Day 6: Meiosis and Mendelian Genetics Homework due Tuesday 5/1/18

1. Day 6: Meiosis and Mendelian Genetics Homework due Tuesday 5/1/18 6F: Predict the possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance 6G: Recognize the significance of meiosis to sexual reproduction. 6H: Describe how techniques such as DNA fingerprinting, genetic modifications, and chromosomal analysis are used to study the genomes of organisms. Word Bank Allele Chromosome Codominance Heterozygous Crossing Over Dihybrid Cross Recessive allele Diploid Meiosis Dominant allele Monohybrid Cross 1. An organism is said to have a _____________________ gene combination if it possesses two different forms of an allele. 2. Also known as sex cells, _________________ are cells that contain half the total number of chromosomes for an organism. 3. The exchange of genetic material between homologous chromosomes during meiosis that contributes to genetic variation is a process called __________________ ___________. 4. A ______________________ gene combination is one in which an individual possesses two identical alleles. 5. All of the possible forms of a gene that can occur in an individual is a(n) ________________. 6. A ______________________ ____________ is a genetic cross used to examine the possible inheritance of one specific set of alleles. 7. A ______________________ ____________ is a genetic cross used to examine the possible inheritance of two specific sets of alleles. 8. The inherited characteristic that is only expressed when no other character is present is the ____________________ ___________. 9. A linear strand of DNA that is wrapped around protein structures, a(n) ____________________ carries the gene sequence of an organism. 10. _____________________ is the process of cell division that results in the production of haploid gametes. 11. The actual allele combination of a gene is called its __________________________________. 12. The physical appearance of an organism is known as its ______________________________. 13. When both alleles are considered dominant, __________________________ occurs, resulting in both phenotypes being expressed. 14. The ___________________ _________________ is the inherited characteristic that is always expressed when present. 15. Represented by the symbol n, a(n) ______________________ cell contains only a single set of chromosomes. 16. Represented by the symbol 2n, a(n) ______________________ cell contains pairs of all of the homologous chromosomes.

2. Meiosis 6G (S) Meiosis creates gametes or sex cells such as sperm and eggs for sexual reproduction. Gametes are haploid cells (half the number of chromosomes). Gametes are reproductive cells and are made in the reproductive system. Using the diagram of meiosis answer the following questions. 1) Label which type of cell division is haploid and which is diploid. 2) How do the number of daughter cells produced differ between meiosis and mitosis? 3) How do the number of copies of chromosomes differ between meiosis and mitosis? 4) Genetic diversity is due to crossing over of sister chromatids during meiosis. Compare the daughter cells to the parent cells. Which of the two types of cell division exhibits genetic diversity in the daughter cells? 5) Why is genetic diversity important? Genetic Crosses 6F (R) Punnett squares allow you to predict the possible genetic combinations of the offspring. There are 4 main steps to solving a punnett square, but all 4 steps may not be needed depending on the questions. These steps are: K – Key; create a key C – Cross; Write the parental genotypes P – Punnet Square; Set up and fill in a punnett square S – Solve; Answer the question (s) 1) The allele for dimples (D) is dominant to the allele for no dimples (d). A heterozygous man marries a woman who is also heterozygous for dimples. What fraction of their offspring will have dimples? K- C- P- S-

3. 2) The allele for hitchhiker’s thumb (h) is recessive to straight thumb (H). If a man and his wife are both homozygous recessive, will any of their offspring potentially have a hitchhikers thumb? K- C- P- S- 3) In a certain breed of dogs, a gene (L) codes for hair length. The dominant trait is short hair and the recessive is long hair. Suppose a heterozygous female dog and a homozygous long hair male dog mate. What will be the genotypic ratio of their offspring? K- C- P- S- 4) Monohybrid = ___________________________ traits 5) Dihybrid = __________________________ traits

4. Dihybrid Crosses 6F (R) In a dihybrid cross, two genes are being studied. The same steps are followed. When gametes are created for the parent, each gamete must have 1 letter from each gene (so a “B” and a “L”), otherwise the offspring will be missing the directions for that particular trait. 1) Gametes can be determined using the FOILmethod or another method your teacher taught you. Using the genotype of the F1 offspring, determine the gametes to be used in the cross between the 2 F1 offspring. The gametes you determined should match the gametes on the outside of the punnett square below. 2) Complete the cross by filling in the genotype for each possible offspring.