unit 3 - genetics

why is mendel's success attributed to his use of peas

- allowed for the observation of simple characteristics (ie. pea color) - peas reproduce quickly (allowing for data collection for multiple generations) - reproduction could be controlled (mendel could cross the peas)

process of DNA sequencing using dideoxy-nucleotides

1. DNA sample is taken and chopped into fragments using restriction enzymes. each fragment is then copied using PCR. 2. a primer is then added to each fragment copy's sequence so that DNA polymerase can add free-floating nucleotides to create its complementary strand. 3. next this reaction mix is added to separate tubes with dideoxynucleotides pertaining to specific nitrogeneous bases (ddA, ddT, ddC, ddG). these nucleotides are missing oxygens on carbons 2 and 3, inhibiting polymerase from being able to add to the sequence once one is randomly reached (sometimes chain termination occurs all the way at the end of the fragment, sometimes at the beginning etc...) 4. then these multiple chains of varying lengths are separated in electrophoresis from longest to shortest. 5. each of the four dideoxynucleotides fluoresces a different color (corresponding with its base) when illuminated by a laser at the end of the electrophoresis chamber. an automatic computer scanner provides an electrogram of the sequence, allowing scientists to line up overlapping segments to map DNA or align its sequence.

describe the process of creating a karyogram

1. cells are harvested (usually from a fetus or white blood cells of adults) 2. cell division is chemically induced. Then mitosis is arrested at metaphase when the chromosomes are condensed + have utmost visibility. 3. chromosomes are immersed in a hypotonic solution that will cause them to swell up for even more visibility. 4. chemicals are used to stain the DNA so that the chromosomes are identifiable under a microscope. 5. with a camera, various photographs are taken of mitotic plates in which the chromosomes are visible.

describe cairns technique for producing images of DNA molecules from e-coli.

1. cells were grown in a culture with the presence of radioactive thymine. cells replicated until the radioactive thymine was present in their DNA. 2. a radioactive sensitive film was placed over the sample so that the radioactive emissions from the DNA would expose the film and create an image of the DNA.

biological research traits pioneered by mendel

1. qualitative results 2. repeated experiments to demonstrate reliability of results (tracked 7 generations) 3. various trials (tracked 7 traits)

state the minimum chromosome number in eukaryotes

2 chromosomes (because the fusion of two haploid cells during fertilization leads to a diploid zygote cell)

state two similarities and two differences between male and female gametes

2 similarities: haploid, created through meiosis 2 differences: male: smaller, female: larger, male: mobile, female: stationary

state the human haploid cell number

23

size in base pairs of the human genome

3,000,000,000

state the human diploid cell number

46

outline the inheritance of C.F.

C.F. is inherited in an autosomal recessive pattern (not on a sex chromosome + needs two mutated alleles to show disease symptoms).

describe the selectivity of PCR

PCR is able to select specific areas to amplify. it is not used to copy the entire set of DNA molecules but is used to copy specific DNA sequences. (a sequence is selected for copying by using a primer that binds to the start of the described sequence. the primer binds by complementary base pairing.) the selectivity of PCR allows particular desired sequences to be copied from a whole genome or even greater mixture of DNA.

describe the mechanism by which the SRY gene regulates embryonic gonad development

SRY gene is present only in the Y chromosome. SRY is a transcription factor which triggers the development of seminiferous tubules in the gonads. presence of the SRY genes means that the gonads will turn into testes, which then secrete testosterone. absence of the SRY gene means the gonads become the ovaries.

outline Thomas Morgan's elucidation of sex linked genes with Drosphila

Thomas Morgan studied the genetics of the fruit fly, or drosophila. he is credited with the discovery of sex linked traits; traits that appear to associate differently in males and females. flies normally have red eyes but there was a mutant male with white eyes. all offspring of the initial generation were red eyed, suggesting that red is dominant over white, and then in the subsequent generation only males had white eyes, suggesting white is carried on an X chromosome.

outline the structure and function of the two human sex chromosomes

X chromosome = heterosome without the SRY gene. In the absence of the SRY gene, female sex organs will develop. Y chromosome = heterosome with the SRY gene → gene for testicular development + formation of the male gonads

describe why it is not possible to be a carrier of a disease caused by a dominant allele

a carrier is an individual who carries the disease but does not show any symptoms. if the disease is due to a dominant allele, the individual would show the symptoms of the disease because dominant alleles mask the traits of recessive alleles.

