User:Atcovi/Spring2024/Child Psychology/Ch. 2

We will explore heredity and conception. Development goes back to evolution, where we were chosen arms rather than wings. We first will examine the blocks of heredity: genes and chromosomes. Then we will go into conception.

Terms to memorize will be on the talk page.

2.1 - Heredity, chromosomes, genes



 * Heredity: Transmission of traits and chracteristics from parent to child through genes. The studying of heredity is called genetics. Genetic influences include eye colore, height, and hair color. Genetic influences range from activity level and intelligence to depression and dependence on alcohol and other harmful substances.
 * The units of heredity are found within chromosomes and genes. Chromosomes are rod-shaped structures located within cells. A healthy cell contains 46 chromosomes divided into 23 pairs. Inside these chromosomes, they contain dozens of segments called genes. Genes regulate the development of traits. They are made up of large strands of DNA (deoxyribonucleic acid). They look like twisting ladders. Check the linked page for the DNA makeup.
 * Some traits (blood type) are derived from a single pair of genes that consist of two genes, each from one parent. Other traits are polygenic, which are determined by a combo of gene pairs.

Check Figure 2.1 img

Mitosis and Meiosis
First, before we explain these two processes, we must begin with some definitions. We begin life as a zygote that divides multiple times, either resulting in mitosis or meiosis.


 * Zygote - A new cell created by the combo of a sperm and an ovum (egg cell). This is what a fertilized egg is.
 * Mitosis - Cell divison; each chromosome splits lengthwise to double in number. Half of each chromosome combines with chemicals to retake its oriignal form and then moves to the new cell. See YT video for demonstration.
 * Mutations - When an error occurs in the composition of genes, a mutation takes place (a sudden variation in a heritable characteristic).

Mitosis in a Nutshell Why? Our genetic code is brought into new cells in the formation of our bodies. We need this genetic code as it makes us, us!


 * 1) Segment of DNA exists in one cell.
 * 2) We unzip the DNA (don't worry, we are keeping it PG-13). Cell divides.
 * 3) Each individual rung is combined with the appropriate molecules, such as C with G and T with A.
 * 4) Now we have two identical DNA strands! Woohoo!
 * 5) These DNA copies move apart when the cell further divides, thereby joining new cells.

Meiosis Meiosis is where each pair of chromosomes (all 46 chromosomes in 23 pairs) breaks in half. Each half moves int a new cell. This new cell has 23 chromosomes only. We only get half of the genetic material vs. in mitosis.

In fertilization, we get 23 chromosomes from the sperm and 23 chromosomes from the ovum, making 46 in total. 22 of the chromosome pairs are autosomes, or pairs that contain genetic information.

The last pair, the 23rd pair, consists of the sex chromosomes - the pair that determines what gender we are. XX is female, XY is male. The mom is #1 since she's always giving the X sex chromosome.

Identical vs. Fraternal Twins
Zygote divides like crazy so an 'individual' can be formed. In these cases...

Dad can either give the X or the Y, and that determines what gender you are. Increasing age of mothers and use of assisted reproductive technologies are the reason why twinning rates are increasing. Ovulation, the release of an ovum from an ovary, decreases towards the end of a woman's "child-bearing years". During this time, the chances of twins increase.
 * Monozygotic twins (identical twins) - 2 people, 1 zygote, same genetic code, same sperm cell.
 * Dizygotic twins (fraternal twins) - 2 people, 2 zygotes, DIFFERENT GENETIC CODE, DIFFERENT SPERM CELL. Runs in families.

Dominant vs. Recessive

 * Allele - Each member of a pair of genes, which ultimately determines traits. Homozygous alleles are 2 identical alleles, whilst heterozygous alleles are 2 different alleles.
 * Gregor Mendel came up with a number of laws of heredity through investigating pea plants.
 * Law of dominence - Dominant traits or recessive traits. Example from Mendel's experiment includes crossing of purebred tall pea plants x dwarf pea plants, with the offspring being tall. This implies that purebred tall is the domaint gene. If two recessive genes combine, then it will show.

Multi-factorial problems are the result of heredity interactions and environmental factors, such as diabetes mellitus and epilepsy.

Chromosomal Abnormalities
A syndrome is a group of symptoms that make up a disorder.


 * Down syndrome - Extra chromosome on 21st pair = 47 chromosomes. Older parents are likely to produce (1:1400 at women giving birth at age between 20 and 24, 1:900 at age of 30, 1:385 at age of 35, 1:106 at age of 40 and at women giving birth at age of 45 risk factor is 1:30 (7)).

A sex-linked chromosomal abnormality is where an abnormality is located on the X sex chromosome. Largely results in infertility. An example are XYY males, who face many problems, including deficiency in intelligence, and color blindness.


 * Klinefelter syndrome - XXY, less testosterone. Pubertic traits, such as deepening of the voice, don't develop the way they normally would. Male only.
 * Turner syndrome - X, less estrogen. Girls are shorter and infertile. No breasts, no menstruation.
 * Triple X syndrome - XXX, deficiency in intelligence (language skills and memory), increased chance of infertility.

