CHAPTER13
MEIOSIS AND SEXUAL LIFE CYCLES
OBJECTIVES
1. Explain why organisms only reproduce their own kind, and why offspring more closely resemble their parents than unrelated individuals of the same species.
Organisms can only reproduce their ownspecies.
Organisms resemble their parents because they are the ones who pass on their genes to us.
3. Distinguish between asexual and sexual reproduction.
In asexual reproduction, a single individual is parent and passes copies of all its genes to its offspring.
In sexual reproduction two parents give rise to offspring that have unique combinations of genes inherited from both parents.
4. Diagram the human life sicle and indicate where it is in the human body that mitosis and meiosis occur; which cells are a result of meiosis and mitosis; and which cells are haploid.
Figure 12.3 pg 228
5. Distinguish among the life cycle patterns of animals, fungi, and plants.
Figure 12.4 pg 228
6. List the phases of meiosis I and meiosis II and describe the events characteristic to each phase.
Figure 12.5 pg 229
7. Recognize the phases of meiosis from diagrams or micrographs.
Figure 12.6 pg 230
9. Describe the process of synapsis doring prophase I, and explain how genetic recombination occurs.
During prophase one of meiosis, the duplicated chromosomes pair with their homologues, aprocess called sinapsis.
10. Describe key differences between mitosis and meiosis; explain how the end result of meiosis differs from that of mitosis.
Figure 12.7 pg 233
11. Explain how independent assortment, crossing over, and random fertilization contribute to genetic variation in sexually reproducing organisms.
Independent asortment- Figure 12.8 pg 235
Crossing over- Figure 12.9 pg 235
Random fertilization- The random nature of fertilization adds to the genetic variation arizing from meiosis.
CHAPTER 14
MENDEL AND THE GENE IDEA
OBJECTIVES
5. What’s mendel’s law of segregation?
Figure 13.4 pg 242
6. Use the Punnet square to predict the results of a monohybrid cross and state the phenotipic and genotipic rations of the F2 generations.
Figure 13.6 pg 243
7. Distinguish between genotype and phenotype; heterozygous and homozygous; dominant and recessive.
genotype- genetic makeuu
phenotype- appearance
heterozygous- organisms having two different alleles for a character
homozygous- organism having a pair of identical alleles for a character
dominant allele- is fully expresed in the organism
recessive allele- has no knoticeable effect in the organism
8. Explain how a testcross can be used to determine if a dominant phenotype; is homozygous or heterozygous.
Figure 13.6 pg 243
9. Define random event and explain why it is significant that alllele segregation during meiosis and fusion of gametes at fertilization are random events.
Figure 13.9 pg 247
13. State, in your own words, Mendel’s law oif independent assortment.
Figure 13.8 pg 246
14. Use a punnett square to predict the results of a dihybrid cross and state the phenotypic and genotypic ratios of the F2 generations.
Figure 13.7 pg 244
16. Give an example of incomplete dominance and explain why it is not evidence for the blending theory of inheritance.
Figure 13.10 pg 248
17. Explain how the phenotypic expression of the heterozygote is affected by complete dominance,incomplete dominance and codominance.
complete dominance- the phenotipe of the heterosigote and dominant homosigote are indistinguishable.
incomplete dominance- Whre the F1 hybrids have an appearence somewhere in between the phenotipes of the two parental varieties.
codominance- both alleles are separatly manifest in the phenotipe.
18. Describe the inheritance of the ABO blood system and explain why the IA and IB alleles are said to be codominant.
They are codominant because both are expresed in the phenotype of the IAIB heterozygote, who has type AB blood.
Figure 13.11 pg 250
19. Define and give examples of pleiotropy.
Pleiotropy is the ability of a gene to affect an organism in many ways.
Example sickle-cell, Figure 13.16 pg 255.
20. Explain in your own words, what is meant by “one gene is epistatic to another.”
This means that one gene at one locus alters the phenotypic expresion of a gene at a second locus.
23. Describe how environmental conditions can influence the phenotypic expression of a character.
Figure 13.14 pg 252
24. Given a simple family pedigree, deduce the genotypes for some of the family members.
Figure 13.15 pg 253
CHAPTER 15
THE CHROMOSOMAL BASIS OF INHERITANCE
OBJECTIVES
4. Deffine linkage and explain why linkage interferes with independent assortment.
Linked genes are located in the same chromosome, they tend to be inherited together in genetic crosses because they are part of a single chromosome that is passed along as a unit.
Sinse the genes are located in the same chromosome as the other, they cant be separated, thus interfearing with independent asortment.
6. Explain how crossing over can unlink genes.
A cross over between homologous chromosomes breaks linkages in the parental chromosomes to form recombinant chromosomes that may bring together alleles in new combinations.
10. Describe sex determination in humans.
Figure 14.8 pg 270
11. Describe the inheritance of a sex-linked gene such as color blindness.
Figure 14.9 pg 271
12. Explain why a recessive sex-linked gene is always expressed in human males.
Any male receiving the recessive allele from his mother will express the trait.
14. Distinguish among nondisjunction, aneuploidy, and polyploidy; explain how these major chromosomal changes occur.
nondisjunction- the members of a pair of homologous chromosomes do not move apart properly during meiosis I, or in which sister chromatids fail to separate during meiosis II.
Figure 14.11 pg 273
aneuploidy- an abnormal chromosome number.
If an aberrant gamete unites with a normal one, the offspring will have an abnormal chromosome number.
polyploidy-more than two complete chromosome sets.
Takes place when nondisjunction takes place in mitosis.
16. Distinguish among deletions, duplications, translocations, and inversions.
deletions- occurs when a chromosomal fragment lacking a sentromere is lost during cell division
duplications- is produced if the fragment joins to the homologous chromosome.
inversions-is produced if the fragment reataches to the original chromosome but in the reverse orientation
translocation- formed if the fragment joins a nonhomologous chromosome