Chapter 27

Define homozygous and heterozygous. (Module 27.15A)

Homozygous means that homologous chromosomes carry the same allele of a given gene. Heterozygous means that homologous chromosomes carry different alleles of a given gene.

Compare strict dominance with codominance. (Module 27.16A)

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 phenotypes for the trait.

Human chromosome 7 is involved in which disorder?

cystic fibrosis

At which day post cleavage does implantation occur?

day 7

The almost identical cells produced by cleavage divisions are called

blastomeres.

The trophoblast has many of the characteristics of ________ cells.

cancer

The first stage of labor is the ________ stage.

dilation

The stage of labor during which the fetus emerges from the vagina is called the ________ stage.

expulsion

By day 12 of embryonic development, mesoderm begins to form through

gastrulation

List the major changes that occur in maternal systems during pregnancy. (Module 27.9A)

increased respiratory rate and tidal volume, increased blood volume and GFR, increased nutrient requirements, and increases in the size of the uterus and mammary glands

After 3 days, a pre-embryo becomes a solid ball of cells known as a

morula

The mesoderm forms

muscle

The ectoderm forms

neural tissues.

Are environmental factors more likely to affect genotype or phenotype?

phenotype

The hormone that increases the flexibility of the pubic symphysis during pregnancy is

relaxin.

Which gestational period is dominated by the development of organs and organ systems?

second trimester

During implantation, the

syncytial trophoblast erodes a path through the endometrium

During the dilation stage of labor:

the amnion ruptures late in the stage.

Each of the following statements concerning development is true except

the first trimester is when the fetus first looks distinctively human.

The endoderm forms

the urinary bladder.

A fetus undergoes its largest absolute weight gain during which trimester? (Module 27.8C)

third trimester

Name the disorder characterized by each of the following chromosome patterns: (1) XO and (2) XXY. (Module 27.17B)

(1) Turner syndrome; (2) Klinefelter syndrome

The infancy stage of life is considered to be over when the baby reaches ________ of age.

1 year

How many chromosomes are contained within a human zygote? (Module 27.2B)

46

How many chromosomes do human somatic cells contain?

46

Trisomy 21 is the clinical term for

Down syndrome.

Why does a man have a deeper voice and a larger larynx than a woman? (Module 27.13B)

During puberty, testosterone causes greater laryngeal development than estrogen so a male will have a larger larynx and a deeper voice.

Distinguish among embryonic, fetal, and prenatal development. (Module 27.1B)

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 consists of both embryonic and fetal development.

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 organogenesis. (Module 27.8A)

Organogenesis is the process of organ formation.

How can you tell that the karyotype shown here is male? (Module 27.14C)

The 23rd pair of chromosomes is XY.

Which event occurs during week 4 of development?

The connections between the embryo and the surrounding trophoblast begin to constrict.

A space opens within the inner cell mass that will form the

amniotic cavity.

Fertilization is complete when which of the follow occurs?

amphimixis and cleavage

Why does a mother's blood volume increase during pregnancy? (Module 27.9B)

A mother's blood volume increases to accommodate for flow through the placenta.

Why are numerous sperm required to fertilize a secondary oocyte? (Module 27.2C)

Acrosomal enzymes from multiple sperm are needed to penetrate the corona radiata.

Define fertilization. (Module 27.2A)

Fertilization is the fusion of a secondary oocyte and a sperm to form a zygote.

________ is the time spent in growing within the uterus.

Gestation

Define gestation. (Module 27.1A)

Gestation is the time a developing embryo and fetus spends in the uterus.

Name the three major interacting hormonal events associated with the onset of puberty. (Module 27.13A)

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.

What is postnatal development? (Module 27.1C)

Postnatal development begins at birth and continues to maturity.

The region known as the primitive streak is the site of

migration of ectodermal cells to form the mesoderm.

Which hormone causes the milk ejection (milk let-down) reflex? (Module 27.11B)

oxytocin

Deoxygenated blood is carried to the placenta by the

umbilical arteries.

Oxygenated blood is carried away from the placenta by the

umbilical vein.