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Genetics Exam 1
Genetics
| Question | Answer |
|---|---|
| What are the components of DNA | Sugar-phosphate backbone + nitrogenous base |
| What DNA nucleotides are purines | Adenine and Guanine |
| What DNA nucleotides are pyrimidines | Thymine and Cytosine |
| What part of DNA contains the genetic info | nitrogenous bases |
| What type of bond joins nucleotide pairs | hydrogen bonds |
| how many H-bonds are between guanine and cytosine | 3 |
| how many H-bonds are between Adenine and Thymine | 2 |
| What are genes | - units of heritable info - linear sequence that encodes some functional biological molecule |
| Why is DNA replication semi-conservative | -Parental strand serves as template for daughter strand synthesis -Replication preserves identical DNA information |
| In what direction does DNA polymerase synthesize daughter strands | 5' to 3' |
| What is the central dogama | DNA --> mRNA (thru transcription) --> protein (thru translation) |
| where does transcription occur | nucleus |
| where does translation occur | cytosol |
| Do prokaryotes or eukaryotes have single circular chromosomes? | prokaryotes |
| Eukaryotes have what type of chromosomes | multiple linear chromosomes |
| in multicellular organisms are genetic info inherited from germ or somatic cells | germ cells |
| what provides variations in gene expression | genetic regulation |
| What type of cells contains the same genome | somatic |
| what is the main driver of phenotypic variation between primates | differences in gene regulation |
| What are Hox genes | - contain homebox DNA sequence - encodes for a homeodomain region of a protein - allows for coordinated gene regulation in early development |
| Phenotype = ____ + _____ | genetics, environment |
| does evolution act on phenotypes or genotypes | phenotypes |
| What is the ultimate source of genetic variation | genetic mutation |
| What is a genotype | unique set of genetic instructions of DNA sequence (genetic trait) |
| what is a phenotype | set of observable traits or characteristics of an organism (morphological trait) |
| What is gel electrophoresis | - uses electrical charges to separate out fragment of DNA/proteins - shorter fragments migrate farther |
| Who is Gregor Mendel | - 19th century monk + natural science teacher - studied heredity of traits in pea plants Pisum Sativum |
| What does Mendel test in pea plants | different varieties of its ability to reproduce identical characteristics through generations |
| What is a pure breeding organism | has a homozygous genotype |
| What is the law of segregation (Mendel's First Law) | two alleles for each trait will separate from one another during gamete formation and each allele will have an equal probability (1/2) of inclusion in a gamete |
| what type of phenotype and genotype will progenies have when pure breeding parents are crossed with different homozygous genotypes | dominant phenotypes and heterozygous genotypes (each homozygous parent contribute one allele of the gene) |
| What is the phenotypic ratio when F1 heterozygotes are self fertilized? | 3/4 dominant and 1/4 recessive phenotype (ratio of 3:1) |
| What are three consistent features of Mendel's results | - Dominance of one phenotype over the other in the F1 generation - Reemergence of the recessive phenotype in F2 generation - Ratio of approx 3:1 (dominant: recessive) among F2 phenotypes |
| What is a test cross | genetic cross between an organism showing a dominant trait and a homozygous recessive organism to determine whether the dominant individual is homozygous sor heterozygous |
| What is the result of a test cross if the organism is heterozygous | - results will show recessive phenotype - ratio of its gametes will be 1:1 |
| What is the law of independent assortment | - during gamete formation, the segregation of alleles of one gene is independent of the segregation of alleles of another gene - demonstrated through dihybrid crosses in pea plants |
| In a dihybrid cross, what is the phenotypic ratio seen | - 9/16: dom phenotype 1, dom phenotype 2 - 3/16: dom phenotype 1, recessive phenotype 2 - 3/16: recessive phenotype 1, dom phenotype 2, - 1/16: recessive phenotype 1, recessive phenotype 2 |
| In a self fertilization analysis of F2 generation, what is the predicted ratio of dominant to recessive | 2:1 ratio |
| In a dihybrid cross, when separating into individual phenotypes what expected ratio do you see | 3:1 phenotypic ratio for individual traits |
| In mitosis, what is the chromosome number in the mother and daughter cell | - chromosome numbers are identical (2n if diploids, n if haploids) |
| What two phases is mitosis split into | interphase and M phase |
| What is the G1 phase | - gene expression highest - active gene expression and cell activity, preparation for DNA synthesis |
