1. Topic 3 Genetics
3.1 Genes

2. Understandings
A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.

3. Understandings
A gene occupies a specific position (loci)on one type of chromosome.

4. Understandings
The various specific forms of genes are called alleles.

5. Understandings
Alleles differ from each other by one or a few bases only.

6. Understandings
New alleles are formed by mutation. Mutations are changes in DNA.

7. Understandings
The genome is whole of the genetic information of an organism.

8. Understandings
The entire base sequence of genes was sequenced in the Human Genome Project.

9. Applications
Sickle cell anemia

10. Applications
Comparison of the number of genes in humans with other organisms.
Task- Students work in pairs to research humans and four other organisms (plant, bacterium, one w/ more, one w/less). We will create a class continuum.
Time-20 minutes

11. Skills
Use a database to determine the differences in the base sequence of a gene in two species.
Video Link:

12. Nature of Science
Developments in scientific research follow improvements in technology; gene sequencers

13. 3.2 chromosomes

14. Understandings
Prokaryotes have one chromosome consisting of a circular DNA molecule.

15. Understandings
Some prokaryotes also have plasmids but eukaryotes do not. Plasmids are small extra DNA molecules. Plasmids can be transferred from one cell to another.

16. Understandings
Eukaryotic chromosomes are linear DNA molecules associated w/ histone proteins.

17. Understandings
In eukaryotic species there are different chromosomes that carry different genes.

18. Understandings
Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes.

19. Diploid nuclei have pairs of homologous chromosomes
Haploid= n
Only gametes (sperm and egg cells) are haploid.
If an organism has 42 chromosomes in their haploid cells, how many would be in their diploid?

20. The number of chromosomes is a characteristic feature of a species

21. Understandings
A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length.

22. Understandings
Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex.

23. Applications
Cairn’s technique for measuring the length of DNA molecules by autoradiography.
(summary handout)

24. Applications
Use of karyotypes to deduce sex and diagnose down syndrome in humans.

25. Skills
Use online databases to identify the locus of a human gene and it’s product.
Go to:
Search Gene Map
Enter the name of a gene (DRD4, CFTR, HBB, F8, TDF). Record chromosome number and position

26. 3.3 Meiosis

27. Understandings Bozeman Biology Intro

28. Understandings
One diploid nucleus divides by meiosis to produce four haploid nuclei.

29. Understandings
The halving of the chromosome number allows a sexual life cycle with fusion of gametes.

30. DNA is replicated before meiosis so that all chromosomes consist of two sister chromatids

31. Understandings
The early stages of meiosis involve pairing of homologous chromosomes and crossing over.