IB 150 Exam 2

genome

(-ome = total sum) All the genetic information in an organism; all of an organism's chromosomes.

how many (not necessarily identical) copies of a single autosomal gene do humans typically have in a cell during the G1 phase of the cell cycle?

humans=diploid (# of sets of each type of chromosome) G1= phase before S phase (not replicated yet) = 2 bc its diploid= has 2 copies of each chromosome (so 2 copies of each gene) = one on each unreplicated homolog of the chromosome type ps. : not replicated, but even if it was = still considered one movable unit = one chromosomme

describe process of gametogenesis: males:

spermatogenesis: continues thru life cycle of organism -male germ cell (2n)---- goes thru mitosis ---> spermatogoneium---more mitosis---> primary spermatocyte (2n)----1st meiotic division---> two secondary spermatocytes formed (haploid)----second meiotic division--> four spermatids that fully divide cytoplasm into sperm (haploid) =maturity starts (embryo to adult) at 1st meiotic division adult male has stem cells hanging around = that divide mitotically and some stay as stem cells for spermatogenesis later

three reasons for sexual reproduction

environmental variability throughout space and time: need to adapt to it= meiosis allows this -if an individual inherits a deleterious mutation, inheriting a normal allele that produces a protein that functions normally = then this mutation might not be so deleterious homologs pairing up durig Meiosis I is a mechanism that allows for matching up copies of genes between the two homologs and allow for the DNA repair of some forms of DNA damage= so further proofreading of DNA

each of the cells in our body was produced from the original fertilized egg cell (the zygote) through mitotic cell divisions. What does that mean about the genetic information carried in each of the many cell types (such as skin cells, white blood cells, muscle cells, neurons, etc)- ignoring mutations?

every cell in our body (barring mutations) has exactly the same genetic information (mitosis results in genetically identical daughter cells)

structure of DNA

-long, chain like molecule -made up of nucleotides -nucleotides: sugar phosphate backbone (phosphate group attached to pentose sugar (deoxyribose)) + nitrogenous base -double helix --chromatin= DNA wrapped around histone proteins --chromatin fiber winds up like a coil = 30nm-fibre --30nm fibre arranges into loops= 300 nm - further winds up = 700 nm wide coil = condensed chromosome complementary bases : A-T, C-G

how many genetically distinct gametes can be produced by an individual with 1 chromosome that contains 2 linked genes where maternal and paternal chromosomes carry a different allele for each of these 2 genes, assuming that crossing over DOES NOT take place?

1 chromosome, 2 linked genes = just have independent assortment = 2 bc. the alleles of the 2 genes cannot be reshuffled without crossing over and create new allelic combinations = only expect parental combinations

What is needed to maintain the unbroken chain of reproduction?

1) ability to pass on genetic information = blueprint of life (meiosis/mitosis) 2) genetic variation= can adapt to different environments = mutations --however, too much mutation= wouldn't work due to non functional genes =needs a source of mutation for genetic variation, but needs to be limited (for next generation to have sufficient functional proteins)

if a protein has 150 amino acids, how many DNA nucleotides (bases) would make up that gene?

150 x 3= 450 base pairs

how many copies of each gene does a diploid cell carry?

2

approximately how many bases long is your genome?

3 billion long 6-billion bases total

Height in humans is a polygenic trait, wherer multiple genes contribute. Assume that 4 genes contribute equally to body height in humans in a simple additive manner and the dominant allele of each of these genes always results in a taller stature than the recessive allele in an incomplete dominance pattern. What is the order of the following genotypes of individuals that arranges them in order of increasing height? (assume incomplete dominance for each gene.) 1. aaBbCCdd 2.AABBccDd 3.aabbccdd 4.AaBbCcDd 5.aaBbccdd

3-5-1-2-4

If a particular gene contains 300 bases, along its sequence, how many amino acids will be strung together during protein synthesis?

300 bases/ 3= 100 codons= 100 amino acids

How many genetically distinct gametes can be produced by an individual with 1 chromosome that contains 2 linked genes , where maternal and paternal chromosomes carry a different allele for each of these 2 genes, assuming that crossing over takes place?

4 1 chromosome, 2 linked genes w/ crossing over= replicated chromosomes have crossing over event = new combination of alleles in both parent's chromsomes = 4 genotypes

result of independent assortment in meiosis:

4 genetically distinct gametes, that occur at the same frequency (1:1:1:1)

how many base pair errors on average occur in your genome?