| What is the S phase | - DNA replication creates identical sister chromatids for each chromosome |
| What occurs in the G2 phase? | - chromosomes are diffuse within nucleus and not distinctly visible - nuclear envelope intact |
| what are centrosomes | cytoplasmic regions containing pair of centrioles from which microtubules form and grow (eventually forming the spindle apparatus during cell division) |
| What occurs in prophase | - chromosomes condense - sister chromatids are attached at their centromeres via kinetochore - centromeres are visible and migrate to opposite ends of the cell cytoplasm |
| what occurs in prometaphase | - nuclear envelope breaks down - centrosome microtubules contact kinetochores and chromosome start to move toward middle of cell |
| what occurs during metaphase | - chromosomes align at metaphase plate at their centromeres - sister chromatids lie on either side of the metaphase plate - kinetochore of sister chromatids are attached to microtubules emanating from centrosomes from respective cell poles |
| What is anaphase | - sister chromatids separate to opposite poles of the cell and can now be considered daughter chromosomes - cell elongates into oblong shape due to polymerization of polar microtubules |
| What occurs during telekinesis | nuclear envelope beings reforming and chromosomes begin to decondense |
| what happens during cytokinesis | it cleaves the cell into two daughter cells at the cleavage furrow |
| What does the G1 checkpoint do | Checks if cell size is adequate, nutrient availability is sufficient, and growth factors (signals from other cells) are present |
| what does the S phase checkpoint check for | Checks for DNA replication completion and DNA has been screened to remove base pair mismatch or errors |
| what does the G2 checkpoint do | Checks if cell size is adequate and if chromosome replication is successful |
| what does the metaphase checkpoint check for | if all chromosomes are attached to mitotic spindle |
| What does the process of meiosis do | - 2 cell divisions forms gametes and reduces the chromosome number from 2n to n in gametes - produces different gametes |
| what occurs in prophase I of meiosis | homologous chromosomes will be in physical contact with one other (synapsis) which allows for crossing over to occur between sister chromatids |
| what occurs in metaphase I | homologous chromosomes align at metaphase plate |
| what occurs in anaphase I | homologous chromosomes separate to opposite poles of the cell |
| what occurs in metaphase II | centromeres align at metaphase plate |
| what occurs in anaphase II | sister chromatids separate |
| what is meiosis a source of | genetic variation |
| what does meiosis I do | separate homologous chromosomes |
| what does meiosis II do | separate sister chromatids |
| genes on the same chromosome are independent if separated by ____ | recombination |
| what is the process of meiosis in haploids | - two opposite mating types (MAT-a, MAT-) fuse to form a diploid "parent" cell (meiocyte) - meiotic products (ascospores) physically connected in an ascus alpha |
| if the hypothetical animal Geneticus introductus is 2n = 48 and each diploid nucleus contains 2ng of DNA in G1 what number of chromosomes and amount of DNA is present per cell at the end of mitotic anaphase | 96 chromosomes and 4ng (during anaphase the sister chromatids are pulled to opposite ends and each of them are considered their own chromosomes) |
| How does meiosis support Mendel's 1st and 2nd laws | - the separation of homologous chromosomes and sister chromatids in Metaphase I and II respectively allows for genes on different chromosomes to segregate and assort independently - Anaphase I physically separates homologous chromosome pairs |
| A single germ cell meiosis will lead to gametes with how many number of distinct genotypes | 2 |
| what are the only cells that undergo meiosis | germ cells |
| what does mitosis produce | two cells each with the SAME number of chromosomes and IDENTICAL genetic content as the parental cell |
| what does an autosomal recessive trait look like in a pedigree | appear equally in both sexes and typically skip generations |
| what does an autosomal dominant trait look like in a pedigree | appear equally in both sexes and almost always appear in each generation and all affected individuals have an affected parent |
| when filling out pedigrees what do you assume about individuals marrying into the pedigree | that they are homozygous for wild type alleles unless told otherwise or implied otherwise by the pedigree |
| when do you assume that the individual marrying into the pedigree isn't homozygous for the wild type | when their child is affected with the trait thus making both parents having to carry that recessive allele |
| what does a chi square test quantify | how closely an experimental observation matches the expected outcome by determining the probability of the observed outcome |
