PSY 2105 Chapter Notes - Chapter 3: Twin, Y Chromosome, Mendelian Inheritance
13 May 2018
School
Department
Course
Professor
PSY2105A Dr. Isabelle Boutet
Chap 3 Genes and Development 03.05.18-08.05.18
Mechanisms of Inheriting Characteristics
Hand-Me-Down Genes: Family Patterns
Brothers and sisters have different genetic makeup – different eggs and sperm carry different information, child
results from the combo of one egg and one sperm (gametes produced from meiosis)
• X and Y chromosomes have different genetic information that allow them to develop into female or male
• chromosomes of each parent assort independently resulting in phenotypic differences
• fraternal twins result from two eggs that are fertilized; identical twins result from one egg that is fertilized
and divides into two
Genes determine a specific trait or disorder – specific trait combo of genes or alleles can lead to specific
chromosomes result in different traits or disorders
Cell Division
Chromosome: chemical strands in the cell nucleus that contain the genes (tightly packed DNA)
• each human cell has 23 pairs of chromosomes (46 total), cept gametes (have 23 chromosomes)
o autosomes – the two chromatin of these 22 chromosomes pairs are similar to one another and
carry the same gens in the same locations
o sex chromosomes – the two chromatin from 23rd pair come in two varieties – X chromosome
which carries more genetic material and then Y chromosome
• a segment of DNA is a gene which codes for the production of proteins, basic unit of inheritance
o alleles are variants of genes that result in different phenotypes; alleles are found at the same
(homologous) place on a pair of chromosome
Mitosis: process by which body cells reproduce, one cell becomes two identical cells
• explains cell reproduction during growth of fetus; needed for growth and repair of hair cells, skin cells etc.
• each new cell has 46 chromosomes and is identical to the parent cell
Meiosis: process of germ cells producing four gametes (sperm or ova), each with half the number of chromosomes
of the parent cell
• crossing over is the exchange of genetic material btwn pairs of chromosomes during meiosis
o explains why sisters and brothers have different genetic make up
• every gamete represents a one-of a kind combo of genetic material
Epigenetics: environment produces alteration to the gene expression not to the DNA sequence
• gene expression can be influenced by exposure to external factors (i.e diet, living conditions, exercise,
stress, chemicals, drugs, and toxins)
• i.e babies of mother who were pregnant during a famine show unique epigenomes including altered
expression of genes linked to schizophrenia
Types of Genetic Disorders (table 3.2)
Mutations are the driving force behind evolution, improvement to species when errors are adaptive
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