development/inheritance

The normal male genotype is __________, and the normal female genotype is __________.

XY; XX

Increases in GnRH, FSH, and LH mark the onset of which stage of development?

puberty

In strict dominance, a dominant allele __________.

will be expressed 100 percent of the time when paired with a recessive allele

Alterations in genetic activity during development result from __________.

the differences in the cytoplasmic compositions of individual cells

Given that albinism is a recessive trait, if an albino mother and a normal father with the genotype AA have a child, that child will __________.

have normal coloration

For a given trait, if the genotype is AA, the individual is __________.

homozygous dominant

For a given trait, if the genotype is aa, the individual is __________.

homozygous recessive

Which fertilization event occurs immediately after the formation of the male and female pronuclei?

spindle formation and cleavage begins

As identified by the Human Genome Project, the total number of protein-encoding genes in human DNA is __________.

20,000 to 25,000

If the father is heterozygous for type B blood and the mother is heterozygous for type A blood, which of the following distributions of phenotypes is likely in their offspring?

25% type AB; 25% type A; 25% type B; 25% type O

The normal chromosome complement of a typical somatic, or body, cell is __________.

46

What is the difference between colostrum and breast milk?

Colostrum has more protein and less fat than breast milk. Colostrum is ingested by the infant during the first two or three days of life. Colostrum has more protein and less fat than breast milk. Many of the proteins in colostrum are antibodies that play an important role in helping ward off infections until the baby's own immune system becomes fully functional.

What is the hormone that causes milk ejection (let-down)?

Oxytocin When the baby sucks on the nipple, sensory impulses are conducted to the spinal cord and brain. This stimulation causes the neurosecretory cells in the hypothalamus to produce oxytocin and release it through the pituitary gland. Oxytocin causes the myoepithelial cells in the walls of the lactiferous ducts and sinuses to contract and eject milk, or milk letdown.

Which of the following is the term for aging, or growing old?

Senescence Senescence, the natural process of growth after maturity has been completed, involves a gradual decline of sex hormones after menopause or the male climacteric. This decline leads to a reduction in functional capabilities, which in turn affects all organ systems. The overall effect of senescence is to reduce the ability of the individual to adapt to and cope with changes in the internal as well as the external environments.

What is the type of inheritance in which the allele is found on the X chromosome and therefore most often affects males?

Sex-linked inheritance

What is the fate of the cluster of cells in the blastocyst known as the inner cell mass?

The cells will develop into the embryo. As cleavage proceeds, the zygote develops into a hollow ball of cells called the blastocyst. The outer layer of the blastocyst is the trophoblast, which will develop into the chorion and then the placenta. The inner cluster of cell in the blastocyst, the inner cell mass, will become the embryo.

Which of the following does NOT happen during oocyte activation?

The first cleavage is completed. The first cleavage is NOT completed during oocyte activation. Oocyte activation happens prior to the formation of the zygote. Cleavage is the series of divisions that take place immediately after fertilization and the formation of a zygote. This series of mitotic cell divisions doubles the cell number in each round of division until the zygote becomes a multicellular complex known as a blastocyst. Enzymes are activated to increase the ovum's metabolic rate during oocyte activation. Meiosis II is completed during oocyte activation. Cortical reaction prevents polyspermy during oocyte activation.

The term inheritance refers to which of the following?

The transfer of genetically determined characteristics from generation to generation.

Throughout embryonic and fetal development, metabolic wastes generated by the fetus are eliminated by their transfer to the __________.

maternal circulation This transfer needs to take place across the placenta, which supports fetal development by transporting nutrients to and wastes out of the fetus. This exchange is necessary because the fetus does not have functioning respiratory, urinary, and digestive tracts.

The chorion develops from the __________.

mesoderm and the trophoblast The chorion develops from the mesoderm and the trophoblast. The mesoderm is one of the germ tissue layers that form during gastrulation and is the source of material for organ systems including the muscular and the skeletal systems. The trophoblast includes the regions of nutrient and gas exchange between mother and fetus that eventually form the placenta.

What is the term for a gene's position on a chromosome?

locus Locus is the term for a gene's position on a chromosome. Each gene in the human genome, which has between 20,000 and 30,000 total genes, has a specific locus in the chromosome, and the loci correspond to specific bands in the chromosome. Each gene codes for at least one protein, many of which are enzymes needed for specific metabolic reactions to take place.

Fertilization usually occurs in the __________.

uterine tube

The Extra-embryonic membranes that develop from the endoderm and the mesoderm are the __________.

yolk sac and the amnion The Extra-embryonic membranes that develop from the endoderm and the mesoderm are the yolk sac and the amnion. The yolk sac serves as a nutrient source for the embryo and as the source of blood cells in adults. The amnion serves as a mechanical buffer against potentially disruptive outside forces that might damage the embryo.

What is the meaning of the term gestation?

All of prenatal development All of the time spent in prenatal development is known as gestation. This time period is divided into first, second, and third trimesters. Different parts of development occur in different trimesters. But all three trimesters are part of gestation.

What is the extra-embryonic membrane that gives rise to the urinary bladder?

Allantois The extra-embryonic membrane that gives rise to the urinary bladder is the allantois. This membrane is formed from the endoderm and the mesoderm after gastrulation. Because the urinary system is not functional during development, the placenta is the site of the exchange of wastes, which include not only gases such as carbon dioxide but also nitrogenous wastes such as ammonia. These wastes are passed on to the maternal circulation and are processed in the mother's kidneys and bladder.