mutation

a gene mutation is a change in the nucleotide sequence of a section of dna (influencing a specific trait). new alleles are caused by mutation.

define carrier as related to genetic diseases

a genetic "carrier" is an individual (or other organism) that has inherited a recessive allele of a gene but does not display the symptoms of the disease because they also have the dominant (normal functioning) allele. they must be heterozygous.

define gene

a heritable factor that is a segment of DNA and influences a specific characteristic.

describe the relationship between the genetic cause of cystic fibrosis and the symptoms of the disease

a mutation in the CFTR gene causes cystic fibrosis. this gene codes for a transport protein that regulates the movement of chlorine and water in and out of cells. If the gene is mutated, the resulting protein has a slight change in shape that limits its proper function, preventing it from regulating the flow of chlorine ions + water across the cell membranes of cells that line the lungs and pancreas, resulting in respiratory failure and pancreatic cysts: symptoms such as lung infections, breathlessness, wheezing, persistent coughs AND bowel difficulty/poor growth.

define homologous

a pair of chromosomes in which one is from the mother and one is from the father.

PMAT of meiosis II

a second growth phase called interkinesis may occur between meiosis I and II, however no DNA replication occurs in this stage. prophase = chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles, new spindle fibers begin to form. metaphase = spindle fibers attach to chromosomes (at centromere) and align them along the cell equator. anaphase = spindle fibers contract and separate the sister chromatids, chromosomes move to opposite poles. telophase = chromosomes decondense, nuclear membrane reforms, cells divide (cytokinesis) to form four haploid daughter cells. these cells may all be genetically distinct if crossing over occurs in prophase I (causes recombination of sister chromatids)

define allele

alleles are alternative forms of a gene that code for different variations of a specific trait (ie. of the same gene + of the same locus) ex: hair color gene (brown, red, blonde, black) ex: eye color gene (brown, blue, green, grey)

natural methods of cloning in plants and animals

animals: monozygotic twins (either of human zygote dividing into two cells that develop into separate embryos or an embryo splitting into two parts where each divide into a separate individual). fragmentation - (starfish, if damaged able to regenerate a whole body from one leg). binary fission - organisms such as flatworms are able to split themselves into two to create two genetically identical organisms from one. plants: runners = organisms such as strawberries send out horizontal structures from which genetically identical clones can form. tubers = organisms such as potatoes form bud-like organisms from which genetically identical organisms can grow and develop.

list example sources of DNA that can be used in DNA profiling

any DNA containing tissue/body fluid - cheek cells - blood - skin - hair - semen

outline the formation of a diploid cell from two haploid gametes

as sexually reproducing organisms receive genetic material from both parents, they have two sets of chromosomes (diploid cells). to reproduce, these organisms must create sex cells (gametes) with half the number of chromosomes (haploid). when two haploid gametes fuse, the resulting diploid cell (zygote) can grow and develop into a new organism.

effects of mutations of protein structure

base substitutions = silent, missense, nonsense mutations 1. silent = DNA change does not alter protein produced (genetic code is degenerate, codons code for the same amino acids) 2. missense = DNA change alters one amino acid within chain of proteins produced (sickle cell anemia). 3. nonsense = DNA change creates a premature STOP codon which truncates the polypeptide. insertions/deletions = frameshift mutations 1. frame shit = every codon beyond the point of mutations is changed (because amino acids are derived by codon, the reading frame shifts)

explain why the typical number of chromosomes in species is always an even number

because chromosomes exist in homologous pairs (one from mom and one from dad)

define bioinformatics

bioinformatics is the use of mathematics and computer science to store, retrieve, and analyze biological data

define bivalent, synapsis, and chiasmata

bivalent: groups of homologous chromosomes formed through synapsis chiasmata: points at which the homologous chromosomes are held together/come into contact

compare meiosis II with mitosis

both meiosis II and mitosis separate replicated sister chromatids to opposite poles of the cell and divide through cytokinesis. however meiosis involves haploid cells (half of the genetic information) and mitosis involves diploid cells (full genetic information) the end result is also different - four haploid cells v.s. two diploid cells

outline the formation and use of bt crops in agriculture

bt corn is derived from inserting a protein that kills insects into a soil bacterium to produce bt crystals which are then inserted into the corn plants DNA. bt crystals are toxic to caterpillars and are now produced by the corn plant/are present in its cells, reducing the amount of pesticides needed to be used by farmers.