6 billion total bases x 1/10,000,000 = 600 mistakes per cell division

Going with the same assumption that 4 genes with 2 alleles each are responsible for the phenotypic trait height in a simple additive manner, how many different height phenotypes are possible?

9

what are alll the possible genotypes in the parental generation that produce a phenotypic ratio of 1:0 in the first offspring generation?

=AA xAA / Aa xAA / AAxaa/

why do many researchers use a model organism such as Drosophila rather than study the questions of interest on humans directly?

=fruit fly -produce large amount of offspring in a relatively short time span -similar to human genes=orthologous genes - more ethical to do certain experiments in flies than humans - the large offspring sample size = more likely to see all genotypes/phenotypes possible

What genotypes would you want to cross in order to only create AaBb (phenotypic/gentoypic ratio= 1:0) gametes in a dihybrid cross?

AAbb x aaBB

Now comes our prediction. IF the 2 genes apterous and ebony (fruit flys) independently assort during meiosis, what are all the different kinds of gametes that these F1 individuals will produce? P- AAbb x aaBB F1- AaBb xAaBb gametes of F1 with independent assortment?

AP EB = AB apEB=aB APeb=Ab apeb=ab if independent assortment takes Place= 4 gametes are produced (2 parental and 2 recombinant) =each gamete produced with same frequency 1:1:1:1

understand how base pairing rules lead to semi-conservative model of DNA replication

DNA repliction: double helix splits thru helicase= creates replication fork =each is a template strand (different directions) --RNA primase creates RNA primer= DNA polymerase binds there and starts adding free nucleotides to template = new DNA strand formed with template strand= semi conservative = only possible bc DNA is formed by the sequence of nucleotides that contain nitrogenous bases that only pair with certain other bases= allows for exact copying of genetic material

describe the central dogma of biology

DNA (genotype: information storage)------transcribed in nucleus-------> mRNA (messenger RNA that is able to leave nucleus and take genetic info to ribosome----where it is translated into---> proteins (tRNA brinds amino acids (triplet codon= 3 base sequence) to form a polypeptide that folds into a protein

Differentiate RNA from DNA

DNA : nucleotide bases: A-T, C-G -double stranded, -functions: stores RNA and protein encoding information + transfers information to daughter cells -sugar: deoxyribose RNA : -single stranded -nucleotides: A-U, C-G -funciton: carries protein encoding information, helps make proteins (makes up ribosome complex), catalyzes some reactions

function of DNA

DNA = contains instructions on how to make proteins and RNA -do this thru base pairing rules --bases can only interact with their complements = creates a code A-T (uracil in RNA) (double h-bond) C-G (triple h-bond) this code is transcribed to RNA and translated to proteins that directly determine every other aspect of the organism

why does S-phase have to precede mitosis?

DNA has to be replicated before cell division

what is the central dogma of biology?

DNA-->RNA--> Protein

Before the structure of DNA was discovered, experiments revealed an interesting, but at the time puzzling result- while the amount of the four nitrogenous bases in DNA samples from different species varied, the relative amount of always two bases was always the same. We now understand that this result is a consequence of the base-pairing rules. In a DNA sample we collected from a flower, we find that 34% of the nitrogenous bases in this organisms DNA is made up of nucleotides that contain the nitrogenous bases Guanine (G) . Based on what you just learned about base pairing rules, predict what proportion of nucleotides in the genome of this flower Adenine (A).

G-34% C-34% 100-34(2) /2 = 16% A

What are all of the gametes that a LlCc can produce?

