Topic 3 Genetics 3.1 Genes. Understandings A gene is a heritable factor that consists of a length of...
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Transcript of Topic 3 Genetics 3.1 Genes. Understandings A gene is a heritable factor that consists of a length of...
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
• Diploid= 2n• 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.
1. Go to: http://www.omim.org/2. Search Gene Map3. 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.