HOMEWORK ASSIGNMENT 4 SOLUTIONS

BIOLOGY1361
HOMEWORK ASSIGNMENT 4 SOLUTIONS

Review Exercises / Critical Thinking problems

Chapter 23: (1 – 23) on page 662

1. Explain what occurs between the time of ovulation and the implantation of the fertilized in the uterus. After ovulation, the ovum enters the abdominal cavity and then finds its way into the uterine tubes. Fertilization of the ovum usually occurs in the outer one third of the uterine tubes; the fertilized egg is then called a zygote. After about 3 days of constant cell division, a solid mass of cells, called the morula, is formed. The cells of the morula continue to divide by the time the developing embryo reaches the uterus, it is a hollow ball of cells called a blastocyst. At this time, implantation into the uterine wall occurs.
2. Explain the function of the chorion and placenta.
a. Chorion – develops into an important fetal membrane in the placenta. The chorionic villi connect the blood vessels of the chorion to the placenta.
b. Placenta – The placenta anchors the developing fetus to the uterus and provides a bridge for the exchange of nutrients and waste products between the mother and baby.
3. Name the three primary germ layers, and name three structures that develop from each layer.
a. One - Endoderm
b. Two - Mesoderm
c. Three – Ectoderm
(there are too many to list for each)
4. Define histogenesis and organogenesis.
a. Histogenesis – development of the primary germ layers into the various tissues of the body.
b. Organogenesis – development of the various tissues into organs
5. Describe and give the approximate length of each of the three stages of labor.
a. Stage One – onset of uterine contractions until dilation of the uterus is complete, from 6 hours to 24 hours;
b. Stage Two – this begins at maximum cervical dilation and lasts until the baby exits through the vagina, usually from a few minutes to an hour
c. Stage Three – begins at birth of the baby and ends when the placenta is expelled through the vagina; this lasts about 15 minutes after birth of the baby.
6. What is the difference between identical and fraternal twins?
a. Identical twins have identical DNA
b. Fraternal twins are no closer in DNA than any two siblings
7. What is an ectopic pregnancy? Where is it most like to occur? This happens when a zygote is implanted outside the uterus. The most common type of ectopic occurs in the uterine tube. This is called tubal pregnancy.
8. What is placenta previa. What is abruptio placentae?
a. Placenta previa – this occurs when the blastocyst implants in the uterine wall too near the cervical opening of the uterus
b. Abruptio placentae – This happens when the placenta separate from the uterine wall after pregnancy of more than 20 weeks.
9. What’s preeclampsia? – A disorder characterized by the onset of acute hypertension after the 24th week of pregnancy, accompanied by proteinuria and edema. It can result in complication such as abruptio placentae, stroke, hemorrhage, fetal malnutrition, and low birth weight.
10. What is a teratogen? An agent that can disrupt the normal histogenesis and organogenesis, causing a congenital abnormality in the fetus.
11. What is the stimulus for a baby’s first breath? An increase in carbon dioxide concentration in blood cells after the umbilical is terminated.
12. Name three developmental changes that occur during infancy.
a. One – birth weight doubles during first 4 months, and triples in first year
b. Two – Length increases by 50% first year
c. Three – Baby fat decreases
d. And others
13. Briefly explain what biological developments occur during childhood. Rapid growth, less chubby, face matures, baby starts smoking cigars
14. Briefly explain what biological developments occur during adolescence. Rapid physical growth; sexual maturity; secretion of sex hormones; and stuff like that.
15. Briefly explain what biological developments occur during adulthood. Maturation of bone, full closure of plates, balding patterns, halitosis, and farts
16. What is progeria? – A genetic disorder causing advance aging in children.
17. Explain the effects of aging on the skeletal system. Bones undergo changes in texture and strength
18. Explain the effects of aging on the respiratory system. Harder cartilage, especially around rib cage
19. Explain the effects of aging on the cardiovascular system. Degenerative heart and blood vessel disease.
20. Explain the effects of aging on vision. Progressive myopia may give way to glaucoma and such.
21. Where do the nutrients used by the zygote between the time of fertilization and implantation come from? Egg cell.
22. Explain the evolution of the function of the yolk sac. Mostly to make blood cells in homo sapien sapien.
23. What hormones are produced by the placenta? What is their function? Chorionic gonadotropins, estrogen, progesterone, and they help maintain the uterine wall during pregnancy.

