Explain how cell division functions in reproduction, growth, and repair

As cells divide, they differentiate into different types of cells. As we grow, we increase the number of cells. They have to divide to replace the old cells in need of repair. 

Prokaryotic- cell division is for reproduction

Eukaryotic- reproduction and sexual reproduction

The DNA is copied and then two copies separated so that each daughter cell ends up with a complete genome.

List the phases of the cell cycle and describe the sequence of events that occurs during each phase.

Interphase- nuclear division:

G1-synthesizes proteins & lipids

S-DNA is replicated

G2- cell prepares for cell division

Prophase- mitotic spindle formed, centrosomes migrate to cell poles, chromosomes condense, nuclear membrane fragments, and metabolic activity decreases.

Metaphase- duplicate chromosomes form single line at the equator/middle of cell.

Anaphase- sister chromatids separate, and the chromosomes are pulled toward opposite poles by microtubules.

Telophase- chromosomes decondense and nuclear membrane starts to form

Cytokinesis- division of cytoplasm right after or during telophase. It pinches the two apart

Prophase- formed

Metaphase- pull the chromosomes toward the metaphase plate

Anaphase- pull the chromosomes apart and to opposite poles and disintegrate  Telophase- not present

Nonkinetichore microtubules elongate stretching the cell, making it longer and pull the chromosomes apart to opposite poles. They stretch to separate and shrink to pull them all together in metaphase.

Animals- the membrane pinches to separate

Plants- a plate is formed between the two 

Bacteria cells split into two halves. nder favorable conditions one bacterium would divide into two bacteria after about every 20 minutes. They have a single circular chromosome made of DNA. Binary fission will be completed.

Benign-not cancerous; grow only in one place

Malignant- cancerous; can spread throughout the body. Metastatic- a tumor that is malignant and tends to spread to other parts of the body. 

Distinguish between asexual and sexual reproduction.

Asexual- one specimen “clones” or make copies of itself Sexual- two gametes (sperm and egg) come together to produce a new specimen of half of each person. 

Haploid cells have half the number of chromosomes

Gametes are Hapliod

Diploid cells have full set of chromosomes.

All other cells are Diploid 

The DNA is copied and then two copies separated so that each daughter cell ends up with a complete genome

Bacteria cells split into two halves. Under favorable conditions one bacterium would divide into two bacteria after about every 20 minutes. They have a single circular chromosome made of DNA. Binary fission will be completed.

internal signal occurs at the M Phase checkpoint. Anaphase, the separation of sister chromatin does not begin until all of the chromosomes are properly attached to the spindle at the metaphase plate. this ensures daughter cells do not end up with missing or extra chromosomes.

external factor can be seen with the growth factor PDGF. Fibroblast, a type of connective tissue cell, have PDGF receptors triggers a signal that allows the cell to pass the G1 checkpoint and divide.

Somatic cells have a full set of chromosomes. (are diploid)

Gametes have half a set of chromosomes. (are haploid)

Autosomes are the somatic chromosomes which control the body characters or somatic characters, 

Sex chromosomes are the allosomes which determines sex of an individual.

Explain why fertilization and meiosis must alternate in all sexual life cycles.

Meiosis creates the cells needed for sexual reproduction

Fertilization must alternate with it because it needs those cells to reproduce.

Meiosis 1: reductional division

Prophase: synapsis occurs, mitotic spindle formed, centrisomes migrate to cell poles, chromosomes condense, nuclear membrane dissolves, and crossing over between homologous pairs possible.

Metaphase: pair of homologous chromosomes line up 

Anaphase: Pairs of chromosomes separated

Telophase: division finished

Meiosis 2:

Prophase: mitotic spindle formed, centrisomes migrate to cell poles, chromosomes condense, nuclear membrane dissolves

Metaphase: Chromosomes form single line at equator of cell

Anaphase: Duplicated chromosomes (chromatids) separate

Telophase: Nuclei made with half the chromosome # This creates 4 hapliods that are all different

 Describe the process of synapsis during prophase I and explain how genetic recombination occurs.

