okay let's see okay it's recording okay so today we'll be going over the patterns of inheritance so patterns that'll be noticed that's the thing that deals with heredity and the genetics is a term that just refers to study of it and there's a man named uh Johan Gregor Mendel who basically set the framework for genetics before the chromosomes or the genes have been identified so he didn't understand what genes were yet still he managed to cope with this Theory so Mendel selected a simple biologic
al system peace and the conducted methodical and quantitative analyzes using a large cell size and because of Mendel's work we now know that the genes on chromosomes are the basic fundamental units of heridity with the ability ability to be replicated expressed or mutated and genes are inherited in either mendelian or non-medelian fashion so his experiments um he was a lifelong learner teacher scientist and Men of Faith he was a monk and Abby and Czech Republic in 1856 he began researching into
pea plants and reported the results from 30 000 key plants in 1865. and published the experiments in P hybridization in 1866 and he demonstrated that the traits are transmitted from parents to offspring and specific patterns his work went unnoticed until some scientists believe that inheritance involved some blending of Parental traits into intermediate appearance of in The Offspring and this result at the time was a result of with this assumption it was a result of continuous very belief in con
tinuous variation or the range that small differences among individuals in traits like height um so Mendel chose to chose the idea of discontinuous variation where individuals showed distinguishable traits so like either violet or white flowers but not pink for instance and that that choice allowed him to see that the traits were not Blended but they were inherited as distinct traits and in 1900s his work was rediscovered before discovering the chromosomal inheritance so what did he do he used G
arden piece of sativa to study the inheritance why did he do that because peace naturally self-fertilized pollen that is Parliament encounters the Volva within the same flower which has both male and female reproductive organs and makes both gametes and the Cardinal fees are true breeding and immediating in brain plant plants because the petals are tidally sealed until the pollination and peace always produced offsprings that looked exactly like the parents which means what which is what true br
eeding means so for instance if a true breeding if you cross a true grading plans purple and white what would you expect to get guard and garden piece also oh yeah and government is also matured in one season allowing the several generation to be observed you know so a short time and the large number of fees could be grown at the same time allowing the uh allowing Mendel to conclude the results were not Randall so he did the hybridization or crosses by mating two troop reading plants with differ
ent traits he basically manually transferred the pollen from answer is here the sustainment and there is right there to the stigma which is right here or shown here so basically it's going from here to there and if it's self-fertilizing so you had to take the pollens from one plant two and then put it on the statement or a stigma excuse me of one of the time so if you were to take the true breeding violet true breeding white flowers then you get all Violet flowers that's kind of strange so in P
generation or parental Generation Um you can grow the seeds from the parental parental across and the offsprings are called the f1s and this is the F1 here all purple flowers or Olive flowers and examine the traits of the F1 generation and allow them to self-fertilize naturally to generate the filial two or a second generation so these flowers are getting sulfurlized or this pee and once you do that you get these strange ratios you get the purple and you get the white and then he extended to F3
F4 and so on and basically ratios of traits in P1 F2 F1 and F2 is what formed the basis of Mendel's theory so in 1865 Mendel reported the results of his process involving seven characteristics same texture or C shapes same color flower color Peapod size or shape Peapod color Ed and flower position and each of these traits have two contrasting traits each of those characteristics rather have two contrasting traits so either round versus wrinkle texture yellow versus green seeds and so on and the
trade is defined as a variation of in the physical appearance of heritable characteristics and Mendel generated large number of F1 and F2 and reported the results from F2 first he confirmed that the plan spread true meaning regardless of uh truth or the color regardless of number Generations that's what true breeding means meaning if you bred purple with purple you always get purple in all generations and all self-crust offsprings of um purple flowers have purple flowers same thing for the white