Gastrulation produces three germ layers. Which of the following is not one of those layers?

Blastocoele the following are correct: ectoderm, mesoderm, endoderm

Which of the following is the term for the events that occur during the first two months of development after fertilization?

Embryological development

Which of the following is the term for the developmental events events that occur between the ninth week and birth?

Fetal development

What is the "moment of conception"?

Fusion of the male and female pronuclei Fusion of the male and female pronuclei occurs in a process called amphimixis. When this happens, a fertilized egg exists, called a zygote. The formation of the zygote is the moment of conception.

What triggers the activation of the secondary oocyte?

Fusion of the sperm and secondary oocyte membranes

How do gametes differ from ordinary somatic cells?

Gametes contain only half the normal number of chromosomes.

What is the term that describes the existence of two different alleles for one gene?

Heterozygous

What happens in the process of hatching?

The zona pellucida is shed from the blastocyst. Remember that the secondary oocyte, when ovulated, is surrounded by a cluster of follicle cells, the corona radiata, and a protein-rich coat, the zona pellucida. The sperm will digest its way through these coverings to fertilize the oocyte. The fertilized egg sheds the corona radiata but is still covered by the zona pellucida. The zygote undergoes cleavage and forms the morula. As the morula forms the blastocyst, enzymes secreted by the outer layer of the blastocyst, the trophoblast, forms an opening in the zona pellucida, which is then shed in a process known as hatching.

Three days postcleavage, the pre-embryo is a solid ball of cells known as which of the following?

a morula;

What term describes different forms of a specific gene?

allele

The fusion of male and female pronuclei is termed __________.

amphimixis The fusion of male and female pronuclei is termed amphimixis. During this fusion, a zygote is formed by the re-creation of the diploid number of chromosomes, which is 46 total chromosomes. This number is the result of 23 chromosomes from the father and 23 chromosomes from the mother. For every trait that is determined by a pair of alleles, an individual in most cases has two copies of each allele because of the equal mixing of the chromosomes from each parent.

A hollow ball of cells created by cleavage is called a __________.

blastocyst A hollow ball of cells created by cleavage is called a blastocyst. This ball forms from a solid complex of cells known as a morula. At this point, the factor that determines whether a cell in the complex gets sufficient oxygen and nutrients from the surrounding fluid is surface area. The formation of the hollow ball of cells known as the blastocyst is necessary to ensure that all cells in the embryo continue to get their required amounts of oxygen and nutrients from the surrounding fluid.

Which of the following forms the placenta?

chorion

A sequence of cell divisions that begin after fertilization is called __________

cleavage A sequence of cell divisions that begin after fertilization is called cleavage. This is a series of mitotic divisions in which the cell number is doubled after each division. This doubling proceeds up to the point at which the zygote becomes a multicellular complex known as a morula. Because of the change in surface area, this solid ball of cells becomes a hollow ball known as a blastocyst. This embryo then implants in the endometrium of the uterus as it enters the uterine cavity.

In which pattern of inheritance does an individual who has different alleles for a given trait exhibit both of the phenotypes for that trait?

codominance

The first secretion produced by the mammary glands for the baby is __________.

colostrum

What event marks the onset of development?

fertilization Development begins at fertilization or conception, when male and female gametes fuse. The sperm penetrates the secondary oocyte and deposits the sperm nucleus into the cytoplasm of the secondary oocyte. The secondary oocyte will finish meiosis and become a mature ovum. At that point the sperm and egg pronuclei will fuse to form a zygote. This marks the beginning of development.

Germ-layer formation results from the process of __________.

gastrulation

What is the study of inheritance called?

genetics

The term for what occurs when the blastocyst touches and grows into the endometrium is __________.

implantation

If an allele is dominant, it will be expressed in the phenotype __________.

regardless of any conflicting instructions carried by the other allele If an allele is dominant, it will be expressed in the phenotype regardless of any conflicting instructions carried by the other allele. This is the typical situation where you have strict dominance and excessiveness expressed for a specific trait. The dominant phenotype will be expressed under two conditions, either as a homozygous or as a heterozygous genotype for the dominant allele. The recessive phenotype is only expressed in one condition, as a homozygous genotype. Both alleles do not have to agree on the outcome of the phenotype for a dominant trait to be expressed.

The umbilical cord, or umbilical stalk, contains __________.

the allantois, blood vessels, and yolk stalk The umbilical cord, or umbilical stalk, contains the allantois, blood vessels, and yolk stalk. These structures connect the fetus to the placenta. The blood vessels enable the embryo to exchange oxygen and carbon dioxide across the placenta. The yolk stalk functions as the connecting channel between the embryo and the yolk sac, which is a source of nutrition and blood cells. The allantois is an extra-embryonic membrane that later forms the urinary bladder.

Exchange between the embryonic and the maternal circulations occurs by diffusion across the syncytial and cellular trophoblast layers via __________.

the chorionic blood vessels Exchange between the embryonic and the maternal circulations occurs by diffusion across the syncytial and cellular trophoblast layers via the chorionic blood vessels. Because of the separation of the layers of the endothelial cells that line the blood vessels, the maternal and embryonic circulations never mix, and their erythrocytes never come into contact. Small soluble molecules, however, can diffuse across these layers: Nutrients from the digestion of food in the mother's GI tract cross over to provide nutrition to the embryo. Antibodies in the mother also cross over to give passive immunity to the embryo.