Chap 2 from conception to birth review

chromosomes

• structures in the nucleus that store the genetic code

  • Humans have 23 pairs of chromosomes (46 chromosome strands)

genes

• the units of the DNA that contains the blueprints for designing proteins

  • Humans have over 20,000 different types

DNA

molecules that make up chromosomes

Allele

different forms of a gene

genotype

an organism’s entire genetic inheritance, or genetic potential

phenotype

• how the genotype is displayed

• The observable characteristics of a person, including appearance, personality, intelligence, and all other traits

mitosis

• Process of cell duplication

• DNA is copied

• End result – two cells that each have 23 pairs of chromosomes

meiosis

• Process of cell division that creates gametes (sex cells)

• Crossover

• Two rounds of cell division

• Number of chromosomes in each cell cut in half

  • Sperm and ova each have 23 chromosomes

female meiosis

• occurs prenatally and leads to the development of one ovum

• can have millions of eggs when born

male meiosis

occurs post puberty and leads to the development of four sperm cells

gamete

a reproductive cell; sperm or ovum

determining sex of the offspring

• The 23rd pair of chromosomes determines the zygote’s sex: XX female; XY male

• The other 22 pairs of chromosomes are autosomes and do not differ for males and females

• Females only have X chromosomes so each ovum’s 23rd chromosome is an X

• Half of sperm cells have X chromosomes and half have Y chromosomes

• The genotype of the zygote is based on whether the sperm cell that fertilizes the ovum has an X or a Y chromosome

zygote

• the single cell formed from the fusing of a sperm and an ovum

  • 23 pairs of chromosomes (46 strands)

monozygotic twins

• one fertilized egg by one sperm split into two cells/eggs

• same gender

• not genetic (not normal), but a mutation

dizygotic twins

• 2 separate eggs and sperm

• not normal

• can be genetic by an ovary condition that releases two eggs and infertility treatment

• can happen over the age of 30 because body response to get pregnant before getting older

dominant - recessive

• If the dominant gene is present, then the phenotype will reflect that gene

  • Both homozygous (BB, bb) dominant and heterozygous (Bb) have phenotypes that reflect the dominant gene

• If the genotype is homozygous recessive, then the phenotype reflects the recessive gene

cystic fibrosis

a recessive gene disorder

lung: think mucus build up → chronic infections, difficulty breathing, damage

digestive system: obstruct pancreas, impairing digestion and nutrient absorption → malnutrition

homozygous

both alleles of a specific gene are the same (BB, bb)

heterozygous

when the alleles of a specific gene are different (Bb)

genetic carriers

• A person whose genotype includes a gene not expressed in their phenotype

• The unexpressed gene occurs in half of their gametes and can be passed on to their offspring

• If that gene is inherited from both parents, then the characteristic will appear in the child’s phenotype

co-dominance gene

• ex: sickle cell anemia (heterozygous sickle cell)

• no dominant or recessive

x-linked genes

• hemophilia

• color blindness

• females: father has it, mother carries it

• males: mother has it

down syndrome

• Presence of 3 or 4, 21st chromosomes

• Physical differences

• Potential cognitive impairments

• feel more positive

XO-Turner syndrome

• females

• Do not menstruate nor develop breasts

• Very feminine

XXX triple x syndrome

• females

• can reproduce, but have same abnormalities

• tall

XXY - Kleinfelter’s syndrome

• males

• small genitals

• infertile

• less masculine

XXY Jacob’s syndrome

• males, more aggressive

• taller

• low IQ

• can reproduce but have their abnormalities

germinal period

• two weeks after conception

• zygote forms the moment a sperm fertilizes an ovum and begins mitotic cell division

• day 4-5, the cell becomes a blastocyst and travels to the uterus via fallopian tube

• the blastocyst then implants on the wall of the uterus

embryonic period

• weeks 3-8, most sensitive and transformative stage

• develops all the important organs (brain, spinal column, head, eyes, ears, nose, mouth)

• trophoblast forms placenta, on the wall of uterus

• umbilical cord connects the embryo to the placenta

• amniotic sac is thin membrane that forms around embryo and inside has amniotic fluid to protect embryo

• by 5 weeks, limbs appear

• 8 weeks, sex organs will develop.

fetal period

• The developing organism is called a fetus from the start of the 9 week after conception until birth

• fetus gains weight and grows bigger

• At the end of the third month, the fetus has all its body parts

teratogens

• agents or conditions that can impair prenatal development and result in:

  • Death

  • Birth defects

  • Impairments in cognitive, social or emotional functioning

• Critical Periods like embryonic period

how much teratogens

• Principle of Dose-Response Relationship – more exposure typically leads to greater negative impact

  • Threshold Effect - situation in which a certain teratogen is relatively harmless in small doses, but harmful once exposure reaches certain level

how many teratogens

• Interaction Effect – the result of a combination of teratogens

  • The risk can be magnified when there is exposure to more than one teratogen at a time

  • some women are more sensitive to certain teratogens

• Sleeper Effects – damage occurs prenatally but the effects do not show up until later in life

fetal alcohol syndrome

• cluster of birth defects, including:

  • abnormal facial characteristics

  • slow physical growth

  • delayed and/or impaired mental development

fetal alcohol effects

• condition in which the child has been exposed to alcohol before birth

  • has signs of fetal alcohol syndrome but does not meet all the criteria

effects of cigarette/smoking/vaping

• expose baby to nicotine

• shrinks vein and arteries

• blood flow slows down and has to work harder, reduce oxygen supply

maternal factors of development of baby

nutrition: 25-30 pounds normal to gain

age: 20-35 years old for pregnancy period

stress: high stress is bad

uterine contractions

• first sign of labor

• regular uterus muscle contractions increase in intensity and duration

dilation of the cervix

the cervix opens until 10 cm to push the baby

crowning

baby is in the birth canal, and the head can be seen in the vagina

pushing/birth

when cervix is at 10 cm, the mother pushes baby out of the birth canal and comes out

afterbirth of placenta

mother delivers the placenta

ultrasound

sonogram to see the baby inside the body

• prenatal testing

amniocentesis

a process of taking a sample of the amniotic fluid that has cells to detect genetic disorder

• during second trimester

• prenatal testing

chorionic villus sampling

a process of taking cells from the placenta to test for genetic disorders

• prenatal testing

pre-term

born prior to 37 weeks of gestation

birth weight

low birth weight → less than 5 ½ pounds

very low birth weight → less than 3 pounds, 5 oz.

small for date

born underweight when the length of the pregnancy is accounted for

risk factors for preterm and low birth weight

• Multiples (twins, triplets)

• Teen (under age 15)

• Too closely spaced births (6 months)

• Poor general health or nutrition of mother

• Sexually Transmitted Diseases

• Teratogens

• Preeclampsia

• Abnormalities of the uterus (big uterus, push organs)

• Unmarried women

passive genotype

same genes and environment based on biological parents, early childhood

• epigenetic theory

evocative genotype

your genetic material affects how others treat you

• epigenetic theory

active genotype

finding environments that match genetic background

• epigenetic theory

epigenetic tags

• born with fixed genetic

• twins have same tags in early childhood, but different at adulthood

• build up on DNA that certain genetics activate based on environment

epigenetic theory

• genes interact with the environment to allow development

• genes can influence traits which affect responses and the environment can affect gene activity