exam 1

Exercise 3B is a study of meiosis. You will simulate the stages of meiosis by using chromosome models. You will study the crossing over and

1) If the frequency of a recessive allele is 30% in a population of 100 people, how many would you predict would be carriers of this allele, but would not express the recessive phenotype?

1 by crossing over in prophase I , 2 , by indpendenent assortment and three by mutations in S phase

For one of the monohybrid crosses you performed in this Investigation, describe how to use the phenotype ratios to determine

---If given traits and parents, be able to use a Punnett square or patterns to predict the probability of offspring for a given cross and express it as a fraction, percent, or ratio.---

Define the term crossing over. (3 points) During meiosis’ prophase the homologous chromatids exchange segments.

The parents are both homozygous. The homozygous dominant would represent the wild type. And the homozygous recessive would represent the other fly parent of a different strain. The F1 generation would consist of 100% Wild Type but they would all be heterozygous in carrying the recessive gene.

You are also provided with a heterozygous female, and a homozygous recessive male for a genetic cross. In this particular female, all the dominant alleles are on one chromosome, and the recessive counterparts are on the other homologous chromosome. Due to a chromosomal condition, in the female no recombination occurs between the M and N loci. Normal recombination occurs between the L and M loci. Diagram this cross, and show the genotypes and frequencies of all offspring expected from this cross.

The gender in this experiment does not matter and so while testing the ratios predicted it seems to be correct because since I predicted a 2:2 ratio the numbers seemed to be really close to each other. When I crossed the flies the vestigial and purple mutations were dominant over the wild type because in the end of the crossing the filial products were 620 for the vestigial and purple mutation, while for the wild type it appeared to be 618. My null hypothesis is that if the genetic characteristic of the fruit flies tested are not linked, then the vestigial wings and the purple eye mutations in the alleles of the offspring flies will be recessive to the wild type flies. My alternate hypothesis is that if the fruit flies tested are linked, then the vestigial wings and purple eyes mutations in the alleles of the offspring flies will be dominant to the wild type flies. The observations that led me to this conclusion is that when following the procedure of the experiment, I observed that my hypothesis is correct because when I finished crossing the fruit flies.

but homozygous recessive for seed color (Ttyy). If 80 offspring are produced, how many are expected to be

The markers showing linkage are markers B, C, and D since they are more prevalent and highly associated with the mutant allele.

Lab 3a had involved 4 F1 generation crosses: a sex-linked cross between white eyed males and heterozygous wild-type female flies (XWY x X+XW), a dihybrid cross between heterozygous wild-type winged flies (Apterous carriers) that have wild-type eyes (but are sepia color carriers (ap+/ap; se+/se x ap+/ap; se+/se) , a monohybrid cross between Apterous and wild-type winged flies (ap/ap x ap+/ap+), and a dihybrid cross between wild type flies that are vestigial winged and sepia trait carriers (vg+/vg; se+/se x vg+/vg; se+/se).

This will result in one gamete receiving extra chromosomes, one not receiving a chromosome, and two gametes with 23 chromosomes each.

15) In a population with two alleles, A and a, the frequency of A is 0.2. Organisms that are homozygous for A die before reaching sexual maturity. In five generations, what would be the frequency of individuals with aa genotypes?

A di-hybrid cross is the mating of two organisms that differ in two traits. These two traits are controlled by pairs of alleles at different loci. A di-hybrid cross will always produce a F2 generation with the ratio of 9:3:3:1. This means that there are 9 individuals that display both dominant traits, 3 that display the first dominant trait and the second recessive trait, 3 that display the first recessive trait and the second dominant trait, and 1 that displays both recessive traits; which is called the homozygote.