Module 28: Development and Inheritance

Lesson 8: Genetics: Overview

Di Truyền: Tổng Quan

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Dưới đây là danh sách những thuật ngữ Y khoa của module Development and Inheritance.
Khái quát được số lượng thuật ngữ sẽ xuất hiện trong bài đọc và nghe sẽ giúp bạn thoải mái tiêu thụ nội dung hơn. Sau khi hoàn thành nội dung đọc và nghe, bạn hãy quay lại đây và luyện tập (practice) để quen dần các thuật ngữ này. Đừng ép bản thân phải nhớ các thuật ngữ này vội vì bạn sẽ gặp và ôn lại danh sách này trong những bài học (lesson) khác của cùng một module.

Medical Terminology: Development and Inheritance

acrosomal reaction
release of digestive enzymes by sperm that enables them to burrow through the corona radiata and penetrate the zona pellucida of an oocyte prior to fertilization
acrosome
cap-like vesicle located at the anterior-most region of a sperm that is rich with lysosomal enzymes capable of digesting the protective layers surrounding the oocyte
afterbirth
third stage of childbirth in which the placenta and associated fetal membranes are expelled
allantois
finger-like outpocketing of yolk sac forms the primitive excretory duct of the embryo; precursor to the urinary bladder
allele
alternative forms of a gene that occupy a specific locus on a specific gene
amnion
transparent membranous sac that encloses the developing fetus and fills with amniotic fluid
amniotic cavity
cavity that opens up between the inner cell mass and the trophoblast; develops into amnion
autosomal chromosome
in humans, the 22 pairs of chromosomes that are not the sex chromosomes (XX or XY)
autosomal dominant
pattern of dominant inheritance that corresponds to a gene on one of the 22 autosomal chromosomes
autosomal recessive
pattern of recessive inheritance that corresponds to a gene on one of the 22 autosomal chromosomes
blastocoel
fluid-filled cavity of the blastocyst
blastocyst
term for the conceptus at the developmental stage that consists of about 100 cells shaped into an inner cell mass that is fated to become the embryo and an outer trophoblast that is fated to become the associated fetal membranes and placenta
blastomere
daughter cell of a cleavage
Braxton Hicks contractions
weak and irregular peristaltic contractions that can occur in the second and third trimesters; they do not indicate that childbirth is imminent
brown adipose tissue
highly vascularized fat tissue that is packed with mitochondria; these properties confer the ability to oxidize fatty acids to generate heat
capacitation
process that occurs in the female reproductive tract in which sperm are prepared for fertilization; leads to increased motility and changes in their outer membrane that improve their ability to release enzymes capable of digesting an oocyte’s outer layers
carrier
heterozygous individual who does not display symptoms of a recessive genetic disorder but can transmit the disorder to their offspring
chorion
membrane that develops from the syncytiotrophoblast, cytotrophoblast, and mesoderm; surrounds the embryo and forms the fetal portion of the placenta through the chorionic villi
chorionic membrane
precursor to the chorion; forms from extra-embryonic mesoderm cells
chorionic villi
projections of the chorionic membrane that burrow into the endometrium and develop into the placenta
cleavage
form of mitotic cell division in which the cell divides but the total volume remains unchanged; this process serves to produce smaller and smaller cells
codominance
pattern of inheritance that corresponds to the equal, distinct, and simultaneous expression of two different alleles
colostrum
thick, yellowish substance secreted from a mother’s breasts in the first postpartum days; rich in immunoglobulins
conceptus
pre-implantation stage of a fertilized egg and its associated membranes
corona radiata
in an oocyte, a layer of granulosa cells that surrounds the oocyte and that must be penetrated by sperm before fertilization can occur
cortical reaction
following fertilization, the release of cortical granules from the oocyte’s plasma membrane into the zona pellucida creating a fertilization membrane that prevents any further attachment or penetration of sperm; part of the slow block to polyspermy
dilation
first stage of childbirth, involving an increase in cervical diameter
dominant
describes a trait that is expressed both in homozygous and heterozygous form
dominant lethal
inheritance pattern in which individuals with one or two copies of a lethal allele do not survive in utero or have a shortened life span