1.Synapsis and crossing over in prophase I: Homologous chromosomes physically connect and exchange genetic information
2.At the metaphase plate, there are paired homologous chromosomes (tetrads), instead of individual replicated chromosomes
3.At anaphase I, it is homologous chromosomes, instead of sister chromatids, that separate

Crossing over occurs during prophase I of meiosis I. It involves the switching of genes between the non-sister chromatids of homologues which allows the novel mixture of maternal and paternal genetic material with new, recombinant
chromosomes. Another layer of variation occurs during independent assortment which is the random lining up of the homologues during metaphase I of meiosis I. Between different gametes, there are 2n different possibilities of how the
homologues could line up. chromosomesmaternal and paternal chromosomes line up during. Finally, it is complete random which sperm fertlizes which egg which creates even more potential variation in the offspring.

Explain why heritable variation was crucial to Darwin's theory of evolution.

If the variations observed in populations are not inherited, then natural selection will have no impact on populations. Natural selection acts on the phenotype and the favorable phenotype is more likely to survive. So the genetic and environmental variations, work in the favor of natural selection: the favorable trait gets passed on and the less favorable is lost.

Natural selection- traits either become more or less prominent in population due to reproduction and the passing on of traits. These traits passed on adapt us to our environment.

Cancer cells lack density-dependent inhibition and anchorage dependence, cancer cells don't stop dividing when growth factors are depleted. 

Define Mendel's discovery hybridization

Define Mendel's discoveries True Breeding and Monohybrid Cross

 True Breeding: two organisms with a particular, heritable phenotype produce only offspring with the same phenotype

Monohybrod cross: a cross between parents who are heterozygous at one locus.

P generation- Parent generation

F1 generation- hybrid offspring or the first filial generation

F2 generation- the offspring of the F1 generation.

The two alleles for a heritable character segregate during gamete formation and end up in different gametes.

dominant and recessive- Dominant determines the organisms appearance and Recessive has no noticeable effect on the organisms appearance.  

heterozygous and homozygous- Heterozygous has two different alleles for a gene and Homozygous has a pair of identical alleles for a character.

genotype and phenotype-Phenotype is appearance/observable traits and Genotype is the genetic makeup 

State Mendel’s law of independent assortment and describe how this law can be explained by the behavior of chromosomes during meiosis.

The law states that each pair of alleles segregates independently of each other pair of alleles during gamete formation. 

The segregation of chromosomes in anaphase I of meiosis explains Mendel's observation that each parent gives one allele for each trait at random to each offspring, regardless of whether the allele is expressed. The segregation of chromosomes at random during anaphase I explains Mendel's observation that factors, or genes, for different traits are inherited independently of each other

Incomplete dominance can be seen in snapdragon flower color. Crossing homozygous red with homozygous white snapdragons produces heterozygous offspring that have pink flowers.

Complete dominance is simple dominance: whichever trait is dominant is the only one which will be expressed. There will be no sign of the recessive trait.

Incomplete Dominace: There is a mixing between the dominant and recessive traits. I.E. Red Snapdragons and White Snapdragons produce Pink Snapdragons. Neither dominant nor recessive traits are fully expressed.

Codominance: A similar mixing, but both traits are clearly evident. This is also usually expressed in color, but would be seen as patches of both colors as in cows. If you can have white or black cows, then a black and white splotched cow would be codominance. It would NOT be White + Black = Gray.

Pleiotrophy- have multiple phenotypic effects

ex. what determines the flower color in pea plants also effects the color of the coating on the outer surface of the seed.

Epistasis- two genes that effect another and determine whether or not it will be expressed.

ex. 1st gene is for color of hair and 2nd gene is for pigment deposition. Brown or Black coat is 1st gene and the 2nd is albino or not

According to Darwin, a species will adapt to it's environment. Things such as oxygen levels, UV exposure, temp etc.could alter depending on the conditions that will be necessary to survive. If the temp. has changed and it has become dryer climate, the animals with the more suitable features will survive and pass on those traits.

Humans are harder to control because mating is not as easily chosen and we have more genes than peas. Mendel was able to control what was crossed and could be specific because the peas had so few genes.

W- no widows peak   w- widows peak

Grandparents         Male- Ww         Female- ww

Parents                  Male-Ww          Female-Ww

Children        Female-WW or Ww     Female-ww    Male-WW or Ww

Because it is recessive, individuals can be carriers of the allele without actually showing the symptoms. So it can be non-lethal to carriers (in fact, they may show no effects at all).
So the allele can be passed down through generations, and hang around indefinitely in the population. 

