Page 133 - Genetics_From_Genes_to_Genomes_6th_FULL_Part1

Problems 125

PROBLEMS

Vocabulary chromosomes are prepared as they would be for a
1. Choose the best matching phrase in the right column karyotype, but they have not yet been ordered in
for each of the terms in the left column. pairs of decreasing size.
a. How many chromosomes are shown?
a. meiosis 1. X and Y
b. gametes 2. chromosomes that do not differ b. How many chromatids are shown?
between the sexes c. How many centromeres are shown? (Count each
c. karyotype 3. one of the two identical halves sister centromere separately.)
of a replicated chromosome d. How many pairs of homologous chromosomes are
d. mitosis 4. microtubule organizing centers shown?
at the spindle poles e. How many chromosomes on the figure are
e. interphase 5. cells in the testes that undergo metacentric? Acrocentric?
meiosis
f. syncytium 6. division of the cytoplasm f. What is the likely mode of sex determination in
this species? What would you predict to be dif-
g. synapsis 7. haploid germ cells that unite ferent about the karyotype of a female in this
at fertilization
h. sex chromosomes 8. an animal cell containing more species?
than one nucleus
i. cytokinesis 9. pairing of homologous
chromosomes
j. anaphase 10. one diploid cell gives rise to two
diploid cells
k. chromatid 11. the array of chromosomes in a
given cell
l. autosomes 12. the part of the cell cycle during
which the chromosomes are not
visible 4. Human XX males who are sex-reversed because they
m. centromere 13. one diploid cell gives rise to four have a mutant X chromosome like that shown in
haploid cells Fig. 4.7 often learn of their condition when they want
n. centrosomes 14. cell produced by meiosis that to have children and discover that they are sterile. Can
does not become a gamete you explain why they are sterile?
o. polar body 15. the time during mitosis when 5. Researchers discovered recently that the sole function
sister chromatids separate of the SRY protein is to activate an autosomal gene
p. spermatocytes 16. site of the closest connection called Sox9 in the presumptive gonad (before it has
between sister chromatids “decided” to become a testis or an ovary).
Section 4.1 a. What would be the sex of an XY individual homo-
2. Humans have 46 chromosomes in each somatic cell. zygous for nonfunctional mutant alleles of Sox9?
Explain.
a. How many chromosomes does a child receive from b. Given your answer to part (a), why is SRY, rather
its father? than Sox9, considered the male determining factor?
b. How many autosomes and how many sex chromo- (Hint: What do you think would happen if you did
somes are present in each somatic cell? an experiment like the one in the Fast Forward Box
c. How many chromosomes are present in a human Transgenic Mice Prove That SRY Is the Maleness
ovum? Factor, except that you used a Sox9 transgene
d. How many sex chromosomes are present in a instead of SRY?)
human ovum?
Section 4.3
Section 4.2 6. One oak tree cell with 14 chromosomes undergoes
3. The figure that follows shows the metaphase chro- mitosis. How many daughter cells are formed, and
mosomes of a male of a particular species. These what is the chromosome number in each cell?