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 extrachromosomal 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