Describe the inheritance and expression of cystic fibrosis and sickle-cell disease.

both are autosomal recessive and it can be inherited by both parents being heterozygous and having the 1/25 chance of having a child with the disease.

Cystic fibrosis- 1/25 are carriers in European descent

Sickle-cell Anemia- 1/400 African Americans heterozygous which makes them partially immune to malaria

Lethal dominant genes are nearly impossible to find because then having one of the gene kills you. And when an organism dies from its lethal gene, it cannot reproduce and pass the gene onto its kin. However, recessive genes exist because they can be passed down if they are found in a person carrying both the recessive and dominant gene.

Give an example of a late-acting lethal dominant in humans and explain how it may escape elimination by natural selection 

Huntingtons disease- has no obvious phenotypic effects/symptoms until individual is about 35 to 40 years of age.

Explain how carrier recognition, fetal testing, and newborn screening can be used in genetic screening and counseling.

Carrirer recognition's key is determing if the parents are heterozygous carriers of the recessive trait and dectects carriers of disease in karyotype

Fetal testing is genetic testing before birth that may help some couples prepare for a child with a disease such as amniocentesis, chronic villus sampling 

Newborn screeningtests performed to help early detection of disease, especially genetic disorders, at birth eg PKU 

Sex in humans is usually determined by the prescence or absence of a y chromosome, where Y carries the male genes. The SRY turns on your gene to make you male.

Explain why sex-linked diseases are more common in human males.

Color blindness- as long as there is one with colorblindness, there is a chance of the offspring inheriting it.

ex. X+X+ is normal, X+Xc is normal, XcXc is colorblind

for males: X+Y is normal, XcY is colorblind so its more prominent in males

Duchenne muscular dystrophy- Duchenne muscular dystrophy is a genetic disease that exhibits X-linked recessive inheritance. Approximately one-third of cases are due to spontaneous dystrophin mutations.

Hemophilia- X-linked recessive pattern. The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, it is very rare for females to have hemophilia.

Describe the process of X inactivation in female mammals. What is a Barr Body? Explain how this phenomenon produces the tortoiseshell coloration in cats.

An X is in activated in Females because of dosage compensation. It produces a Barr Body. This yeilds differing coloration in cats because the different alleles are inactivated.

Barr Body- inactivated sex (X) chromosome

Aneuploidies among the sex chromosomes is more common than autosomal aneuploidy. Aneuploidies come about due to errors in meiosis during the gamete formation in one of the parents so the zygote starts out with the wrong chromosomal count.

Sex linked genes-genes located on a sex chromosome and most are X linked.

Linked genes- genes located on the same chromosome pair

Recombination between unlinked genes is the random orientation of homologous chromosomes at metaphase I of meiosis, which leads to the independent assortment of two unlinked genes

Parental types- offspring expected to inherit a phenotype that matches one of the parental phenotypes.

Rocombinant types- the offspring have new combinations of phenotypes, therefore they are recombinants

Linked genes do not assort independently because they are located on the same chromosome. In crossing over, a set of proteins orchestrates an exchange of corresponding segments of one maternal or one paternal chromatid, making portions of each chromosome different

Sturtevant predicted that the farther apart two genes are, the higher the chance that crossing over will occur between them and are therefore the higher the recombination frequency

Nondisjunction can cause either too many or too few chromosomes 

Define trisomy, triploidy, and polyploidy. Explain how these major chromosomal changes occur and describe possible consequences

Trisomy- wrong number of chromosomes in an individual; If the chromosome pairs fail to separate properly during cell division the egg or sperm may have a second copy of one of the chromosomes. 

Triploidy-cell or organism having three complete sets of chromosomes; it is always fatal because it has three copies.

Polyploidy-cells and organisms containing more than two paired (homologous) sets of chromosomes; produces seedless fruits and stops reproduction

Describe why some watermelons/bananas have trouble producing seeds and thus are sold as “seedless”

They are polyploids; people are trying to make bigger fruit by crossing 2n plants with n plants to get 3n plants that are larger. But they become seedless in the process

Distinguish among deletions, duplications, inversions, and translocations.

