Chapter 4: Notes Flashcards
What are genes?
Units of heredity that maintain their structural identity from one generation to another. Gregor Mendel demonstrated that inheritance depends on genes.
What shapes human behavior—genes or environment?
A combination of both; the fundamental issue is how much each contributes to what aspect of a human.
Prior to Monk Gregor Mendel, what was the assumed way gene inheritance worked?
It was a blending of the properties of the egg and sperm, like paint.
Autosomal
Contribute most to physical characteristics; all chromosomes other than X and Y.
What is a gene composed of?
DNA (deoxyribonucleic acid).
RNA
A single strand of chemicals that serve as a template model. One type of RNA molecule (messenger RNA) provides the template for the synthesis of protein molecules.
Chromosome
Strands of genes composed of DNA (deoxyribonucleic acid). The exception to the rule is a male mammal—that has unpaired X and Y chromosomes with different genes.
DNA contains what four “bases”?
- adenine
- guanine
- cytosine
- thymine
What determines the development of a body?
Proteins; serve as enzymes and biocatalysts that regulate chemical reactions in the body.
Order is critical; changing just one base can make a huge difference.
What determines the order of amino acids that compose a protein?
The order of bases along an RNA molecule.
Enzymes
biological catalysts that regulate chemical reactions in the body.
Homozygous
Identical pair of genes on the chromosome.
Heterozygous
unmatched pair of genes.
e.g. you might have a gene for blue eyes on one chromosome and a gene for brown eyes on another.
Dominate gene
Shows a strong effect in either homozygous or heterozygous conditions.
e.g. ability to taste PTC
Recessive gene
Shows its effect only in the homozygous condition
e.g. low taste sensitivity to PTC
Gene dominance
Intermediate gene occurs in a phenotype where there is an incomplete heterozygous condition.
What are 2 common misconceptions about genes?
- If you have a gene for a trait, it always produces that outcome.
- A single gene completely controls a characteristic.
Sex-linked genes
Genes located on the sex chromosomes. In mammals, two sex chromosomes are designated X and Y.
Females have 2 X chromosomes.
Males have an X and a Y chromosome.
Sex-limited genes
Genes that are present in both sexes, but active mainly in one sex.
e.g. chest hair in men; breast size in women.
Genetic mutation
Heritable change in a DNA molecule.
Are mutations advantageous in humans?
No; evolution has already occurred.
One exception is the Fox p2 gene, which allows humans to speak while chimps could not.
Gene microduplication/microdeletion
Part of a chromosome that might appear once might appear twice or not at all.
e.g. some believe certain disorders, like schizophrenia, are the result of microduplication/microdeletion of brain-relevant genes.
Epigenetics
Deals with changes in gene expressions without modification of DNA sequence.
A gene might be present in every cell of the body, but with epigenetics, it might…
- be active only in certain types of cells.
- only be active at a particular time of life.
Can experience turn a gene on or off?
Yes, various experiences can turn genes on or off. Results of an experience brings proteins into a cell or in some ways alters the chemical environment.
How is a gene activated?
A “nucleosome” DNA strand needs to be partially unwound from a core of histones.
What chemical can turn a gene on or off?
In some cases of an outside experience of some sort, acetyl groups (COCH3) is added to histone tails near a gene, causing them to loosen their grip on DNA and change the expression of that gene.
Heritability
The degree to which variations in some characteristics depend on genetic differences.
“Virtual twins”
Children born at the same time, adopted at the same time, and raised in the same household, but not biologically related.
Is heredity important for behavior?
Researchers have found evidence for heritability in almost every behavior that have tested.
Monozygotic twins
Developed from one egg; “Identical twins”
Dizygotic twins
Developed from two eggs; fraternal twins
What are the three types of research that researchers do in regard to heredity and environment on behavior?
Biological children or twins, studies of adopted children, the candidate gene approach, and genome-wide association studies.
Candidate gene approach
Researchers test hypothesis
e.g. a gene that increases the activity of the serotonin transporter may be linked to an increased risk of depression.
Genome-wide association studies
Examines all the genes while comparing two groups
e.g. people with and without schizophrenia
Environmental modification
Changing genes through environmental intervention.
e.g. Phenylketonuria (PKU): The genetic inability to metabolize the amino acid phenylalanine—PKU is a hereditary condition, but environmental intervention, such as diet, can modify it.
How do genes influence or affect the body?
By using proteins.
Evolution
Change over generations in the frequencies of various genes in a population.
What are two major questions in evolution?
- How did some species evolve?
- How do species evolve?
How did some species evolve?
How some species evolved is based on inferences from fossils/comparisons of living species.