Bio 101: Lactase Persistance

allele

an alternative form of a gene

Biological Hierarchy

atom molecules biomolecules cells tissues organs organ systems organisms population community ecosystem

calculate the probability of a specific genotype and phenotype of an offspring using a punnett square.

a true classic

describe the source of genetic variation in populations

all genetic variation comes from mutation - random change in structure of genes genomes; rearrangements, duplications, change in nucleotides

relationship between alleles and traits

alternative forms of genes express different traits via the phenotype

explain how the polymerase chain reaction (PCR) amplifies DNA and why the development of PCR was so significant.

amplification or replication of tiny sequences of DNA many times using the power of exponential growth

lactose intolerance

decrease in lactase production post-weening undigested lactose passes into large intestine increased sugar concentration - draws water into gut - diarrhea bacteria in large intestine digests lactose as food - cramping - gas

dominant

An allele that is always expressed

genotype

genetic makeup of an organism

briefly describe the basic process of DNA replication

"semi-conservative" 1/2 of parental DNA strand restrained (1/2 old + 1/2 new) DNA polymerase enzyme - synthesizes DNA split/separate about central axis into 2 strands new, complementary nucleotides bond with split parental strand result: 2 daughter strands that are 1/2 old, 1/2 new

recessive

An allele that is masked when a dominant allele is present

homozygous

An organism that has two identical alleles for a trait

central dogma of biology

DNA makes RNA makes protein DNA transcribed to RNA which ribosomes translates from RNA nucleotide language to chemical language of proteins

Central Themes/ Concepts of Biology

Systems - interconnection of living things structure and function - basic units of structure define the function of all living things information flow/exchange/storage - genetic info determines the structure, function, growth, and behavior of organisms pathways & transformations of energy and matter - biological systems grow and change based on chemical processes governed by thermodynamics evolution - diversity of life overtime due to natural selection and genetic change

describe the structure and function of eukaryotic chromosomes

double helix DNA wrapped around histone proteins, then completely condensed/compressed 23 pairs (last pair = sex chromosomes) contain condensed genetic information

lactase persistence

enzyme continued to be produced post-weening breaks down lactose in the small intestine

relationship between genes and chromosomes

genes are DNA sequence found in chromosomes

summarize the three main 'drivers' of evolution

genetic variation - sexual reproduction - mutation change that acts on variation - natural / sexual / artificial selection - genetic drift - genetic flow 3rd: ??

relate the importance of genetic variation to the process of evolution

genetic variation allows natural selection to increase or decrease allows adaptation to the environment

heterozygous

having two different alleles for a trait

How are evolutionary relationships determined?

homologies - the more similar the structures the more related - anatomical (functional) - developmental - molecular/cellular historical homologies - fossil record - molecular fossils (sequences of information)

explain the role of the lactase enzyme in digestion

lactase is the "brush border" of enterocytes that line the stomach lactase breaks down lactose into 2 monosaccharides glucose & galactose these can then be absorbed in the small intestine

describe the different mechanisms by which allele frequencies can change in populations, including natural selection, genetic drift, and gene flow

natural selection - certain alleles may die out in a population due to a disadvantage it causes for organisms in a population and vice versa ex: if an allele makes a tiger run faster than others, if only slightly, that tiger and its progeny will be more likely to live and reproduce, passing down that allele through generations until it is more frequent than the allele that makes a tiger slower. The tiger with the "slower" alleles will be less like to out-live and out- reproduce the faster tigers genetic drift - random sampling of alleles in a population - random loss of alleles ex: this change in allele frequencies is the chance of random selection of individuals who die or don't reproduce for whatever. Their alleles, without being passed on, have generally decreased the presence of those alleles in a population genetic flow - variation from one population to another if there is high genetic flow, that means they have equivalent allele frequencies

phenotype

physical characteristics of an organism

detail how transcription is regulated in eukaryotes using the lactase gene as an example

regulated by specific transcription factors that turn on and off the transcription of genes ex: reason most people are lactose intolerant post-weening b/c it takes energy to produce lactase mammals used to not really consume lactose post-weening w/o milk consumption, waste to produce unused lactase so more efficient to turn off the transcription of the lactase gene with the mutation in the lactase gene, the transcription factor of OCT1 produced which increases the activity of RNA polymerase, transcription of the LCT gene, and overall production of lactase post-weening

gene

sequence of DNA that codes for a protein and thus determines a trait

evolution

the change in the frequency of alleles (alternate forms of genetic info/genes) in populations of organisms that occurs over time

using the story of lactase persistence as an example, explain how the change in the frequencies of alleles (related to lactase regulation) in populations resulted in biological evolution in humans

the random mutations that occurred in the lactase gene that resulted in the continued transcription of LCT and production lactase post-weening postitive selection these mutations were advantageous and people with them were better able to digest dairy and therefore get more/better/cheaper nutrients this allowed them to be more "fit", live longer, produce more offspring, and therefore spread the allele for post-weening lactase production