ductus arteriosus
shunt in the pulmonary trunk that diverts oxygenated blood back to the aorta
ductus venosus
shunt that causes oxygenated blood to bypass the fetal liver on its way to the inferior vena cava
ectoderm
primary germ layer that develops into the central and peripheral nervous systems, sensory organs, epidermis, hair, and nails
ectopic pregnancy
implantation of an embryo outside of the uterus
embryo
developing human during weeks 3–8
embryonic folding
process by which an embryo develops from a flat disc of cells to a three-dimensional shape resembling a cylinder
endoderm
primary germ layer that goes on to form the gastrointestinal tract, liver, pancreas, and lungs
epiblast
upper layer of cells of the embryonic disc that forms from the inner cell mass; gives rise to all three germ layers
episiotomy
incision made in the posterior vaginal wall and perineum that facilitates vaginal birth
expulsion
second stage of childbirth, during which the mother bears down with contractions; this stage ends in birth
fertilization
unification of genetic material from male and female haploid gametes
fertilization membrane
impenetrable barrier that coats a nascent zygote; part of the slow block to polyspermy
fetus
developing human during the time from the end of the embryonic period (week 9) to birth
foramen ovale
shunt that directly connects the right and left atria and helps divert oxygenated blood from the fetal pulmonary circuit
foremilk
watery, translucent breast milk that is secreted first during a feeding and is rich in lactose and protein; quenches the infant’s thirst
gastrulation
process of cell migration and differentiation into three primary germ layers following cleavage and implantation
genotype
complete genetic makeup of an individual
gestation
in human development, the period required for embryonic and fetal development in utero; pregnancy
heterozygous
having two different alleles for a given gene
hindmilk
opaque, creamy breast milk delivered toward the end of a feeding; rich in fat; satisfies the infant’s appetite
homozygous
having two identical alleles for a given gene
human chorionic gonadotropin (hCG)
hormone that directs the corpus luteum to survive, enlarge, and continue producing progesterone and estrogen to suppress menses and secure an environment suitable for the developing embryo
hypoblast
lower layer of cells of the embryonic disc that extend into the blastocoel to form the yolk sac
implantation
process by which a blastocyst embeds itself in the uterine endometrium
incomplete dominance
pattern of inheritance in which a heterozygous genotype expresses a phenotype intermediate between dominant and recessive phenotypes
inner cell mass
cluster of cells within the blastocyst that is fated to become the embryo
involution
postpartum shrinkage of the uterus back to its pre-pregnancy volume
karyotype
systematic arrangement of images of chromosomes into homologous pairs
lactation
process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to sucking at the nipple
lanugo
silk-like hairs that coat the fetus; shed later in fetal development
let-down reflex
release of milk from the alveoli triggered by infant suckling
lightening
descent of the fetus lower into the pelvis in late pregnancy; also called “dropping”
lochia
postpartum vaginal discharge that begins as blood and ends as a whitish discharge; the end of lochia signals that the site of placental attachment has healed
meconium
fetal wastes consisting of ingested amniotic fluid, cellular debris, mucus, and bile
mesoderm
primary germ layer that becomes the skeleton, muscles, connective tissue, heart, blood vessels, and kidneys
morula
tightly packed sphere of blastomeres that has reached the uterus but has not yet implanted itself
mutation
change in the nucleotide sequence of DNA
neural fold
elevated edge of the neural groove
neural plate
thickened layer of neuroepithelium that runs longitudinally along the dorsal surface of an embryo and gives rise to nervous system tissue
neural tube
precursor to structures of the central nervous system, formed by the invagination and separation of neuroepithelium
neurulation
embryonic process that establishes the central nervous system
nonshivering thermogenesis
process of breaking down brown adipose tissue to produce heat in the absence of a shivering response
notochord
rod-shaped, mesoderm-derived structure that provides support for growing fetus
organogenesis
development of the rudimentary structures of all of an embryo’s organs from the germ layers
parturition
