03-Heredity & Environment
Genes
 DNA (deoxyribonucleic acid)
 The basis of heredity
 Chromosome
Molecule of DNA
 Make up chromosomes
 Humans = 46 (23 pairs) of chromosomes
 Genes = Section of chromosomes
 Allele = Slight normal variation in a gene

Genome = Code for making an individual
 20,000 genes (99% in other creatures also)
 Genotype = The full set of genes for a specific orgasm
organism (entire genetic inheritance)
 Phenotype

What you look like based on your genes

Appearance, personality, intelligence
 Genotype = Hidden in your genes
 Phenotype = Observable characteristics based on
genes – E.g. brown eyes
Beginning of life
Gamete
 Sperm
 Ovum (egg)
 Each has23 chromosomes (one half of 46)
Zygote
 Single cell from two gametes
Male or female?
 23rd pair of chromosomes
 Female = XX
 Male = XY
Twins
 Monozygotic (identical) twins
 From one zygote
 Share 100% genes
 Dizygotic (fraternal) twins
 Two sperm penetrating two ova

Share 50% of their genes
ART = Assisted Reproduction Technology
 IVF = In Vitro Fertilization
 Sperm mixed with ova in glass dish
 Viable embryos implanted
 ICSI (Intracytoplasmic sperm
injection)
 Intrafallopian sperm injection
One cell to many
 How genes interact
 Genotype = Entire set of genes (about 20,000)
 Phenotype = Appearance (blue eyes) and behavior
(alcoholic)
Genotype to phenotype
 How genes affect appearance and behavior
 Genes + Environment = Phenotype (Appearance &
behavior)
 E.g. Alcoholism

Genes(Varies in intensity) + Environment (Encourages or
discourages drinking) = Result
Epigenetic
 All characteristics are determined by both genes and
environment

E.g. height and nutrition
Additive heredity
 Some alleles (gene variations) combine to affect
appearance and behavior
Dominant – recessive heredity
 Dominate genes are more influential than recessive
genes.
 E.g. Brown eyes (Mother-dominate) + Blue eyes
(Father-recessive) = Brown eyed child
 Being a carrier for blue eyes can effect this
Genetic (chromosomal) abnormalities
 Most often related to age of mother
 Extra chromosome
 E.g. Down Syndrome = 47 chromosomes
Abnormalities of the 23rd. Pair
 Humans have 44 chromosomes + one X + an “X” or
”Y”

Embryos do not develop without one X
 Missing chromosome
 E.g. XO
 Three sex chromosomes
 XXY
 XYY
 Appear normal until puberty
Genetic Counseling
 Find harmful conditions
 Affect insurance coverage
 Jeopardize the marriage