bio test 3

describe the different levels of DNA packaging (e.g., double helix (2 nm), nucleosome level (10 nm), 30-nm fiber (30 nm), looped domains (300 nm), metaphase sister chromatid (700 nm), metaphase duplicated chromosome (1400 nm);

- 2nm: just DNA with no proteins, lowest level of packaging - 10nm: requires histone proteins (H1 cause nucleosomes to form next level) - 30nm: result of H1 organizing nucleosomes to higher level - 300nm: has looped domains, - 700nm: a chromatid - 1400nm: replicated chromosome; metaphase chromosome

Explain the difference between genes and alleles

- Alleles are traits, a form of genes (blue vs. brown eyes) - Genes are a mendelian factor/characteristic (eye color)

distinguish between amniocentesis and chorionic villus sampling.

- Amniocentesis: withdraw amniotic fluid using needle and ultrasound, centrifuge to separate fetal cells and then wait several weeks for karyotyping - Chorionic villus sampling: suction tube inserted through cervix to extract fetal cells

state the three main roles of cell division for eukaryotic organisms;

- Asexual reproduction - Growth and development - Tissue renewal- after damage - (1) the reproduction of an entire unicellular organism - (2) the growth and repair of tissues in multicellular animals - (3) the formation of gametes (eggs and sperm) for sexual reproduction in multicellular animals

describe the importance of DNA replication

- Cell division would not happen without dna replication

distinguish among complete (simple) dominance, incomplete dominance, and codominance;

- Complete dominance: the phenotypes of the heterozygote and the dominate homozygote are indistinguishable; heterozygous phenotype is the same as that of homozygous dominant - Incomplete dominance: neither allele is completely dominant; heterozygous phenotype is an intermediate between the two homozygous phenotypes - Codominance: the two alleles each affect the phenotype in separate, distinguishable ways; both phenotypes expressed in heterozygotes

describe the different packaging levels of chromatin

- DNA wraps around histone proteins, forming nucleosomes and the so-called "beads on a string" structure (euchromatin). - Multiple histones wrap into a 30-nanometer fiber consisting of nucleosome arrays in their most compact form (heterochromatin). - Higher-level DNA supercoiling of the 30-nm fiber produces the metaphase chromosome (during mitosis and meiosis).

distinguish among deletion, inversion, duplication, and translocation events during meiosis;

- Deletion: occurs when a chromosomal fraction is lost; the affected chromosome is then missing certain genes - Inversion: chromosomal fragment may reattach to the original chromosome but in the reverse orientation - Translocation: fragment to join a non homologous chromosome - Duplication: portions of DNA gets duplicated which results in extra genetic information

distinguish between euchromatin and heterochromatin;

- Euchromatin: the less condensed form of eukaryotic chromatin that is available for transcription - Heterochromatin: eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed

describe the function of a microtubule organizing center (MTOC);

- Ex: centrosomes with centrioles - 1) the organization of eukaryotic flagella and cilia - 2) the organization of the mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division.

nonkinetochore microtubules

- polymers that work with kinetochores to align and separate chromosomes

Watson and Crick

- proposed a 3D structure for DNA using information from Rosalind Franklin

Topoisomerase

- relieves "overwinding" strain ahead of replications forks by breaking, swiveling and rejoining DNA strands

DNA polymerase I

- removes RNA nucleotides of primer from 5 prime end and replaces them with DNA nucleotides

cytoplasm

- the region between the nucleus and the plasma membrane, the cell's outer boundary

state in carefully worded sentences four major categories of evidence in favor of the Chromosomal Theory of Inheritance;

1. The "behavior" of Mendel's factors is isomorphic to the "behavior" of chromosomes during meiosis 2. Sex-linked genes: (white-eyed male by Thomas Hunt Morgan) could be correlated to XY situation in males 3. Linked genes on somatic chromosomes exist, something must link them together 4. The number of linkage groups for somatic genes equals the haploid number of chromosomes minus one! (no matter the species)

sturtevant

A student of Morgan, Worked out how to create linkage maps using segregating traits in fruit flies; tested fruit fly, worked in Morgans research lab

helicase

An enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands.

