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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