childbirth
phenotype
physical or biochemical manifestation of the genotype; expression of the alleles
placenta
organ that forms during pregnancy to nourish the developing fetus; also regulates waste and gas exchange between mother and fetus
placenta previa
low placement of fetus within uterus causes placenta to partially or completely cover the opening of the cervix as it grows
placentation
formation of the placenta; complete by weeks 14–16 of pregnancy
polyspermy
penetration of an oocyte by more than one sperm
primitive streak
indentation along the dorsal surface of the epiblast through which cells migrate to form the endoderm and mesoderm during gastrulation
prolactin
pituitary hormone that establishes and maintains the supply of breast milk; also important for the mobilization of maternal micronutrients for breast milk
Punnett square
grid used to display all possible combinations of alleles transmitted by parents to offspring and predict the mathematical probability of offspring inheriting a given genotype
quickening
fetal movements that are strong enough to be felt by the mother
recessive
describes a trait that is only expressed in homozygous form and is masked in heterozygous form
recessive lethal
inheritance pattern in which individuals with two copies of a lethal allele do not survive in utero or have a shortened life span
sex chromosomes
pair of chromosomes involved in sex determination; in males, the XY chromosomes; in females, the XX chromosomes
shunt
circulatory shortcut that diverts the flow of blood from one region to another
somite
one of the paired, repeating blocks of tissue located on either side of the notochord in the early embryo
syncytiotrophoblast
superficial cells of the trophoblast that fuse to form a multinucleated body that digests endometrial cells to firmly secure the blastocyst to the uterine wall
trait
variation of an expressed characteristic
trimester
division of the duration of a pregnancy into three 3-month terms
trophoblast
fluid-filled shell of squamous cells destined to become the chorionic villi, placenta, and associated fetal membranes
true labor
regular contractions that immediately precede childbirth; they do not abate with hydration or rest, and they become more frequent and powerful with time
umbilical cord
connection between the developing conceptus and the placenta; carries deoxygenated blood and wastes from the fetus and returns nutrients and oxygen from the mother
vernix caseosa
waxy, cheese-like substance that protects the delicate fetal skin until birth
X-linked
pattern of inheritance in which an allele is carried on the X chromosome of the 23rd pair
X-linked dominant
pattern of dominant inheritance that corresponds to a gene on the X chromosome of the 23rd pair
X-linked recessive
pattern of recessive inheritance that corresponds to a gene on the X chromosome of the 23rd pair
yolk sac
membrane associated with primitive circulation to the developing embryo; source of the first blood cells and germ cells and contributes to the umbilical cord structure
zona pellucida
thick, gel-like glycoprotein membrane that coats the oocyte and must be penetrated by sperm before fertilization can occur
zygote
fertilized egg; a diploid cell resulting from the fertilization of haploid gametes from the male and female lines
Nội dung này đang được cập nhật.
Dưới đây là các bài văn nằm ở bên trái. Ở bên phải là các bài luyện tập (practice) để đánh giá khả năng đọc hiểu của bạn. Sẽ khó khăn trong thời gian đầu nếu vốn từ vựng của bạn còn hạn chế, đặc biệt là từ vựng Y khoa. Hãy kiên nhẫn và đọc nhiều nhất có kể, lượng kiến thức tích tụ dần sẽ giúp bạn đọc thoải mái hơn.
What makes each newborn unique? The answer lies, of course, in the DNA in the sperm and oocyte that combined to produce that first diploid cell, the human zygote.
Each human body cell has a full complement of DNA stored in 23 pairs of chromosomes. Figure 1 shows the pairs in a systematic arrangement called a karyotype. Among these is one pair of chromosomes, called the sex chromosomes, that determines the sex of the individual (XX in females, XY in males). The remaining 22 chromosome pairs are called autosomal chromosomes. Each of these chromosomes carries hundreds or even thousands of genes, each of which codes for the assembly of a particular protein—that is, genes are “expressed” as proteins. An individual’s complete genetic makeup is referred to as their genotype. The characteristics that the genes express, whether they are physical, behavioral, or biochemical, are a person’s phenotype.

