Chromosomes Worksheet (Answers)

Chromosomes Chromosome Structure Compare the structure of prokaryotic and eukaryotic chromosomes Prokaryotic Chromosomes Eukaryotic Chromosomes DNA is circular ………………………………………………………………………… DNA is linear ………………………………………………………………………… DNA is naked (not bound to proteins) ………………………………………………………………………… DNA is bound to histone proteins ………………………………………………………………………… Single chromosome (called the genophore) ………………………………………………………………………… Chromosome may exist in pairs (diploid) ………………………………………………………………………… Found in the nucleoid region of the cytosol ………………………………………………………………………… Found in the nucleus ………………………………………………………………………… Outline the role of plasmids in bacterial cells Plasmids are circular DNA molecules capable of autonomous replication and transcription ………………………………………………………………………………………………………………………………………………….......... They can be transferred between 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 chromosomes via autoradiography Cells were grown in a solution including radioactive thymidine (tritiated 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 if exposed to radiation) ………………………………………………………………………………………………………………………………………………….......... The silver grains appear only where the DNA was present, allowing chromosome length to be determined ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Chromosome Identification Define homologous chromosomes Chromosome 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 a 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 possess pairs of homologous chromosomes (e.g. body cells = 2n) ………………………………………………………………………………………………………………………………………………….......... Haploid nuclei possess only one copy of each chromosome (e.g. gametes = n) ………………………………………………………………………………………………………………………………………………….......... Outline the importance of chromosome number to the reproduction of species Chromosome number is a characteristic feature of a species - organisms with different haploid numbers will ………………………………………………………………………………………………………………………………………………….......... generally be unable to produce viable diploid zygotes (hybrid species are infertile) ………………………………………………………………………………………………………………………………………………….......... Identify the general characteristics of the following individuals based on their karyograms Normal male (46, XY) ………………………………………………………………………... Female with Down Syndrome (47, XX) …..……………………………………………………………………