outline the function of the buffer, the marker, and the loading dye in gel electrophoresis

buffer = has a high ion count, so the current is easily carried around the gel sheet and allows the different bands to move marker = a known sample: it contains many DNA fragments of known lengths and acts as a point of comparison from which the scientist can compare sample fragment sizes to ensure the process has been done correctly. loading dye = to make the bands visual to the human eye + to add density to ensure the DNA sinks through the well and into the gel, ultimately helping separation to occur.

describe the causes and symptoms of down syndrome

causes = down syndrome is most often caused by trisomy 21, a condition where there is an extra chromosome number 21. the extra chromosome is the result of nondisjunction during meiosis, which leaves a sperm or egg cell with an extra chromosome. symptoms = this condition leads to cognitive and physical impairments that result in mild to moderate disability.

animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells

cells are separated from the fertilized growing embryo of an animal (undifferentiated cells), split into various groups of cells, and then placed in the uterus of a female of that species to create artificial twins, triplets, quadruplets etc... depending on how many cells were divided.

define haploid

cells posessing only one set of chromosomes

define diploid

cells possessing pairs of homologous chromosomes (half genetic material from mom, half from dad)

state two consequences of chiasmata formation between non-sister chromatids

chiasmata formation between non-sister chromatids results in increased stability of bivalents. chiasmata formation between non-sister chromatids that creates a stable bivalent can result in the exchange of alleles.

list mechanisms by which a species chromosome number can change

chromosome splitting + chromosome fusing

outline eukaryotic chromosome structure

chromosomes carry the genetic information necessary for the cell to exist. when the cell is not dividing, chromosomes are not visible - the cell's DNA is in the form of chromatin, or strands of DNA. chromatin refers to unfolded DNA wrapped twice around nucleosomes, or two molecules, each of four different histones.

list three events that occur in prophase I

chromosomes condense (condensation/coiling) nuclear membrane dissolves homologous chromosomes form bivalents/tetrads (groups) crossing over (exchange of genetic material at specific points called chiasmata occurs)

explain sickle cell anemia as an example of a genetic disease caused by co-dominant alleles

codominant = when both alleles of a gene in a heterozygote are expressed. sickle cell anemia = disease where blood cells become thin and elongated. if a person has one copy of the sickle cell allele (heterozygous dominant), half of their cells remain able to carry enough oxygen (codominance) so no symptoms of the disease are shown. however if a person has two copies of the sickle cell allele (homozygous dominant), symptoms of the disease are shown as none of their blood cells carry enough oxygen.

using the correct notation, outline an example of co-dominant alleles

correct notation = two different capital letters are used and placed as superscript to a common letter that represents the name of the gene. see blood type + chickens example above.

outline the process and result of crossing over

crossing over = during prophase I, homologous chromosomes may exchange pieces of DNA material between non-sister homologous chromatids. this results in new combinations of genes, creating "recombinant chromosomes."

list five example genetic diseases

cystic fibrosis (autosomal recessive) hemophilia (sex linked recessive) phenylketonuria/PKU (autosomal recessive) red-green color blindness (sex linked recessive) sickle cell anemia (autosomal codominant)

outline the process of PCR

denature: double stranded DNA is denatured by heating to 95 degrees celsius (separates it into two strands). anneal at approximately 60 degrees, primers anneal to complementary base pairs flanking the region of interest (temperature is cooled down so that DNA primers can attach to opposite ends of the target sequence, and initiate polymerization). extend at 72 degrees, Taq polymerase extends the single stranded DNA molecule creating new double stranded DNA (copying of the strands). This process is repeated for 25-35 cycles to amplify sufficient material for visualization.

define dominant and recessive allele

dominant alleles show their effect even if the individual is heterozygous, they can mask the presence of another allele recessive alleles only show their effect if the individual is homozygous, otherwise their presence is masked by a dominant allele

describe the use of a karyogram to diagnose down syndrome

down syndrome is a condition whereby the individual has three copies of chromosome 21. it is caused by a non-disjunction event in one of the parental gametes. the extra genetic material causes mental and physical delays in the way the child develops.