Genetic Abnormalities
Males are at a bigger risk of sex-linked genetic abnormalities since they have only one X, compared to females who have two X's and would need the genes to be on both Xs. Duchenne muscular dystrophy is sex-linked.
 * Phenylketonuria (PKU) - Recessive gene. 2 parents possess --> 1 child will not get it, 2 children will carry, 1 will display it. Cannot 'metabolize' phenylalanine, disrupts nervous system, causes a variety of problems. Blood/urine test can determine & early diets can save.
 * Huntington disease (HD) - Fatal, uncontrollable muscle movement, onset of HD is in middle adulthood, no cure.
 * Sickle-cell anemia - Recessive gene. Red blood cells sickle and clump with one another, disrupting blood vells and decreasing oxygen supply. Intelligence deficiency & physical problems, including jaundice.
 * Tay-Sachs disease - Recessive gene. Disrupts the CNS slowly, causing death.
 * Cystic Fibrosis - Recessive gene. Thick mucus clogs pancreas and lungs, death by 20s.
 * Hemophilia - Blood does not clot properly. Carried only on X sex choromosome.

How to Determine?

 * Genetic counseling
 * Prenatal testing
 * Blood tests: Amniocentesis on fetus, alpha-fetoprotein [substance linked to fetal neural tube defects] assay (include spina bifida).
 * Ultrasound: Sound waves with a high pitch that cannot be heard by human ears. Provides sonograms, images of an embryo/fetus. Can be used to track fetus growth, figure out fetal age and sex, and detect prengnancies.
 * Amniocentesis - 14-16 weeks after conception, doctor draws out fetal cells that was in amniotic fluid and determines if disorders are present. Can be used to determine sex, but has risks with it.
 * Chorionic Villus Sampling (CVS) - Similar to amniocentesis, but diagnoses are earler in pregnancy process (9-12 weeks). Small syringe goes into vagina to the uterus, sucks out villi from membrane that covers the amniotic sac + fetus, and results are seen in days. CVS has risks of 'automatic abortion'.

2.3 - Heredity and the Environment: The Nature of Nurture
We investigate the power of nurture in this section.

Genotype leads to -->
 * Reaction range - The variable expression of inherited traits due to environmental factors.
 * Genotype - Genetic form of a person, determined by heredity, given to us by our parents.
 * Phenotype - Our REAL genetic form, determined by nature and nurture.


 * Canalization - Growth rates returning to what nature decided after going through nurturable change.

What Is Meant by Genetic–Environmental Correlation?
Sandra Scarr came up with three terms, passive, evocative, and active, that describe correlations between genetic and environmental influences.


 * Passive correlation - The environment their parents put the child in, child has no say in the matter (parents putting child into soccer environment because both parents are pro soccer players, like Joah Reyna).
 * Evocative correlation - A child's genotype holds behaviors that have reactions from others. Other people will be drawn more towards a talkative baby than a reserved baby.
 * Active correlation - As the child develops, the child will want to participate in activities or events within their interest (a Muslim teenager wanting to become a Christian, so he goes to church often). If this Muslim teenager specifically sought out more Christian friends in order to submerge themselves more into Christianity, this is an example of niche-picking.

Epigenesis is the belief that our development comes from both nature and nurture & that they are in constant exchange throughout our lives.

How Do Researchers Sort Out the Effects of Genetics and Environmental Influences on Development? (Are the Traits of Relatives Related?)

 * 1) Twin Studies - Monozygotic twins are much more in common than dizygotic twins, since the former shares 100% of their genes in comparison to the latter (onlt 50%). Minnesota Study of Twins Reared Apart (Wilson et al., 2019) study shows traits that ARE heredity, by displaying monozygotic twins who were separated at birth and reunited at a later time.
 * 2) Adoption Studies - Adopted kids show behaviors that are strikingly similar to their real parents vs. adopted parents.

2.4 - Conception: Against All Odds
Conception is the uniting of the ovum and sperm cell. Beginning of human life, end of adventure of the single ovum uniting with the one sperm. There are 200-400 million sperms in a male ejaculation.

Every month, an egg goes from the ovarian follicle to a fallopian tube (a tube from the ovary to the uterus). If the egg is not fertilized, it is discharged.

The one sperm has to withstand the vagina acid juice, swim against the current, reach the fallopian tube and pick the right tube which has the egg in it. Only about 2 manage to swim against the cilia-generated current to get to the egg.

2.5 - Infertility and Assisted Reproductive Technology
1/6-7 American couples experience fertility, with 40% of men also playing a role.

Causes (Men)

 * Low sperm count (most common)
 * Deformed sperm
 * Sperm lackin' in their swimming (lack of motility)
 * STDs, diabetes, autoimmune disorders
 * Testes are injured.
 * Aging, certain prescriptions, horrible drugs
 * Too much athleticism.

Causes (Women)

 * Irregular ovulation (most common)
 * Aging
 * Inflammation of endometrial tissue, causing the tissue to back up into her fallopian tubes/abdomen (endometriosis)
 * Infections/diseases disrupting reproductive tract (PID).

How Are Couples with Fertility Problems Assisted in Becoming Parents?

 * Artificial Insemination - Artificial injection of sperm into uterus in order to fertilize an ovum.
 * Gay couples - Lesbians can concieve through at-home insemination, intrauterine insemination (IUI), in-vitro fertilization (IVF), or reciprocal in vitro fertilization (RIVF). Males can get surrogate moms to do the job.
 * IUI: low-technology, sperm inserted into uterus through catheter.
 * IVF: harvest eggs, fertilize with donor sperm on a lab dish, insert in embryos into uterus [embryonic transplant] --> pregnant. Both partners? --> RIVF. Good if fallopian tubes are blocked.
 * Adoption