✭ topic 1 & 2 flashcards (mixed)

• lipids

  non polar and hydrophobic
• what are triglycerides

  kind of lipid that forms main component of fats and oils
• what are triglycerides formed by

  three fatty acids and one glycerol molecule
• two types of fats

  saturated and unsaturated
• what reaction are triglycerides formed through

  condensation reactions
• what is the bond that forms between each fatty acid and glycerol

  ester bond
• how many ester bonds in a triglyceride

  three
• saturated fats

  if fatty acid chain in lipid contains the maximum number of hydrogen atoms

  chain is long and straight

  no carbon carbon double bonds

  solid at room temp, are straight and packed closely together
• unsaturated fats

  contain one carbon carbon double bond

  polyunsaturated fats have a large number of double bonds

  double bond causes kink in hydrocarbon chain
• what do kinks in unsaturated fats dod

  prevent unsaturated hydrocarbon chains from packing closely together

  results in oils that are liquid at room temperature
• when does an ester bond form

  when a -OH group from glycerol bonds with -COOH group of fatty acid
• formation of an ester bond

  condensation reaction
• uses of genetic screening


  to confirm a diagnosis

  to identify carriers

  for testing embryos
• prenatal genetic testing

  the testing of DNA from an embryo or fetus
• fetal testing

  amniocentesis

  chorionic villus sampling

  NIPD

  PGD
• amniocentesis

  involves inserting a needle into the amniotic fluid to collect fetal cells that have fallen off the placenta and fetus

  when amniocentesis is carried out (15-17 weeks of pregnancy) there is about 1% risk of causing miscarriage
• chorionic villus sampling (CVS)


  small sample of placental tissue is removed either through abdomen or vagina

  can be carried out earlier in pregnancy (8-12 weeks) since no need to wait for amniotic fluid to develop

  high risk of inducing miscarriage than 15 week amniocentesis
• implications associated with amniocentesis and CVS

  • risk of miscarriage
  • if any tests positive for disease, option for abortion available
  • however false positive exists
• non-invasive prenatal diagnosis (NIPD)

  • works by analysing data fragments in mother's blood plasma during pregnancy
  • cffDNA becomes detectable in mother at about 4-5 weeks of pregnancy (but too low levels to be analysed, so samples likely to be collected after 7-9 weeks of pregnancy)
• pre-implantation genetic diagnosis (PGD)

  couple will have to undergo IVF to create embryoss that can be tested before transfer to uterus

  when early embryo growing inculture and has around eight cells, one cell can be removed for genetic testing without harming embryo

  dna of cell is analysed and results of genscreen are used to decide whether to place embryo in uterus
• Preimplantation Genetic Diagnosis

  • IVF, or in vitro fertilisation is a type of fertility treatment during which fertilisation is carried out in the lab; embryos produced in this way can be implanted into the uterus where they develop into a foetus
  • PGD involves analysis of the DNA of an embryo prior to implanting it into the uterus
  • The sample of DNA to be analysed can be obtained by taking cell samples from embryos produced during IVF
  • Benefits
  • Reduces the chances of having a baby with a genetic disorder
  • It avoids abortion as it is carried out before implantation of the embryo
• • Chorionic villus sampling
  • This involves removing and testing a small sample of cells from the placenta using a fine needle
  • The cells contain foetal DNA which can be analysed for genetic disorders, allowing parents to make informed decisions about the pregnancy and foetus
  • It is carried out at around 11-14 weeks of pregnancy
  • The process has a  1-2 % risk of miscarriage
• • Amniocentesis
  • This involves removing and testing a small sample of cells from amniotic fluid using a fine needle
  • The amniotic fluid is the fluid that surrounds the foetus within the uterus
  • The fluid contains foetal cells which contain DNA to be analysed
  • It is carried out at around 15-20 weeks of pregnancy
  • The procedure has a 1% risk of miscarriage
  • Benefits
  • The tests allow parents to make informed decisions
  • Results can help parents prepare for the future care of the child, including medical treatment
• Each use of genetic screening brings potential concerns that should be considered

  • Identification of Carriers
  • Finding out you are a carrier can cause emotional stress and upset
  • It may impact your ability to find a partner 
  • Other genetic disorders may be identified 
  • Employers and insurance companies may use the data against an individual 
  • The tests are not always 100 % accurate; false positives or negatives may be given
• • Preimplantation Genetic Diagnosis
  • There are concerns it could lead to "designer babies" where parents select embryos with certain traits such as eye colour or sex
  • False results could lead to inaccurate information and poor decisions being made about the fate of embryos
• • Prenatal testing
  • Each procedure brings risk of miscarriage
  • False results could provide inaccurate information and poor decisions being made
  • There are ethical implications involved if parents decide to abort the fetus 
• gene

  length of DNA that codes for a protein

  every cell contains two copies of each gene from each parent
• allele

  alternative form of a gene
• genotype

  • The genotype of an organism refers to the alleles of a gene possessed by that individual. The different alleles can be represented by letters
• phenotype

  • The observable characteristics of an organism are its phenotype
• incomplete dominance


  A type of inheritance where a dominant allele does not completely mask the recessive allele and so the trait produced is a combination of both alleles.
• homozygote

  An organism which has two of the same versions of a gene.
• heterozygote

  An organism which has two different versions of the same gene.
• monohybrid inheritance


  characteristic controlled by one gene
• • Unlike DNA, RNA molecules are only made up of one polynucleotide strand (they are single-stranded)
• n example of an RNA molecule is messenger RNA (mRNA), which is the transcript copy of a gene that encodes a specific polypeptide. Two other examples are transfer RNA (tRNA) and ribosomal RNA (rRNA)
• • Cholesterol is transported around the body as lipoproteins 
  • Lipoproteins are molecules composed of lipid and protein
  • There are two types of lipoproteins; high density lipoproteins (HDLs) and low density lipoproteins (LDLs)
  • The balance of HDLs and LDLs in the blood is thought to be an important factor in the risk of developing heart disease
• High density lipoproteins

  • HDLs contain unsaturated fat, cholesterol, and protein
  • These moloecules transport cholesterol from body tissues to the liver to be recycled or excreted; they are responsible for reducing blood cholesterol levels when it is too high
  • HDLs are also thought to contribute to the removal of cholesterol from the fatty plaques that form during atherosclerosis
• Low density lipoproteins

  • LDLs contain saturated fat, cholesterol, and protein
  • The role of LDL is to move cholesterol from the liver into the bloodstream where it remains until it is required by the cells; they increase blood cholesterol levels when it is too low
  • LDLs bind to receptors on cell surface membranes, enabling them to be taken up by the cells that need them and removing cholesterol from the blood
  • High levels of LDLs can lead to blockage of these membrane receptors, causing blood cholesterol to rise
• LDLs

  'Bad cholesterol'