Keystone Review - Genes Alleles and Meiosis
1. C – the original number of
chromosomes (60)is halved by the end
of meiosis I (30) and remains constant
through the end of meiosis II (30).
2. C – One allele for each gene is found
on each chromatid in a tetrad.
3. D – At the beginning of prophase I of
meiosis and prophase of mitosis the
full set of chromosomes is present and
they have replicated their DNA to form
identical sister chromatids.
Keystone Review - Genes Alleles and Meiosis
4. D – The two alleles for a gene in an animal
body cell, which contains homologous pairs of
chromosomes, may have either the same of
different DNA sequences. Therefore choices A
and B are incorrect. Each allele is located on
one of the homologous pairs of chromosomes.
Therefore, choice C is incorrect, and choice D is
correct.
Keystone Review - Genes Alleles and Meiosis
Constructed Response:
A. Any two of the following phases should be identified:
– Prophase: nuclear envelope dissolves and chromosomes
condense
– Metaphase: the chromosome or tetrads align at the center of
the cell
– Anaphase: chromatids or homologous chromosomes separate
and are pulled to opposite sides.
– Telophase: the nuclear envelope reforms around the two
separated sets of chromosomes.
Keystone Review - Genes Alleles and Meiosis
Constructed Response:
B. In meiosis, homologous chromosomes pair and crossingover occurs between them. Homologs separate, producing
haploid daughter cells. All the stages of mitosis occur twice
in meiosis.
Keystone Review - Genes Alleles and Meiosis
Constructed Response:
C – Daughter cells resulting from meiosis have half the
normal chromosome number (haploid) and can function as
gametes. The daughter cells all differ in the genetic
information (alleles) they contain, while mitosis produces
identical daughter cells which are diploid.