Genetics Review Bell Ringer: Copy All of Agenda (Leave it out so I can see!)
Meiosis • Remember that meiosis creates 4 different sex cells (sperm or egg) • These sex cells are HAPLOID so they have half the number of chromosomes • Thanks to INDEPENDENT ASSORTMENT we are never sure which allele is going to end up in the sex cell
Fertilization • When two sex cells come together they form a DIPLOID zygote • This zygote is a combination of the mother and father’s alleles. • Thus, everyone has TWO alleles for any gene
Mendel • Gregor Mendel was the “father of genetics” • He studied pea plants and determined that the way they looked was due to unseen “factors” • We now know that these factors he was • referring to were genes
Genes & alleles • Any TRAIT (characteristic about you) is determined by your GENES. • GENES are regions of your DNA. Genes come in different kinds. • ALLELES are different versions of the same gene. For example, there might be a gene for hair color and the alleles can be black, blonde or brown.
Alleles • For simple traits, there are dominant and recessive alleles • DOMAINANT alleles always mask the recessive ones • The only way for recessive traits to show up is if they are the only alleles present.
Genotype & Phenotype • GENOTYPE is the actual alleles someone gets (Example: AA or aa) • PHENOTYPE is how those alleles appear in the organism (Example: blonde hair, blue eyes, attached earlobes)
HETEROZYGOUS VS. HOMOzYGOUS • HETEROZYGOUS means an individual had two different alleles (one dominant, one recessive) • HOMOZYGOUS means that an individual has two of the same allele (AA or aa, both dominant or both recessive)
ALLELEs • What is the genotype of a person who is heterozygous for Hitchhiker’s thumb (H) • Having a straight thumb is recessive. What is the genotype of someone
Punnett Squares • When we want to know the outcome of a particular cross (two parents breeding), we can use a punnett square. • PUNNETT SQUARES are ways to predict the potential offspring
Punnett squares • Punnett squares model what would happen if two organisms had offspring. Since we don’t know what alleles a mom or dad will give we show all 4 possibilities. • We put the parent’s alleles along the • sides and top. Then we fill in the • boxes so each child has 2 • alleles.
Punnett Squares • What is wrong with the following punnett square?
Vocab Words • Morphemes are the smallest unit of meaningful language • The following at the vocab words for you to define: • Homozygous • Heterozygous • Genotype • Phenotype • Haploid • Diploid