describe random orientation/independent assortment of chromosomes during meiosis

during metaphase of meiosis I, all homologous chromosomes line up at the equator as bivalents in one of two arrangements: maternal copy left /paternal copy right OR paternal copy left /maternal copy right this orientation of pairs of homologous chromosomes is random, as is the subsequent assortment of chromosomes into gametes - each allele on a chromosome has the same chance of being paired with/separated from any allele on another chromosome: the orientation of one homologous pair does not affect the orientation of any other homologous pairs. the final gametes will differ depending on whether they received the maternal or paternal copy of a chromosome following anaphase I this random orientation occurs for each homologous pair, meaning the number of possible gamete combinations is dependent on the number of homologous pairs 2 ^ the number of haploid chromosomes = number of possible gamete combinations if crossing over also occurs, the number of different gamete combinations becomes immeasurable

describe how and why DNA fragments separate during electrophoresis

electrical current of DNA is negative due to phosphate groups found in DNA. the electrical current run through the gel has a positive end and a negative end. therefore, the DNA is attracted to the positive end, and pushes small bands further (move quicker through electrical current) than longer bands (move slower through electrical current) proving a visual separation of DNA fragments by size.

outline potential environmental, health and agricultural benefits and risks associated with genetic modification of crops.

environmental benefits: pest-resistant crops = less spraying of insecticides/pesticides, less fuel burned in management of crops, longer shelf-life for fruits and vegetables --> less spoilage, greater quantity/shorter growing time/less land needed environmental risks: GMO encourages monotony among species and reduction in biodiversity, non-target organisms can be affected health benefits: increase in nutritional value, could be altered to provide disease resistance health risks: effects of influence to GMO exposure are unclear

outline gender determination by sex chromosomes

females tend to possess two X chromosomes and males tend to possess one X and one Y - the absence/presence of the SRY gene is what leads gonads (either testes or ovaries) to develop. the male can pass on either the Y or the X *gender depends on whether the sperm which fertilizes the egg is carrying an X or a Y chromosome if the male passes on the X = girl, Y = boy

match restriction enzymes to the bacteria in which they are naturally found

first couple of letters should line up with bacteria species: ecor1 = e coli

differentiate between gamete and zygote

gamete = sex cells (haploid) zygote = fused sex cells (now diploid)

explain how meiosis leads to genetic variation in gametes

genetic variation = a term used to describe the variation (differences) in the DNA sequences in each of our genomes. meiosis can lead to variation in DNA sequence combinations. 1. crossing over - involves the exchange of segments of DNA between homologous chromosomes during prophase I, occurs between non-sister chromatids at points called chiasmata. as a consequence all four chromatids that comprise the bivalent will be different, offspring with recombinant chromosomes will have unique genetic combinations unseen in either parent. 2. independent assortment of chromosomes/random orientation - when homologous chromosomes line up in metaphase I, their orientation towards the opposing poles is random. the orientation of each bivalent occurs independently, meaning different combinations of maternal/paternal chromosomes can be inherited when bivalents separate in anaphase I. random fusion of gametes/fertilization - sperm meeting egg is a randomized process. there are billions of possible chromosome combinations between the genetic material of sperm and the egg, allowing for immense genetic variation, or differences in the DNA sequence/genotypes to occur between zygotes.

assess the risks and benefits of an example of a genetically modified crop (i.e. golden rice)

golden rice = genetically modified to include beta carotene as a nutrient which is converted into vitamin A in the body benefit: provides vitamins to those in nutrient deficient areas (prevents vitamin a deficiency which can cause blindness), ability to provide specific nutrients to those who lack. risk: lack of awareness of potential environmental and health risks, beta carotene levels might not be enough to make an impact, can cross breed + unintentionally influence wild rice (outside target species).

clones (+ differentiate between types of human induced cloning)

groups of genetically identical organisms, derived from a single parent cell. therapeutic cloning: making copies of embryonic stem cells reproductive cloning: making copies of entire organisms

describe the causes and effects of hemophilia

hemophilia is caused by a mutated allele of a gene that codes for a protein essential in the blood clotting process. without proper clotting (as a result of the gene's impact), excessive bleeding often occurs.

explain inheritance patterns of hemophilia

hemophilia is x-linked recessive (gene on the x chromosome: xH = normal, Xh = hemophilia)

outline the possible combinations for a gene w/ two alleles

homozygous dominant - two copies of the dominant allele (ie. AA) heterozygous - one copy of the dominant allele and one copy of the recessive allele (ie. Aa) homozygous recessive - two copies of the recessive allele (ie. aa)

explain the relationship between the number of human and chimpanzee chromosomes.

