Genes, environment, and development (ch 3) Flashcards
Species heredity
- genetic endowment that members of a species have in common including genes that influence maturation and aging processes
- Reason that certain patterns of development and aging are universal
Darwin – three arguments
- Genetic variation in species otherwise no way for genetic makeup to change over time
- Some genes aid adaptation more than others do
- Genes that aid their bearers in adapting to their environment will be passed to future generations more frequently than genes that do not
Natural selection
nature selects those members of species whose genes permit them to adapt to their environment
Conception
new cell nucleus formed from general material of ovum and genetic material of sperm
Zygote
new cell
How many chromosomes does each parent contribute?
Each parent contributes 23 chromosomes
- 46 total
- organized into 23 pairs
Chromosomes
threadlike bodies in nucleus of each cell made up of genes
Sperm and ova each have only 23 chromosomes because produced through the …
cell division process of meiosis
Single cell zygote becomes multiple-cell organism through the …
process of mitosis
Human Genome Project
- Researchers mapped sequence of chemical units (A, C, G, T) that make up strands of DNA in full set of human chromosomes
- Human genome consists of genes that serve as template for the production of particular proteins and DNA that regulates the activity of the protein-producing genes
- 999 of 1000 base chemicals are identical; only 1 of 1000 accounts for human differences
Father determines child’s sex
- If sperm carries Y chromosome, the XY zygote is genetic male
- If sperm carries X chromosome, the XX zygote is a genetic female
Genotype:
Genetic makeup a person inherits
Phenotype:
characteristics or traits that are expressed
Gene expression:
activation of particular genes in particular cells at particular times
Sex-linked characteristics
Influenced by
- single genes located on sex chromosomes
- Actually X-linked because most attributes are associated with genes on the X
- Y chromosomes are smaller and have fewer genes to serve as counterpart to dominate
Single gene-pair inheritance:
- each of thousands of human characteristics influenced by only one pair of genes – one from mother and one from father
- Dominant gene will be expressed with paired with recessive gene (weaker gene that can be dominated)
Polygenetic:
- traits such as height, weight, intelligence, personality, and susceptibility to cancer and depression
- Influenced by multiple pairs of genes and interactions with environment
- Many degrees of expression possible with polygenetic traits
- Traits tend to be distributed in the population according to normal curve
Mutations:
change in gene structure or arrangement that produces a new phenotype
- Beneficial or harmful
- Eg sickle cell disease
Chromosomal abnormalities:
occur when there are errors in the chromosome division during meiosis
- Ovum or sperm will have too many or too few chromosomes
- Main source of pregnancy loss
Turner syndrome
Chrom. abnormality
- female born with single X chromosome (XO)
- Physically small, stubby fingers and toes, “webbed” neck, underdeveloped breasts
Down syndrome
Chrom abnormality
- aka trisomy 21 because associated with three rather than two 21st chromosomes
- Distinctive eyelid folds, short stubby limbs, thick tongues, typically MR
Klinefelter syndrome
Chrom. abnormality
- male born with one or more extra X chromosome (XXY)
- Tall, generally masculine but sterile and at puberty develop feminine sex characteristics like enlarged breasts; many below average intelligence
Fragile X
Chrom. abnormality
- X chromosome barely connected and looks like it is about it break off
Most common hereditary cause of mental retardation
Findings from behavioral genetics research – IQ
- Correlation highest in identical twins
- Heritability of IQ is about .50
- Genetic differences account for 50 percent of variation in IQ and environmental differences for 50 percent
