Heredity and Environment

1
Part I
Chapter Three

• Heredity and Environment

The Genetic Code From One Cell to Many From
Genotype to Phenotype Chromosomal and Genetic
Abnormalities
2
The Genetic Code

• Genes play a leading role in the drama of human
  development, yet they rarely take center stage.
  Genes are pervasive and powerful, but they are
  also hidden and elusive.

3
What Genes Are

• DNA (deoxyribonucleic acid)
• Molecule that contains the chemical instructions
  for cells to manufacture various proteins.
• Chromosome
• a molecule of DNA that contains the instructions
  to make proteins
• Humans have 46 chromosomes (23 pairs), and about
  25,000 genes.
• Genome
• the code for making a human being
• Every person has a slightly different code, but
  the human genome is 99.5 the same for any 2
  people.

4
What Genes Are

• Genes are as section of chromosomes and the basic
  unit for the transmission of heredity, consisting
  of a string of chemicals that code for the
  manufacture of certain proteins.

5
The Beginnings of Life

• development begins at conceptioneach human
  reproductive cell or gamete, contains 23
  chromosomes, half of that persons 46
• gamete
• A reproductive cell that is, a sperm or ovum
  that can produce a new individual if it combines
  with a gamete from the other sex to make a zygote

6
The Beginnings of Life

• Matching Genes
• conception occurs in the usual way
• zygote
• the single cell formed from the fusing of two
  gametes, a sperm and an ovum
• genotype
• An organisms entire genetic inheritance, or
  genetic potential

7
From Genotype to Phenotype

• Scientist in many nations have studied thousands
  of twins, both monozygotic and dizygotic, raised
  together in the same home and raised separately
  in different homes

8
From Genotype to Phenotype

• Genes affect every aspect of human behavior,
  including social and cognitive behavior
• Most environmental influences on children raised
  in the same home are not shared

9
From Genotype to Phenotype

• Each childs genes elicit other peoples
  responses, and these responses shape development.
  In other words, a childs environment is partly
  the result of his or her genes.
• Children, adolescents, and especially adults
  choose environments that are compatible with
  their genes (called niche-picking), and thus
  genetic influences in adulthood