humans have 46 chromosomes and chimpanzees have 48. research has suggested that the chimpanzees' chromosome pair #2 merged into 1 human chromosome through chromosome fusion (the centromeres, genes, and banding patterns of the chimp chromosomes match those of the one human chromosome).

outline the inheritance pattern of huntington's disease

huntington's is inherited in an autosomal dominant pattern (not on a sex chromosome + needs only one mutated alleles to show symptoms).

deduce the sex of an individual given a karyotype

identification of the sex determination chromosomes - y = shorter than x, two x = female, one x one y = male.

given the parent genotypes, determine the allele possibilities due to independent assortment and random orientation (for two alleles of a gene, A and a)

if there were two alleles of a gene, A and a, the zygote could contain two copies of either allele or one of each. the three combinations are AA, Aa, and aa.

describe the role of restriction enzymes in nature and in biotechnology applications

in nature: restriction enzymes are present in bacteria for them to defend themselves and to cut apart foreign DNA molecules (such as protection from bacteriophages) in biotechnology: repurposed for use in biotechnology and in genetic engineering as they allow DNA to be cut in areas of specific base pair sequences (restriction sites, or 4 to 6 base pair sequences that are palindromes). ex: used in gel electrophoresis. restriction sites.

explain uses/applications of DNA profiling

in paternity suits when the identity of the biological father is required for legal reasons in forensics, samples containing DNA can be taken and compared with suspects to identify behavioral patterns and relationships between animals

sickle cell anemia (gene mutation, effect on protein structure and function)

in sickle cell anemia, the GAG on the non-coding strand is switched to GTG. this changes the mRNA codon read, and consequently changes the glutamic acid within the polypeptide chain to valine, ultimately shifting the structure of the hemoglobin protein and the shape of red blood cells. while this protein typically assumes a disc-like shape, with this mutation it becomes thin and sickled, making the transport of oxygen highly difficult for the impacted individual and leading them to feel excess fatigue. this structure also clogs up capillaries, inflicting great pain. sickle cell anemia is an example of a missense mutation, in which the substituted base leads to a difference in the structure and later function of a cell.

outline inheritance patterns of genetic diseases caused by dominant alleles

in the case of a disease caused by a dominant allele, only one copy of the disease allele is needed for the individual to express the disease phenotype. if one parent is homozygous dominant, there is a 100% chance the child will inherit the disease. if one parent is heterozygous dominant, there is a 50% chance the child will inherit the disease.

list the characteristics by which chromosomes are arranged on the karyogram

individual chromosomes are paired up according to size and banding pattern. larger chromosomes (#1-5) are arranged on the top row, and in order of descending size, four more rows are constructed with the paired chromosomes. after the 22 pairs of autosomes have been organized, the sex chromosomes are seen at the bottom right of the karyotype.

outline the benefits of using gene transfer technology in the production of pharmaceutical insulin.

large quantities of the protein can be produced for treating diabetes in humans, relatively quickly (due to rapid growth of bacteria) lack of ethical concerns and allergy concerns that were evident in previous method (harvesting it from animal carcasses)

compare divisions of meiosis I with divisions of meiosis II

meiosis I = preceded by DNA replication, crossing over occurs, reductive division (diploid to haploid), results in two haploid cells. meiosis II = not preceded by DNA replication (interkinesis, which has no DNA replication), no crossing over, non-reductive division, results in four haploid cells.

explain why most genetic disorders are rare in a population

most genetic diseases are caused by alleles that are uncommon in the population. if you have a heterozygous parent with a dominant disease allele, the chance of inheriting one allele (and the disease) is 50%. in the case of a recessive disease, a person must inherit one copy of the rare allele from each parent.

define nondisjunction + explain how it may occur.

nondisjunction refers to the chromosomes failing to separate correctly, resulting in an abnormal number of chromosomes in the daughter cells - gametes with one extra, or one missing, chromosome (aneuploidy) it may occur via: failure of homologous pairs to separate in anaphase I (resulting in four affected daughter cells), failure of sister chromatids to separate in anaphase II (resulting in only two daughter cells being affected)

explain why genetic diseases usually appear unexpectedly in a population

oftentimes genetic diseases seem to appear in a family without prior history. this is typically because the disease is caused by a recessive allele that has been masked by dominant alleles. if two carriers, who show no disease symptoms mate, there is a ¼ chance of the offspring showing disease characteristics.