LC,Lc,lC,lc

Describe cell cycle

Interphase: G1-->S phase --> G2---> during interphase =chromatin is relaxed M phase: mitosis--> cytokinesis ---> interphase overall: G1: parent cell is unreplicated; largest portion of cycle= all organelles and cytoplasmic contents are replicated (centrioles in animals) Sphase: synthesis phase- DNA replication using semi conservative model (mutation occurs here) G2: parent cell is now replicated ; all enzymes needed for cell division are produced entering M phase now: mitosis: order of events: -nuclear envelope breaks down, chromosomes condense, spindle apparatus starts forming as centrioles move to opposite sides of pole -microtubules attach to kinetochores (at centromere) = there is 2 kinetochores on each side of chromosome= one kinetochore tubule from either pole attaches to each sister chromatid here -all chromosomes are aligned at metaphase plate -formation of spindle apparatus is now complete: kinetochore tubules hold chromosomes , astral tubules : hold spindle fibers in place and interact with proteins on plasma membrane ; polar tubules: overlap eachother and connect either poles side of tubules = allow movement due to tension and motor proteins -the cohesions that hold sister chromatids together at centromere are cleaved by enzyme -bc, newly separated sister chromatids are under tension via microtubules= pulled to oppositie sides of cell -nuclear envelop reforms around each set of chromosomes -chromosomes begin to decondense -=division of nucleus is complete -cytokinesis: cytoplasm is fully divided and two new identical daughter cells formed --in plants: cell plate formed thru fused together vesicles containing components to build cell wall and fuse with existing plasma membrane and fully divide cell --animals: cytokinesis begins at cleavage furrow= an indentation in the cell surface that occurs as the plasma membrane is pulled inward due to interactions between actin-myosin proteins= indentation deepens until membranes fuse and fully divides cell

when in cell cycle mutation occurs:

S-stage- during DNA replication

T o F: Bacteria sex allows for the passage of toxin resistance to bacterias of even distant relation.

True due to how plasmids can be shared

Mitosis produces two genetically identical daughter cells , except if there was any mutations that may have occured during DNA replication. T o F ?

True, errors in DNA replications lead to mutations that can be beneficial or deleterious

Explain how oogenesis can result in very large egg cells:

Want enough resources: for nutrients (yolk) = division are not equal -Have polar bodies after each meiotic division (very small compared to other cell)

why might a diploid organism (an organism that has 2 copies of each chromosome type) have 2 homologous chromosomes -2 chromosomes that carry the same genes in the same order-although each homologous chromosome may carry a different version (allele) of the gene from the copy that is carried by its homolog?

a diploid organism inherited 1 homolog from 1 parent and the other from the other parent

what is a gene?

a gene is a stretch of DNA that codes for a protein

why do we need a large sample size in test crosses?

a larger sample size = counting more and more phenotypes = results in a smaller error, compared to the "real" underlying pattern more individuals accounted for= smaller fluctuations from real pattern that we are trying to see thus, larger sample size = stronger the visible patter n

depict life cycle of fungi:

haplontic life cycle: mature organism is haploid and the zygote is the only diploid stage cells fuse= two haploid cells form to become a diploid cell (zygote) = this cell immediately undergoes meiosis= form haploid daughter cells = these become spores that grow up into next mature fungi =this is the exact inverse of cycle of animals

depict life cycle of plant:

alternation of generations: the organism passes thru haploid and diploid stages that are both multicellular = individuals look and are genetically distinct from one another =alternation of sexual and aseuxual phase in a organism's life how plants do this: -adults=diploid individuals--- when going thru reproduction= produce a spore instead of gametes---spore produced thru meiosis---once spore is released it can start dividing thru mitosis into a mutlicellular individual =essentially a diploid cell into a haploid cell that goes thru mitosis= fully grown daughter is haploid different from adult diploid that is a --> (sphorocyte= makes spore) the haploid daughter= gametophytes : produces gametes = fertilization occurs at gametophyte stage, then goes thru mitosis and form sperm/egg cell= fertilized zygote forms from fusion and diploid cell is formed = matures to adult

substitution cause and effect:

an exchange of a single nucleotide for another

why have many organisms evolved to have sexual reproduction?

asexual- might produce some genetic variation, thru the mutations done thru S phase = but limits the genetic variation =sexual reproduction has higher genetic variation

compare and contrast "bacterial sex" to "true sex"

bacterial sex: sharing of plasmids --plasmids = small satelies of DNA segments that can be passed thru cell replication or swapped with a distant relative of bacteria = play role in toxin resistance true sex: syngamy (fusion of sex cells) resulting in new allelic combinations =key process in true sex thru fertilization = recombining entire genome (haploid x2 =diploid) by fusion of sex cells

every organism alive today is related to the very first ______ through an unbroken ______________________.

cell ; chain of reproduction

without statistical analyses of our results, we actually don't know what our results mean. what do we use to help with this?

chi square test: allows us to compare the observed events (the observed numbers of individuals of each phenotype) with the number of individuals we would have expected

be able to transcribe and translate a gene sequence to the protein product, if given an mRNA codon chart:

codons: 3 base pairs that read for a single amino acid = represents a word of the genetic code

what feature of DNA allows for faithful copies to be made during DNA replication and passed on to the daughter cells?