| High P values are associated with ____ chi square value | low |
| Low P values are associate with _____ chi square values | high |
| how do you determine the degrees of freedom | # of classes - 1 |
| if the number of observed individuals of a particular phenotypic class MOVES CLOSER to the expected number of individuals, the value of the X^2 statistic _________ and the likelihood of REJECTING the null hypothesis _______ | decreases, decreases |
| How to solve the for the p(A AND B) when it comes to two independent events | p(AB) = p(A) * p(B) |
| How to solve the for the p(A OR B) | p(A) + p(B) - p(AB) - probability that either of two events will occur is the SUM of the probability of each occurring minus the probability that both occur |
| How to solve the for the p(A OR B) if events are mutually exclusive (can't be both simultaneously) | p(AB) = 0 so p(A or B) = p(A) +p (B) |
| how to solve conditional probability: probability of event A given event B | p(A|B) =p(A and B)/p(B) |
| When is the binomial theorem used | for unordered events |
| in the binomial theorem equation what does each letter represent | n = number of trials k = # of desired events p = probability of desired event 1-p = probability of alternative event |
| What did Bateson and Punnett study | studied two dichotomous traits (color and pollen shape) in flowers to test the law of independent assortment |
| what plants did Bateson and Punnett cross | pure breeding plants with two dominant traits, purple flowers and long pollen (PPLL) to pure breeding recessive plants with red flowers and round pollen (ppll) |
| True or false: can genes on the same chromosome be physically linked? | True |
| what are some benefits of using fruit flies as a model organism | - small and easy to maintain - short generation time (10-12 days) - many offsprings from each female - 4 chromosomes: 3 autosomes + 1 sex pair (X/Y) - unparalleled genetic tools, sequenced genome |
| what did Morgan identify that violates Mendel's 2nd law | - X linked genes in fruit flies - identified genetic recombinants - obtained unexpected ratios and observed unexpected recombinant phenotypes |
| What is genetic linkage | genes sit on the exact same physical chromosome (linked) |
| what was the expected phenotypic ratio in Morgan's two-point test cross | 1:1:1:1 ratio only if unlinked, heavily skewed toward parental types if linked |
| what is a characteristic of genetic linkage | Rate of recombination between linked genes is low; parental allele combinations usually stay together during meiosis leading to production of parental gametes at a combined frequency greater than 50% |
| recombination frequency is proportionate to what | the distance between genes on a chromosome |
| What did Morgan postulate about non parental phenotypes | they are the result of recombination between homologous X chromosomes during F1 female meiosis |
| what does the production of recombinant chromosomes require | physical rearrangement (recombination) of homologous X chromosomes |
| What did Creighton and McClintock obtain cytological evidence for | recombination involved physical exchange between homologous chromosomes by detecting genetic recombinants |
| what are the steps in the formation of recombinant gametes | 1. selection of recombination site 2. form chiasma 3 chromosome exchange |
| the production of recombinant phenotypes depends on the location of what | - genes on the chromosome - crossover site |
| How to tell in a pedigree if a trait is X linked recessive? | - more common in males (a single recessive allele on their X chromosome will result in them having the trait) - Females require two copies of the recessive allele to express the trait so they are usually unaffected - may skip generations |
| In a x-linked recessive pedigree what is the rate that carrier females will pass on the allele to their kids | 50% chance of passing to the son (who will be affected) and 50% of passing to daughters (who will become carriers if the other X from father is normal) |
| what are the key features of X linked dominant inheritance | - if the father is affected, all daughters will inherit the trait but son's don't - if mother is affected, each child has a 50% chance of inheriting the trait depending on which X chromosome is passed on - doesn't skip generations |
| What is Mendel's law of dominance | - the dominant allele determines the organism's phenotype while the recessive allele remains latent but is transmitted to the next generation - recessive allele only expressed when the organism inherits two copies of the recessive allele |
| What is non disjunction | failure of chromosomes (homologous chromosomes or sister chromatids) to separate properly during meiosis or mitosis, leading to daughter cells with an abnormal number of chromosomes (aneuploidy) |
Created by:
rach6774