Prokaryotic Chromosome Structure Answers to page 78 Prokaryotic Chromosome Structure

1. The prokaryotic chromosome is a singular circular chromosome. Eukaryote chromosomes comprise linear DNA packaged with proteins. In prokaryotes, some genes are carried on extra-chromosomal plasmid DNA The prokaryote chromosome is attached to the plasma membrane and is not enclosed in a nuclear membrane(unlike the eukaryotic chromosome) Prokaryotic chromosomes consist almost entirely of protein coding genes and their regulatory sequences. Eukaryotic chromosomes contain much intronic DNA that does not code for proteins.

2. Transcription(making of mRNA) and translation(protein synthesis) can occur at the same time because the DNA in prokaryotes is in direct contact with the cytoplasm. The entire process of gene expression occurs much more rapidly than in eukaryotic cells, where the mRNA must leave the nucleus and enter the cytoplasm before translation can begin

3. The bacterial genome(chromosome) is much smaller than the eukaryotic genome(all chromosomes)

Answers to page 72 - Alleles 1. A. Heterozygous. Each of the homologous chromosomes contain a different allele for the gene(one Dominant one recessive) B. Homozygous dominant: Each of the homologous chromosomes cnotain an identical dominant allele C. Homozygous recessive: Each of the homologous chromosomes contain an identical recessive allele

2. A) Aa B) AA C) aa 3. Each chromosome of a homologous pair comes from a different parent: one of maternal origin, one of paternal origin(they originated from the egg and sperm that formed the zygote) They contain the same sequence fo genes for the same traits. But the versions of the genes(alleles) on each chromosome may differ

4. Alleles are different versions of the same gene that code for the same trait. Different alleles provide phenotypic variationfor the expression of a gene. There are often two alleles for a gene, one dominant, one recessive. In this case, the dominant allele will be expressed in the phenotype. Sometimes alleles for a gene can be equally dominant, in which case, both alleles will be expressed in the phenotype. Where three or more alleles for a gene exist(multiple alleles), there is more phenotypic variation in the population( for that trait) than would be the case with just 2 alleles