Chapter 24: (1-17) on page 684

1. Explain how the DNA code is able to regulate the biochemistry of the cell. Each gene is a sequence of nucleotide bases in the DNA molecule, containing a genetic code that the cell transcribes to a messenger RNA molecule. Each messenger RNA molecule moves to a ribosome where the code is translated into a specific protein molecule. Many of the protein molecules are enzymes that permit specific biochemical reactions to occur.
2. As they are used in this chapter, define chromosome and gene. The first is DNA, and the second is a code in the DNA.
3. What is meant by independent assortment? As the sperm and egg are formed, chromosome pairs are separate; the original maternal and paternal chromosomes get mixed up and re-distribute the sleeve independently of the other chromosome pairs. According each sperm and egg is like to have a different test of 23 chromosomes. This process I called independent assortment of chromosomes, and it ensures that each offspring will very likely be genetically unique.
4. Define or explain the terms dominant, recessive, and codominant in regards to genetics.
a. Dominant – a gene that is able to express itself and mask the presence of a recessive train
b. Recessive – a gene that is only able to express itself in the absence of a dominant gene
c. Co-dominant – gens that will express themselves differently in the respect of co-dominant genes
5. What is a sex-linked trait? Nonsexual traits that are carried on the sex-determining chromosomes. Because most are carried on the X chromosome, they are also referred to as X-lined traits.
6. Define or explain the terms nondisjunction, trisomy, and monosomy.
a. Nondisjunction – when a pair of chromosomes fails to separate
b. Trisomy – A triplet of a chromosome pair in a cell rather than the usual two.
c. Monosomy – there is a single chromosome of a chromosome pair rather than the usual two.
7. What’s a pedigree chart? A family tree
8. What is a Punnett square? A grid used to determine the probability of an inherited and genetic trait.
9. What is a karyotype? – Photograph of chromosomes that are cut and pasted on a chart. What are the two methods used to harvest cells for a karyotype? The cells can be harvested for karyotype by scraping the inside of the cheek, or by taking a sample of blood containing white blood cells. The cells can be harvested from a fetus by amniocentesis or villus sampling.
10. Explain the difference between gene augmentation and gene replacement therapy. In gene augmentation therapy, normal genes are introduced in to the body with the hope that the genes will add to or augment the production of a needed protein. In gene replacement therapy, the genes that specify production of abnormal , disease-causing proteins are replaced by normal or therapeutic genes.
11. Name and briefly describe the two single-gene diseases discussed in this chapter. Cystic fibrosis is caused by recessive genes in chromosomes pair 7. The primary effect is the impairment of chloride ion transport across cell membranes. The disruption causes exocrine cells to secrete thick mucus and swat. The thickened mucus is especially trouble in the g.i. and respiratory tract where it can cause obstruction. Phylketornuir is causes b the recessive genets that fail to produced the enzyme phelalanine hydroxilase. This enzyme is needed to convert the amino acid phenylalanine into thyroxide. Phylalanine absorbed from the ingested food accumulates, resulting in the abnormal presence of phylketone in the urine. A high concentration of phelalanine destroys brain tissue; babies born with this condition are at risk for progressive mental retardation and possibly death.
12. Name and briefly describe the three chromosomal diseases discussed in this chapter. Indicate whether the diseases are the result of the trisomy or monosomy.
a. One – Down Syndrome
b. Two - Klinefelter Syndrome xxy
c. Three - Turner Syndrome xo
13. Explain why the particular sperm that fertilizes the egg determine the sex of the offspring. The female as the sex chromosomes of xx; the male has xy; all of the eggs produced by the male have x chromosomes. The permp permitted by the male will have either X or Y. If the sperm with X fertilizes the eggs, a female offspring will be produce. If the sperm with a y chromosome fertilizes the egg, a male offspring will be produced.
14. What is crossing-over? How does this process add to generic variation?
During one phase of mitosis, pairs of matching chromosomes line of up along the equator of the cell and exchange genes. This process is called crossing over; genes from a particular location over to the same location of the matching genes. Sometimes a whole group stays together and crosses over as a single unit. Crossing over changes the linkage patterns on individual chromosomes and thereby increases the genetic variation among offspring of a set of parents.
15. Explain why men have more six-linked disorders than women. Many sex linked disorders in men are recessive Because women have two X chromosome, both chromosomes would have to carry the trait to be expressed. Because men have only one x chromosome, if that chromosome carries the train it will be express because there is no corresponding gene on the Y chromosome. Therefore, in men, even recessive trains on the X chromosome act if they were dominant traits.
16. Which type of genetic mutation has the greatest long-term impact on the population? Harmful or beneficial? Explain your answer. Beneficial mutations allow organization to adapt to their environment; therefore they tend to spread throughout a population over the course of several generations. Harmful mutations inhibit survival and are not as likely to spread through the population.
17. If parents are concern that their child might be born with Down syndrome, what would be the best way to determine this: a pedigree, a Punnett square, or karyotype? Explain your answer. A karyotype would be the best method of determining whether a child has Down syndrome. Down Syndrome is a chromosome disorder (trisoly21) A karyotype looks at chromosomes so that the presence of an extra chromosome if the 21st pair would determined

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