Inheritance, Variation, Evolution

    Cards (98)

    • DNA stands for deoxyribonucleic acid
      it is the chemical that all of the genetic material is made up of
    • DNA contains coded information 

      what is in the DNA determines the characteristics
    • DNA is found in the nucleus in long structures called chromosomes
      Chromosomes normally come in pairs
    • DNA is a polymer
      it is made up of two strands coiled together in the shape of a double helix
    • A gene is a small section of DNA found on a chromosome
      each gene codes for a particular sequence of amino acids which are put together to make a specific protein
    • 20 amino acids are used but they make up thousands of different proteins

      genes tell cells in what order to put the amino acids together
      determines what proteins the cell produces
      determines what type of cell it is
    • genome is the entire set of genetic material in an organism

      scientists have worked out the entire human genome
      Human genome project 1990- team of scientists from all over the world worked together in tandem to map the human genome
    • The human genome project allowed scientists to
      identify genes that are linked to different types of disease
      knowing which genes are linked to which diseases helps develop effective treatments
      trace migration to see where and when new populations split off
    • DNA strands are polymers made up of nucleotides
      each nucleotide consists of a sugar, a phosphate, a base
      each base links to a base on the other strand of the helix (ATCG)
      this is complementary base pairing
    • the order of bases in a gene decides

      the order of amino acids in a protein
    • each amino acid is coded for by a sequence of three bases in a gene

      the amino acids are joined together to make various proteins, depending on the order of the gene's bases
      there are parts of the DNA that don't code for proteins, some non-coding DNA switches on and off so control whether or not a gene is expressed
    • proteins are made in the cell cytoplasm ribosomes
      to make proteins, ribosomes use the code in the DNA, DNA is found in the nucleus and can't move out because it is too big
      the code is transferred between the nucleus and ribosome using mRNA which acts as a messenger between the DNA and ribosome
      the correct amino acids are brought to the ribosomes in the correct order by carrier molecules
    • when a chain of amino acids has been assembled it folds into a unique shape
      this allows the protein to perform the task it is designed to do
      enzymes-biological catalysts
      hormones-carry messages around the body
      structural proteins-physically strong
    • mutations are changes to the genetic code

      mutations can occur spontaneously
      the chance of mutations can be increased by exposure to certain substances or types of radiation
    • mutations change the sequence of the DNA bases in a gene which produces a different genetic variant

      as a sequence of DNA bases code for the sequence of amino acids that make up a protein, mutations to a gene can lead to changes in the protein that it codes for
    • most mutations have little to no effect
      some will change it to such a small extent that its function or appearance in unchanged
      mutations can severely affect a protein, can change its shape which can change its function
    • if the shape of an enzymes active site is changed, it may not be able to bind to a substrate

      structural proteins could lose their strength
    • if there is a mutation in non-coding DNA

      it can alter how genes are expressed
    • there are different ways mutations can change the DNA base sequence

      insertions
      deletions
      substitutions
    • insertions
      insertions are when a new base is inserted into a DNA base sequence
      an insertion changes the way the groups of three are read which can change the amino acid they code for
      can change more than one amino acid as they have a knock on effect
    • deletions
      deletions are when a random base is deleted from a sequence
      they change the way that the base sequence is read and have knock on effects
    • substitutions
      substitution mutations are when a random base in the DNA sequence is changed to a different base
    • sexual reproduction produces genetically different cells

      sexual reproduction is where genetic information from two organisms is combined to produce offspring which are genetically different to either parent
      the mother and father produce gametes via meiosis
      each gamete contains 23 chromosomes
      the egg and sperm fuse together to from a cell with 46 chromosomes
    • sexual reproduction
      involves the fusion of female and male gametes
      there are two parents so the offspring contains a mixture of their parent's genes
    • the mixture of genetic information creates variation
      flowering plants can reproduce this way
    • asexual reproduction produces genetically identical cells

      there is only one parent so offspring are genetically identical
      happens by mitosis
      new cell has exactly the same genetic information- it is a clone
      bacteria/some plant/animals reproduce asexually
    • asexual reproduction
      only one parent
      no fusion of gametes no mixing of chromosomes and no genetic variation
      the offspring are genetically identical to their parent
    • gametes are produces by meiosis

      gametes have only one copy of chromosomes so when gamete fusion takes place, there is the right number of chromosomes
      meiosis involves two cell divisions, in humans this only happens in reproductive organs
    • meiosis
      before the cell divides, it duplicates genetic information + chromosomes arrange themselves into pairs- they line up in the centre of the cell. they are pulled apart so each cell has one copy of each chromosome some of the fathers and mothers go into each new cell
      in the second division, the chromosomes line up again and get split apart Produces four gametes with a single set of chromosomes, each gamete is genetically different from the others as the chromosomes get all shuffled up during meiosis
    • after two gametes have fused during fertilisation, the new cell divides by mitosis to make a copy of itself

      mitosis repeats many times to produce lots of new cells in an embryo
      as an embryo develops, the cells start to differentiate into the different types of specialised cell that make up a whole organism
    • sexual reproduction VS asexual reproduction
      mixture of chromosomes- variation which increases the likelihood of an organism surviving a change in the environment
      individuals with characteristics that make them better adapted to the environment have better chances of survival and more likely to breed successfully and pass on characteristics- natural selection
      selective breeding speeds up natural selection
    • asexual reproduction VS sexual reproduction

      one parent
      less energy
      faster
      produced in favourable conditions
    • some organisms can reproduce by both methods
      malarial parasites
      fungi
      plants
    • malarial parasites
      malaria is cause by a parasite that's spread by mosquitoes
      when a mosquito carrying the parasite bites a human, the parasite can be transferred to the human
      the parasite reproduces sexually when its in the mosquito and asexually in the human
    • fungi
      release spores which can become new fungi when they land in a suitable place
      asexually-produced spores are identical to the parent
      sexually-produces spores introduce variation and are in response to an unfavourable change in the environment
    • plants
      asexual reproduction can take place in many different ways- strawberry plants produce runners that grow horizontally on the surface of the soil away from a plant and at various points a new strawberry plant forms
      bulbs- new bulbs can form and divide off- each can form an identical plant
    • there are 23 pairs of chromosomes

      22 matched pairs control characteristics
      the 23rd pair are XX or XY
      these two chromosomes decide your sex
    • females have XX chromosomes 

      males have XY chromosomes
    • when making sperm, the X and Y chromosomes are drawn apart
      this gives a 50% chance of the sperm cell getting either chromosome
    • what genes you inherit control what characteristic you develop
      different genes control different characteristics, some are controlled by a single gene
      most are controlled by several genes interacting
      they exist in different version called alleles
    See similar decks