Deletions- lacking some important genes; parts of the chromosome are deleted

Duplications- Having more of some genes on the chromosome; there are multiples of the same genes in the sequence

Inversions- can change the nature of how genes are expressed; some genes are flipped in direction on the sequence

Translocations-can cause some genes that aren't usually expressed to be expressed; takes genes and relocates them on the sequence

Down Syndrome- trisomy 21; extra of chromosome 21

Turner Syndrome- monosomy X; absence of sex chromosome

Cri du chat syndrome- deletion of chromosome 5

chronic myelogenous leukemia- chromosomal translocation between 9 and 22

Explain why researchers originally thought protein was the genetic material.

The chromatin is 50% protein and 50% DNA and proteins are more complex

Explain how the experiments performed by the following scientists provided evidence that DNA is the genetic material: Frederick Griffith, Oswald Avery, Maclyn McCarty, and Colin MacLeod, Alfred Hershey and Martha Chase, and Erwin Chargaff

Frederick Griffith: pneumonia causing bacteria; named unknown factor the "transforming principle"

Oswald Avery, Maclyn McCarty, and Colin MacLeod: transforming principle is DNA

Alfred Hershey and Martha Chase: nucleic acids, not proteins, are the heredity material, at least for viruses

Erwin Chargaff: nucleotide composition in many organisms is same. The % of A= % of T and % of G= % of C

X-ray diffraction crystallography; they used what they knew from Chargoff and other scientists as evidence. 

Rosalind Franklin took photograph 51 using x ray crystalography process which showed double helix nature of dna as well as the spacing between "steps of ladder"

DNA as we know it to be, is a double helix and is made up of nucleotides. Each nucleotide comprises a 5-carbon sugar, a nitrogenous base and a phosphate group.Guanine always bonds to Cytosine and Adenine to Thymine. In RNA however, the base thymine is replaced with Uracil. The main significance of base pairing is to enable the maintanance of the gene pool within a species.

The significance of base pairing: to maintain genetic stability and the genetic characteristics that pass on to the offspring of a species.

DNA replication: DNA strand synthesized from 5' to 3' end

Starts at origin of replication which is a sequence that have a specific sequence of nucleotides which tells it where to begin.

Proteins that initiate DNA replication recognize sequence, bind to it and separate the strands and open up replication bubble. Goes in both directions until the entire molecule is copied. At the end of each bubble is a replication fork, the region where the strands are being unwound.

Explain the role of DNA polymerases in replication.

They catalyze the synthesis of new DNA by adding nucleotides to a reexisting chain. It also proofreads the copies and fixes them to make correct sequence.

Loss of the two phosphates; splitting pyrophosphate from the uncoming nucleotide

Leading Strand:  is synthesized in the same direction as the movement of the replication fork and is synthesized continously

Lagging Strand: is synthesized in the opposite direction and must be done in a series of segements (Okazaki fragments) and loop outward in order to replicate.

Synthesized discontinuously in Okazaki fragments. Each fragment must be primed seperately. After it is primed, DNA polymerase I replaces the RNA to DNA nucleotides. Then DNA ligase bonds the fragments. It can only add to the 3' end because it results in elogation of the new strand in 5' to 3' direction 

Joins 3' end of DNA that replaces primer to the rest of the leading strand and joins Okazaki fragments on lagging strand. (fixes the nick in DNA)

(RNA) short nucleic acid that initiates the replication

the enzyme that synthesizes the primer 

     RNA polymerase

unwinds the DNA

-separates the 2 strands from each other by breaking the hydrogen bonds between them

makes nick in the backbone of the DNA and allows it to swivel

prevent the 2 strands from reconnecting

Define “antiparallel” and explain why continuous synthesis of both DNA strands is not possible.

The two strands of DNA run in different directions. One is 5' to 3', the other is the reverse. Replication can only occur from 5' to 3'. So the strand running 3' to 5' must be done in pieces running from 5 to 3 in fragments

DNA polymerase removes the RNA and replaces it with DNA nucleotides

Mismatch repair enzyme remove and replace incorrectly paired nucleotides

Nuclease in DNA proofreading and repair: cuts out the damaged DNA strand and then it fills the gap with nucleotides using the undamaged strand

Prevents the ends of chromosomes from being damaged

Bacterial chromosomes don't have non-coding regions or introns.

In interphase, the chromatin is highly extended. Preparing for mitosis, the chromatin coils or condenses and forms chromosomes in metaphase. 

DNA is composed of A, T, G, and C

RNA is composed of A, U, G, and C

DNA unwinds, creates an RNA copy (transcription) of the DNA strand (single strand). RNA goes to a ribosome and it clamps on to the RNA strand. The ribosome reads the code on the RNA strand (translation), and creates a protein from strand.

