Page 5:

• The single prokaryotic chromosome is coiled up and concentrated in the nucleoid region.

• Prokaryotes have two types of DNA: a single chromosome and plasmids.

Page 6: Features of Plasmids

• Features of plasmids:

  • naked DNA (no histone)

  • small circular rings of DNA

  • not responsible for normal life processes

  • contain survival characteristics

  • can be passed between prokaryotes

  • can be incorporated into nucleoid chromosome

Page 8:

• Cairns' technique for measuring the length of DNA molecules by autoradiography.

• John Cairns used autoradiography to visualize and measure DNA molecules in E. coli.

• E. coli possesses a single circular chromosome that is 1,100 μm long.

Page 9:

• Cairns' technique for measuring the length of DNA molecules by autoradiography.

• John Cairns produced images of DNA molecules from E. coli using autoradiography.

• The images showed that E. coli possesses a single circular chromosome that is 1,100 μm long.

• Cairns' images also provided evidence to support the theory of semi-conservative replication.

Page 10:

• Eukaryote chromosomes are linear DNA molecules associated with histone proteins.

  • Eukaryotic chromosomes may be up to 85mm in length.

  • DNA has to be coiled in a predictable fashion to fit into the nucleus.

• Nucleosomes are formed by wrapping DNA around histone proteins.

• Prokaryotic DNA is supercoiled but not organized by histones.

Page 11:

• Eukaryotes possess multiple chromosomes.

• All individuals of a species possess the same chromosomes with the same gene loci.

• Chromosomes can vary in length, position of the centromere, and genes at specific loci.

Page 12:

• Use of databases to identify the locus of a human gene and its polypeptide product.

• Use the online database to search for genes and loci responsible for synthesizing specific polypeptides.

Page 13:

• The number of chromosomes is a characteristic feature of a species.

• Chromosome number reflects the complexity of an organism.

• Organisms with different numbers of chromosomes are unlikely to interbreed successfully.

Page 14:

• Diploid nuclei have pairs of homologous chromosomes.

• Haploid nuclei have one chromosome of each pair.

• Diploid nuclei have two copies of every gene, except for genes on the sex chromosomes.

• Gametes have haploid nuclei, while the fertilized egg cell is diploid.

Page 15:

• Comparison of diploid chromosome numbers of different species.

Page 16:

• Comparison of diploid chromosome numbers of different species.

Page 17:

• Comparison of diploid chromosome numbers of different species.

Page 18:

• Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles.

• Somatic cell nuclei are diploid and contain homologous pairs of each chromosome.

• Homologous chromosomes are the same size and carry the same genes at the same loci.

Page 19:

• Mammals, including humans, are diploid organisms.

• Many other eukaryotes may have more than two copies of a particular chromosome.

Page 20:

• Humans have 23 pairs of chromosomes in diploid somatic cells.

• One pair is the sex chromosomes (XX for female, XY for male).

• The X chromosome is larger and carries more genes than the Y chromosome.

• The presence of the SRY/TDF gene on the Y chromosome leads to male development.

Page 21:

• Chromosome pairs segregate in meiosis.

• Females produce eggs containing the X chromosome.

• Males produce sperm containing either X or Y chromosomes.

• The SRY gene determines maleness.

Page 22:

• Genome size is the total number of DNA base pairs in one copy of a haploid genome.

• Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens, and Paris japonica.

• Homo sapiens has 3.2 billion base pairs.

Page 23:

• Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens, and Paris japonica.

• Canopy plant (Paris japonica) has 150 billion base pairs.

• Escherichia coli has 130 million base pairs.

• T2 phage has 4.6 million base pairs.

• Fruit fly (Drosophila melanogaster) has 164 thousand base pairs.

Page 25:

• A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length.

• Stains used to make the chromosomes visible also give each chromosome a distinctive banding pattern.

• Karyogram is a diagram or photograph of the chromosomes present in a nucleus arranged in homologous pairs of decreasing length.

Page 27:

• Description of methods used to obtain cells for karyotype analysis (e.g., chorionic villus sampling and amniocentesis) and the associated risks.

• Age of parents influences chances of non-disjunction.

• It is advisable for mothers in a high-risk category to choose to have a prenatal test.

• The risk of a child having a trisomy such as Down Syndrome increases greatly in older mothers.

• Amniocentesis or chorionic villus samples can be taken and from them a karyotype can be constructed.

• Data from a positive test can be used to decide the best course of action, which at times can be to abort the fetus.

Page 29:

• Chorionic villus sampling and amniocentesis can be carried out in the 16th week of pregnancy with around a 1% chance of a miscarriage.

Page 30:

• Chorionic villus sampling and amniocentesis can be carried out in the 11th week of pregnancy with around a 2% chance of a miscarriage.

Page 31:

• Process of karyotyping:

  • Add tissue and chemical to sample.

  • Stimulate mitosis.

  • Add chemical to transfer cells to a tube.

  • Incubate.

  • Stop mitosis and centrifuge.

  • Concentrate in layers.

  • Culture in a growth medium.

  • Put cells onto a microscope slide.

  • Transfer to a tube containing fixative.

  • Cut out chromosomes.

  • Identify and add stain to pictures.

  • Arrange and photograph chromosomes.

Page 32:

• Use of karyograms to deduce sex and diagnose Down syndrome in humans.

• Karyograms can be used to determine sex and whether a person has Down Syndrome.

Page 33:

• Bibliography / Ack