell divides twice leaving 4 sex cells with half the chromosomes
  3. Introduces variety
  4. random chromosome areas
2. Fertilisation
  1. more variety as they each have 23 chromosomes which pair
  2. Meiosis then Mitosis
3. Variation
  1. Asexual = no variation
  2. sexual = variation
Stem Cells
1. The Function
  1. egg and sperm fuse to form a zygote (a single cell). This divides to form a ball of cells (embryo). The inner cells of this ball are stem cells which will differentiate
  2. bone marrow is a stem cell
  3. They are needed for diseased or injured tissue
2. Using Stem Cells
  1. Spinal injuries cause paralysis
  2. Embryonic stem cells can be cultured and differentiated into the right cells
  3. We may be able to grow whole organs
3. Problems with Stem Cells
  1. Some embryonic stem cells come from abortions, some from fertility treatment which may cause ethical issues
  2. Human rights
  3. Slow, difficult, expensive and hard to control
  4. May cause cancer
4. The Future
  1. There are stem cells in the umbilical cord blood solving ethical issues
  2. new ways of growing adult stem cells, and have even grown tracheas.
  3. Theraputic cloning uses adult cells to clone an embryo of themselves,
From Mendel to DNA
1. Mendel's discoveries
  1. Born 1822 worked in a monestry
  2. cross bred peas
    1. Found a pattern in the characteristic of offspring
  3. considered dominant genes
2. DNA
  1. Chromosomes are made up of long chain of DNA and are found in nuclei
  2. Double helix structure
  3. Genes are a small section of DNA
  4. Carries instructions to make the proteins that form cell structures
    1. include enzymes to control cell chemistry
  5. The Genetic code
    1. DNA is made of 4 different chemicals
      1. grouped into 3s. Each 3 is an amino acid
        A gene is made of hundreds of thousands of these bases
    2. The order of bases controls the order of amino acids to make protein.
    3. A mutation in a base will change the whole protein structure
3. DNA fingerprinting
  1. DNA is unique to you
    1. UNLESS YOU HAVE AN IDENTICAL TWIN
      1. Both developed from one cell
  2. Your DNA can be used to identify you.
  3. Your DNA pattern is more similar to relatives. You can get your pattern from bodily fluids
  4. Can be used for crimes and DNA tests in parenting
Inheritance in action
1. How inheritance works
  1. Sex Chromosomes
    1. XX is female, XY is male
  2. Genes have different alleles which result in a different protein
  3. Most characteristics are controlled by a number of genes but some are only 1.
  4. You get dominant and recessive alleles
2. Genetic terms
  1. Homozygous - two identical alleles (DD,dd)
  2. Heterozygous - an individual with different alleles (Dd)
  3. Genotype - the genetic makeup of an individual
  4. Phenotype - physical appearance (dimples)
3. Family Trees
  1. Can be used for tracing genetic changes
  2. Can track diseases
Inherited conditions in humans
1. Polydactyly
  1. When a baby has excess fingers or toes
  2. Caused by a dominant allele
  3. If 1 parent has it, you have a 50% chance as half the gametes have the fault. If they are homozygous, you have no chance
2. Cyctic Fibrosis
  1. Organs get clogged by mucus
  2. Treatment = physiotherapy and antibiotics
  3. Caused by a recessive allele
    1. must be inherited by both parents
  4. Carriers have both alleles but no symptoms because the dominant is healthy
3. The Genetic Lottery
  1. When an egg and sperm combine it is up to luck which alleles combine
  2. Use a punnet square
4. Curing Genetic Disease
  1. Scientists hope genetic engineering will be the answer as they can cut out faulty alleles and replace them with healthy ones
  2. Genetic tests show people what faulty alleles they have and the probability of children having them
    1. They can then decide whether they want a family. It raises ethical issues
Stem Cells and Embryos
1. RELIGION AND SHIZZLE

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B2.5 Simple Inheritance in Animals and Plants

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	Created by mhancoc3 about 10 years ago