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, intelligenceGenotype = Hidden in your genesPhenotype = Observable characteristics
based on genes – E.g. brown eyes
Beginning of life
Gamete
SpermOvum (egg)Each has23 chromosomes (one half of 46)
Zygote
Single cell from two gametes
Male or female?
23rd pair of chromosomesFemale = XXMale = 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 interactGenotype = 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 motherExtra 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 conditionsAffect insurance coverageJeopardize the marriage