Chapter 2.1 - Heredity and Prenatal Development

genetics

the branch of biology that studies heredity

chromosomes

rod-shaped structures composed of genes that are found within the nuclei of cells

gene

the basic unit of heredity. Genes are composed of deoxyribonucleic acid (DNA)

polygenic

resulting from many genes

deoxyribonucleic acid (DNA)

genetic material that takes the form of a double helix composed of phosphates sugars and bases

Is it true that your father determined whether you are female or male?

unknown

is it true or false that 120 to 150 boys are conceived for every 100 girls?

true; sperm with y sex chromosomes swim more rapidly, resulting in the conception of more boys than girls.

is it true or false that sperm travel randomly inside the womans reproductive tract, so reaching the ovum is a matter of luck?

false: it is not true that sperm travel about at random inside the woman’s reproductive tract. The direction in which sperm travel is influenced by a change in calcium ions that occurs when an ovum is released.

is it true or false that “test0tube babies” are grown in a laboratory dish throughout their nine-month gestation period?

false: it is not true that “test-tube babies” are grown in a laboratory dish throughout their nine-month gestation period. So-called “test-tube babies” are conceived in a laboratory dish, and then the embryos are implanted into the mother’s uterus for gestation.

is it true of false that newly fertilized eggs survive without any nourishment from the mother for more than a week?

It is true that newly fertilized egg cells survive without any nourishment from the mother for more than a week. And because of that, they make no gains in mass.

is it true or false that fetuses suck their thumbs, sometimes for hours on end?

it Is true that they suck their thumbs, sometimes to do so for hours on end.

Is it true or false that a fathers age at the time of conception can influence the development of the fetus?

It is true that a father;s age at the time of conception can influence the development of the fetus. The older the father, the greater the risk of chromosomal abnormalities.

mitosis

the form of cell division in which each chromosome splits lengthwise to double in number. Half of each chromosome combines with chemicals to retake its original form and then moves to the new cell.

mutation

a sudden variation in a heritable characteristic, as by an accident that affects the composition of genes.

meiosis

the form of cell division in which each pair of chromosomes splits so that one member of each pair moves to the new cell. Asa a result, each new cell has 23 chromosomes.au

autosome

a member of a pair of chromosomes (with the exception of sex chromosomes)

sex chromosome

a chromosome in the shape of a Y (male) or an X (Female) that determines the anatomic sex of the child.

monozygotic (MZ) twins

twins that derive from a single zygote that has split into two; identical twins. Each MZ twin carries the same genetic code.

dizygotic (DZ) twins

twins that derive from two zygotes; fraternal twins.

ovulation

the releasing of an ovum from an ovary

allele

a member of a pair of genes

homozygous

having two identical alleles

heterozygous

having two different alleles

dominant trait

a trait that is expressed

recessive trait

a trait that is not expressed when the gene or genes involved have been paired with dominant genes.

carrier

a person who carries and transmits characteristics but does not exhibit them.

multifactorial problems

problems that stem from the interaction of heredity and environmental factors.

Down’s syndrome

a chromosomal abnormality characterized by intellectual disabilities and caused by an extra chromosome in the 21st pair.

sex-linked chromosomal abnormalities

abnormalities that are transmitted from generation to generation and carried by a sex chromosome

Klinefelter syndrome

a chromosomal disorder found among males that is caused by an extra X chromosome and that is characterized by infertility and mild intellectual disabilities.

testosterone

a male sex hormone produced mainly by the testes.

Turner syndrome

a chromosomal disorder found among females that is caused by having a single X sex chromosome and is characterized by infertility.

estrogen

a female sex hormone produced mainly by the ovaries.

phetylketonuria (PKU)

a genetic abnormality in which phenylalanine builds up and causes intellectual disabilities.

Huntington’s Disease (HD)

a fatal genetic neurological disorder whose onset is in middle age.

sickle cell disease

a genetic disorder that decreases the blood’s capacity to carry oxygen.

Tay-Sachs disease

a fatal genetic neurological disorder.

cystic fibrosis

a fatal genetic disorder in which mucus obstructs the lungs and pancreas.

hemophilia

a genetic disorder in which blood does not clot properly.a

sex-linked genetic abnormalities

abnormalities resulting from genes that are foudn on the X sex chromosome. They are more likely to be shown by male offspring (who do not have an opposing gene from a second X chromosome) than by female offspring.

muscular dystrophy

a chronic disease characterized by a progressive wasting away of the muscles.g

enetic counselors

health workers who compile information about a couples genetic heritage to advise them as to whether their children might develop genetic abnormalities.

prenatal

before birtha

mniocentesis

a procedure for drawing and examining fetal cells sloughed off into a amniotic fluid to determine the presence of various disorders.

miscarriage

the expulsion of an embryo or fetus before it can sustain life on its own, most often due to defective development.

chorionic villus sampling (CVS)

a method for the prenatal detection of genetic abnormalities that samples the membrane enveloping the amniotic sac and fetus.

