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Heredity & Environment
WHAT CREATED YOU AT THE VERY BEGINNING?
What are genes?
 DNA (deoxyribonucleic acid)
 The basis of heredity
 Humans = 46 (23 pairs) of chromosomes
 Chromosome


Molecule of DNA
 Make up chromosomes
Genes = Section of chromosomes

Allele = Slight normal variation in a gene
In cell nucleus
 Chromosomes

DNA

Genes
What is the code for making an individual?
 Genome = The full set of genes for a specific
organism (entire genetic inheritance)
 20,000 genes (99% in other creatures also)
 Phenotype

What you look like based on your genes

Appearance, personality, intelligence
 Genotype = Hidden in your genes (e.g. Cancer)
 Phenotype = Observable characteristics based on
genes – E.g. brown eyes
Do you remember?
 You have how many pairs of chromosomes?
 Your chromosomes are made up of what type of
molecule?
 What is the genome for a human?
 What is the difference between your genotype and
phenotype?
How does life begin?
What are gamete?
 Sperm
 Ovum (egg)
 Each has 23 chromosomes (one half of 46)
What happens after fertilization?
 A zygote develops
 Single cell from two gametes
 The first stage of development after fertilization of
the egg (ovum).
Male or female?
 23rd pair of chromosomes
 Female = XX
 Male = XY
What creates twins?
 Monozygotic (identical) twins
 From one zygote


(One egg & sperm)
Share 100% genes
 Dizygotic (fraternal) twins
 Two sperm penetrating two ova

Share 50% of their genes
Do you remember?
 After an egg is fertilized, it is called what?
 The 23rd. Pair of chromosomes in women are:
 The 23rd. Pair of chromosomes in men are:
 What is the monozygotic and dizygotic twins?
How can we help fertilization occur?
 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
From one cell to many:
How do genes affect appearance and behavior?
 Genes + Environment = Phenotype (Appearance &
behavior)
 E.g. Alcoholism

Genes(Varies in intensity) + Environment (Encourages or
discourages drinking) = Result
 Large breasts and shyness
If something is epigenetic, what is it?
 Characteristics that are determined by both genes
and environment

E.g. height and nutrition
Additive heredity
 Some alleles (gene variations) combine to affect
appearance and behavior
Are some genes more powerful than others?
 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
What can cause genetic abnormalities?
 Most often related to age of mother
 E.g.: 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 = Turner’s syndrome (looks female)
 Three sex chromosomes
 XXY = Klienfelters Syndrome (Looks male)
 XYY = “XYY” Syndrome (looks male)
 Appear normal until puberty
What is the effect of genetic counseling?
 Find harmful conditions
 Affect insurance coverage
 Jeopardize the marriage
Do you remember?
 What are some methods of assisted reproduction?
 How do genes and the environment interact?
 How do dominate and recessive genes control who
you became?
 What is the most common cause of genetic
abnormalities?
 What are some abnormalities of the sex
chromosomes?
 What are some of the positive and negative effects of
genetic counseling?