flowers and plants otherwise were identical for 70 other six characteristics and this was important as a control because this was a key in understanding alleles and genes and he was lucky enough to choose the traits and characteristic where one gene was solely responsible for one characteristics in the middle system he got lucky you know so he took otherwise identical true breeding plans purple and white again he brushed upon from purple flower on the stigma of white flower and let this plant p
roduce the peas then he plants the peas again this is the F1 hybrids now and a hundred percent of airport hybrids had purple flowers if continuous variation was indeed the mechanism what would you expect purple mixed with white should produce something like pinkish color except men will show that wine flower trait disappeared in the F1 trade F1 Generations uh metal and then allow the F1 plants to self-fertilize these are the f1s self being self-fertilized here and produced the filial two or seco
nd generation plants and the 705 plants in F2 have put purple flowers and 224 had white flowers I about ratios of 3.15 to one approximately three to one middle and tested if there's a difference in inheritance inheritance of traits carried in the pollen versus the over so he took the instead of taking the pollen from the purple flower he took the apollon from white flowers and did the same thing and he approximately observed same ratios irrespective of which gamete contributed which get trade an
d that was called the reciprocal cross it's the reciprocal cross is cross where the traits of the male and the female in one cross become the respective traits of female and male in the other cross in other words pollen from White Flower a pollen from purple flower on the OVA versus pollen foam white flower on diwala and vice versa so all of six other characteristics show the same pattern in F1 and F2 one of two traits would disappear in F1 generation and the Disappeared trait would reappear in
F2 in the ratios of three three to one and after thousands of plants Mendo concluded that characteristics could be divided into expressed he named it or latent traits we call these dominant versus recessive these days so the dominant traits are the inherit inherited unchanged in the hybrid hybridization in other words purple flower in this case is the dominant rate recessive trait disappears in The Offspring in the hybridization experiment or F1 but reappears in the progeny of the hybrids or F2
and that was the white vlog reoccurring recessive trait means the traits are not Blended but remain separate so Mendel proposed the plans possessed two copies for the traits for the flower color characteristic and each parent transmitted one of their two copies to The Offspring where they came together in the physical observation of the dominant trait could mean that organism had two versions of the trades two dominant two or two of two two yeah two dominant or one dominant and one recessive in
other words to them having the two dominant characteristics would be now that is called homozygous dominant and one dominant and one recessive would be heterozygous dominant and this observation that the recessive trait meant that organisms lacked any dominant version of this characteristics or in purple and white example white flowers so the seven characteristics that Mendel evaluated were expressed as one of two traits and Mendel's deduced that the plant had two copies of the characteristic th
at are passed to the offsprings and now we call those copies of characteristics these days genes and there are two because they're on homolog chromosomes from our moms and dads and in meiosis remember the homologs separate in the metaphase mode and it's the separation of the homolog means that only one of the genes that gets into gamete and these genes have variants alleles how do these arise these arise because chromosomes remember remember chromosomes at the metaplate line up precisely if this
is Mom and if this is Dad's the genes on that line up precisely and these Gene copies of these genes on these separate chromosomes are what we call alleles and because they're different they're they're from our mom and our dad and because there are different people they have different sequences so the Domino of the old purple is the recessive then must be white so mental examined inheritance inheritance of two alleles but some genes have more than two alleles remember blood types remember are c
odominant um so the two alleles of proteogene in a diploid organisms are expressed and interact to produce of physical characteristics we call this phenotype phenotype is the observable trait expressed by an organism colors and the genotype is the organism's genetic makeup consists consisting of both invisible and invisible alleles or dominant or recessive okay and the true reading yellow and true breeding green seeds yields all yellow f1s and now you should know that the yellow then must be the
dominant we know that green trade is not lost because we it reappears in F2 so here's yellow here's green F1 all yellow but F2 green reappears in ratios of three to one and so then F1 is no longer true breeding and F1 must be different somehow from the parent generation plans so menus and Mendel's plans happen to be homozygous for the traits that he would study because they were all true breeding and the homozygous diploid has two identical alleles on the homologs at the same location remember
