8.11: Alternate Text Descriptions

Figure 8.1.1: Steps of Fertilization

This image illustrates fertilization in three labeled steps, showing how sperm cells reach and penetrate the oocyte and how one sperm ultimately fuses with the oocyte.

Figure 8.1.2: In Vitro Fertilization (IVF)

This image illustrates in vitro fertilization (IVF) labeled steps 1a, 1b, 2, 3, and 4.

Step 1a: “Eggs are collected after ovulation or directly from the follicles. Sperm are collected and concentrated.” The image shows an Egg (oocyte) being removed using a Catheter.

Step 1b: “Sperm sample is collected and concentrated by removing seminal fluid.” Two test tubes are shown, with an arrow indicating concentration of the sperm sample.

Step 2: “Both the collected egg(s) and the sperm sample are mixed in a petri dish, allowing fertilization to occur.” A petri dish shows sperm surrounding an oocyte.

Step 3: “The fertilized zygote is then removed from the petri dish for implantation.” A catheter removes the Fertilized zygote from the dish.

Step 4: “The zygote is then surgically implanted into the endometrium of the uterus. After successful implantation, the zygote should develop normally, as if it had been fertilized in the female’s oviducts.” The image labels Implanted zygote and Endometrium inside the uterus.

Arrows indicate progression between steps from collection to implantation

Figure 8.2.1: Stages of Early Embryonic Development

This image shows stages of early embryonic development and where they occur.

The top row, labeled as occurring in the uterine tube (red background), shows three stages: Two-cell, Four-cell, and Eight-cell, each illustrating increasing numbers of cells within the same overall size.

The bottom row, labeled as occurring in the uterus (blue background), shows later stages: Morula (16 cells), appearing as a solid ball of cells, and Blastocyst (70–100 cells), which contains a fluid-filled cavity labeled Blastocoel. The blastocyst also includes an outer layer labeled Trophoblast and a cluster of cells labeled Inner cell mass.

A legend indicates red corresponds to “Occurs in uterine tube” and blue corresponds to “Occurs in uterus.”

As the blastocyst forms, the trophoblast excretes enzymes that begin to degrade the zona pellucida. In a process called “hatching,” the conceptus breaks free of the zona pellucida in preparation for implantation.

Figure 8.2.2: The Sequence of Early Human Development

This image shows the sequence of early human development from ovulation through implantation, with numbered stages 1 through 8 arranged along the uterine tube and into the uterus.

• Stage 1: “Unfertilized Oocyte” shows an oocyte before fertilization.
• Stage 2: “Fertilized Oocyte” shows sperm surrounding and penetrating the oocyte.
• Stage 3: “Two-cell stage” shows the zygote divided into two blastomeres.
• Stage 4: “Four-cell stage” shows four cells within the same outer boundary.
• Stage 5: Two panels show progression to the Eight-cell stage and then Morula (16 cells), a solid ball of cells.
• Stage 6: “Blastocyst (70–100 cells)” shows a structure with a fluid-filled cavity labeled Blastocoel, an outer layer labeled Trophoblast, and a cluster labeled Inner cell mass. Arrows trace movement along the uterine tube toward the uterus, indicating progression of development during transport.
• Stage 7: “Embryo hatches (sheds zona pellucida)” shows the blastocyst emerging from its outer covering.
• Stage 8: “Blastocyst rotates and implants into endometrium of the uterus” shows attachment to the uterine lining.

Figure 8.2.3: Steps of Blastocyst Implantation

This image illustrates the process of implantation of the blastocyst into the uterine lining in three labeled steps.

At the top, the uterine wall is labeled with Endometrium and Uterine cavity, and individual cells are labeled Uterine mucosa cells.

• Step 1: “The blastocyst digests the uterine mucosa when it initially implants into the endometrium.” The blastocyst is shown attaching to and beginning to embed into the uterine lining. An arrow indicates progression downward.
• Step 2: “Eventually, the endometrium grows over and surrounds the embryo, fully securing it to the uterine lining.” The blastocyst is shown more deeply embedded, with surrounding endometrial tissue enclosing it. Another arrow indicates further progression.
• Step 3: “Implanted embryo continues to grow within endometrium (depicted embryo is 7–8 weeks after conception).” A cross-section of the uterus shows the developing embryo within the uterine wall.