state that the chromosome number and type is a distinguishing characteristic of a species

organisms with different numbers of chromosomes are unlikely to be interbred (different sizes, different gene loci). therefore all interbreeding members of a species need to have the SAME # of chromosomes.

analyze a dna sample to determine relatedness or forensic guilt

paternity/Maternity = 50% of DNA bands should correspond with each parent forensic guilt = to determine that a crime has been committed, around 50-100% of the DNA should correspond to the crime scene depending on the type of crime committed + what other data you are presented with (victim's DNA)

outline conclusions drawn from the images produced using cairns autoradiography technique

previously, chromosome length could only be measured while condensed during mitosis (very inaccurate due to supercoiling). cairns used autoradiography to visualize the chromosomes whilst uncoiled, allowing for more accurate indications of length. he was also able to deduce that prokaryotic DNA is circular and provide evidence that replication is bi-directional (radioactive DNA extends from both directions).

outline the source of pharmaceutical insulin prior to the use of gene transfer technology

prior to the use of gene transfer technology, pharmaceutical insulin was obtained by extracting animal insulin from cow and pig carcasses. however this caused allergy problems as well as raised ethical questions regarding the treatment of animals. utilizing recombinant human DNA avoids these issues.

PMAT of meiosis I

prophase = chromosomes condense/coil, nuclear membrane dissolves, homologous chromosomes form bivalents/tetrads (groups), crossing over (exchange of genetic material at specific points called chiasmata) occurs , spindle fibers begin to form metaphase = spindle fibers connect to bivalents/tetrads (at centromeres) and align them along the middle of the cell anaphase = spindle fibers contract and split the bivalents, homologous chromosomes move to opposite poles of the cell telophase = chromosomes decondense/uncoil, nuclear membrane may reform, cell divides in cytokinesis to form two haploid daughter cells

describe the cause and effect of red-green color blindness

red green color blindness is caused by a sex-linked recessive allele of a gene that codes for a protein (opsin - found on cone cells in the retina of the eyes) that is sensitive to particular wavelengths of light. the recessive allele (or mutation) causes color vision differences (causes individuals to have trouble distinguishing between red, greens, and yellows.)

explain inheritance patterns of red-green color blindness

red-green color blindness = x-linked recessive (on the x chromosome, males only need one mutated allele to express color blindness phenotype, females need two mutated alleles to express).

meiosis I

reduction division (diploid → haploid) in which homologous chromosomes are separated preceded by interphase, in which DNA is replicated to produce chromosomes consisting of two sister chromatids.

explain the function and purpose of gel electrophoresis

restriction enzymes are used to chop-up the long DNA fragments into smaller fragments. DNA fragments are placed in wells at one end of a sheet of gel which is then hooked up to an electrical current (positive on one end, negative on the other). the result is a DNA profile in which DNA fragments are ordered by size (as longer fragments become entangled on their travel to the positive end and shorter ones travel freely).

how are alleles the same/different

same: same gene, code for the same protein w/ the same role in the cell, occupy the same locus on homologous chromosomes. different: differ by one to two bases (one difference is called an SNP), several SNPS can be present in one gene

diagram the process and result of crossing over

see image

draw PMAT I and II

see image

define sex linkage

sex linkage refers to when a gene controlling a characteristic is located on a sex chromosome (X or Y)

compare sexual and asexual life styles

sexual: - sexual reproduction involves genetic input from two parents. - most sexually reproducing organisms are diploid, meaning they have two copies of each chromosome (1 maternal, 1 paternal). - in order to reproduce, these organisms must make cells that are haploid (or have one copy of each chromosome). - fertilization of two haploid gametes (egg + sperm) results in the formation of a diploid zygote that can grow via mitosis. - if the chromosome number was not halved in gametes, the total number of chromosomes would double each generation (polyploidy). asexual: - an organism clones itself to make a genetically identical offspring, only requires genetic input from one parent. - any reproductive process that is not dependent on meiosis = asexual - prokaryotes + single celled eukaryotes reproduce by binary fission (involves the single parent cell dividing into two daughter cells) - multicellular eukaryotic organisms can also reproduce by budding, in which a part of the parent body is pinched off to create a clone.