and the genotype Big Y by or little y little y represents the two alleles in the genotype cap typically caps typically represent the dominant lowercase resistive and typically letters are used you know the dominant trait so if it's a yellow P letter y is used and F1 yellow piece are obviously heterozygous Big Y little y in all and the law of dominance the mental proposed few laws in all seven characteristics one of the two trades is dominant he calls this expressed unit vector we call it dominan
t recessive is the he called it latent unit Factor so the Mendel's Law of dominance states that in a heterozygote one trait will conceal the presence of another trade which is exactly what dominant those two the recessive alleles so example purple flower again and the yellow seeds in F1 Generations are heterozygous and their dominant traits are showing through hiding the white flower and hiding the green seeds here a child is shown here she had he she child baby has albinism is called the ocular
cutaneous albinism and this trait is recessive so you know immediately if this is the child's mother this child the child's mother must have been the carrier where this Mother's child must have been D if these are the two parents they must be heterozygous for that recessive trait so uh monohybrid cross uh does this refers to the cross between two true breeding parents that differ only in the characteristic being studied one single characteristic and the monohybrids are the offsprings of the Cro
ss and Mendel has seven types of monohybrid crosses each for contrasting characteristic or contrasting traits for the seven characteristics and all F1 phenotypes had one of the parents parents uh traits traits which one is showing up obviously dominant is short up but F2 always revealed the recessive in three to one ratios so he postulated that each parents intercours contribute contributed one of two paired unit Vector to each spring offspring and every possible combination of unit vectors were
equally likely then he used probability or likelihoods probability of one this means that carrying to talk probably probability of zero is guaranteed to not occur probability of 0.5 means it has equal chance of occurring or not occurring true breeding yellow seeds crossed with green is shown in this monohybrid cross here and we'll go over how to do this pun of squares in dominant is denoted as Pig y b y recessive little y little y these are the parental genotypes and then all possible combinati
on of the parental alleles are listed along the top and the side well that's I'm getting ahead of myself here these are the possible gametes from yellow true breeding parent this is the possible gamete from true breeding green Steed but F1 is a heterozygote so they it can produce two types of gametes so if you were to self-cross this F1 generation then we need to do the Punnett square and on the top is the gametes from one parent and on the side are the gametes from number two parent and then yo
u just combine the alleles in a grid and each box represent fertilized zygote separate zygote with diploid genotype and each box is equally likely or they all have the same probability of bookery and this now allows us to calculate the progeny ratios in F1 self cross each parent has has the same probability of giving either Big Y or little y to the F2 progeny and that this is the reason why one in four chance of both parents giving the Big Y to the progeny and this is also why there are one in f
our uh there are two heterozygotes but by two different Pathways there's one in four chance that parent a giving the Big Y or one is same chance in parent B Iving the Big Y and the other parent giving the recessive small lines and then obviously there's the one in four chance that both parents giving the little ones so each parent has in one in four chance of giving Y which leads to Big Y Big Y F2 which is the homozygous uh dominant and each parent also has one in four chance of giving little y
little y recessive homozygous and then there are two Pathways to producing Big Y little y progeny so if you count the colors in F2 you get three yellows and one green three to one ratio and he used this math model to predict the outcomes in the cross and then he also proposed this law of segregation and he postulated that the pair of paired unit factors or genes must segregate equally into gametes such that the offsprings have equal likelihood of inheriting either Factor in F2 Generation the pos
sible genotypes are homozygous dominant heterozygous Big Y little y little y Big Y or homozygous recessive and the heterozygous arise as a result of two parent Pathways as we have shown and the herozygous and the dominant dominant homozygen have the same phenotype that is same color and this explains the three to one ratio and equal segregation stems from well each chemistor are allowed to each canvas are equal and they segregate equally and which allows the punish scores to be used and the basi
