Ch. 4: Genetics, Evolution, Development, Plasticity Flashcards
Mendel
demonstrated inheritance occurs through genes
Genes
units of heredity that maintain structural identity
Chromosomes
strands of genes that come in pairs
DNA: Deoxyribonucleic acid
composed of genes
Strand of DNA serves as template model for
ribonucleic acid (RNA) molecules, a single-strand chemical. One type of RNA molecule—messenger RNA— serves as a template for the synthesis of protein molecules.
DNA has 4 bases
- Adenine
- Guanine
- Cytosine
- Thymine
The order of those bases determines the order of corresponding bases along an RNA molecule—adenine, guanine, cytosine, and uracil (in RNA and not DNA). The order of bases along an RNA mole- cule in turn determines the order of amino acids that compose a protein.
Some proteins serve as enzymes
catalysts that regulate chemical reactions in the body
Homozygous
same genes on your two copies of some chromosome
Heterozygous
an unmatched pair of genes
Dominant gene
shows a strong effect in either the homozygous or heterozygous condition
Recessive gene
shows its effects only in the homozygous condition
Can single gene produce particular outcome
No
Sex linked genes
The genes on the sex chromosomes (designated X and Y in mammals)
Autosomal genes
All other chromosomes are autosomal chromosomes and their genes are
You express most of your genes in certain cells and not others
changes in the environment can increase/decrease expression of a gene
RNA=
1 copy strand of DNA
Sex limited genes
present in both sexes but active mainly in one sex
Mutations
heritable change in a DNA molecule. Changing just one base in DNA to any of the other three types means that the mutant gene will code for a protein with a different amino acid at one location in the molecule.
Another kind of mutation is a duplication or deletion. During the process of reproduction, part of a chromosome that ordinarily appears once might instead appear twice or not at all. When this process happens to just a tiny portion of a chromosome, we call it a microduplication or microdele- tion.
Epigenetics
Changes in gene expression. Various experiences can turn a gene on or off. Epigenetic changes can be inherited for a generation or 2
Histones
Proteins that bind DNA. Histones tighten, stop expression of gene. If they relax, express gene. Adding methyl groups to a promoter turns off a gene
Difference b/w mutation and epigenetic change
A mutation is a permanent change in part of a chromosome. An epigenetic change is an increase or decrease in the activity of a gene or group of genes. Adding a methyl group turns genes off. An acetyl group loosens histone’s grip and increases gene activation
Heritability
If the variations in some characteristic depend largely on genetic differences, the characteristic has high heritability. Heritability ranges from zero, indicating no genetic contribution to the variation, to one, indicating complete control.
Monozygotic twins
Have the same genes. Not necessarily identical
Dizygotic twins
Don’t have same genes
Evidence of heritability
- Twin studies
- Children who have been adopted
- Candidate gene approach: Studies 1 gene
- Genome wide association study: Studies many genes b/w 2 distinct groups
Estimate of heritability of a trait
Specific to a pop at a given time
PKU
genetic inability to metabolize amino acid phenylalanine
Almost every human behavior
Has some degree of heritability
Evolution
Change over generations in frequencies of various genes in a pop
artificial selection
plant and animal breeders have long understood this idea, they choose individuals with a desired trait and make them the parents of the next generation
myth of Lamarckian evolution
use or disuse of some structure or behavior cause an evolutionary increase or decrease in that feature
Evolution depends on
reproduction, not survival