complementary base-pairing rules

Identify two natural mechanisms that help prevent mutations from occurring

complimentary base pairing- no restrictions on sequences of nucleotides along a single strand, A only pairs with T , and C only paris with G -different number of H bonds DNA proofreading: catches mismatches during replication

how does meiosis increase genetic diversity among individuals?

crossing over in synapsis: -each homologous chromosomes have physical exchange of non sister chromatid gene segments independent assortment: -the bivalent can lay on either side = 2 different ways for two homologs to lay on metaphase plate in meiosis I =new combinations of alleles (traits) key word independent: no influence on other instances of meiosis

depict cell life of animals

diplontic life cycle: the organisms is diploid and the gametes are the only haploid stage during meiosis: reduction division (meiosis I) = halves number of chromosomes and allows diploid stage to become haploid gametes that can combine again thru fertilization and become a zygote

which of the following is true about the life cycle of animals? -gametes are produced by meiosis;somatic (body) cells are produced by mitosis -gametes are produced by mitosis ; somatic (body ) cells are produced by meiosis -gametes and somatic cells are produced by mitosis -gametes and somatic cells are produced by meiosis

gametes are produced by meiosis; somatic cells are produced by mitosis

distinguish between genotype and phenotype.....what is there relationship?

genotype: genetic makeup of an organism (DNA sequence) , heritable, allows to take on a particular phenotype phenotype: observable features of an organisms genotype: DNA sequence that is transcribed to mRNA that is translated to protein -enzymatic proteins : catalyze reactions that manufacture the creation of different macromolecules that are important for bodily functions

what are the genotypic and phenotypic ratios that will result from this cross of these two true breeding lines? AA x aa

genotypic ratio: 1:0 phenotypic ratio: 1:0

By the end of Meiosis I , we have 2 daughter cells that are:

haploid, but each chromosome is a replicated chromosome with 2 sister chromatids

understand how genes and alleles are distributed among homologs and sister chromatids in karyotype:

homologs: = in diploid organisms a member of a pair of chromosomes that are similar in size , shape and gene content (but not identical = could differ in alleles of genes) sister chromatids: two identical chromatids connected at centromere that form one single chromosome= replicated form (same alleles and same genes)

DNA only encodes for:

how to make RNA, or make proteins

Identify and define the property of the triplet genetic code that permits a genetic code that permits a genetic mutation to have no effect on the resulting protein product:

indel mutation that involve multiples of three base pairs = will not result in a frameshift mutation (codon= 3 base pairs) = ultimately removing a codon= thus reading fram of codons in the rest of the mRNA molecule is preserved code is unambiguous, and redundant

why did organisms evolve mechanisms to share genetic variation, including conjugation and sex?

it allows the sharing of beneficial mutations, rather than waiting a long time to obtain your own

understand how our genome is organized in a karyotype, and be able to locate gene loci on chromosomes

karyotype: the distinctive appearance of all metaphase or prometaphase chromosomes in an individual = includes # of chromosomes, their length and their banding patterns diploid: 2 sets of each type of chromosome ( chromosome = one whole movable unit of DNA) =have 2 alleles for each gene haploid: have one allele for each gene gene loci: a specific, fixed position on a chromosome where a particular gene or genetic marker is located

_______________genes can be reshuffled , the process used is crossing over rather (also independent assortment of genes between two non sister chromatids.

linked

explain the significance of events that occur during mitosis and why these events result in the production of two genetically identical daughter cells:

major events in mitosis: -sister chromatids are separated when aligned at metaphase plate and moved to opposite poles via microtubules -formation of spindle apparatus= important part of separation- need to correctly connect to kinetochore at centromere and create tension so once bonds between sister chromatids are cleaved= can immediatly pulll away chromatids = sister chromatids are identical copies of DNA attached at centromere = replicated DNA - separating to opposite sides of poles= two new cells can form that have the identical DNA and are both diploid still

must accomplish 2 things in meiosis:

meiosis I : replicated homologs (diploid) are split into two new cells (haploid ) = reduction division meiosis II: sister chromatids are split into two new cells (two haploid to four haploid)