s of the equal segregation is the metaphase one of the meiosis Mandel didn't know about this because meiosis is when you separate the homologs inherited from Mom and Dad and they can line up differently that like with Mom on the left and dad on the right or Mom on dad on the left or Mom on the right and so on and so forth right on the left Below on the right or blue on the left red on the right and the homologs have the alleles Big A and a little a and these have equal chance of making it into t
he gamuty cell so Mendel developed a way to determine If an organism that expressed the dominant trait was heterozygen or homozygen and this is the what test cross is in the test cross the the dominant phenotype is crossed with known homozygous recessive then what would you expect in other words your first current is either Big Y Big Y or Big Y little Y and that's being crossed with little y little y if it's homozygous nominate all paleo generation will lead to one phenotype that is of the domin
ant Beyond type if it's heterozygous the other half will be recessive so here's an example of test cross uh you you cross it with little white little Y and you ended up getting all yellow seeds then you know that all of these uh all of these progenies are heterozygous which means the parent obviously was homozygous dominant and if this cross heals um half yellow and half green and you know the parents had the little y otherwise it otherwise these progenies are not possible so you have a pea plan
t with a dominant phenotyping color it's yellow you want to find out if it's homozygous stamina or heterozygous you do the test cross with homozygous recessive which is green what would you expect which is let's show it here in this case you get all you get all yellow seeds yellow peas but if you were to get half yellow seeds and half green seeds then you know the parental genotype was heterozygon and he also proposed this Law of Independent Assortment it just means that again we're going back t
o the meiosis idea it's the idea that genes do not influence each other in sorting alleles into gametes or how it enters into the gamete and all possible combination of alleles for all genes are equally likely likely to occur and this again results from homologous or chromosome from Mom and Dad lining up at The Meta plate randomly you can have Mom's chromosome a on the left or Dad's chromosome a on the left or vice versa and each of these homolog combination A and B will separate into different
gametes here's blue blue red red but this particular example has blue on the left red on the right but red small chromosome the left blue a small chromosome on the on the right and if you look at it these gametes are different from these campaigns which only has this one only has blue chromosomes this will only have red chromosomes but this one has big what big blue little red big red and little blue so there are four different types of gametes stemming from two chromosomes alone uh in the lab y
ou did a two pairs of chromosomes for the meiosis why is that because independent assortment can only be shown by doing the Thai hybrid class and the dihybrid cross deals with two characteristics or four different traits so state color and the texture will be example wrinkled green round yellow wrinkle green is homozygous recessive round yellow is homozygous dominant parents are homozygous here because they are true breeding and the law of segregation detects the gametes only get one allele one
of the traits and the wrinkle green gametes are all little white a little r little y round yellow camiso gametes are all big walk Big R little y a Big Y I'm sorry Big R Big Y and then F1 generation must be heterozygous or big r and little r pink y with little y so then that phone gametes must have one allele from each of the two genes being y little y Big R little r i e example Cami a gamete with Big Y allele can either get Big R or literal r it cannot have two Big Y or two Big R alleles because
it has to segregate it has to separate homologs have separated and the gamut was a little r allele is equally like to get again Big Y or little y on Leo then you do the DI hybrid cross it's the pun of square with four equally likely gametes from big white little white pick our little our heterozygous is being self-crossed here so you write down all possible gametes from uh this genotype so those are big py Little Big Y Big R little y Big R Big Y little r little y little r and you then um I shou
ld go over what foil is but I didn't you should probably know what foil first Outside Inside last that's what foil is so first allele outside Leo inside allele last allele this is what generates these combinations or just one way to figure out how to generate the candidates and then you arrange them and on the top and the left of the Punnett Square which yields 16 equally likely genotype combinations and when you do that you get the ratios of nine round yellow three round green three wrinkle yel
low one wrinkle green and Mendel's ideas on inheritance followed a simple pattern of dominant and recessive allele for single characteristics so it basically showed that two units or alleles are present for a gene and the alleles maintain their integrity in his case but there are some uh okay that's not important okay recessive allele is hidden and on other important modes of inheritance that do not follow the dominant recessive single Gene models are things like incomplete dominance Mendel was
