Chapter 27 mastering A&P
Codominance
In which pattern of inheritance does an individual who has different alleles for a given trait exhibit both of the phenotypes for that trait?
Name the three major interacting hormonal events associated with the onset of puberty.
Increased GnRH production, increased sensitivity of the anterior pituitary to GnRH and the subsequent release of LH and FSH, and increased sensitivity of ovaries and testes to LH and FSH.
A _______is used to show all possible combinations of genes that can result from a give parental cross.
Punnett square
All of the following are true of the allantois except
it acts as the fetal bone marrow.
In strict dominance, one allele dominates another so a heterozygote will exhibit the dominant phenotype for the trait. In codominance, both alleles are expressed so a heterozygote will exhibit both the phenotype for the trait.
Compare strict dominance with codominance.
At which day post cleavage does implantation occur?
Day 7
Why does a man have a deeper voice and a larger larynx than a woman?
During puberty, testosterone causes greater laryngeal development than estrogen so a male will have a larger larynx and a deeper voice.
Distinguishing among embryonic, fetal, and prenatal development.
Embryonic development refers to the events that occur during the first 2 months after fertilization. Fetal development begins at the 9th week and continues until birth. Prenatal development consist of both embryonic and fetal development.
All of the following occur at puberty except
GnRH levels decline.
Which structure, exposed to the blastocoel, will form the embryo?
Inner cell mass
Why are sex-linked traits expressed more frequently in males than in females?
Males have a smaller Y chromosome that contains fewer genes that correspond to the larger X chromosome.
List and describe the factors involved in initiating labor contractions.
Relaxin causes cervical dilation, fetal weight distorts the myometrium, and the distortion of the cervix and the myometrium triggers release of oxytocin.
An individual has two of the same alleles for a gene for eye color. One of her eyes is deep blue, and the other is a lighter blue. Which of the following is true?
She is homozygous for that gene.
The Pitocin the doctors gave to Zoey helped her labor progress by
Stimulating myometrial contractions
How can you tell that the Karyotype shown here is male?
The 23rd pair of chromosomes is XY.
The gush of water Zoey felt resulted from
The amnion rupturing
neural tissues.
The ectoderm forms
the urinary bladder.
The endoderm forms
muscle
The mesoderm forms
The trait "freckles" operates through strict dominance . What would be the phenotype of a person who is heterozygous for this trait?
The person would have the dominant allele for freckles and the phenotype would be "freckles"
In Klinefelter syndrome,
The phenotype is male, but the extra X chromosome causes reduced androgen production
Identify the structure labeled "7"
chorion
The extra-embryonic membrane that forms the fetal portion of the placenta is the
chorion
Which chemicals are primarily responsible for initiating contractions of true labor?
estrogen and oxytocin stimulate the production of prostaglandin
Embryonic in early fetal development occurs in the______trimester.
first
The period of gestation when the rudiments of all major organ systems are established is the________trimester.
first
What is the developmental fate of "9"
forms the embryo
In pregnancy expansion of the uterus results from
hypertrophy of smooth muscle cells
Attachment to and penetration of the endometrium by the blastocyte is referred to as
implantation.
Which of the following descriptors regarding the trophoblast is false?
is derived from the inner cell mass
Progesterone comes the myometrium and prevents contraction. What factor does not antagonize progesterone and trigger labor and delivery?
relaxation of the cervix
Cervical dilation is caused by which of the following placental hormones?
relaxin
The hormone that increases the flexibility of the pubic symphysis during pregnancy is
relaxin
During the dilation stage of labor:
the amnion ruptures late in the stage.
Name the four extra-embryonic membranes
yolk sac, amnion, allantois, and the chorion
The extra-embryonic membrane that forms blood cells is the
yolk sac.
Where in the female reproductive system does fertilization normally occur?
uterine tube
Stretching of the cervix causes an increase in the blood levels of
oxytocin
Turner Syndrome
A child born with one lone X chromosome will have
Why does a mother's blood volume increase during pregnancy?
A mother's blood volume increases to accommodate for flow through the placenta.
Which of the following statements is most accurate in explaining the value of the large numbers of sperm ejaculated to cause fertilization?
A single sperm does not possess enough acrosomal enzymes to penetrate the oocyte by itself.
female
A zygote whose genotype is XX will develop as a
male
A zygote whose genotype is XY will develop as a
Which hormone causes the milk ejection (milk let-down) reflex?
oxytocin
Are environmental factors more likely to affect genotype or phenotype?
phenotype
The traits of an individual controlled by his or her genotype are his or her
phenotype
Identify the structure labeled "4"
placenta
Identify the structures labeled "4"
polar bodies
During gestation, contractions of the myometrium is inhibited by___________,produced by the placenta.
progesterone
The placenta is not a source of which of the following hormones?
prolactin
Identify the stage labeled "12"
trophoblast
Deoxygenated blood is carried to the placenta by the
umbilical arteries
Identify the structure at labeled "3"
umbilical cord
The________is formed by a portion of the allantois, blood vessels, and remnants of the yolk sac.
umbilical cord
Identify the structure connecting the fetus to the placenta, and name the extra-embryonic membrane from which it is derived.
umbilical cord; allantois
Oxygenated blood is carried away from the placenta by the
umbilical vein
Indicate the type of inheritance involved in each of the following situations: (1) Children who exhibit the trait have at least one parent who also exhibits it; (2) Children exhibit the trait even though neither parent exhibit it; and (3) The trait is expressed equally in daughters and sons.
