Life Science CST Prep
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Transcript of Life Science CST Prep
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Life Science CST PrepMr. McCabe and his former students!DIPSOBMITOHAPSEGMEIODIP
SOB
MITODiploid
Somatic/Body
MitosisHAP
SEG
MEIOHaploid
Sex/Germline
Meiosis4623HAPSEGMEIODIPSOBMITOMitosisMeiosis1 Round of Division
2 Cells Made/Produced
Cells are diploid
No tetrads (pairs of 4)
No crossing over2 Rounds of Division
4 Cells Made/Produced
Cells are haploid
Prophase I hasTetrads (pairs of 4)Crossing overCell Division Mitosis Meiosis
PMATProphase Pairing
Metaphase Middle
Anaphase Apart
Telophase Two nuclei/cellsCrossing OverTo make more combinations of gametes
This is done during prophase I of meiosis when chromosome arms switch places
GeneticsGenePart of DNA that makes a trait
AlleleThe different kinds/versions of the traitGenotypeHow we write the DNA
PhenotypeHow the trait looksZygosityHomozygousHeterozygousCell gets the same allele from each parent
BB, dd, FF, jjCell gets a different allele from each parent
Bb, Dd, Ff, Jj DominanceDominantRecessiveCell needs only one copy of a dominant allele to have a dominant phenotype
BB, Dd, FF, JjCell needs two copies of a recessive allele to have a recessive phenotype
bb, dd, ff, jj
VocabHomozygousOrganism has the same allele from both parentsHeterozygousOrganism has different alleles from both parentsDominantOnly one copy of the gene is neededHides the recessive alleleRecessiveRequires two copies of the geneCentral DogmaDNA RNA Protein
DNA ReplicationDNA DNA
A binds TT binds AG binds CC binds GMutationsA change in the type, number or order of nucleotide bases
DNA MutationsFrameshiftPoint MutationFrameshift mutationsAny number of bases are added or deleted.This can throw off the codon reading framePoint MutationsPoint mutations are when just one nucleotide gets changed to another.May or may not have a large effect.
Amino Acid EffectsSilent MutationA mutation in which no amino acid change happens
Missense MutationA mutation in which the amino acid gets switched
Nonsense MutationA mutation in which the protein gets stopped early
InheritanceInheritance is how we pass on traits from one generation to the next
P F1 F2Human Chromosomes23 different chromosomes22 autosomal chromosomes1 set of sex chromosomes
Sex ChromosomesFemales are XX
Males are XY
XXX YXXXYXYXXMaleFemaleMode of InheritanceMode of inheritance What type of chromosomes we will find the gene/trait on.
2 TypesAutosomalSex-linkedMode of InheritanceAutosomalTraits found on chromosomes 1-22 (most traits)
Sex-linkedTraits found on either of the sex chromosomes (X or Y)
Some terminology.We write autosomal with regular letters.AaA aAAAaaaAaSome terminology.We write X-linked like this:XHXhXh YXHXhXHYXhYXhXhSome terminology.We write Y-linked like this:XXX YtXXXYtXYtXXThink-Pair-ShareSex linked traits are more likely to affect males. Why do you think this is?hemizygousMales are hemizygous.
Since males only have one X and one Y, they only need one copy to be dominant or recessive
Since females do not have a Y, they cannot be affected by Y linked traits/diseases. Dominance?And Announcing..Born last night10.2 oz.22 inches long
15.5 inch head diatmeterTRISTAN ALEXANDER MCCABE
What we knowWe have two alleles of each trait: the dominant allele (A) and the recessive allele (a)
The dominant allele always hides the recessive allele
This is called complete dominanceBaking a CakeDifferent rules of DominanceSometimes genes dont follow the dominant/recessive rules of dominance.
There are other ways to inherit traits Incomplete dominance and codominance.Todays ExampleRed flower x White flower
XAAaa
AAaaParent 1Parent 2
Complete DominanceComplete Dominance
The dominant allele always covers the recessive allele for phenotypes
AA = Dominant phenotypeAa = Dominant phenotypeaa = Recessive phenotypeAaAAaaParent 1Parent 2
AaAaAa
Complete DominanceIncomplete DominanceIncomplete dominanceInstead of 2 phenotypes, we see 3
Red Flowers + White Flowers = Pink Flower
AaAAaaParent 1Parent 2
AaAaAaIncomplete Dominance
CodominanceCodominanceBoth the dominant and recessive allele are shown but they are not mixed together
Red + white flowers = flower with red and white spots
AaAAaaParent 1Parent 2
AaAaAaCo-dominance
Different Rules of DominanceComplete DominanceIncompleteDominanceCo-dominance
Different Rules of DominanceCodominanceBlood is co-dominant
There are three alleles: A, B and i
Natural SelectionThe process in which the environment determines what traits are beneficial and should be passed onto future generations
Ex: Peppered Moth
Artificial SelectionThe process in which humans determine which traits are beneficial and should be passed onto future generations.
Ex: Humans mating different dogs
Genetic Drift
Genetic DriftRandom changes in allele frequency in a population
Evolution by chance
Evolution not based on the environmentThe Founder EffectExtreme genetic drift
A small population breaks off from the main population and moves to live in a new place.
Small population new foundersLike the Pilgrims coming to America
The Founder EffectKeypoint:
The founder effectREDUCESGenetic diversity
Why?Only the alleles/phenotypes in the small gene pool that broke off will exist in the new populationExample: The AmishThe AmishLive in small communities, don't use modern technology
A small group isolated themselves (broke off from a large population) and set up colonies in Pennsylvania.
Example: The AmishHigh Frequency of Ellis-van Creveld Syndrome because a founder had the allele for the trait6-fingered dwarfism (short + 6 fingers)
Example: The AmishWhy so much Ellis-van Creveld Syndrome? One of the Amish founders, Samuel King, had the mutation and the Amish only reproduce within a small population
Bottleneck EffectExtreme case of genetic drift
A population decreases to a very small number (due to death) but reproduce before the species goes extinct.
The Bottleneck EffectKeypoint:
The bottleneck effectREDUCESGenetic diversityExample: CheetahsScientists believe that 10,000 years ago, almost all the cheetahs IN THE WORLD died except 7.
Those 7 reproduced the whole cheetah species
Example: CheetahsAll cheetahs are similar because they have only had 10,000 years of evolution to create diversity
Humans have had at least 4 million
Bottom Line:Extreme Genetic Drift (ex: bottleneck or founder effects)
genetic variation / genetic diversity.
DECREASES