To the right, additional diagrams labeled Anterior view and Lateral view indicate the most common site of implantation (posterior uterine wall). The figure emphasizes the sequence of implantation and the typical location within the uterus.

Figure 8.2.4: Normal Placental Position and Placenta Previa

This image is a side‑by‑side diagram that compares the normal location of the placenta with a condition called placenta previa.

On the left, labeled “Normal location of placenta,” a cross‑section of the uterus shows the fetus positioned inside the uterine cavity. The placenta is attached to the upper uterine wall, away from the cervix. A label indicates that the cervix is not obstructed, allowing a clear passage for birth.

On the right, labeled “Placenta previa,” a similar cross‑section shows the placenta attached lower in the uterus. A label identifies the internal os, the opening of the cervix. The placenta is covering the cervix, which obstructs the passage and would prevent normal vaginal delivery.

The diagram emphasizes the difference between a normal placental position and one that blocks the cervical opening.

Figure 8.2.5: Implanted Blastocyst and Early Embryonic Layers

This image shows the structure of an implanted blastocyst within the uterine lining and the formation of early embryonic layers.

On the right side, the uterine wall is labeled Endometrium, shown as a layered tissue with blood vessels. The implanted structure is embedded within this lining. Within the implanted blastocyst, a central space is labeled Blastocyst cavity (develops into the yolk sac). Adjacent to this cavity is the embryonic disc, which consists of two labeled layers:

• Hypoblast (lower layer)
• Epiblast (upper layer)

Above the embryonic disc is a small space labeled Amniotic cavity, enclosed by a membrane labeled Amnion. Surrounding the blastocyst is the trophoblast, which is divided into two labeled layers:

• Cytotrophoblast, the inner cellular layer
• Syncytiotrophoblast, the outer invasive layer that extends into the endometrium

The diagram emphasizes the organization of embryonic tissues and supporting membranes after implantation and their relationship to the uterine lining.

Figure 8.2.6: Early Post-Implantation Development and Germ Layer Formation

This image illustrates early post-implantation development and the formation of the three primary embryonic germ layers.

Figure 8.2.7: Early Embryo, Extraembryonic Membranes, and Germ Layer Derivatives

This image illustrates an early embryo within the uterus and shows how the three primary germ layers and extraembryonic membranes contribute to embryonic development.

The embryo is surrounded by several protective and supportive structures. The outermost membrane is the chorion, which lies within the endometrium, the lining of the uterus. Spaces within the surrounding tissue contain maternal blood pools, which bring nutrients and oxygen close to the developing embryo.

Within the chorion is the amniotic cavity, a fluid-filled space surrounding the embryo. The cavity is enclosed by the amnion, a membrane that protects the embryo and provides a stable environment for growth. Inferior to the embryo is the yolk sac, which is lined with endoderm and contributes to early nutrient transfer and blood cell formation. Extending from the embryo is the allantois, an embryonic structure involved in the development of the umbilical cord and early circulatory connections.

The embryo itself contains three primary germ layers formed during gastrulation:

• Ectoderm, the outer layer
• Mesoderm, the middle layer
• Endoderm, the inner layer

The figure emphasizes that these germ layers give rise to different tissues and organ systems.

• Endoderm develops into much of the digestive tract and associated organs, including the liver and pancreas, as well as the inner lining of the lungs.
• Mesoderm forms structures involved in support, movement, and transport, including the circulatory system, skeletal system, muscular system, and portions of the lungs.
• Ectoderm develops into external coverings and the nervous system, producing structures such as the skin, hair, nails, and the nervous system.

The figure demonstrates how the early embryo is supported by extraembryonic membranes while simultaneously undergoing differentiation into three germ layers. These germ layers serve as the foundation for all tissues and organs of the body. The chorion, amnion, yolk sac, and allantois support growth and survival of the embryo, while the ectoderm, mesoderm, and endoderm establish the developmental pathways that lead to the formation of the body's organ systems.

Figure 8.2.8: Placenta and Maternal-Fetal Exchange

This image illustrates the relationship between the developing fetus, the placenta, and the maternal blood supply. It shows how nutrients, gases, and wastes are exchanged between the fetus and the mother during pregnancy.

Figure 8.2.9: Human Placenta

This image shows a post‑expulsion human placenta placed in a shallow medical tray. The tray is light blue with visible fluid and blood staining around the placenta.

