3.2 Chromosomes

Question 1

Prokaryotic DNA

Answer 1

one chromosome consisting of a circular DNA molecule
some also have plasmids

Question 2

Eukaryotic Chromosomes

Answer 2

are linear DNA molecules associated with histone proteins
there are different chromosomes that carry different genes

Question 3

Homologous Chromosomes

Answer 3

carry the same sequence of genes but not necessarily the same alleles of those genes

Question 4

Autosomes

Answer 4

are chromosomes that do not determine sex

Question 5

Sex Chromosomes

Answer 5

are chromosomes that determine sex

Question 6

Diploid Nuclei

Answer 6

have pairs of homologous chromosomes
two copies of alleles for each trait
e.g. somatic cells
diploid number = 2n

Question 7

Haploid Nuclei

Answer 7

have one chromosome of each pair
one single gene copy
e.g. gametes
haploid number = n

Question 8

Comparison of Diploid Numbers

Answer 8

Homo sapiens - 46
Pan troglodytes (chimp) - 48
Canis familiaris (dog) - 78
Oryza sativa (rice) - 24
Parascaris equorum (equine roundworm) - 2

Question 9

Cairn’s technique for measuring length of DNA molecules

Answer 9

used technique called autoradiography
grew bacterial cells on thymidine; deoxynucleotide made of heavy H3 hydrogen isotope
the radioactive deoxynucleotide was only taken up by the replication of DNA
he then viewed these strands using autoradiography

Question 10

Karyotype

Answer 10

is the full complement of chromosomes in an organism

Question 11

Steps in Preparing a Karyotype

Answer 11

• a sample of cells in taken
• white blood cells are removed
• the cells are induced to undergo mitosis and stop at metaphase
• the chromosomes are now visible, are stained and spread out on a slide and photographed
• the photograph is cut up and the chromosomes are arranged in homologous pairs according to size

Question 12

Karyogram

Answer 12

is the diagram or photograph of the isolated and stained homologous pairs