Chapter 2 Flashcards
DNA (deoxyribonucleic acid)
The Beginning of Life
- Molecule that contains the chemical instructions for cells to manufacture various proteins
- Promotes growth and sustains life
- All living things are composed of DNA molecules
Chromosome
The Beginning of Life
One of the 46 molecules of DNA (in 23 pairs) that almost every cell of the human body contains and that, together, contain all the genes.
- Each molecule of DNA is called a chromosome.
- Chromosomes contain units of instructions called genes
- Consists of 46 chromosomes arranged in 23 pairs.
Zygote
The Beginning of Life
The single cell that is formed from the fusing of two gametes, a sperm and an ovum.
• Every person starts life as a single cell, called a zygote
• The zygote contains genes that have been passed down for hundreds of thousands of years
• The first hours of development are:
– universal to all humans yet
– provide characteristics that are unique to each human
Genes
- Chromosomes contain units of instructions called genes (which code for proteins)
- Each gene is located on a particular chromosome
Genotype
– An organism’s genetic inheritance / genetic potential
– Unique for each organism
– Genes are passed down from generation to generation
Phenotype
The observable characteristics of an organism, including appearance, personality,
intelligence, and all other traits
The Human Genome
the complete set of nucleic acid sequence for humans encoded as DNA
• It is made up of 23 chromosome pairs in cell nuclei
• Involves the full set of genes that are the instructions that make an individual who they are
Similarity between two people
The Human Genome
99.5%
Similarity between humans and chimpanzees
The Human Genome
98%
Similarity between humans and every other mammals
The Human Genome
90%
Human Genome Project
international effort to map the complete genetic code
• About 18,000 – 23,000 shared genes in humans
• The regulator genes and the “junk” around the genes are responsible for differences among species
Genomic DNA
Junk DNA that does not encode proteins and whose function, if it has one, is not well understood.
• Junk. Barren. Non-functioning. Dark matter. That’s how scientists described the 98% of human genome that lies between our 20,000+ genes (DNA) a decade ago
Sex/Gender
Humans usually possess 46 chromosomes: 44 autosomes and 2 sex chromosomes
– Females: XX and Males: XY
How is sex determined?
By the father:
• Sex of offspring depends on whether the father’s Y sperm or X sperm fertilizes the ovum (50% chance for either sex)
Gametes
The Beginning of Life
Sperm and ovum/egg reproductive (SEX) cells
• Each gamete consists of 23 chromosomes
Zygote
Two gametes (sperm and ovum) combine and produce a new individual with 23 chromosomes from each parent. – the two nuclei will fuse, bringing together about 20,000 genes to guide development
Fertilization
Sperm and ovum fuse to create zygote
Intersex**
Child born with genetilia of both sexes
o Every now and then, a baby is born with “ambiguous genitals,” meaning that the child’s sex is not abundantly clear.
o When this happens, a quick analysis of the chromosomes is needed to make sure there are exactly 46 and to see whether the 23rd pair is XY or XX.
Monozygotic twins
Identical twins
• Originate from one zygote that splits apart very early in development.
• Incomplete split results in conjoined twins.
• Same genotype but slight variations in phenotype are possible due to environmental influences.
Dizygotic twins
Fraternal twins
• Result from fertilization of two separate ova by two separate sperm.
• Dizygotic twins have half their genes in common and occur twice as ofen as monozygotic twins.
• Incidence is genetic and varies by ethnicity and age.
Prenatal development
Is the process of which a single cell develops after conception into an embryo and later into a fetus /offspring (full-term baby)
o Takes about 38 weeks to complete
o Takes place in the mother’s womb
o Consists of 3 main periods
Three main periods of Prenatal Development
- Germinal Period
- Embryonic Period
- Fetal Period
Germinal Period
Prenatal development
The first two weeks of development after conception, characterized by rapid cell division and the beginning of cell differentiation.
Conception is the beginning of the germinal period.
This stage occurs during the first 2 weeks of zygote development
Embryonic Period
Prenatal development
This stage lasts from implantation until ~8 weeks from the time of conception
– This is the most important time of prenatal development bc the embryo is developing the foundations for a healthy baby
Fetal Period
Prenatal development
Final stage of development. – From the end of the embryonic stage (week 9) until birth
Fetus (scientifically)
Not a fetus until brain has developed
First 14 Days
First Stages of the Germinal Period
Zygote begins duplication and division within hours of conception
• Development of the placenta
• Implantation (about 10 days after conception)
• Organism grows rapidly
Occasionally at this early stage, the cells separate completely, forming the beginning of monozygotic twins, quadruplets, or octuplets.
