The Argument Of Nature Vs. Nurture

• Nature

  • The influence on physical and mental traits as well as behavior, is caused by genetics and biology.

• Nurture

  • The influence on physical and mental traits as well as behavior, is caused by experiences, learning socialization, and the environment.

• It is better to this of it as nature and nurture rather than Nature Vs. Nurture because their influence is interconnected.

Twins & Research

• Research has shown that the more genetic similarity between family members, the higher the concordance rates; similarly, in twin studies, concordance rates in monozygotic twins (MZ) are higher than in dizygotic (DZ) twins.

• Heritability

  • The percentage of variation in a characteristic that is attributed to genetics.

• Monozygotic twins MZ (Identical twins):

  • Are genetically identical.

  • Develop from the same egg.

  • Have the same sex.

  • Share the same DNA and womb.

• Dizygotic twins DZ (fraternal twins):

  • Are no more alike than other siblings.

  • Develop from two different eggs.

  • Have the ability to be of different sexes.

  • Share only 50% of their genes on average and share the same womb.

Epigenetics

• The study of how experiences and behaviors influence the expression of genes.

• Epigenetic effects are linked to a number of disorders.

• Can affect multiple generations by affecting the sperm and egg.

Terminology

• DNA:

  • The molecule of heredity/shape of a double helix.

• Gene:

  • A portion of DNA coding for a particular trait.

• Chromosomes:

  • A much larger structure with two types:

    • Autosomes

    • Sex chromosomes

    • There are 23 chromosomes, 22 autosomes, and 1 sex chromosome; females produce XX, and males produce XY.

• Alleles:

  • Two forms of the same gene.

  • One allele is found in each paired chromosome.

  • Are either dominant or recessive.

• Homozygous:

  • Are alleles/genes of the same type (either dominant or both recessive.)

• Heterozygous:

  • Has one dominant and one recessive allele.

• Genotype:

  • Actual genes/alleles inherited (BB, Bb, bb)

• Phenotype:

  • An outward expression is the physical or behavioral representation of genes (Brown or Blue eyes.)

• Dominant:

  • An allele that is expressed if present.

• Recessive:

  • An allele that is masked.

Genetic Testing

• Test prospective parents to see if they are carriers of recessive alleles for disorders such as PKU or Sickle-cell anemia.

• Prenatal genetic testing types include:

  • Amniocentesis

    • The insertion of a needle into the abdomen to remove a portion of amniotic fluid to test for genetic disorders.

  • Chorionic Villus Sampling (CVS)

    • Tests cells from the placenta.

• Karyotype:

  • A photograph of chromosomes.

• An example of newborn screening is a Guthrie test for PKU.

• An autosomal dominant will have the disorder if they get one defective gene. Autosomal dominant disorders cannot be a carrier form.

• An autosomal recessive needs to obtain two defective genes to have the disorder; however, a person who has one of two genes as defective they are a carrier.

Types of Disorders

• An abnormal number of autosomes.

• An abnormal number of sex chromosomes.

• Polygenic.

• Disorders include:

  • PKU: Phenylketonuria: autosomal recessive.

  • Sickle-cell anemia: autosomal recessive.

  • Huntington’s: autosomal dominant.

  • Color blindness: X-linked and recessive.

  • Down Syndrome: Extra autosome.

  • Sex Chromosomes: any variation from XX or XY

Phenylketonuria

• Is an autosomal recessive disorder.

• There can be carriers.

• Is a metabolic disorder where a person lacks the enzyme to convert phenylalanine into tyrosine.

• Without proper treatment, phenylalanine builds up, causing severe intellectual disabilities.

• Tested for in newborns using the Guthrie test.

• Treatment consists of diet therapy; those who have the disorder are treated with a diet that is free of phenylalanine and are given tyrosine supplements.

Sickle-Cell Anemia

• An autosomal recessive disorder.

• Requires two defective genes.

Huntington’s Disease

• Symptoms are listed in the previous sheet of notes.

• Autosomal dominant disorder.

• Needs only one defective gene.

• If one parent has the disorder, each child has a 50% chance of receiving the disorder.

Color Blindness

• An X-linked disorder | A gene carried on the X chromosome.

• A recessive disorder.

• More common in males because males only need one defective gene to be color blind, and females need two defective genes to be affected.

Down Syndrome

• Mainly a genetic cause but is not hereditary.

• Its cause is nondisjunction, an extra 21st chromosome.

• An increased amount of cases in elder mothers.

• Tests include Amniocentesis & CVS (chorionic villus sampling.)

  • Symptoms include:

    • Distinct facial features.

    • Short stature.

    • Mild or moderate intellectual disability.

    • Heart defects: Can be corrected with surgery.

    • Increased risk of developing dementia around the age of 50.

Genotype Syndromes

• XO: Turners.

• XXX: Trisomy X.

• XXY: Klinefelter.

• XYY: Jacob’s.

• YO: Not viable.

Turner’s Syndrome

• Only one X chromosome.

• Occurs only in females.

• Problems with ovaries lead to infertility and hormonal problems.

• It’s the failure to develop a secondary sex characteristic at puberty/given hormones to develop.

• Usually have problems with visual-spatial skills.

Klinefelters Syndrome

• XXY: A male with an extra chromosome.

• Smaller testes and penis | Less testosterone.

• Sterility.

• Most have normal intelligence, but some have learning disabilities.

• Variations such as XXXY and XXXXY and more likely to have intellectual disabilities.

Jacob’s Syndrome

• XYY: A male with an extra Y chromosome.

• Has been referred to as supermale syndrome in the past.

• Taller.

• Some fertility problems.

• Usually have normal intelligence, but some can have learning disabilities.