state an example of a dominant and recessive allele found in pea plants

shape of seeds: dominant = round, recessive = wrinkled

identify sticky and blunt ends, as well as contrast them

similarities: the way they function is the same = both have to recognize the palindrome/specific sequence, both use enzymes to break bonds of backbone differences: blunt cut cuts straight through, sticky cut is a open/hanging cut which results in exposed bases

state a similarity and a difference between pairs of homologous chromosomes

similarity = same structural features (same size, same banding patterns, same centromere position) difference = origin (one from mom one from dad) + while genes are the same, the alleles may be different

methods have been developed for cloning adult animals using differentiated cells

somatic cells are taken from a donor adult animal and collected/cultured. an unfertilized egg is collected from another donor adult animal and its nucleus is removed. using an electrical current, the egg and nucleus from the cultured somatic cell are fused together. the new cell develops similarly to a zygote and begins to form an embryo. the embryo is placed in the womb of a female surrogate of the same species to develop. (ex: dolly, first clone whose genetical material did not originate from an egg cell)

list example haploid cells

sperm and egg

list effects of Huntington's disease on an affected individual

symptoms of Huntington's disease develop between the ages of 30 and 50. - uncontrolled movements - decline in cognition - loss of memory - changes in mood

explain the use of taq DNA polymerase in the PCR

taq DNA polymerase = found in yellowstone national park, is able to withstand protein denaturing conditions and therefore is resistant to the high temperatures/shifting temperatures needed to undergo the process of PCR. it functions like DNA polymerase and synthesizes the opposing strand of both strands of the original DNA molecule, creating two semi-conservative double helices using free floating nucleotides.

state the function of PCR

technique utilized to rapidly amplify/make copies of a specific DNA sample allows scientists to make various copies of a small fragment of DNA for studying

define test cross, true breeding, and F1

testcross = a genetic cross between two individuals tracking one gene of interest (done with known homozygous recessive) true-breeding = organisms that have been bred to have a homozygous genotype F1 = the offspring of the parent generation cross (generation 1)

identify tetrads/bivalents, sister chromatids, and non sister chromatids in diagrams of replicated chromosomes

tetrads/bivalents = through synapsis, homologous chromosomes pair up to form larger groups (bivalents or tetrads). groups are referred to as tetrads because they are each composed of four chromatids, groups are referred to as bivalent because each group is composed of a homologous pair. sister chromatids/non-sister chromatids = sister chromatids are held together by a centromere, and are identical to one another

describe ABO blood types as an example of complete dominance and codominance

the ABO blood groups are determined by a single gene (I). the gene codes for an enzyme protein that modifies the carbohydrate molecule attached to an antigen protein on the surface of red blood cells (glycoprotein). the I gene has three different alleles. IA = codes for an enzyme that attaches galactosamine to RBC antigens IB = codes for an enzyme that attaches galactose to RBC i = codes for inactive protein alleles A and B are completely dominant over allele i IAi = type A IBi = type B alleles IA and IB are codominant so both are expressed in a heterozygous individual - IAIB = type AB, ii = type O

explain the relationship between parental age and chances of non-disjunction

the age of a parent (particularly of the mother) is positively associated with the chance of a nondisjunction event.

state the usual cause of one allele being dominant over another

the cause of allele dominance is complex and can vary between genes. However, in general, dominant alleles code for functioning proteins and recessive alleles code for less/non functioning proteins.

what was the human genome project and what were its outcomes

the human genome project was an international collaborative effort to map and sequence the DNA of the entire human genome. outcomes: complete sequencing of the human genome (the number, location, size and sequence of human genes is now established), find evidence for evolutionary relationships/origins/ancestors by comparing human to other genomes, the discovery of genes that cause diseases (production of specific gene probes to detect sufferers and carriers of genetic diseases).

assess the impact of bt corn on monarch butterflies

the larvae of the monarch butterfly feed on leaves of milkweed. this plant sometimes grows close enough to corn crops to become dusted with the wind-dispersed corn pollen. there is therefore a risk that monarch larvae might be poisoned by Bt toxin in pollen from GM corn crops, which could lead to the indirect killing of monarch butterflies as a result of BT corn.

outline prokaryotic chromosome structure

the nucleoid region of a bacterial cell contains a single, long, continuous, circular thread of DNA. they reproduce asexually = only have one chromosome. in addition to chromosomal DNA, many prokaryotes have plasmids, small loops of DNA that are not connected to the main bacterial chromosome.

