Intro to Genetics (3.1)

• Gene: A heritable factor that consists of a length of DNA and influences a specific characteristic.

• Allele: One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene.• Example: hair color, eye color, thumb curling,

ear lobe attachment

Comparing number of genes

• Check out the table on pg. 142.

• Which species has the greatest number genes?

• Which group has the smallest number of genes?• Why do you think this is?

• Are there any numbers that surprised you?

Alleles

• Differences in alleles are usually changes in one or a few bases.

• Single Nucleotide Polymorphisms (SNPs) are the positions in a gene where more than one base may be present.• Several SNPs can be present in a gene.

Comparing Genes

• Do the activity on pg. 144 “Comparing Genes”

• Genome: The whole of the genetic information of an organism.

• The entire base sequence of each of its DNA molecules.

• In humans, the 46 molecules that form chromosomes, plus the DNA molecule in the mitochondria.

• The entire human genome was sequenced in the Human Genome Project which began in 1990 and was completed in 2003.

• There are approx. 23,000 protein coding genes in the human genome, but most DNA is not transcribed.

• Most base sequences are the same for all humans, but SNPs are what make each person unique.

• Read about genome sequencing on pg. 148 & check out the interactive timeline (link on Haiku)

Mutations

• New alleles are formed by gene mutations – random changes to the base sequence of a gene.

• Mutations can be:• Neutral – don’t affect the organism• Beneficial – could be good for the organism• Harmful – can even be deadly

• One type is a base substitution mutation.

Sickle Cell ANemia

Base Substitution Mutation

Base substitution Mutation

• When you substitute only one base in a DNA code…

GAG

• during translation…

• amino acid: glutamic acid

• Changing one amino acid changes the shape of the whole hemoglobin protein,

• which changes the shape of the whole red blood cell.

GTG

valine

Hemoglobin

• Oxygen that should be carried on the Hemoglobin cannot be carried as efficiently (anemia).

• The less flexible, long shaped cells get stuck in capillaries so blood flow is inhibited.

• Mutations can be passed to offspring.

• Here, the sickle cell gene is correlated with the frequency of malaria in Africa, where there is natural selection in favor of the gene, as it provides some protection against malaria.

Sickle Cell Anemia

• Do the sickle cell anemia activity posted on Haiku.

Mutations

• Causes:• Radiation: ex. Gamma rays, UV rays, X rays• Mutagenic chemicals: ex. some components of

tobacco smoke, mustard gas

• Effect: If a mutation develops in the genes that control cell division, it can cause unregulated cell division and therefore, a tumor / cancer.

• Mutations in somatic cells vs. gamete-producing cells.

Consequences of nuclear radiation

• 1. Read about the nuclear bombings of Hiroshima and Nagasaki and the nuclear accident at Chernobyl on pg. 184 – 185.

• 2. Read the article and watch the video on the NY Times article on Chernobyl (find link on Haiku).

• 3. Read the Science Daily article on Fukushima (find link on Haiku).

Opening Question

• Outline three results of nuclear radiation as evidenced by specific locations in the word where nuclear contamination has occurred.

• In your opinion, is the risk to the scientist’s health justified by the importance of the research?

PRokaryotes

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

• Some prokaryotes also have plasmids, but eukaryotes do not.• Plasmids are not always replicated at the same time

or at the same rate as a prokaryote’s chromosome.• Plasmids are not always passed on to both cells

formed by cell division.• Plasmids are often used in genetic engineering for

gene transfer.

Chromosomes

• http://learn.genetics.utah.edu/content/chromosomes/

• Homo sapiens have 46 chromosomes.

How Long is DNA?

• Read 150 – 151 in the textbook

• Summarize Carin’s technique and its importance to modern science:

Genome size vs. number of genes

• Genome size is the total length of DNA in an organism.

• It depends on the size and number of chromosomes.

• Take a look at the table on pg. 154.

What can we find on chromosomes?

• Finding the Loci of Human Genes: Page 154

• Go to the Haiku Link “Browse Your Genome”

• On the left side of the page, type in a gene name to search for. For ideas of genes to use, look at the purple box on pg. 154.

• Click on the gene and then scroll to the section “Genomic Content”

• Write the Location and Exon count of the gene.

Homologous Chromosomes

• Homologous chromosomes carry the same sequence of genes, but not necessarily the same alleles.

• Diploid nuclei have pairs of homologous chromosomes.• Homo sapiens diploid cells

have 46 chromosomes.

• Haploid nuclei have one chromosome of each pair (such as in sex cells).

Practice

• Do the DBQ on pg. 153 – Comparing the chromosomes of mice and humans.

• Do the DBQ on pg. 156 – Differences in chromosome number.

• Activity for Finding the Loci of Human Genes – see Haiku.