In genetics and reproduction, “parent” is often used to describe the individual organisms that contribute genetic material to offspring, usually in the form of gamete cells and their chromosomes. The concept of a genetic parent is distinct from social and legal concepts of parenthood, and may differ from those whom people consider their parents.

You inherit one chromosome in each pair—a full complement of 23—from each parent. This occurs when the sperm and oocyte combine at the moment of your conception. Homologous chromosomes—those that make up a complementary pair—have genes for the same characteristics in the same location on the chromosome. Because one copy of a gene, an allele, is inherited from each parent, the alleles in these complementary pairs may vary. Take for example an allele that encodes for dimples. A child may inherit the allele encoding for dimples on the chromosome from the one parent and the allele that encodes for smooth skin (no dimples) on the chromosome from the other parent.

Although a person can have two identical alleles for a single gene (a homozygous state), it is also possible for a person to have two different alleles (a heterozygous state). The two alleles can interact in several different ways. The expression of an allele can be dominant, for which the activity of this gene will mask the expression of a nondominant, or recessive, allele. Sometimes dominance is complete; at other times, it is incomplete. In some cases, both alleles are expressed at the same time in a form of expression known as codominance.

In the simplest scenario, a single pair of genes will determine a single heritable characteristic. However, it is quite common for multiple genes to interact to confer a feature. For instance, eight or more genes—each with their own alleles—determine eye color in humans. Moreover, although any one person can only have two alleles corresponding to a given gene, more than two alleles commonly exist in a population. This phenomenon is called multiple alleles. For example, there are three different alleles that encode ABO blood type; these are designated IA, IB, and i.

Over 100 years of theoretical and experimental genetics studies, and the more recent sequencing and annotation of the human genome, have helped scientists to develop a better understanding of how an individual’s genotype is expressed as their phenotype. This body of knowledge can help scientists and medical professionals to predict, or at least estimate, some of the features that an offspring will inherit by examining the genotypes or phenotypes of the parents. One important application of this knowledge is to identify an individual’s risk for certain heritable genetic disorders. However, most diseases have a multigenic pattern of inheritance and can also be affected by the environment, so examining the genotypes or phenotypes of a person’s parents will provide only limited information about the risk of inheriting a disease. Only for a handful of single-gene disorders can genetic testing allow clinicians to calculate the probability with which a child born to the two parents tested may inherit a specific disease.
A mutation is a change in the sequence of DNA nucleotides that may or may not affect a person’s phenotype. Mutations can arise spontaneously from errors during DNA replication, or they can result from environmental insults such as radiation, certain viruses, or exposure to tobacco smoke or other toxic chemicals. Because genes encode for the assembly of proteins, a mutation in the nucleotide sequence of a gene can change amino acid sequence and, consequently, a protein’s structure and function. Spontaneous mutations occurring during meiosis are thought to account for many spontaneous abortions (miscarriages).
Sometimes a genetic disease is not caused by a mutation in a gene, but by the presence of an incorrect number of chromosomes. For example, Down syndrome is caused by having three copies of chromosome 21. This is known as trisomy 21. The most common cause of trisomy 21 is chromosomal nondisjunction during meiosis. The frequency of nondisjunction events appears to increase with age, so the frequency of bearing a child with Down syndrome increases in females over 36. The age of the male parent matters less because nondisjunction is much less likely to occur in a sperm than in an egg.

Whereas Down syndrome is caused by having three copies of a chromosome, Turner syndrome is caused by having just one copy of the X chromosome. This is known as monosomy. The affected child is always female. Women with Turner syndrome are sterile because their sexual organs do not mature.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at openstax.org.

Each pair of chromosomes contains hundreds to thousands of genes. The banding patterns are nearly identical for the two chromosomes within each pair, indicating the same organization of genes. As is visible in this karyotype, the only exception to this is the XY sex chromosome pair in males. (credit: National Human Genome Research Institute)

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Xem video và cảm nhận nội dung bài. Bạn có thể thả trôi, cảm nhận dòng chảy ngôn ngữ và không nhất thiết phải hiểu toàn bộ bài. Bên dưới là script để bạn khái quát nội dụng và tra từ mới.
Script:
  1. There are two aspects to a person’s genetic makeup.
  2. Their genotype refers to the genetic makeup of the chromosomes found in all their cells and the alleles that are passed down from their parents.
  3. Their phenotype is the expression of that genotype, based on the interaction of the paired alleles, as well as how environmental conditions affect that expression.
  4. Working with pea plants, Mendel discovered that the factors that account for different traits in parents are discretely transmitted to offspring in pairs, one from each parent.
  5. He articulated the principles of random segregation and independent assortment to account for the inheritance patterns he observed.
  6. Mendel’s factors are genes, with differing variants being referred to as alleles and those alleles being dominant or recessive in expression.
  7. Each parent passes one allele for every gene on to offspring, and offspring are equally likely to inherit any combination of allele pairs.
  8. When Mendel crossed heterozygous individuals, he repeatedly found a 3/1 dominant–recessive ratio.
  9. He correctly postulated that the expression of the recessive trait was masked in heterozygotes but would resurface in their offspring in a predictable manner.
  10. Human genetics focuses on identifying different alleles and understanding how they express themselves.
  11. Medical researchers are especially interested in the identification of inheritance patterns for genetic disorders, which provides the means to estimate the risk that a given couple’s offspring will inherit a genetic disease or disorder.
  12. Patterns of inheritance in humans include autosomal dominance and recessiveness, X-linked dominance and recessiveness, incomplete dominance, codominance, and lethality.
  13. A change in the nucleotide sequence of DNA, which may or may not manifest in a phenotype, is called a mutation.
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