The placenta appears as a round, flattened organ with a smooth, slightly shiny surface. Numerous branching blood vessels are visible across its surface, radiating outward from a central point.

An umbilical cord is attached near the top of the placenta. The cord is thick, pale, and slightly twisted, extending outward from the placental surface.

A gloved hand is visible at the top left of the image, with one finger pointing toward the placental surface and the attachment site of the umbilical cord.

The image emphasizes the physical structure of the placenta, including its vascular network and umbilical cord connection.

Figure 8.2.10: Neurulation: Formation of the Neural Tube and Neural Crest

Figure 8.2.11: Embryonic Folding

This image is a multi‑panel diagram illustrates embryonic folding and the formation of the primitive gut from different germ layers. A color legend identifies Ectoderm (blue), Mesoderm (red), Endoderm (yellow), Amnion (green), and Hypoblast (purple).

Left column (transverse sections): The top image shows a flat embryonic disc with layers arranged from top to bottom: amnion, ectoderm, and hypoblast.

In the next transverse section, the embryo begins to fold inward. The outer layer labeled Ectoderm curves around the forming body, while Mesoderm lies beneath it, and Endoderm lines the inner surface. The Amnion surrounds the upper portion.

In the third transverse section, folding progresses further. The lateral edges move toward the midline, enclosing internal structures. The Endoderm begins forming a tube-like structure.

Arrows indicate the continuation of folding into the panels on the right.

Right column: sagittal and transverse views:

The top right image, labeled Sagittal section, shows longitudinal folding. The embryo curves, bringing the yolk sac closer to the body as folding occurs.

The next image, labeled Transverse section, shows the yolk sac narrowing and being incorporated into the embryo.

In the final transverse section, a structure labeled Gut is formed from the endoderm and enclosed within the body. The surrounding layers include Mesoderm, which forms the middle tissues, and Ectoderm, which forms the outer surface.

Figure 8.2.12: Embryo at 7 Weeks

This figure shows an early human embryo within surrounding embryonic membranes.

The embryo appears highly curved in a C‑shape, with a prominent head region and a tapering tail-like structure. Small limb buds are visible, indicating early development of arms and legs. A circular structure near the head represents the developing eye.

The embryo lies within a semi‑transparent environment of surrounding tissues and fluids. Thin, translucent membranes and vascular structures are visible around it, suggesting the embryonic support structures.

The overall coloration ranges from pale beige for the embryo to reddish and translucent tones in the surrounding tissues. The image emphasizes early organ formation and the curved body shape typical of early embryonic development.

Figure 8.3.1: Differentiation of the Embryonic Reproductive Ducts

This image illustrates the differentiation of the reproductive ducts from a common embryonic stage into male and female systems.

Top panel: An early embryo is shown with paired structures labeled Müllerian ducts (upper, red) and Wolffian ducts (lower, blue). On each side are Bipotential gonads, indicating that the gonads can develop into either testes or ovaries. At the bottom, a common outlet is labeled Cloaca.

Two labeled pathways extend downward: Masculinization on the left and Feminization on the right.

Left pathway (Masculinization): The label states Müllerian ducts degrade, shown as dashed outlines fading. The Wolffian ducts remain and develop further.

In the final male stage, the diagram shows Wolffian ducts become epididymis and ductus (vas) deferens, with structures labeled Testes, Urinary bladder, and Urethra.

Right pathway (Feminization): The label shows Wolffian ducts degrade, indicated by dashed outlines. The Müllerian ducts remain and develop into female reproductive structures.

In the final female stage, the diagram shows Müllerian ducts become uterine tubes and uterus, with structures labeled Ovaries, Urinary bladder, Urethra, Uterus, and Vagina.

Figure 8.3.2: Fetal Circulation and Major Fetal Shunts

This image is a multi-panel diagram illustrates fetal circulation, showing blood flow between the placenta, umbilical cord, and fetal heart.

Left panel: The Placenta is shown with branching blood vessels. A structure labeled Umbilical cord (contains umbilical artery and umbilical vein) connects the placenta to the fetus. Within the cord, the Umbilical vein carries oxygenated blood toward the fetus, while the Umbilical artery carries deoxygenated blood back to the placenta.

Bottom right panel (liver region): Blood labeled “1 Blood arrives via umbilical vein” enters the fetus. The label “2 The ductus venosus shunts oxygenated blood from the placenta away from the semi functional liver and toward the heart” shows blood bypassing much of the liver through the ductus venosus and entering the inferior vena cava.