major events in meiosis for a diploid organism

meiosis: specialized type of cell division that reduces the chromosome number by half, creating four haploid cells each genetically distinct from the parent cell that gave rise to them (sperm /eggs) Meiosis I after S phase : duplication of centrioles and DNA enter meiosis: -nuclear envelope breaksdown -centrioles begin forming spindle aparatus -chromosomes condense -sister chromatids held together at centromeres Synapsis: here crossing over occurs- BIGGEST DIFFERENCE WITH Mitosis - formation of bivalent thru synaptonemal complex that allows crossing over to occur= physical exchange between chromosome segments between non sister chromatids =increases genetic diversity -sister chromatids (bivalents) connect at kinetochores w/ microtubules another key diff: microtubules attach to one homolog each from either side of cell -Bivalents line up at metaphase plate --independent assortment= alignment is random - one homolog on either side homologs are separated and pulled to either side =Meiosis I ends with telophase I when chromosomes decondense and nuclear envelope reforms , cytokinesis cleaves cell into two (2n = two haploids with sister chromatids) =reduction division = halving the number of chromosomes (what allows true sex reproduction to occur) meiosis II (two 1n--> 4 1n cells) = most similar to mitosis: BUT no DNA replication prior -centrioles again replicate and move to either side of poles -chromosomes condens and nuclear envelope disappears -microtubules from either side attach to both sides of sister chromatids -spindle fibers lines the sister chromatids along metaphase plate -sister chromatids separate -chromosomes decondense -nuclear envelope reforms cytokinesis - cleavage formation (thru actin-myosin interactions indentation grows more and more until cell membranes fuse together) =4 haploid cells that are genetically different

are gametes produced by mitosis or thru meiosis in fungi/plants?

mitosis in a haploid multicellular stage (fungi) or gametophyte (plants)

describe the fundamental similarities and differences between mitosis and meiosis:

mitosis: -division of body cells into more body cells (somatic cells) -diploid cell produces 2 diploid daughters -genetic variation doesn't change -daughter cells have identical DNA -chromosome number remains the same -purpose=cellular proliferation meiosis: -division of germ cells into gametes -two phases -1st phase has : --genetic recombination -thru synapsis (crossing over) --independent assortment of homologs and in sister chromatids in second phase -diploid germ cell produces four haploid gametes that are genetically unique -genetic variation increased purpose is sexual reprodtion -chromosome number is halved thru reduction division (allows for sexual reproduction to occur)

define mutation and relate it to alleles and genetic diversity in a population

mutation: a permanent change in the DNA sequence -can be beneficial (rare) or deletirous or no effect -alleles: products of mutations ( a particular version of a gene) Mutations: random (dont occur when needed) rare(about 100 every generation)

what form of producing genetic diversity is a source for all organisms?

mutations

explain when mutation occurs during the cell cycle

mutations =result of mistakes in DNA replication -DNA polymerase mismatches once every 10 million bases - even with proofreading Proofreading: during DNA replication, an incorrect nucleotide may be added to the growing chain= the proteins of the DNA polymerase complex immediately excise the incorrect nucleotide and addthe correct nucleotide and replication proceeds post synthesis repair: drastically reduces mutation rate -immediately after DNA synthesis, any remaining mispaired bases can be detected and replaced in a process called mismatch repair: =the mismatch repair proteins excise the mismatched nucleotide and some adjacent nucleotides = DNA polymerase I adds the correct nucleotides Then DNA ligase repairs the remaining nicks

what changed as a result of meiosis II?

replicated to unreplicated chromosomes in daughter cells in meiosis II, sister chromatids get separated (similar to mitosis)= this means chromosomes go from replicated to being unreplicated (sister chromatids= identical) but this in no way changes the ploidy= still haploid - ploidy does not count chromatids per chromosome, but how many homologs of each chromosome type the cell has

can 2 genes independently assort with respect two each to each other if they are on the same chromosome (if they are in the same linkage group)?

no, they are stuck on same chromosome, = limits to genetic diversity independent assortment can do alone= it is directly related to how many separate molecules of DNA you have in a cell = separate chromosome types present in a particular cell Ex: humans have 23 types= 2 possible arrangements on metaphase plates= 2^23= 8,388,608 possible unique gametes from independent assortment alone BUT: independent assortment cannot produce new combinations of maternally and paternally inherited alleles of genes that form a linkage group on the same chromosome type solution to this issue: answer would be yes with genetic recombination in meiosis I when synopsis occurs : -chiasmata: location on chromosome where genes ---cross over during synapsis -happens @ least once per chromosome- not rare , but common- can have multiple ---little bit of a limit- due to tension created in molecule itself from crossing over= physical limit -new combinations of alleles (and their traits) on the -same chromosome type -different than thos contributed by either parent= recombinant

