Topic 3 Genetics 3.1 Genes

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

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

Understandings The various specific forms of genes are called alleles.

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

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

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

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

Applications Sickle cell anemia

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

Skills Use a database to determine the differences in the base sequence of a gene in two species. Video Link: https://www.youtube.com/watch?v=OSKwuOccAak

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

3.2 chromosomes

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

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.

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

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

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

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?

The number of chromosomes is a characteristic feature of a species

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

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

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

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

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

3.3 Meiosis

Understandings Bozeman Biology Intro https://www.youtube.com/watch?v=rB_8dTuh73c

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

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

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

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