Top right panel (heart): The fetal heart diagram includes numbered steps:

1. “Oxygenated blood from placenta enters right atrium via inferior vena cava.”
2. “The foramen ovale allows oxygenated blood in the right atrium to reach the left atrium.”
3. “The ductus arteriosus connects the aorta with the pulmonary artery, further shunting blood away from the lungs and into the aorta.”
4. “Mixed blood travels to the head and body, and back to the placenta via the aorta.”

Arrows (red, blue, and purple) show directions of blood flow and mixing. The diagram emphasizes three key fetal shunts:

• Ductus venosus (liver bypass)
• Foramen ovale (right atrium to left atrium)
• Ductus arteriosus (pulmonary artery to aorta)

Figure 8.4.1: Fetal Growth Across the Three Trimesters

This image shows the relative size and position of the fetus within the uterus across the three trimesters of pregnancy, overlaid on an outline of the human torso.

In the center, a simplified cross‑section of the lower abdomen shows the uterus with a fetus inside, connected to the fallopian tubes and ovaries on either side.

Three horizontal labels appear on the left side:

• “End of 1st trimester” points to the lower pelvis region. At this stage, the fetus is small and located within the pelvis, with minimal upward expansion of the uterus.
• “End of 2nd trimester” points to the middle abdomen. The uterus has expanded upward, occupying more space in the abdominal cavity as the fetus grows larger.
• “End of 3rd trimester” points to the upper abdomen near the ribcage. The uterus is greatly enlarged, extending high into the abdomen and approaching the chest area.

Behind the labels, shaded overlapping regions illustrate increasing uterine size, progressing from small (first trimester) to very large (third trimester). The diagram emphasizes how the uterus and fetus grow upward and expand significantly in size throughout pregnancy.

Figure 8.4.3: Hormones Initiating Labor

This image shows changes in relative hormone concentration over the course of pregnancy, measured from 0 to 40 weeks on the horizontal axis. Three hormones are represented:

• Human chorionic gonadotropin (hCG) is shown as a solid green line. It rises rapidly during early pregnancy, reaching a peak around weeks 8 to 10. After this peak, hCG levels decline sharply and then level off at a lower, steady concentration for the remainder of pregnancy.
• Progesterone is shown as a dashed blue line. Progesterone levels increase gradually throughout pregnancy, with a more pronounced rise after approximately week 20. The levels peak near the end of pregnancy and then slightly decrease.
• Estrogens are shown as a solid orange line. Estrogen levels begin low, increase slowly in early pregnancy, then rise steeply after about week 20. Estrogen concentrations continue increasing and reach their highest levels near week 40.

Overall, the graph demonstrates that:

• hCG dominates early pregnancy and then declines
• Progesterone and estrogen increase steadily and become the dominant hormones in later pregnancy

Figure 8.4.4: Stages of Childbirth

This image is a multi‑panel diagram illustrates the three stages of labor and delivery: dilation, birth, and afterbirth.

Stage 1: Dilation - Two side‑by‑side illustrations show the uterus and fetus. An arrow indicates progression from an undilated to a fully dilated cervix.

• On the left, the cervix is labeled “Undilated cervix.” The opening is small and closed at the top of the vagina. Labels identify Amniotic fluid within uterus, Cervix, and Vagina.
• On the right, the cervix is labeled “Fully dilated cervix (greater than 10 cm in diameter).” The opening is wide, allowing passage of the fetus.

Stage 2: Birth - Four sequential panels show the delivery of the baby. Arrows between panels show the sequence of movement through the birth canal.

1. “Presentation of head” – The fetus is positioned head‑down, with the head entering the birth canal.
2. “Rotation and delivery of anterior shoulder” – The head rotates as the front shoulder emerges.
3. “Delivery of posterior shoulder” – The second shoulder passes through the birth canal.
4. “Delivery of lower body and umbilical cord” – The rest of the body is delivered, followed by the umbilical cord.

Stage 3: Afterbirth delivery - Two images show the placenta after the baby is delivered:

• The diagram on the left shows the placenta detaching from the uterine wall and moving toward the cervix. A label reads: “Placenta detaches and exits through vagina.”
• The image on the right is a photograph of an expelled placenta placed in a medical tray, showing its tissue structure and attached umbilical cord.