lucky enough to choose true breeding plants that didn't blend the trades and blending of the traits occur when you have incomplete dominance or sometimes even more uh co-dominance and you kind of sometimes more than multi more than two alleles and the linked genes violate the law of Independence Urban linked genes do not follow because they're too close to each other and epistasis which is hiding a trade or a characteristic that arise from uh interactional genes basically so incomplete incomplet
e dominance heterozygous appear to be somewhat intermediate between the two parents and this Snapdragon plan shown here is a cross between homozygote white and homozygote Rift blower and that will make offspring with pink flowers which is somewhat pink here and in other words red is incompletely dominant to the White what are some of the genotypes for this dihybrid cross what would you expect you would expect these are the genotypes that are possible and you will get one white two pink and one r
ed and the variation on the incomplete dominance is called the codominance this is where both alleles for the same characteristic is are expressed in the heterozygote meaning they're both dominant example is blood group A and B antigens are both on the cell surface then what is your genotype your blood genotype is a b so you also get if you were to cross a b with another a b you also get one to two to one homozygen ratios homozygous heterozygous to another homozygote foreign and you can also hav
e multiple alleles that violate Mendel's Laws and individual humans may only have two alleles per candidates but multiple alleles may exist at the population level and many combinations of multiple alleles have been observed in the past and typically we note the wild type with plus sign and all the other phenotypes or genotypes are considered variants or the mutants of this typical form and the variant may be either recessive or dominant to the wild type and blood type is again an example there
are four blood types using three alleles and six genotypes here's Big A and big a there's blood type a ba o That's blood type A type B O blood type B oh blood typo and so a antigen on RBC IB no antigen if you have no antigen that's how you get blood type zero blue type O rather so if you were to do the cross to determine multiple alleles parents have two alleles both the population of three others so you need three rows and columns for the punish Square a b and O a p no and this allows us to fig
ure out all possible combinations of genotypes in a population but individuals only get two alleles despite their the there being three alleles in the population and also multiple drug resistance population in this Gene in malaria parasite during haploid stage haploid stage and this only allows allows the parasite to develop resistance easier because you need only you need mutations in only one of the multiple alleles for the drug resistance resistance and that's how you can actually get uh resi
stance faster and we should talk about the sex-linked traits X has about uh we said 900 genes and Y has about 55 genes X is about three times longer though and the so x-linked traits are more common but why linked trades also exist so eye color in drosophila is was the first x-linked trait that was discovered and the one type eye color is X Big W Big Y or big yeah is dominant to White little y little w and we say males are hemizygous only has one of billios because we only have we have X and Y s
o in respect to X linked trades we are hemozygous so that also applies to transaction so fly males are hemozygous for the icology and they will Express whatever the trait the the fair X chromosome carry so in a in an x-linked cross genotypes of F1 and F2 depends on the recessive trait being in the male or the female in the parental generation if here's a male who's expressing red eye and here's a male here's a female expressing homozygous trait or Little W Little W wide-eyed if you were to cross
that what would you expect female gametes are Big W little w but male gametes are X and big w and y but y males males with x y and uh uh genotype appendezygous must receive their X chromosome from the females but the females have homozygous recessive traits so in this cross all males only males will Express the recessive trait and all females conversely will Express the dominant trait as a heterozygote so Big W Little W Big W from that little W from Ma so the homozygous female parents with rece
ssive x-linked trait will pass the trade to 100 percent of their male offsprings some color blindness hemophilia muscular dystrophy nail pattern baldness you should observe the mother's father for hence why would that be because the mother gets one of her exes from her father and his father is involved and that means mother is the carrier heterozygous females are called the carriers and they don't show any phenotypes and the carriers will pass the trait to half of their male progenies and Pastor
