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11 Dec 2019

Which statement correctly distinguishes monozygotic from dizygotic twins?

Monozygotic twins have identical phenotypes, and dizygotic twins have identical genotypes.

Monozygotic twins result from the fertilization of a single egg with two different sperm, while dizygotic twins result from the fusion of two eggs and then the subsequent fertilization with a sperm.

Dizygotic twins arise from splitting of an embryo into two embryos, while monozygotic twins result from the fertilization of a single egg with two different sperm.

Monozygotic twins are often of the same sex and genetically similar, while dizygotic twins are always of the same sex and genetically identical.

Monozygotic twins result from the splitting of the early embryo into two sections, while dizygotic twins result from two different fertilization events.

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Related questions

**For each answer, explain why when possible.**

1.) Cats contain a chromosome # of 2N=38. How many chromosomeswould be located in a maturing sperm in a feline testis, assumingthat the sperm has entered Meiosis II?

-76
-19
-38
-32

2.) A sperm is small and an egg is large. Why could this be? Canchoose more than one answer.

-Eggs need to be able to move completely outside of the mother forfertilization.
-Eggs are stationary and contain a supply of proteins, mRNAs,stored energy etc of the embryo-to-be.
-Sperm are motile, sometimes traveling considerable distances (on acellular scale).
-Twins will results from eggs that have the same genetic materialoriginally.

3.) Tons of organisms have evolved sex as a means of reproduction.Why? Tough question, choose the one most sensible answer.

-Sex helps an organism reproduce faster than any othermethod.
-Sex allows greater genetic variation in a population.
-Sex allows a species to mutate more accurately.
-Sex speeds up the rate of natural selection on a mutation.

4.) Zoonotic diseases are diseases that can be spread from otheranimal species to us. In this part of the lab we'll be taking somereasonable precautions to make sure that we don't allow unduecontact between their parasites and the interior of our bodies. Whyare we more vigilant about zoonotic diseases for the Gametogenesislab?

-The samples are fresh (they were part of a living organism just aday before)
-The samples are from mammals, so their parasites are closerevolved to us
-We are using sharp tools and razor blades, making access into ourbloodstream potentially easier
-The samples are from warm-blooded animals which have similardiseases to ours

5.) Echinarachnius parma (the common sand dollar) releases largeamounts of sperm and oocytes into the water. To avoid wasting spermwhenever possible, these gamete cells will not self-fertilize. Thismeans that you (Choose one):

-Will need to use sperm and eggs from different individuals inorder to successfully fertilize the oocytes.
-Can use room temperature conditions.
-Don't need to worry where the oocytes came from.
-Should focus your microscope as quickly as possible.

Question: Think about these questions, and post your thoughts on the use of cloning. Specifically, think the about the use of human cloning and discuss the potential impact on society.

Background Discussion: The scientific research terms, cloning means making exact copies of genes, a cell, or an organism. Therefore, cloning has been around for a long time. Identical twins are clones of a single zygote. When a single bacterium reproduces asexually on a petri dish, a colony of cells results, and each member of the colony is a clone of the original cell. Through biotechnology, bacteria now produce clone copies of human genes.

Through recent advances in science, it is possible to produce a clone of a mammal- and perhaps even one day, a human. The parent need not contribute sperm or egg to the process. During the so-called reproductive cloning, a nucleus (which contains the genetic material of a person) from one adult cell is placed in an enucleated egg. That egg is then allowed to develop. The developing embryo is placed in the uterus of a surrogate mother, and when birth occurs, the clone is an exact genetic copy of the original parent (of course the clone is younger). The process of cloning whole animals, and certainly humans, has not been perfected. Until it is, therapeutic cloning is more likely to become widespread.

Suppose it were possible to put the nucleus from a cell of a burn victim into an enucleated egg that is forced to become skin cells in the laboratory. These cells could be used to provide grafts of new skin that would not be rejected by the recipient. Would this be a proper use of cloning in humans?

Now, suppose parents want to produce a child free of genetic diseases. Scientists produce an embryo though in vitro fertilization, and then they clone the embryo to produce several embryos. Genetic engineering is then used to remove the genetic defect, and the defect free embryos are implanted into the uterus of a surrogate where they are allowed to grow to term. Would this be proper use of cloning in humans?

What if later scientists were able to produce children with increased intelligence or athletic abilities using the same technique? Would this be an acceptable use of cloning in humans?

Which one of the following examples could serve as an example to illustrate what is meant by "norm of reaction"?AnswerIn some reptiles, sex-type is determined by the egg-incubation temperature. For some species, eggs with the same genotype developing at higher temperatures develop into a different sex type than eggs with that genotype developing at lower temperatures.In birds and some moths, males develop if embryos have two Z chromosomes and females develop if they have a Z and W chromosome.In ants and bees, diploid individuals are typically female while most males arise from unfertilized haploid eggs.In humans, XXY individuals are Klinefelter males.

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