replicated chromosome vs non replicated

non replicated: single chromosome replicated : single chromosome, with two identical chromatids= sister chromatids

complete dominance:

only phenotype of dominant allele is expressed, bc presence of one functional allele is sufficient to provide neededfunction

describe process of gametogenesis: females:

oogenesis: limited amounts of eggs available= restricted to embryonic stage= set amount of germ cells set aside female germ cell (diploid)----mitosis---> oogonium (diploid)---mitosis---> primary oocyte (diploid)----1st meiotic division--->secondary oocyte + first polar body --- second meiotic division---> ootid (haploid) + second polar body +first polar if present---- differentiation and growth= ovum + polar bodies degrade maturity from adult to embryo during the 1st instance of meiotic division

Explain how a cell can make a macromolecule such as a lipid from its glycerine and fatty acid subcomponents using the information that is stored in genes along a stretch of a DNA molecule.

our genome encodes information on how to make proteins DNA (genetic information stored here ) ---- (transcription in nucleus) ---> mRNA -----(translation in cytoplasm via ribosome) ----> polypeptide ----> fold into protein with specific function important to make enzymatic protein: crucial for catalyzying bodily reactions= answer to how we are able to specify what other kinds of molecules body can make = enzymes manufacture how to make = = macromolecules

co-dominance;

phenotype exhibits both phenotypic traits of either allele - both alleles yield functional (though different) proteins Ex: ABO a(blood)

incomplete dominance:

phenotype is an intermediate -this often results from an amount effect, where one functional allele cannot produce enough of its genes to produce the yield the "wild type" phenotypes

what is the pheontypic ratio of all possible phenotypes for a dihybrid cross : LlCc x LlCc

phenotypic ratio: 9:3:3:1

Be able to draw out ploidy of a cell

ploidy : the number of complete chromosome sets (types) in a cell #n=amount of chromsomes total n= distinct types of chromosomes #= number of set of types ex: Humans 2n=46 n= 23 (23 different types of chromosomes) 2 sets of each type =46 total chromosomes

Types of mutations:

point mutations: a mutation that alters the sequence of one or a small number of base pairs -silent= change in nucleotide sequence does not change the amino acid specified by a codon no change in phenotype, neutral with respect to fitness=NO EFFECT ON PROTEIN PRODUCT -missense= change in nucleotide sequence that changes the amino acid specified by codon change in primary structure of protein, may be beneficial , neutral or deleterious= PROTEIN PRODUCT ALTERED< BUT DIFFERS IN SEVERITY -nonsense= change in nucleotide sequence that results in an early stop codon leads to mRNA breakdown or a shortened polypeptide= usually deleterious= FINAL PROTIEN PRODUCT IS TRUNCATED (shortens) -frameshift mutations= addition or deletion of a nucleotide reading frame is shifted , altering the meaning of all subsequent codons= almost always deleterious, unless deleted/inserted 3 bases= just removing one codon= one amino acid =VERY SEVERE EFFECT ON PROTEIN PRODUCT chromosomal mutations: permanent changes in the DNA -changes in chromosome number --results from mistakes in moving chromosomes into daughter cells during meiosis or mitosis -- polyploidy and aneulploidy don't change DNA sequences but do cause permanent change in organism's DNA by altering the number of copies of each sequence --the formation of polyploids play a major role in the evoluton of many species (paricularly plants) -changes in chromosome structure: -deletion- breaks in chromosomes ; common- a broken segment may become lost= results in deletion -inversion- segments of a broken chromosome may be flipped and rejoined -duplication- errors in crossing over or in DNA synthesis can lead to the presence of one or more additional copies of segments= creates families of related genes -translocation = a broken piece of chromosome can become attached to a different chromosome

Mutations are the result of mistakes in __________________

replication

indels (insertions/deletions)

segments of DNA (one or more bases in length) are inserted or deleting =results in a frameshift mutation

what ploidy are prokaryotes or eukaryotes?

