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Genetics first exam
genetics exam #1 chp 1-7
| Question | Answer |
|---|---|
| DNA | building block of genetics, made up of A, T, C and G nitrogenous bases in strands that are anti parallel to each other |
| gene: | part of dna that codes for a protein |
| chromosome: | long pieces of DNA wrapped into characteristic X shape |
| noncoding regions | areas between gene that code for nothing and regulate how the gene is expressed |
| genome | all the genetic information of a single living organism |
| primary structure | linear sequence of amino acids that eventually lead to proteins, primary sequences determine protein shape, different sequence = different shape |
| Mendel's biggest contribution to genetics? | simplification |
| mendel showed that hybrid offspring | always show traits of one parent, THE DOMINANT PARENT, recessive trait appeared when the hybrid self fertilized |
| probability rules | AND = multiply || OR = add || |
| Mendel's laws: LAW OF SEGREGATION | alleles separate during gamete production and are united randomly during fertilization |
| Mendel's laws: LAW OF INDEPENDENT ASSORTMENT | alleles for different, unrelated traits, do not influence how each other are sorted/split up during gamete production |
| what's the ratio of a typical dihybrid cross? | AaBb x AaBb = 9:3:3:1 ratio, and because of independent assortment, you can split it into a cross of Aa x Aa and Bb x Bb. to connect them again, use branched diagrams, much easier |
| ratios to remember: Aa x Aa | 1:2:1 or (1/4):(1/2):(1/4) |
| ratios to remember: AA x AA or aa x aa | 100% or 4/4 |
| ratios to remember: Aa x aa | 1:1 or (1/2):(1/2) |
| determining inheritance patterns in people is harder because... | no purebreeding lines, its unethical to control breeding between humans, small number of progeny and loooong generation times |
| then we can still use pedigrees because...? | humans still follow laws of segregation and independent assortment, still follow the same inheritance patterns but traits influenced by the environment and multiple genes are harder to trace through this process |
| dominant inheritance pattern | half, most or all kids of the affected will have the same trait and atleast ONE of the affected's parents must also have the same trait, dominant alleles can't hide, vertical inheritance |
| recessive inheritance pattern | individual may show the trait but the parents don't bc they are carriers/maybe one parent is unaffected. related parents (consanguineal relationships) bring out recessive genes more, two affected parents will have affected kids, horizontal inheritance |
| pleiotropy | one gene contributes to several characteristics |
| extensions of mendels laws | |
| dominant inheritance patterns (vertical inheritance) | half/most/all of affected's offspring will have the trait, atleast ONE of affected's parents must also have the trait, which means it shows up atleast once in every generation, dominant trait cannot hide |
| recessive inheritance patterns (horizontal inheritance) | affected's parents dont necessarily have the trait, can just be carriers, parents are often related, two affected parents will have all affected kids, trait may not show up for generations and then show up in everyone in a single generation |
| extensions to mendel's laws | genotype always the same, phenotype, not necessarily, incomplete dominance, codominance, pleiotropy, etc |
| pleiotropy | one gene contributes to several characteristics |
| incomplete dominance | heterozygotes don't resemble either parents, they're a weird fusion of the two |
| codominance | heterozygotes have traits of both parents/looks like both parents |
| haploinsufficiency | one allele isn't providing enough to have a fully homozygous phenotype |
| lethal alleles | one of the homozygotes just do not produce, terminated before production, have a 2:1 ratio instead of 1:2:1 or 3:1, cannot get a true breeding homozygote for the trait, all individuals w that quality are heterozygous, fewer offspring than expected |
| ratios to remember: lethal alleles | 2:1 |
| multiple alleles | many alleles for a specific trait, alleles can have a series of dominant and recessive relationships w the other alleles for the trait. alleles can also be codominant/incompletely dominant w other alleles for that trait |
| wild type allele | the most common allele for the trait, ie. red eyed flies |
| mutant allele | the rare trait among organism populations |
| rules of multiple alleles | there can be hundreds of alleles for a gene, but, at a single time a single individual can only have two of those alleles |
| allelic series | describes relationships between different alleles for a gene |
| lethal alleles in drosophilia | its hard to mantain lethal fly alleles in a lab bc the heterozygotes are weaker than the surviving homozygotes. so give it another lethal allele so both homozygotes die and only heterozygotes survive and reproduce |
| can all genes be pleiotropic? | yes, depending on how you look at it |
| polymorphic | a trait that has multiple alleles as a wild type, exp. human eye color |
| complementary gene action | when you need both gene 1 and gene 2 for the phenotype to exist |
| epistasis | expression of one gene hides the other |
| heterogenous trait | mutations in different genes can lead to the same phenotype |
| complementation test | testing to see if two traits are in the same gene or in different genes |
| temperature sensitive | the environment affects phenotype expression, ie. smoking and chances of getting lung cancer or acidity and hydrangea color |
| penetrance | even though an individual has the genotype, it doesnt necessarily express it |
| expressivity | an individual expresses the phenotype with differing intensity, some show it strongly, others not so much |
| how do you know that, for sure, two traits are not on the same gene? | if the ratios are adding up to 16 |
| complementary genes continued | usually the genes code for two enzymes on a metabolic pathway, or are two subunits of the same protein |