Figure 8.5.1: Neonatal Circulatory System

Figure 8.6.1: Let-Down Reflex

This image illustrates the positive feedback loop that regulates lactation, showing how infant suckling stimulates both milk production and milk ejection.

At the top of the figure, an infant suckles at the breast. Sensory receptors in the areola detect suckling and send nerve impulses to the brain. These signals travel to the hypothalamus and posterior pituitary gland, which respond by releasing oxytocin into the bloodstream. An inset diagram shows oxytocin-producing neurosecretory cells in the hypothalamus connected to the posterior pituitary through the hypothalamo-hypophyseal tract, where oxytocin enters nearby capillaries and is carried throughout the body.

At the same time, sensory stimulation from suckling promotes milk production within the mammary glands. In the right panel, mammary alveoli are shown producing milk. The alveoli are lined with lactocytes, specialized cells that synthesize and secrete milk into the hollow interior of each alveolus. Arrows indicate milk accumulating within these structures.

As circulating oxytocin reaches the breast, it stimulates myoepithelial cells surrounding the alveoli to contract. This contraction squeezes milk from the alveoli into the lactiferous ducts. A diagram of breast tissue shows milk moving through branching ducts toward the nipple. Milk collects temporarily in the lactiferous sinus before leaving the breast through openings in the nipple, where it becomes available to the nursing infant.

The left side of the figure shows a large arrow forming a loop labeled as a positive feedback cycle. As milk is produced and released, the infant continues to suckle. Continued suckling generates additional sensory stimulation, which promotes further oxytocin release and ongoing milk production and ejection. The result is a self-reinforcing cycle in which suckling increases milk availability, and increased milk availability encourages continued suckling.

This figure demonstrates how lactation is regulated through a positive feedback mechanism: infant suckling stimulates neural and hormonal responses that increase milk production and milk letdown, which in turn encourages further suckling and sustains the cycle.

Figure 8.7.1: A Human Karyotype

This image shows a human karyotype, which is an organized display of chromosomes arranged in numbered pairs. The chromosomes are shown as small, rod‑shaped structures with banding patterns, grouped into pairs and labeled below each pair with numbers. Across the image, there are 22 numbered pairs of autosomes, labeled sequentially from 1 through 22. Each numbered group contains two chromosomes of similar size and shape, indicating homologous pairs.

• Chromosomes 1 through 3 appear largest and are shown at the top left.
• Chromosomes gradually decrease in size from left to right and top to bottom.
• Chromosomes 13 through 15 and 21 through 22 appear smaller and more compact.

At the bottom right, a final pair is labeled “X/Y”, representing the sex chromosomes. One chromosome is larger (X), and the other is smaller (Y), indicating a typical male karyotype. Each chromosome pair shows characteristic dark and light banding patterns, which reflect regions of differing DNA composition.

Figure 8.7.2: Random Segregation

This image illustrates inheritance of a trait controlled by one dominant allele and one recessive allele across two generations using Punnett squares.

In the first generation, a parent with two dominant alleles is crossed with a parent that has two recessive alleles. The Punnett square shows that every possible offspring receives one dominant allele from one parent and one recessive allele from the other parent. As a result, all offspring are heterozygous and express the dominant trait. The figure indicates that 100 percent of the second-generation offspring display the dominant phenotype.

In the second generation, two heterozygous individuals are crossed. Each parent can contribute either a dominant allele or a recessive allele. The Punnett square shows four possible offspring combinations. One offspring inherits two dominant alleles, two offspring inherit one dominant and one recessive allele, and one offspring inherits two recessive alleles. This produces a genotypic ratio of 1 homozygous dominant, 2 heterozygous, and 1 homozygous recessive.

Because both homozygous dominant and heterozygous individuals express the dominant trait, three of the four possible offspring display the dominant phenotype. Only the offspring with two recessive alleles expresses the recessive phenotype. The figure summarizes this outcome as 75 percent dominant phenotype and 25 percent recessive phenotype.

This figure demonstrates Mendel’s principle of inheritance for a single gene, showing that crossing two true-breeding parents produces a generation of heterozygous offspring and that crossing those heterozygous offspring results in a 3:1 dominant-to-recessive phenotype ratio and a 1:2:1 genotype ratio in the next generation.