uterus

the hollow organ within females in which the embryo and fetus develop

ultrasound

high-frequency sound waves that are reflected off a fetus or an internal organ to provide information to generate a computer image.

sonogram

an image generated by ultrasonic sound waves to create a picture of an embryo or fetus.

alpha-fetoprotein (AFP) assay

a blood test that assesses the mother’s blood level of alpha-fetoprotein, a substance that is linked with fetal neural tube defects.

genotype

the genetic form or constitution of a person as determined by heredity

phenotype

the actual form or constitution of a person as determined by heredity and environmental factors.

autism

a developmental disorder characterized by failture to relate to others, communication problems, intolerance of change, and ritualistic behaviour.

conception

the union of a sperm cell and an ovum that occurs when the chromosomes of each of these cells combine to form 23 new pairs.

endometrium

the inner lining of the uterus.

motility

self-propulsion

pelvic inflammatory disease (PID)

an infection of the abdominal region that may have various causes and that may impair fertility.

endometriosis

an inflammation of endometrial tissue sloughed off into the abdominal cavity rather than out of the body during menstruation; the condition is characterized by abdominal pain and sometimes infertility.

artificial insemination

injection of sperm into the uterus to fertilize an ovum

in vitro fertilization (IVF)

fertilization of an ovum in a laboratory dish.

intrauterine insemination (IUI)

a method of assisted reproduction in which sperm are injected directly into the uterus.

donor IVF

the transfer of a donor’s ovum, fertilized in a laboratory dish, to the uterus of another woman.

germinal stage

the period of development between conception and the implantation of the embryo.

blastocyst

A stage within the germinal period of prenatal development in which the zygote has the form of a sphere of cells surrounding a cavity of fluid.

embryonic disk

the platelike inner part of the blastocyst that differentiates into the ectoderm, mesoderm, and endoderm of the embryo.

trophoblast

the outer part of the blastocyst from which the amniotic sac, placenta, and umbilical cord develop.

umbilical cord

a tube that connects the fetus to the placenta.

placenta

an organ connected to the uterine wall and to the fetus by the umbilical cord. The placenta serves as a relay station between mother and fetus for the exchange of nutrients and wastes.

embryonic stage

the stage of prenatal development that lasts from implantation through the eighth week of pregnancy; it is characterized by the development of the major organ systems.

cephalocaudal

from head to tail

proximodistal

from the inner part (or axis) of the body outward.

ectoderm

the outermost cell layer of the newly formed embryo from which the skin and nervous system develop.

neural tube

a hollowed-out area in the blastocyst from which the nervous system develops.

endoderm

the inner layer of the embryo from which the lungs and digestive system develop.

mesoderm

the central layer of the embryo from which the bones and muscles develop

androgens

male sex hormones

amniotic sac

the sac containing the fetus

amniotic fluid

fluid within the amniotic sac that suspends and protects the fetus.

placenta

the organ formed in the lining of the uterus that provides nourishment for the fetus and elimination of its waste products.

fetal stage

the stage that begins with the third month of pregnancy and ends with childbirth, during which organ systems mature and there are gains in size.

stillbirth

the birth of a dead fetus

teratogens

environmental influences or agents that can damage the embryo or fetus.

critical period

in this usage, a period during which an embryo is particularly vulnerable to a certain teratogen

syphilis

a sexually transmitted infection that, in advanced stages, can attack major organ systems.

congenital

present at birth and resulting from genetic or chromosomal abnormalities or from exposure to the prenatal environment

HIV/AIDS

HIV stands for human immunodeficiency virus, which cirrples the body’s immune system. AIDS stands for acquired immunodeficiency syndrome, a condition in which the immune system is weakend such that it is vulnerable to diseases it would otherwise fight off.

rubella

a viral infection that can cause intellectual disabilities and heart disease in the embryo. Also called German measles.

preeclampsia (or toxemia)

a life-threatening disease that can afflict pregnant women; it is characterized by high blood pressure.

premature

born before the full term of gestation. Also referred to as preterm.

Rh incompatibility

a condition in which antibodies produced by the mother are transmitted to the child, possibly causing brain damage or death.

thalidomide

a sedative used in the 1960s that has been linked to birth defects, especially deformed or absent limbs

Progestin

a synthetic hormone used to maintain pregnancy that can cause masculinization of the fetus.

DES

diethylstilbestrol, an estrogen that has been linked to cancer in the reproductive organs of children of women who used the hormone when pregnant.

fetal alcohol spectrum disorder (FASD)

a cluster of symptoms shown by children of women who drank heavily during pregnancy, including characteristic facial features and intellectual disabilities.

1. _____ are the bioligical materials that regulate the development of traits.

genes

2. Dizygotic twins share _____% of their genes.

50

3. “Supermales” have ______ sex-chromosomal structure

xyy

4. ______ cell disease is most common among African Americans.

sickle

5. Sperm are apparently guided toward an egg cell (ovum) by changes in ______ ions.

calcium

6 Some women are infertile due to _______, which can obstruct the fallopian tubes.

endometriosis