Mitosis and Meiosis and Cell Cycle

1.      The centromere is a region in which…

The answer is chromatids are attached to one another

2.      What is a chromatid?

A replicated chromosome

3.      During which phase do centioles begin to move apart in animal cells

Prometaphase

4.      Which phase is the longest phase of the mitotic stages?

Prophase

5.      During which phase do centromeres uncouple, sister chromatids are separated, and the two new chromosomes move to opposite poles of the cell?

Anaphase

6.      A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei containing how many chromosomes?

46

7.      The formation of a cell plate is beginning across the middle of a cell and nuclei are re-forming at opposite ends of the cell. What kind of cell is this?

A plant cell undergoing cytokinesis

8.      Movement of the chromosomes during anaphase would be most affected by a drug that…

Prevents shortening of microtubules

Genotype of the Father

The mother is eebb since she has yellow fur and brown nose and brown eyes. The puppies have black fur and brown fur so the dad has to be at least EE. Also, the picture shows that the puppies have brown ears, black nose, or brown nose. So based on the picture the fathers genotype would be EEBb.

 

 

 

 

Your Inner Fish: Chapter 6 The Best-Laid (Body) Plans

Biologists study embryos as the first stage of life. They found that embryos of species like fish, amphibians, birds, and mammals look very similar in the beginning stages of embryonic development. The study of similarities, differences, and development in embryos is called embryology.

Biologists found that there are three layers of tissues in  developing embryos that are responsible for developing all body parts which vary from one species to another. The outer layer is called the ectoderm, the inner layer is called the endoderm, and the middle layer is called the mesoderm. The ectoderm forms much of the body (skins and nervous system). The endoderm forms the inner structures of the body (digestive tract). The mesoderm forms tissues between guts and skin (skeletons and muscles).



DNA control controls how the body is formed. Hilde Mangold discovered a small patch of tissues that was able to direct other cells to form an entire body plan this patch of tissues is known as the Organizer.

 

 

Dihybrid Cross

Unlike a monohybrid cross, a dihybrid cross deals with two traits. Here are a couple problems.

1. In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The recessive trait causes mice to run in circles only. Mice with this trait are called waltzing mice (r). Hair color is also inherited in mice. Black hair (B) is dominant over brown hair (b). Cross a heterozygous running, heterozygous black mouse with a homozygous running, homozygous black mouse. What is the offspring phenotypic ratio?

        First we have to cross a  heterozygous running, heterozygous black mouse (RrBb) with a homozygous running, homozygous black(RRBB). The results would be 4 homozygous running, homozygous black (RRBB), 4 homozygous black, heterozygous running(RrBB), 4 heterozygous black, heterozygous running (RrBb), and 4 heterozygous black and homozygous running(BbRR). So the answer would be all running, black. 

2. Cross a homozygous running, heterozygous black mouse with a waltzing brown mouse. What are the parental genotypes?

          The genotypes would be RRBb x rrbb

3. Cross a heterozygous running, brown mouse with a heterozygous running, homozygous black mouse. What are the genotypes for the offspring at the running allele?

           So you would just focus on the crossing the running gametes so you would cross Rr x Rr. and the running genotypes would be RR, Rr, rr, because when you cross Rr x Rr you get 1 RR: 2 Rr: 1 rr.

4. Cross a heterozygous running, heterozygous black mouse with a heterozygous black mouse. What is the offspring phenotypic ratio?

           So you would cross RrBb x RrBb and you would get 9 running black : 3 running brown: 3 waltzing, black: 1 waltzing, brown.