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- DNA - double stranded deoxyribose sugar
- Two complementary strands: Phosphate and Sugar bind with a base
- Thymine - Adenine
- Guanine - Cytosine
- Chromosomes are tightly wounded DNA
- Locust/Loci - carrying genetic information
- 1 strand of DNA carries multiple genes.
Each gene carries information to make one protein molecule.
Proteins are both the building blocks of cells and the machines (enzymes) that build cells and keep them running.
- Proteins are made of amino acids.
- Three DNA bases "code" for an amino acid.
Genes therefore code for a sequence of amino acids which form a specific protein chain.
Step 1: Transcription
- DNA in cell nucleus makes a copy to send to the ribosome
- DNA transcribes (double stranded) into mRNA (single stranded)
DNA unwinds to two strands. Bases stay the same so RNA can be created through transcription.
RNA contains Uracil as a complimentary base to Adenine instead of Thymine, but Thymine's base is still Adenine.
Step 2: Translation
- RNA enters ribosomes to co code for protein chain - meets tRNA
- Ribosome translates the instructions into codons
- Amino acids are linked and protein is folded into correct form.
- Each gene codes for a specific protein.
- Gene variants are called alleles.
For most genes you can have multiple alleles.
Each person carries two versions of each of their 23 chromosomes (from parents)
Humans are diploid
Genes are arranged on chromosomes like beads on a string.
Loci refers to the location of the gene (greek for places)
Pairs can have the same allele at the same locus on both versions of the chromosome
Heterozygous - different allele on each chromosomes.
- Phenotype: physical expression
- Genotype: the alleles (genes) that you carry
Dominant & Recessive Alleles
Dominance - when one allele is expressed over another
- Heterozygous dominance (Bb)
- Homozygous dominance (BB)
- Homozygous recessive (bb)
A dominant allele over rides the effects of a recessive allele.
Mitosis - to make a new body cell (cloning)
Meiosis - to make gametes (sexual reproduction)
gametes (sex cells. 23rd XX,XY)
When somatic (body) cells divide chromosomes are doubled.
Each daughter cell has same genes as original cell.
- Chromosome number:
- 2 copies - diploid
When sex cells divide one copy of each chromosome goes into a gamete
Chromosome number: 1 copy - haploid
**When gametes fuse during reproduction they create a zygote w/ full set.
Monk Gregory Mendel discovered that parents make gametes, gametes from two parents fuse to form offspring, offspring carry two copies of each chromosome one from each parent before modern genetics.
FO - parent genetics, F1 - generation mated
1. Hereditary characteristics are controlled by particulate unit factors that exist in pairs in organisms (genes)
Phenotype expression of alleles. Alleles exist in pairs.
2. When an individual has two unit factors, only one is expressed (dominant) and the other is recessive
3. During the formation of gametes, the paired unit factors separate or segregate randomly, so that each sex cell receives one with equal likelihood. (Law of Segregation)
4. During gamete formation, pairs of unit factors assort independently of each other.
Law of independent assortment.
Mendel also looked at the inheritance of multiple traits and whether they influence each other, because of independent assortment, seed color and texture combination in new and different ways.
Independent assortment of genes importance to evolution
It allows alleles to become uncoupled from each other. Variation - each offspring has a new unique combination of alleles
entails making the gene pool as big as possible for the law of independent assortment to take place. Larger gene pools has more possible combinations of alleles available. Strongest alleles are more likely to be expressed.
Linkage - genes on the same chromosome stay together
Crossing over - when chromosomes get tangled and break during meiosis
Mutation - is an error that occurs during DNA replication. Mutations are the only source of new genetic info.
Point mutation - is a change in a single base example: sickle cell disorder results from mutation in the gene that codes for hemoglobin
- Insertion mutation - repeats the amino acid
- example: huntington disease
- Deletion mutation
- example: duchenne muscular dystrophy/ leads to muscular degeneration and death.
x-linked disorders result from mutations on the x-chromosome
expressed in males because Y chromosome contains a smaller # of genes and lacks the normal functioning allele
ex. hemophilia, muscular dystrophy, red/green color blindness
continuous traits that are affected by genes at many loci
- allows for more variation in phenotypes
- results in a bell-curve distribution for the expression of the trait
Pleiotropy is when one gene cacn have many phenotypic effects
ex. marfan's syndrome, sickle cells disorder
Much of genetic variation is hidden from selection
Recessive or non-expressed genes continue to be passed on through reproduction.
New combinations w/ more alleles will be outside the initial range of variation
Genetic Drift/ Genetic bottle neck
Genetic drift is when random processes affect variation. More likely when populations are small.
A genetic bottle neck reduces a population temporarily to very low levels, removing much of it's genetic diversity.
Genetic vs. Environmental Variation
- Genetic variation
- Differences caused by different alleles inherited from parents
- Environmental variation
- Differences caused by environmental factors
- Differences caused by culture
- 8 pack is genetic ability to express it
- Apendix aids with digestion, but it is useless now. Before the paleolithic diet consisted of rocks, bones, sand, dirt. Which the appendix use to break down in the digestive system.
- Pica - individual that has the craving to consume dirt.
Natural selection causes genetic variation between groups
Selective forces in different environments may favor different traits/
Gene flow will lead to homogenize populations
but if selection is strong enough, genetic variation will be maintained.
Ability to digest lactose varies around the world
Mother's milk contains large amounts of lactose.
Lactose is too big to absorb. Infants produce a large amount of lactase which breaks down lactose.
Most mammals lose ability to digest lactose after weaning, but because of pastoralism populations can digest milk.
In general African Americans and Asian Americans in the U.S. are more likely to be more lactose intolerant.
Bergmann's Rule, Allen's Rule
- 1. body size corresponds to climate
- 2. limb length corresponds to climate
Melanin is a Natural sunscreen
Melanin prevents and repairs damage from UV rays. It absorbs UV rays and cause them to lose energy. It also neutralizes free radicals that form after damage by UV rays.
Mate Preference Study
Reproductive difference between males & females
- Maximum female reproduction
- Russia - 1725-1765 27 pregnancies 16 twins, 7 triplets, 4 quadruplets 69/67 survived infancy
Chilean woman 55 children
- Maximum Male repoduction
- Mulai Ismarl, Morocco emperor 800 children by his harem of 500 women 1646-1727
Kirk Maxey donated sperm over 16 year period and believed to be biological father of 200-400 children
David Buss: Mate Preference Study
Collected data in the 1950s during the cold war and did not collect data from communist areas. Missing a large portion of individuals.
- Short term mates
- For women: genes
- Long term
- For women: genes and resources
Sex similarities in mating strategies
Mutual attraction, dependability, emotional maturity, pleasing disposition.
Aesthetics and Attractiveness
Fertility: age, body condition, width of feet, waist/hip
Health: complexion, muscle tone, hair/nails
Illness: symmetry is an indicator of parasite resistance or lack of disease, scent may indicate genetic compatibility.
Women preferred the scent of the most symmetrical masculine and dominant males when at point in cycle when conception risk was highest.
Incest has very bad fitness consequences
Deleterious recessives: alleles which have damaging effects when two copies are present.
Hamilton's rule: probability of kin sharing an allele through descent
The Westermarck Mechanism
Children raised together experience diminished sexual attraction towards each other.
The mechanism uses a cue to kinship that was reliable in past but can be "wrong"
- Mechanism does not detect actual kinship
- Uses child hood cohabitation as a cue to kinship
- This bet is probably right often enough, but can be wrong