PSY 2105 Lecture Notes - Lecture 3: Twin, Neurofibromatosis, 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
Mitosis: process by which one cell becomes two cells, explains cell reproduction during growth of fetus
• growth and repair of hair cells, skin cells etc.
Meiosis: leads to production of gametes, during cross-over there is an exchange of genetic material, explains why
sisters and brothers have different genetic make up
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)
• a segment of DNA is a gene (contains alleles that determines phenotypes)
• alleles are variants of genes that result in different phenotypes; alleles are found at the same
(homologous) place on a chromosome
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)
Hereditary Disorders
Dominant traits
• Hutigto’s disease – inherit one affected allele which is enough to cause deterioration of the nervous
system, uncontrollable, muscular movements, disordered brain function, and death
• Neurofibromatosis (type 1)
Recessive traits – inherit two recessive alleles which cause a disease; parents may be carriers (not affected b/c only
one copy of the recessive allele)
• cystic fibrosis – affect the gene expression of the protein for lung development thus causing cystic fibrosis
• tay-sachs diseases – nervous system disintegrates b/c of lack of an enzyme that breaks down fats in brain
cells which causes brain cells the swell and die
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
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) 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. Mitosis: process by which one cell becomes two cells, explains cell reproduction during growth of fetus growth and repair of hair cells, skin cells etc. Meiosis: leads to production of gametes, during cross-over there is an exchange of genetic material, explains why sisters and brothers have different genetic make up. Dominant traits: hu(cid:374)ti(cid:374)gto(cid:374)"s disease inherit one affected allele which is enough to cause deterioration of the nervous system, uncontrollable, muscular movements, disordered brain function, and death, neurofibromatosis (type 1) Klinefleter"s sy(cid:374)dro(cid:373)e (xxy) nondisjunction even in the x chromosomes during meiosis, produce a male who is taller than normal but infertile.
