10.2: Dihybrid Crosses

1. 10.2: Dihybrid Crosses By: Sydney Thames & Nayira Warren

2. Assessment Statement 10.2.1 • Calculate and predict the genotypic and phenotypic ratio of offspring of dihybrid crosses involving unlinked autosomal genes.

3. 10.2.1 • Genotype-The genetic makeup of an organism that includes their biological characteristics. • Phenotype-The physical makeup of an organism that includes their physical characteristics YY = 2 dominant Yy = one dominant, one recessive yy = 2 recessive

4. 10.2.1 • Dihybrid Crosses -involve two genes which control two characteristics. • We can use dihybrid crosses to calculate and predict the genotypic and phenotypic ratio of offspring involving unlinked autosomal genes.

5. 10.2.1 • Autosomal Genes- A gene that is not located on a sex chromosome. *When a gene is unlinked, they are found on different chromosomes and can be segregated by Random Assortment of meiosis, during Metaphase II.

6. Calculating and Predicting example • In order to calculate the genotypic and phenotypic ratio: • 1) Determine the parent’s genotypes • 2) Make and solve dihybrid cross • 3) Calculate and predict genotypic and phenotypic ratios. • http://www.siskiyous.edu/class/bio1/genetics/dihybrid_v2.html • http://www.sumanasinc.com/webcontent/animations/content/mendel/mendel.html

7. Assessment Statement 10.2.2 • Distinguish between autosomes and sex chromosomes.

8. 10.2.2 • Autosomes- General chromosomes that carry genetic instruction and any chromosome other than a sex chromosome; come in pairs. • Sex chromosomes- Come in pairs also, but there are two types, X & Y. For humans, the Y chromosome is the “determining factor” as it determines whether or not the embryo is male or female.

9. Assessment Statement 10.2.3 • Explain how crossing over between non-sister chromatids of a homologous pair in prophase I can result in an exchange of alleles.

10. 10.2.3 • Crossing over, also known as recombination, is the exchange of chromosome segments between non-sister chromatids in meiosis.

11. 10.2.3 • Alleles - an alternative form of a gene (one member of a pair) that are located at a specific position on a specific chromosome. The DNA codings on an allele determine traits that are passed on from parents to offspring.

12. 10.2.3 • During crossing over, “slices” of homologous chromosomes’ DNA are exchanged with non-sister chromatids of a homologous pair. Because of this, alleles are exchanged as the alleles from one chromatid are being exchanged with the alleles on a non-sister chromatid. • http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation5.html

13. 10.2.3

14. Works Cited • "Dihybrid Cross." The Biology Project. Web. 09 Feb. 2012. <http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cross/03t.html>. • http://library.thinkquest.org/20830/Textbook/Genetics.htm • http://www.sumanasinc.com/webcontent/animations/content/mendel/mendel.html • http://newton.dep.anl.gov/askasci/mole00/mole00388.htm • http://www.bookrags.com/research/crossing-over-gen-01/ • http://en.wikibooks.org/wiki/IB_Biology/Genetics,pt2 • http://click4biology.info/c4b/10/gene10.2.htm#1 • http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation5.html • http://www.ibguides.com/biology/notes/dihybrid-crosses-hl?PHPSESSID=8a17514703a1a528f6e35ae35079158d