Topic 3.2: Chromosomes Flashcards
Prokaryotes chromosomes
a) Have a single circular molecule made of naked DNA (Genophore)
b) May have additional plasmids
Eukaryotes chromosomes
a) Multiple linear DNA molecules packaged with histones
b) Do not have plasmids
Plasmids
Small, autonomous circular DNA molecules
Centromere
Constriction point of a chromosome
a) p-arm (short)
b) q-arm (long)
Identifying the region in which a gene is positioned
a) Chromosome
b) Arm
c) G band location
Homologous Chromosomes
Paired chromosomes inherited from both parents in sexually reproducing animals
Characteristics of Homologous Chromosomes
a) Structural features
b) Genes at the same loci positions
Diploid
a) Two sets of chromosomes
b) Somatic cells in the organism
Haploid
a) One set of chromosomes
b) Sex cells / Gametes
Number of chromosomes in humans
23 pairs of chromosomes
Homologous Autosomes
a) 22 pairs
b) Do not determine sex
Sex chromosomes
a) 23rd pair
b) XX / XY
Y Chromosome
Contains the genes for developing male sex characteristics (SRY gene)
Karyotype
Identify the number and types of chromosomes in a eukaryotic cell
Functions of karyotyping
a) Identify the sex of offspring
b) Diagnose potential chromosome abnormalities
Processo of karyotyping
a) Harvesting cells
b) Chemically inducing cell division, arresting mitosis while the chromosomes are condensed
c) Determine whether chromosomes appear with sister chromatids or not
Karyogram
Visual profile that shows the chromosomes of a
cell in homologous pairs of decreasing length
Autoradiography (John Cairns)
Technique for measuring the length of DNA molecules while uncoiled
Process of Autoradiography
a) Radioactive thymidine is incorporated into a cell’s DNA
b) Chromosomes were fixed to a photographic surface and treated with silver bromide (AgBr)
c) Radiation converts silver ions into insoluble grains that is visible via electron microscopy when a film is developed
Chromosome number and species
Chromosome number is a characteristic feature of members of a particular species
What happens if two organisms with different diploid numbers interbreed?
a) Unlikely to interbreed
b) Offsprings are infertile (Donkey 62 + Horse 64 = Mule 63)
Chromosome number of:
a) Parascaris equorum
b) Oryza sativa
c) Homo sapiens
d) Pan troglodytes
e) Canis familiaris
a) 4
b) 24
c) 46
d) 48
e) 78
Genome size of:
a) T2 phage 170,000 bp
b) E. Coli. 4.6 million bp
c) Drosophila melanogaster 130 million bp
d) Homo Sapiens 3.2 billion bp
e) Paris Japonica 150 billion bp
a) Viruses and bacteria tend to have very small genomes
b) Prokaryotes have smaller genomes than eukaryotes
c) Sizes of plant genomes can vary dramatically
Chromosome number, genome size and genetic complexity
Chromosome number and genome size do not provide a valid indication of genetic complexity
Number of genes and biological complexity
The number of genes present in an organism will differ between species and is not a valid indicator of biological complexity