explain why the chromosome number of a species does not indicate the number of genes in the species

the number of chromosomes in a species has no significance in terms of the size of its genome - the size of chromosome differs from species to species

define gene locus

the part of a chromosome on which a gene is located

meiosis II

the second division separates sister chromatids (these chromatids may no longer be identical due to crossing over in prophase I)

explain why meiosis must occur as a part of a sexual lifestyle

the sexual life cycle requires genetic information from two parents. in order to maintain the same number of chromosomes in each offspring, the parents must undergo meiosis to create gametes with half of the genetic information that will fuse with the gametes of the opposite sex to create a zygote with the same amount of genetic information.

outline how the universality of the genetic code allows for gene transfer between species

the transfer of genes from one species to another is known as genetic modification. it is possible because the genetic code is universal, so when genes are transferred between species, the amino acid sequence translated from them is unchanged and the same polypeptide is produced. (genes have been transferred from eukaryotes to bacteria. one of the early examples was the transfer of the gene for making human insulin to a bacterium. this was done so that large quantities of this hormone can be produced for treating diabetics.)

define genome

the whole of the genetic information of an organism

describe the pattern of inheritance for sex-linked genes

there are many X-linked genes: in the vast majority of cases, the dominant allele codes for the normal condition, and the recessive codes for the disease/disorder. because men only have one X chromosome, recessive genes on the X must be expressed in the male phenotype. in females, a recessive gene on one X chromosome can be masked by a dominant allele on the other X chromosome, however all males who possess a recessive gene will express the traits of the disease. this explains why females can be carriers for X-linked diseases as well as why X-linked diseases are more often observed in males.

outline the possible combinations for a zygote with three alleles

though many genes have more than two alleles within the population, within a diploid individual there can only be two alleles. ie. in ABO blood typing there are three common alleles for the isoagglutinogen gene: the A and B alleles are co-dominant and each modify the structure of the antigen to produce different variants, the O allele is recessive and does not modify the basic antigenic structure. an individual may only have any combination of two of the alleles: blood type a = IA IA or IA ii blood type b = IB IB or IB ii blood type AB = IA IB blood type o = ii

describe mendel's pea plant experiment

through the selective breeding of pea plants, mendel discovered that certain traits show up in offspring without blending of the parent characteristics. mendel observed seven traits (ie. flower color/position, stem length, seed color/shape, pod color/shape) and concluded that genetic "units" of inheritance are passed from parent to offspring. the offspring inherits one "unit" from each parent for each trait. the "unit" may be masked or hidden (ie. recessive) in an individual but can still be passed on to the next generation. each gamete contains only one version of each factor (sex cells are now recognized to be haploid). parents contribute equally to the inheritance of offspring as a result of the fusion between randomly selected egg and sperm.

describe a technique for genetic modification including plasmids, restriction enzymes, reverse transcriptase, and ligase

transfer of eukaryotic genes into prokaryotes (gene splicing) 1. gene is isolated from the human genome, it is cut using a restriction enzyme (resulting in hanging sticky ends.) 2. plasmid is cut using the same enzyme, ensuring the sticky ends of the cut DNA are complementary to one another and can bind together. 3. gene is added to the plasmid. because sticky ends are complementary to the plasmid, they stick together and form hydrogen bonds. ligase is then used to connect the backbone of the two DNA sources together, creating a recombinant plasmid. 4. the recombinant plasmid is inserted into a bacteria cell. 5. the bacteria cell divides (binary fission). each time the cell replicates the plasmid also replicates. the gene is transcribed and translated until it can be harvested from the cells. example: production of human insulin to give to diabetic patients, spider skill gene so that large quantities of silk can be made for human use.

describe the two procedures for obtaining fetal cells for the production of a karyotype

ultrasound equipment - a hollow needle is inserted through the mother's abdomen into the uterus and amniotic fluid is used. chorionic villus sampling - a prenatal test in which a sample of placental tissue is taken and analyzed.

state two ways in which the risk of scientific can be assessed

what is the chance of an accident or other harmful consequence? how harmful would the consequence be?

define codominant alleles

with co-dominant alleles, two alleles are expressed equally; there isn't a masking of a recessive allele by a dominant allele. an example of co-dominance is feathering in chickens - black (CBCB) and white (CWCW) feathers create a speckled coat (CBCW)