(1) simple inheritance (dominant); (2) simple inheritance (recessive); (3) autosomal inheritance
Consider a dihybrid cross (AaBb* AaBb). How many offspring would be predicted to be heterozygous for both traits?
1/4
In a monohybrid cross, what is the predicted ratio of offspring with the dominant phenotype compared to those with the recessive phenotype?
3:1
How many chromosomes are contained within a human zygote?
46
How many chromosomes do human somatic cells contain?
46
Why are numerous sperm required to fertilize a secondary oocyte?
Acrosomal enzymes from multiple sperm are needed to penetrate the corona radiate.
How do autosomes and sex chromosomes differ?
Autosomes are chromosome pairs 1-22 that affect somatic characteristics. Sex chromosomes are the 23rd pair that determine whether an individual is male (XY) or female (XX).
Define homozygous and heterozygous.
Homozygous means that homologous chromosomes carry the same allele of a given gene. Heterozygous means that homologous chromosome carry different alleles of a given gene.
An individual who expresses a recessive phenotype must have what genotype?
Homozygous recessive
cystic fibrosis
Human chromosome 7 is involved in which disorder?
There are three alleles that determine blood type. IA and IB are codominant, and i is recessive to both of them. Serina has Type B blood. Which of the following might be Serina's genotype?
IBIB or IBi
1/2
If a color-blind (X-linked recessive trait) man marries a woman who is heterozygous for the trait, what portion of their male offspring can be expected to be color blind.
determined by interactions among several genes.
In polygenic inheritance, phenotypic characters are
a single pair of alleles
In simple autosomal inheritance, phenotypic characters are determined, or controlled, by
Molly is homozygous for the dominant black hair trait. therefore,
Molly has black hair.
(1) Turner syndrome; (2) Klinefelter syndrome
Name the disorder characterized by each of the following chromosome patterns: (1) XO and (2) XXY.
Nicole has the following genotype:
Nicole is heterozygous only for gene 1.
Regarding maternal nourishment after delivery, which is correct?
Oxytocin causes the contraction of myoepithelial cells in the walls of the lactiferous ducts and sinuses.
Why are premenopausal women at lesser risk of atherosclerosis than men?
Premenopausal women have higher estrogen levels that decrease plasma cholesterol.
Down Syndrome
Trisomy 21 is the clinical term for
The embryonic heart starts beating as blood begins to flow through chorionic vessels at approximately______of development
Week 3
structure of albumins
Which is an example of codominance of inheritance?
astigmatism
Which of the following conditions is caused by a dominant trait, in which one allele dominates the other allele and determines the phenotype?
All of the following occur during pregnancy except
a woman's bladder capacity increases.
Which of the following is a puberty-related change caused by increased testosterone levels?
accelerated bone deposition and skeletal growth
Identify the stage labeled "8"
advanced morula
When does the placenta become sufficiently functional to continue the pregnancy?
after the first trimester
What term describes different forms of a specific gene?
allele
Identify the structure labeled "6"
amnion
Identify the structure labeled "5"
amniotic cavity
Fertilization is complete when which of the following occurs?
amphimixis and cleavage
A secondary oocyte, not a mature ovum, is ejected from the ovary during ovulation. Oocyte activation brings about all of the following changes except:
an increase in stored nutrient levels of the oocyte
If an individual carries two different alleles for the same trait the individual is________for the trait.
heterozygous
If an individual carries a pair of alleles that are the same, the individual is________for the trait.
homozygous
The presence of which hormone in the urine provides a reliable indicator of pregnancy, as detected by home pregnancy test?
human chorionic gonadotrophin
After fertilization the first cell division is completed
more than a day later
A pre-embryo that consist of a solid ball of cells is known as what type of structure?
morula
After 3 days, a pre-embryo becomes a solid ball of cells known as a
morula
Which gestational period is dominated by the development of organs and organ systems?
second trimester
Which of the following provides all the cellular organelles and inclusions, nourishment, and genetic programming necessary to support development of the embryo for nearly a week after conception?
secondary oocyte
The prostaglandins produced in the endometrium
stimulate smooth muscle contractions
During implantation, the
syncytial trophoblast erodes a path through the endometrium.
A fetus undergoes it's largest absolute weight gain during which trimester?
third trimester
The infancy stage of life is considered to be over when the baby reaches_______of age.
1 year
Describe the process that forms the primary germ layers and cite the layer that contributes to nearly all body systems.
Gastrulation forms the primary germ layers from the embryonic disc. The mesoderm contribute to nearly all body systems.
Which of the following best summarizes the difference between genotype and phenotype?
Genotype refers to the gene alleles that one has, and phenotype refers to the trait that is expressed in response to those alleles.
Define gestation
Gestation is the time a developing embryo and fetus spends in the uterus.
Zoey's doctor advised her to be especially careful with her diet in the first trimester. If you had to explain to Zoey why this time period is so important, you could accurately say that which of the following happens in the first trimester?
The baby forms all of its organ systems