Figure 8.7.3: Autosomal Dominant Inheritance

This image illustrates inheritance of neurofibromatosis using a Punnett square. The disorder is associated with a dominant allele, meaning that a person needs only one copy of the disease-associated allele to express the condition.

The cross shown involves a parent who carries one disease-associated dominant allele and one normal recessive allele and a second parent who carries two recessive alleles and does not have the condition. The parent with the dominant allele can pass either the disease-associated allele or the recessive allele to offspring, whereas the unaffected parent can pass only recessive alleles.

The Punnett square shows four possible offspring outcomes. Two of the four offspring inherit the disease-associated dominant allele from the heterozygous parent and a recessive allele from the unaffected parent. These offspring have neurofibromatosis because the dominant allele is expressed. The other two offspring inherit recessive alleles from both parents and therefore do not have the condition.

The figure summarizes the results as a 50 percent probability that offspring will inherit neurofibromatosis and a 50 percent probability that offspring will not inherit the disorder.

This figure demonstrates the inheritance pattern of an autosomal dominant disorder. When an affected heterozygous parent and an unaffected parent have children, each child has a one-in-two chance of inheriting the dominant disease-associated allele and expressing the condition, and a one-in-two chance of inheriting only recessive alleles and remaining unaffected.

Figure 8.7.4: Autosomal Recessive Inheritance of Cystic Fibrosis

illustrates autosomal recessive inheritance using cystic fibrosis as an example. Two carrier parents are shown at the top of the figure. Each parent carries one normal allele and one recessive disease-associated allele but does not have cystic fibrosis because the normal allele masks the effect of the recessive allele.

Lines connect the parents to four possible offspring outcomes. One offspring inherits a normal allele from each parent and is unaffected and does not carry the disease-associated allele. Two offspring inherit one normal allele and one recessive disease-associated allele. Like the parents, these offspring are carriers who do not show symptoms but can pass the allele to future generations. One offspring inherits two recessive disease-associated alleles and is affected with cystic fibrosis.

A Punnett square on the right summarizes these possible genetic combinations. The results show one offspring with two normal alleles, two carrier offspring with one normal and one recessive allele, and one affected offspring with two recessive alleles. This produces a genotypic ratio of 1 unaffected non-carrier : 2 carriers : 1 affected individual.

The figure also summarizes the phenotypic outcomes. Three of the four possible offspring do not express cystic fibrosis because they inherit at least one normal allele. One of the four offspring inherits two recessive disease-associated alleles and expresses cystic fibrosis. This corresponds to a 75 percent probability that cystic fibrosis is not expressed and a 25 percent probability that the disorder is expressed.

This figure demonstrates the inheritance pattern of an autosomal recessive disorder. When two carrier parents have children, each child has a 25 percent chance of being unaffected and not a carrier, a 50 percent chance of being an unaffected carrier, and a 25 percent chance of inheriting two recessive alleles and developing the disorder.

Figure 8.7.5: X-Linked Dominant Inheritance Patterns

This image illustrates two inheritance patterns for an X-linked dominant trait, comparing the outcomes when either the father or the mother carries the affected allele.

Panel (a): Affected father and unaffected mother

The first example shows a father who has an X-linked dominant trait and a mother who does not have the trait. Because fathers pass their X chromosome only to their daughters and their Y chromosome only to their sons, all daughters inherit the affected X chromosome and express the trait. None of the sons inherit the affected X chromosome because they receive the Y chromosome from the father. As a result, all daughters are affected and all sons are unaffected.

The figure summarizes these outcomes as 100 percent of females affected and 0 percent of males affected.

Panel (b): Unaffected father and affected mother

The second example shows a father without the trait and a mother who carries one affected X chromosome and one unaffected X chromosome. Each child has a 50 percent chance of inheriting the affected X chromosome from the mother. Sons who inherit the affected X chromosome express the trait because they have only one X chromosome. Daughters who inherit the affected X chromosome also express the trait because the allele is dominant. The remaining sons and daughters inherit the unaffected X chromosome and do not express the trait.

The figure summarizes these outcomes as 50 percent of males affected and 50 percent of females affected.

This figure demonstrates the characteristic inheritance pattern of X-linked dominant traits. An affected father passes the trait to all daughters and none of his sons, whereas an affected heterozygous mother can pass the trait to approximately half of both sons and daughters.

Figure 8.7.6: X-Linked Recessive Inheritance with a Carrier Mother