| ratios to remember: dihybrid cross of complementary genes | 9:7 |
| dominant epistasis | dominant allele masks other alleles |
| recessive epistasis | recessive alleles masks other alleles |
| hypostatic | the gene that is being masked by an epistatic gene |
| ratios to remember: recessive epistatis | F2 ratio is 9:3:4 |
| ratios to remember: dominant epistatis | F2 ratio is 12:3:1 or 13:3 |
| tip#1 to calculate ratios | 1.make the smallest #'s ratio =1 and divide the other two #'s by the smallest #'s to get their ratio, round up |
| tip#2 | divide the biggest number by 9, then take that quotient and divide all 3 numbers by that quotient to get your ratios |
| novel phenotype | a new look, an organism has a phenotype that did not previously exist |
| chromatin | DNA in its uncondensed, blobby form, wrapped around histone proteins |
| diploid organism | organism that has 2 sets of chromosomes |
| n and 2n? | n = number of unique chromosomes in a set, 2n=number of sets of chromosomes |
| An organism is 6n, and has 54 total chromosomes. How many unique chromosomes are there, and how many homologous copies of each are there? | n = 54/6 = 9 There are 9 unique chromosomes, and six homologous copies of each one |
| centromere | place where chromatids attach, does not break during recombination, any break that could switch the centromere would not occur |
| chromotids | single line of DNA |
| chromosome | two chromotids attached |
| homologous chromosomes | chromosomes containing the same genes, maybe different alleles in those genes, but they code for the same gene |
| metacentric | centromere is located in the middle |
| arocentric | centromere is located near the top or bottom |
| mitosis | occurs in body cells, diploid -> diploid cells, asexual reproduction, exact copies |
| meiosis | occurs in gametes, gonads, diploid -> haploid cells, creates 4 haploid, unique gametes |
| when does recombination occur | when the inital diploid cell is going to split into haploid cells |
| cell cycle | interphase (G1, S, G2), Mitosis (prophase, metaphase, anaphase, telophase) |
| interphase | G1: gap 1, cell keeps on growing, protein synthesis || Sphase: DNA is replicated, still in blobby chromatin form || G2 phase: organelles replicate, otherwise cell stays normal |
| Mitosis | prophase: DNA condenses into chromosomes, nuclear envelope melts, centrioles begin to create microtubules.metaphase: chromosomes line up on metaphase plate, microtubules attach to chromosomes.anaphase: spindle fibers retract and split chromatids. |
| mitosis contintued | telophase: cytokinesis occurs, nuclear envelope reforms, chromosomes unwind into chromatin againc |
| how do you know how many chromosomes are in a cell? | count the number of centromeres |
| how do you know if a cell is haploid or diploid | if it has a copy, then its a diploid, if that's the only one then its haploid |
| meiosis 1: prophase 1 | homologous chromosomes undergo recombination, crossing over occurs and homologous chromosomes stick together. in mitosis the homologous |
| meiosis 1: metaphase 1 | tetrads line up on metaphase plate, chromatids are not identical bc of crossing over. in mitosis the chromatids would be identical |
| meiosis 1: anaphase 1 | homologous chromosomes separate. in mitosis the chromatids would separate |
| meiosis 1: telophase 1 | cytokinesis occurs, dna usually remains condensed. in mitosis dna uncondenses |
| meiosis 1: interkinesis | first division done, daughter cells are haploid, only have one copy of each chromosome |
| meiosis 2: prophase 2 | cells are haploid, chromatids not identical |
| meiosis 2: metaphase 2 | chromosomes line up on metaphase plate |
| meiosis 2: anaphase 2 | sister chromatids are pulled apart, they are not identical thanks to crossing over that occured in prophase 1 |
| meiosis 2: telophase 2 | cytokinesis, nuclear envelope reforms, chromasomes form back into chromatin |
| meiosis 2: done | 4 haploid gametes formed with recombinant chromosomes |
| physical process of crossing over, what occurs: lepotene | chromosomes have not condensed, sister chromatids are too close to distinguish |
| physical process of crossing over, what occurs: zygotene | conjugation, homologous chromosomes find their partner and "zip", attach very very precisely |
| physical process of crossing over, what occurs: pachyotene | thick and fat, exchange of genetic materials at certain areas, usually equal exchange |
| physical process of crossing over, what occurs: diplotene | double, the zipper starts dissolving, exchange is complete, tetrads remain attached at recombination areas called chiasmata |
| physical process of crossing over, what occurs: | |
| determining sex in: humans and flies | XX and XY, determined by sex chromosomes |
| determining sex in: birds and butterflies | ZW and ZZ, determined by sex chromosomes |
| determining sex in: turtles | warm temp= gilrs, cold temp = boys |
| determining sex in: bees and wasps | diploid = girls, haploid = boys |
| sex chromosomes | contain genes that specify sex |
| psuedoautosomal regions | on sex chromosomes, the tops and botoms, only part of the x and y that are the same, where the chromosomes attach to form tetrads and where recombination occurs |
| hemizygous: | bc there is no dominant or recessive for guys when its sexlinked they're just hemizygous, only one chromosome, meaning they can never be carriers for these things |
| x linked recessive disease patterns | if mom is affected, ALL of her sons are affected. if a daughter is affected, her father MUST be affected. guys are more affected than girls bc they only have one x |
| x linked dominant disease patterns | tends to affect more females than males. an affected father will have ALL affected daughters and NO affected sons. if a son is affected, mom's always affected |
| recombinant genotypes | chromatids have undergone recombination |
| recombination | switching of alleles during prophase of meiosis 1, creates variety, only occurs between homolgous chromosomes and does not change mendelian genetcis at all |
Created by:
hsinha93
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