carrier status to have of their female progenies in other words carrier heterozygote females okay in humans males have non-homologous sex chromosomes because we have X and Y in Birds females have the non-homologous pair so female birds are hemizygous for sexual interest rates so the ratio will be opposite of what we're seeing here in Birds so like I said linked genes violate the law of independent absorbance some traits are not inherited independently of each other because they are located on t
he separate or genes that are located under separate non-homologous chromosome will always sort independently they're not linked but if genes are close to each other on the same chromosomes are considered linked and what happens in the prophase of meiosis you can have crossovers and you produce recombinant chromosomes chromatids and the chromosomes can make the same genes and the same chromosome PA like they're they're not linked so recombination crossover or crossover mix misses the paternal an
d maternal genes and the order but the order of the genes are not altered we can change the order like we talked about last time inversions or translocations which are the chromosomal disorders there can be more than one recombination on one chromosome so this can occur multiple times so um dihybrid no self-cross a dictatility Big R little r tall red heterozygotes shows the typical ratios of nine to three to three to one see independent assortment that allows this alleles separate independently
of each other and but now imagine if the parental genes Big T Big R are located on the same chromosome they cannot separate from each other except by crossing over if the Big T Little T Big R little heterozygote is the parent you can only contribute Big T Big R little r Little T little r but it cannot produce Big T little r unless it's recombined and that's being shown here down here 's Big R Big T Big R Little T little r and that's getting crossed see if you look at it all possible gametes from
these two parents these two parents are shown here Big T Big R Little T little r but if the crossover to to crossover were to occur then you produce these recombinant chromosomes chromatids with recombined possibilities and this is showing this crosses showing the conventional independently Authority um Thai hyper cross so let's go over that again Blue from Mom read from that each sister chromatids will be the gametes without the crossover there'll be two big T Big R two little T little arms wi
th crossover you get the varied combination or type of uh type you get with the independent assortment even though they're linked because you have the crossover and the genes for the tall red color are on the same chromosome and cannot independent or sort yet with the crossover they can seem kind of assorting independently so some people in the history have suggested that Mendel initially chose the seven characters for this very reason because this really messes up the ratios and it really becom
es really difficult to make sense of the ratios and then there's also the epistasis Mendel studies in peace show that the phenotypes completely are controlled by the single Gene or the unit vectors and he also may have chosen them for for the for that reason and this these seven are not the rule but they're the exceptions almost all characteristics that we have are controlled by multiple multiple genes for instance eye color is controlled by a genes as far as we can tell so in development genes
are expressed sequentially without protein protein interaction and the skin color is a result of three or more genes and these are called the polygenic inheritance because the one single trade depends on many many genes and genes Also may interact with each other to activate or inhibit and be epistasis refers to that scenario so one gene can activate or inhibit the other Gene then the dealer Gene is either turned on or turned off and has nothing to do with dominance or resistive but and hypog st
atic allele is the allele that is masked by this epistatic uh allele between the masking or is the gene that gets inactivated and often biochemical basis for the epistasis is a gene pathway in which the expression of one gene depends on the function of a gene that precedes it in the pathway so aguri wild type coat color in mice is dominant to solid colors and but there's a separate Gene C when present is recessive homozygous little sea level see negates expression of any pigment from the big agi
ng or a goody color chain so if homozygote is present little C little C then what would you expect to a dihybrid process of heterozygous goodie mice what would you expect it's a big a little CK little a Big C little C is a herozygons if little C little C negates the pigment production even if dominant and big a allele is present as either homozygous or heterozygous big a little a color cannot be expressed in other words all little C little C mice are albinos so typically you would expect nine to
three to three to one but there are four uh little C's possible or two of these so you get the ratios of nine to three to four of items so here's homozygous recessive heterozygous recessive and it's homozygous dominant for the ogre Gene but they're all albinos in other words c g is epistatic to a or a gene is hypostatic to C Gene okay [Music] um let's see if I want to you know what let's let's leave it there okay that's all for today
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