From the 3rd Through 8th Week - EMBRYO
The Embryonic Period
• Primitive streak becomes the neural tube and later forms the brain and
spine of the CNS.
• Head takes shape
• Eyes, ears, nose, and mouth form
• Heart begins to pulsate
• Extremities develop and webbed fingers and toes separate
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From 9th Week Until Birth - FETUS
The Fetal Period
- Genitals form and sex hormones cause differences in fetal brain organization
- At 3 months, the fetus weighs about 3 ounces
- Experiences the period of greatest brain growth during the 4th, 5th,and 6th months
Age of viability
The Fetal Period
• Age at which a preterm newborn may survive outside the mother’s uterus if medical care is available
– About 22 weeks after conception
• Brain is able to regulate basic body functions: breathing, heart beat
Teratogens
Harm to the Fetus
Any agent or condition, including viruses and drugs, resulting in birth defects or complications
-All teratogens increase the risk of harm to the developing child, though not all cause damage; the ultimate impact depends on the complex interplay of many factors
Behavioral teratogens
Agents and conditions that can harm the prenatal BRAIN, impairing the future child’s intellectual and emotional functioning
Threshold effect
Risk Analysis
Certain teratogens are relatively harmless
until exposure reaches a certain level (the threshold).
(Glass of wine in last trimester won’t cause much harm)
Fetal alcohol syndrome (FAS)
Risk Analysis
A cluster of birth defects, including abnormal facial characteristics, slow physical growth, and intellectual disabilities, that may occur in the child of a woman who drinks alcohol while pregnant.
Genetic vulnerability
Risk Analysis
- Some zygotes carry genes that make them vulnerable.
* Male fetuses are more vulnerable to teratogens than female ones.
Neural-tube defects (NTDs)
Risk Analysis
a group of conditions in which an opening in the spinal cord or brain remains from early in human development.
– More common in certain ethnic groups (e.g., Irish, English, and Egyptian).
Critical period - Timing
Risk Analysis
– First days and weeks are critical for body formation.
– Final months are important for body weight.
– Health during the entire fetal period is important for brain development.
Vulnerability During Prenatal Development (estimates)
– Germinal Period:
60% of zygotes do not survive
– Embryonic
Period: 20% of embryos are aborted spontaneously (early miscarriage)
– Fetal Period:
5% of fetuses are aborted spontaneously or are stillborn
– Birth: Only 31% of all zygotes survive until birth
Chromosomal Miscounts
About once in every 200 births, an infant is born with 45, 47, 48 or even 49 chromosomes that produces a syndrome – Most common is Down syndrome (trisomy-21) – Full or partial extra copy of chromosome 21
– INTERSEX: About 1 in every 500 infants is born with only one sex chromosome (no Y) or with three or more sex chromosome (e.g., XXY)
Gene disorders
Abnormal Genes
• Inherited gene is dominant or when both parents carry the recessive gene • Most dominant disorders begin in adulthood • Examples – Huntington‘s disease – Cystic fibrosis – Thalassemia – Sickle-cell disease – Fragile X
Huntington‘s disease
Fatal genetic disorder that causes the progressive breakdown of nerve cells in the brain. It deteriorates a person’s physical
and mental abilities during their prime working years. Has no cure. Treatment is limited.
Cystic fibrosis
An inherited life-threatening disorder that damages the lungs and digestive system.
Thalassemia
A blood disorder involving less than normal amounts of an oxygen-carrying protein.
Sickle-cell disease
A group of disorders that cause red blood cells to become misshapen and break down. Can be treated. Cannot be cured.
Fragile X
A genetic condition that involves the X chromosome and that causes slow development and intellectual disability. Can be treated. Cannot be cured.
Prenatal Testing
Some serious conditions can be diagnosed and treated during pregnancy.
Issues with Prenatal Testing
– 20% of early pregnancy tests raise anxiety.
– Parents may not want to know information.
– Couples may argue about risk.
• False positives
• False negatives
AFP test
– Alpha-fetaprotein (AFP): a protein produced by a fetus that is present in amniotic fluid and the bloodstream of the mother.
– AFP test: Levels of AFP can be measured to detect certain congenital defects such as spina bifida and Down syndrome
Preterm (before term ends)
- Birth that occurs at 35 or fewer weeks after conception
* Usually associated with low birthweight
Small for gestational age (SGA)
• Birthweight is significantly lower than expected, given the time since conception.