prokaryotes (some eukaryotes) = haploid =one copy of each chromosome type eukaryotes: most are diploid , some are polyploid (more than 2)

which of the following 3 models correctly represents the relationship between newly replicated and old DNA after DNA replication: semi conservative: would produce two copies that each contained on of the original strands and one new strand conservative: would leave the two original template DNA strand together in a double helix and would produce a copy composed of two new sstrands containing all of the new DNA base pairs dispersive replication: would produce two copies of DNA both containing distinct regions of DNA composed of either original strands or both new strands:

semi-conservative -DNA is replicated by separating the two complementary strands via DNA polymerase --> and then creates a new complementary strand from free nucleotides for each of the two separated strands

need to remember: what is overall sequence of events during course of mitosis and the consequences of all of these events : on genetic material (parent cell vs. daughter cell) (don't need to remember exact phase or anything like that )

sequence of mitosis (and consequences in bold) after interphase --- > chromosomes are replicated, long ,spread out- also held at centromere region together---> enter mitosis ----> chromosomes begin to condense down (1st instance of visibility )---> machinery that will pull them apart (spindle apparatus) = centrosome= moves to opposite poles ----> nuclear envelope starts to breakdown so microtubules can enter near that area---. microtubules start growing from centrosomes that have now reached poles----> microtubules have found centromeres of chromosomes that hold chromatids together and attach with help of protein that attaches to spindle fibers ----> one microtubule will attach on either side of chromosome to both poles---> if there is any chromosome that has not enough or none spindle fibers attached to it is sensed by a protein complex that signals mitosis to stop before it pulls chromosomes apart =fail safe to make sure that each daughter cell has the correct amount of identical chromatids --- after last checkpoint---pull them apart ---> chromatids are split apart and spindle fibers are pulled back to either sides ----> sister chromatids ---become single chromosomes themselves/ non replicated now--> now each daughter cell will have identical genetic material (same number of replicated copies) if no mistakes--> start pinching off, nuclear envelope reforms around both sets of chromosomes---> cytokinesis completes = two daughter cells that are hopefully genetically identical

autosomal chromosomes vs. sex chromosomes

sex chromosomes: chromosomes that differ in shape or in number in males vs females ' autosomals: any chromosome other than sex chromosomes

where do you find mitosis in nature?

simplest form of reproduction- asexual -simple cell division

How would it be possible for a bacteria to obtain two different beneficial mutations?

since bacteria is an asexual reproductive organism, there would have to be two separate mutation events that are both beneficial (which is rare) = would take a long time for this to occur during mitosis mitosis= ineffective in obtaining beneficial mutations to promote genetic variation

explain what the trade offs is that may have posed some individuals to produce very large gametes (ova) and others very small gametes with a flagellum (mobile tail) -selection pressure that may have led to the origin of the two different sexes with different phenotypes in the same speicies: (what is origin of two sexes?)

sperm: flagellum to swim to egg egg: larger target= more likely actually be "hit" (lots of energy to make) both need to swim in aq. medium, if have a large gamete= hard to move thru aqeuos environmet = hard to get a successful reproductive event

what issue would you run into if we simply keep merging cells through fusing them together, over and over again?

the number of homologs of each chromosome type would double every generation this is why we need reduction division done thru meiosis

explain how the steps of mitosis guarantee that the 2 daughter cells that are produced after cytokinesis are genetically identical copies of the original parent.

the steps of mitosis: -failsafe before pulling chromatids apart: make sure each chromosome has a microtubule attached on either side of centromere if not : signal to stop next phase of anaphase

why are the phases of mitosis fairly arbitrary or unpredictable?

there is a continous range of motion during mitosis no stops between phases use phases to make it easier to study

what is the function of sexual reproduction?

to increase genetic diversity

a true breeding culture can only exclusively consist of each one of which of the following genotypes:

true breeding lines: AA , aa

codons are :

unambiguous: a codon never codes for more than one amino acid redundant: amino acids can be encoded by more than one codon non overlapping: always in sets of three conservative: several codons specify the amino acid= the 1st two bases are usually identical

only ________________ genes (genes with gene loci on different chromosome types) should independently assort.

unlinked

why are both unreplicated and replicated chromosomes considered a single chromosome?

unreplicated : one chromosome strand = chromatid replicated : two identical chromosomes attached at centromere= sister chromatids= since attached and can move as one unit= considered a single chromosome

What kind of cross may help determine the unknown genotype of a dominant phenotype?

using a test cross= crossing a fly of unknown genotype with a homozygous recessive , A__ x aa = ratio of phenotypes if A____= Aa= then phenotypic ratio will be 1:1 AA = then phenotypic ratio: 1:0