© Goodheart-Willcox Co., Inc.. 4 Pregnancy © Goodheart-Willcox Co., Inc. Conception Cell is the smallest unit of life that is able to reproduce itself.

© Goodheart-Willcox Co., Inc.


4Pregnancy


Conception

• Cell is the smallest unit of life that is able to reproduce itself

• Sperm is the male germ cell• Ovum is the female germ cell• Conception occurs when ovum and

sperm combine• Zygote is a single cell formed at

conception– also called a fertilized egg

continued


Conception

• Fallopian tubes extend from the sides of the uterus– where the ovum is

fertilized

• Uterus is the organ in which the baby develops


Genetic Factors and the Unborn Baby

• Genetic factors are traits passed through the genes– affect all stages of growth and

development

• Genome is a genetic blueprint that guides growth and development during pregnancy– gives cells instructions for family-like

traits that will unfold throughout life

continued


Genetic Factors and the Unborn Baby

• Nucleus is the center of the cell

• Genetic code is a set of instructions for development

• DNA store the genetic code

• Chromosomes carry the DNA


Objective

• Describe how a person inherits traits through genes.


Chromosomes and Genes

• Chromosomes– each person has 46, pairs of 23– half from sperm, half from egg– contains 20,000 genes

• Genes– each human cell contains about 1 million

genes– a gene, or group of genes, decides a trait


Dominant and Recessive Traits

• Dominant traits always show in a person even if only one gene of the pair is inherited for that trait

• Recessive traits typically do not show in a person unless both genes for the trait are inherited– one from each parent– person who inherits only one recessive

gene for a trait becomes a carrier of that trait


Sex Chromosomes

• Sex chromosomes determine genetic sex of baby– XX female

• ovum always carries only X chromosomes

– XY male• sperm can carry either X or Y chromosome• boys’ sex-linked traits are determined only

by their mothers


Multiple Pregnancy

• Multiple pregnancy occurs when two or more babies develop in the same pregnancy

continued


Multiple Pregnancy

• Fraternal children develop from two or more ova– most common– each baby has own chorion

• Identical children develop from same ova and sperm

• Mixed types of pregnancy must include fraternal and identical babies


What Do You Think?

How can parents help identical twins maintain separate identities while still nurturing a close sibling relationship?


Stages in Prenatal Development

• Prenatal development takes place between conception and birth

–germinal stage–embryonic stage– fetal stage


Germinal Stage

• Germinal stage is the first stage of development

continued


Germinal Stage

• Amnion is a fluid-filled sac that surrounds the baby in the uterus

• Placenta is an organ filled with blood vessels that nourish the baby in the uterus

• Umbilical cord is a cord that connects the baby to the placenta


Embryonic Stage

• Embryonic stage is the second stage of development, lasts about six weeks– most crucial to development– baby is called an embryo– development of most body systems– heart begins to beat– cartilage is present before bones form– substances pass from mother’s placenta

through the umbilical cord


Fetal Stage

• Fetal stage is the third stage of pregnancy, lasts from about nine weeks after conception until birth– bone starts to replace

cartilage– baby is known as a fetus

continued


Fetal Stage

• During the fetal stage,– all parts of the body mature– overall size increases quickly– hear heartbeat in the third month– quickening begins between the fourth

and fifth months

continued


Fetal Stage

• Age of viability is the age at which a baby could survive if born, 28 weeks– still need extensive medical care– better chance of survival each week the

baby is not born• During last two months of pregnancy,

– inner layer of lungs produces substance that allows for breathing air

– receives immunities from mother in the ninth month


What Do You Think?• Pregnancies that end before 20 weeks

are considered a miscarriage, resulting in no record of the life, such as a birth or death certificate.

• How do you think this impacts a parent after the loss of a wanted pregnancy?


Glossary of Key Terms

• age of viability. Age at which most babies could survive if they were born (28th week of pregnancy).

• amnion. Fluid-filled sac that surrounds the baby in the uterus.

• cartilage. Soft, elastic, flexible tissue that provides structure for the body.



• cell. Smallest unit of life that is able to reproduce itself.

• chorion. Membrane that surrounds the baby in the uterus.

• chromosomes. Threadlike structures that carry genes in living cells.

• conception. Union of the ovum and sperm cells.



• dominant traits. Traits that always show in a person even if only one gene of the pair is inherited for that trait.

• embryo. Medical term used to describe the unborn baby in the embryonic stage of development (week 3 through 8 of pregnancy).



• embryonic stage. Second stage of prenatal development, lasting about six weeks.

• fallopian tubes. Two hollow tubes that connect to the uterus and have fingerlike projections that reach toward each ovary.

• fetal stage. Third stage of pregnancy, lasting from about nine weeks after conception until birth.



• fetus. Medical term used to describe the unborn baby in the fetal stage of development (week 9 until the end of pregnancy).

• fraternal. Term used to describe children from multiple pregnancies who develop from two or more fertilized ova and differ in genetic makeup.



• genetic factors. Traits that are passed through the genes.

• germinal stage. First stage of prenatal development, lasting about two weeks after conception.

• identical. Term used to describe children from multiple pregnancies who develop from one fertilized ovum and have the same genetic makeup.



• multiple pregnancy. Pregnancy in which two or more babies develop.

• ovum. Female sex cell; also called egg.• placenta. Organ filled with blood

vessels that nourish baby in the uterus.• prenatal development. Development

that takes place between conception and birth.



• quickening. Movements of the fetus that can be felt by the mother.

• recessive traits. Traits that typically do not show in a person unless both genes for the trait are inherited.

• sperm. Male sex cell.• umbilical cord. Cord that connects the

baby to the placenta.



• uterus. Organ in which the baby develops and is protected until birth.

• zygote. Single cell formed at conception; also called fertilized egg.

© Goodheart-Willcox Co., Inc.. 4 Pregnancy © Goodheart-Willcox Co., Inc. Conception Cell is the smallest unit of life that is able to reproduce itself.

Documents

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trait slide

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genes genes

genes chromosomes

life continued slide

genes genetic factors

germinal stage germinal