DNA transcripted to mRNA to a ribosome where its translated and creates a polypeptide

Transcription- synthesis of RNA under the direction of DNA 

Translation- synthesis of a polypeptide, which occurs under the direction of mRNA

Bacteria can do it at the same time; lack nucleus so it occurs in cytolplasm

Eukaryotes need transcription factors, a 5' cap and 3' tail, extra proteins and the ribosomes are different; Transcription is in the nucleus and translation is in ribosomes

Define “codon” and explain the relationship between the linear sequence of codons on mRNA and the linear sequence of amino acids in a polypeptide.

Codon: mRNA base triplets written in 5' to 3' direction

Because codons are base triplets, the number of nucleotides making up the genetic message must be three times the number of amino acids in the protein product

Redundant because amino acids can encode for many codons 

Unambiguous because it can as a whole only encode for one thing.

The start codon that signals where a polypeptide chain should start is AUG or Met which is always the start codon. It specifies which of the possible reading frames of a sequence will be translated. Each reading frame can encode a different amino acid sequence and, thus, a different protein.

RNA polymerase finds the promoter region

Promoter is the DNA sequence where RNA polymerase attaches and initiates transcription

Terminator is the sequence that signals the end of transcription

Transcription unit is the stretch of DNA that is transcribed into an RNA molecule

Initiation: occurs at promoter, unwinds DNA and starts laying in RNA nucleotides

Elogation: RNA polymerase will unwind and add nucleotides until it reaches the terminator.

Termination: comes to the terminator and will release the completed RNA

A 5' cap is put on; adds special guanine to 5' end

3' poly A tail added; adenines added to 3' end

Splicing; makes each different

Explain why, due to alternative RNA splicing, the number of different protein products an organism can produce is much greater than its number of genes.

Many genes are known to give rise to two or more different polypeptides , depending on which are exons. One gene can encode for more than one kind of polypeptide.

transfer RNA interpret the mRNA and transfer amino acids from the cytoplasmic pool of amino acids to a ribosome

Have sites A, P, and E. At the start of translation, the ribosome positions itself over the mRNA tape so as to expose to the A site the codon on the tape that represents the next amino acid due to be added to the chain. This site is occupied by a tRNA to which the growing polypeptide chain is attached, called a peptidyl-tRNA.Goes then to the E site and once released, an appropriate aminoacyl-tRNA synthetase enzyme attaches to the deacylated tRNA, adds the appropriate amino acid

The ribosomes have 3 sites when the tRNA can bind to to synthesize the RNA. (A, P, and E)

The ribosomes facilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesis

Describe the process of translation (including initiation, elongation, and termination) and explain which enzymes, protein factors, and energy sources are needed for each stage.

Charging of tRNA- enzymes attach to amino acids

Initiation: small subunit, mRNA, tRNA form complex; larger complex docks on it

Elongation: new tRNA in A site; form peptide bond between P site peptides and A site peptide; peptide chain that lost peptide exits and another moves into P site. Hydrolyze 2 GTP

Termination: Release factor will come form base pairs with stop codon, freeing peptide and then it stops

They enable a cell to make many copies of a polypeptide very quickly

A gene determines the primary structure, which then determines the shape.

It can be modified by the attachments of sugars, lipids, phosphate groups, or others. Some remove one or more amino acids from the leading end of the polypeptide chain. or it can be cleaved into two or more pieces

The signal sequence found at the start of a protein being coded by the ribosome alerts the ribosome to attach itself to the ER. If the sequence is missing it will remain free.

mRNA out of the nucleus binds to a signal molecule then it is taken to the cytosol.

Chemical changes in a single base pair of a gene

Base pair substitiution- replacement of one nucleotide and its partner with another pair of nucleotides.

ex. silent mutation: one a.a. changed but doesn't change codon

Base pair insertion- additons of nucleotide pairs in a gene

ex. Frameshift- addition of an extra A wgich can create stop codon early

one change that makes the codon change

Why is an insertion or deletion more likely to be deleterious than a substitution?

They shift the whole sequence which could cause extensive missense whereas a codon can just change with substitutions

Define the term ‘mutation’. Give an example of a physical and a chemical agent of mutation.

Mutation:change in genetic info of a cell

physical: UV light

chemical: carcinogens