3.2 chromosomes Flashcards
compare the structure of prokaryotic and eukaryotic chromosomes
P:
-DNA is circular
-DNA is naked (not bound to proteins)
-Single chromosome (called the genephore)
-Found in the nucleons region of the cytosol
E:
-DNA is linear
-DNA is bound to histone proteins
-Chromosome may exist in pairs (diploid)
-Found in the nucleus
outline the top of plasmids on bacteria cells
plasmids are circular DNA molecules capable of autonomous replication and transcription
they can be transferred between the bacteria via bacterial conjugation
they are also used as a vector for gene transfer in scientific experiments
outline how john cairns elucidated the length of the chromosomes via autoradiography
cells were grown in a solution including radioactive thymidine (triturateur thymidine)
the radioactive thymidine was incorporated into the DNA of the cell (T present in DNA but NOT found in RNA)
the chromosomes were then isolated and fixed to a photographic surface
this surface was immersed in a solution of silver bromide (which turns into metal grain of exposed to radiation)
the silver grains appear only where the DNA was present, allowing chromosome length to be determined.
define homologous chromosomes
chromosomes pairs that share the same structural features and have the same genes at the same loci positions
they represent the maternal and paternal copies of chromosome
differentiate between autosomes and sex chromosomes (heterosomes)
sex chromosomes X and Y determine sex
Autosomes represent all other chromosomes (those that do not determine sex)
distinguish between diploid and haploid
diploid nuclei posses pairs of homologous chromosomes (body cells = 2n)
haploid nuclei posses only one copy of each chromosome (gametes = n)
outline the importance of chromosome number to the reproduction of species
chromosome number is a characteristic feature for a species - organisms with different haploid numbers will generally be unable to produce viable diploid zygotes (hybrid species are infertile)
