IB syllabus 3.4.U2 Gametes are haploid so contain only one allele of each gene. 3.4.U3 The two alleles of each gene separate into different haploid daughter nuclei during meiosis. 3.4.U4 Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles. 3.4.U8 Many genetic diseases have been identified in humans but most are very rare. 3.4.U9 Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer. 3.4.A4 Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl.

Genetics 12: Mutations and genetic diseases Objectives Warm Up Explain why zygotes have two alleles for each gene State that radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer. How many copies of each gene would you find in a sperm cell? Why? How many copies of each gene would you find in a zygote (fertilized egg)? Why? permanent alteration of the nucleotide sequence of the genome

Outline Allele segregation Mutagens Chernobyl and Hiroshima

Allele segregation

Genes come in varieties called ________. Adult diploid organisms have ___#___ alleles for each gene. The process of meiosis produces (adjective) cells with ___#___ of each chromosome and ___#___ allele of each gene.

Turn and talk: describe to your partner what’s happening in this diagram. Partner who goes first is the one whose birthday is earliest in the year

Adult diploid organisms have two alleles for each gene. Homozygous= alleles are the same (ex: rr, RR) Heterozygous= alleles are different (ex: Rr)

Takeaways A gene can exist in more than one form (allele.) Organisms inherit two alleles for each trait. When sex cells are produced (by meiosis), allele pairs separate leaving each haploid cell with a single allele for each trait. When sex cells combine (fertilization) a new diploid organism is created, with two alleles for each trait.

Mutagens

Review Mutation =? Mutagens (=?) are involved in the development of tumors Mutagen examples? Prompt students for these. Some possible examples: UV rays, x-rays, radiation, compounds in cigarette smoke, benzene, ethidium bromide

Mutagens include radiation and mutagenic chemicals increase the mutation rate Cause genetic diseases and cancer

When could a mutation lead to cancer? When could a mutation lead to a genetic disease? Cancer- mutation in body cells Genetic disease- mutation in germline cell that would be passed on to offspring

Chernobyl and Hiroshima

Radiation is a mutagen. What happened when people were exposed to radiation in 1945 in Hiroshima and in 1986 at Chernobyl? Chernobyl is the name of the nuclear plant. It was near the town of Pripyat in Ukraine.

Partner activity Read about your assigned event. As you read, answer questions in your notebook. When done, teach your partner about your event. Your partner will answer the same questions in his or her notebook.

What was the event that caused radiation? Where and when did it happen? What were some of the consequences that resulted for people in that area?