• Suggests impairment throughout prenatal development and
serious problems.
Low birth weight (LBW)
Less than 5½ pounds at birth
• In contrast, the average newborn weighs about 8 pounds.
Very low birth weight (VLBW)
Under 3 pounds, 5 ounces at birth
Extremely low birth weight (ELBW)
Under 2 pounds, 3 ounces at birth
High risk infants and children
Consequences of LBW
- Nearly every developmental accomplishment is late.
* Cry more, pay less attention, disobey more, and experience language and developmental outcome delays
Middle childhood, formerly SGA children
Consequences of LBW
Have more neurological problems, smaller brain volume
Low Birthweight: Comparing Nations
• Over 8% of all newborn babies in the US have LBW, ranking worse than most developed nations
• Worldwide, far fewer LBW
babies are born today than 20 years ago.
– Neonatal deaths have been reduced by 1/3 as a result.
Nature and Nurture: Alcoholism
- Inherited psychological traits (genes) affect alcoholism
- Biological sex (XX or XY) and gender (cultural) also affect the risk of alcoholism
- Environmental conditions can modify the genetic effects
- Nature and nurture must combine to create an alcoholic
Labor begins when…
Birth
Fetal brain signals the release of hormones to trigger the female’s uterine muscles.
Average labor duration for firstborn babies
Birth
12 hours
– Quicker labor for later-born babies
Apgar scale
– Quick assessment of newborn’s heart rate, breathing, muscle tone, color, and reflexes
– Completed twice (1 minute and 5 minutes after birth) – Score of 0, 1, or 2 in each category
***Desired score of 7 or above after each assessment (required to take baby home)
Medical Intervention’s role in childbirth
- Childbirth has become safer for mothers.
* Infant mortality has decreased due to better medical care.
Disadvantages of excessive medical care??????
• Excessive medical care also has disadvantages.
Cesarean section (c-section)
- SURGICAL BIRTH
- Fetus can be removed quickly
- Usually safe for mother and baby, saving lives when the fetal head is too large for the pelvis
Too Many Cesareans or Too Few?
The underlying issue is whether some women who should have cesareans do not get them, while other women have unnecessary cesareans.
• A major issue is that c-sections can weaken abdomen muscles
Home births
Traditional and Modern Birthing Practices
In developed countries is childbirth in a non-clinical setting, typically using natural childbirth methods
Hospital births
Traditional and Modern Birthing Practices
Births in a controlled sterile hospital environment using IV and fetal monitors and a transducer to monitor contractions
Doula
Traditional and Modern Birthing Practices
A woman who is trained to assist another woman during childbirth and who may provide support to the family after the baby is born.
Reflex
The New Family: The Newborn
An unlearned, involuntary action or movement in response to a stimulus, and without conscious thought
Rooting Reflex
The New Family: The Newborn
- Seen in normal newborn babies, who automatically turn the face toward the stimulus and make sucking (ROOTING) motions with the mouth when the cheek or lip is touched.
- Helps to ensure successful breastfeeding
Brazelton Neonatal Behavioral Assessment Scale
The New Family: The Newborn
A test often administered to newborns that measures responsiveness and records 46 behaviors, including 20 reflexes.
Postpartum depression
The New Family: Mothers
• Many women experience significant physical problems after birth
– Problems include such things as incisions from a c-section, painfully sore nipples, or problems with urination.
• Psychological symptoms range from “baby blues” to postpartum psychosis.
• May involve struggles with adequate baby care
• Varied causes
Father’s role
The New Family: Fathers
- Helping mother stay healthy
- Helping mother manage stress (affects fetus)
- Experiencing COUVADE in some cultures
Couvade
The New Family: Fathers
Dads-to-be go through what’s commonly
called “sympathetic pregnancy.”
– men whose partners were pregnant develop their own pregnancy symptoms, such as nausea, dizziness, hormonal fluctuations, back pain, cramps, irritability, and even cravings.
Implantation
The process, beginning about 10 days after conception, in which the developing organism burrows into the tissue that lines the uterus, where it will be nourished.
Heritability
A statistic that indicates what percentage of the variation in a trait within a population, in a particular context and era, can be traced to genes.
Down syndrome
A condition in which a person has 47 chromosomes instead of the usual 46, with three rather than two chromosomes at the 21st position. People with Down syndrome often have a distinctive appearance.
Preterm birth
A birth that occurs three or more weeks before the full 38 weeks of the pregnancy - that is, at 35 or fewer weeks after conception.