describe the three sources of genetic recombination (e.g., crossing over, independent assortment, and random fertilization) and when they occur during meiosis or the life cycle;

Crossing over: during prophase I, when homologs exchange genetic material between nonsister chromatids Independent assortment: during anaphase I, where the maternal and paternal chromosomes end up is completely by chance (if you have 4 chromosomes then there are 2 possibilities slide 22) Random Fertilization: genetic information from each of the parents; genetic combination in sperm is different from the egg

nucleolus

Found inside the nucleus and produces ribosomes

distinguish (in part by using specific examples) among gametic meiosis, sporic meiosis, and zygotic meiosis;

Gametes are the only haploid cell in the human life cycle In sporic meiosis it doesn't produce gametes it produces spores which go through mitosis to produce alteration of generation Zygotic meiosis: zygote is the only diploid cell- the only one to go through meiosis, produces spores which then become gametes ex. Coprinus

explain when homologous chromosomes separate and when sister chromatids separate during meiosis;

Homologous chromosomes separate during meiosis I and the sister chromatids separate during meiosis II

synapsis

Pairing of homologous chromosomes;; the DNA breaks are closed up so that each broken end is joined to the corresponding segment of the nonsister chromatid. Thus, a paternal chromatid is joined to a piece of maternal chromatid beyond the crossover point, and vice versa

template strand

The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript.

Telophase II and Cytokinesis (Meiosis)

The cells have now been formed into 4 new cells, and the nuclear membranes come back. These cells are known as haploid cells, and each has half the usual number of chromosomes;; o if you're a human meiosis results in 4 gametes (have half the amount of DNA as any diploid cells) a spore is also haploid but that cell can also go through mitosis to produce a larger multicellular generation o nuclei form, the chromosomes begin decondensing, and cytokinesis occurs o meiotic division of one parent cell produces four daughter cells, each with a haploid set of unduplicated chromosomes o daughter cells are genetically distinct from one another and from the parent cell

daughter strand

The strand of DNA that is newly replicated from an existing template strand of DNA.

plasma membrane

a microscopic membrane of lipids and proteins which forms the external boundary of the cytoplasm of a cell or encloses a vacuole, and regulates the passage of molecules in and out of the cytoplasm

replication bubble

a region of DNA, in front of the replication fork, where helicase has unwound the double helix; an unwound and open region of a DNA helix where DNA replication occurs

synaptonemal complex

after this disassembles, the chiasmata becomes visible. This also holds one homologous tightly to the other for synapsis to occur

unduplicated chromosome

are single linear strands of DNA

chromatin

can be expanded or condensed; 1/3 DNA, 1/3 histone proteins, 1/3 non histone proteins and RNA

nucleus

central organelle holding most of the cells DNA

pyrophosphatase

cleave another high energy bond to make 2 inorganic phosphates. This makes the reaction energetically possible

Hershey and Chase

concluded that the genetic material of the bacteriophage was DNA, not protein.; - use radioactivity to support that the transforming principle is DNA; radioactive phosphorus in the phase DNA (in the pellet) radioactive sulfur was found in the phage protein

duplicated chromosome

contain two identical copies (called chromatids or sister chromatids) joined by a centromere

Mendel

crossed for characteristic in pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits

Griffith

injected living S cells (mouse dies), living R cells (mouse healthy), heat killed S cells (mouse healthy) and a mixture of heat killed S cells and living R cells (mouse dies). During the 4th trial he found that the living R cells turned into living S cells finds that there is a transforming principle

explain what a karyotype is and what it is used for;

it is a display of condensed chromosomes and it can be used to detect defective chromosomes or an abnormal number of chromosomes

metaphase

o The centrosomes are now at opposite poles of the cell o The chromosomes have all arrived at the metaphase plate, a plane that is equidistant between the spindles two poles. The chromosomes centromeres lie at the metaphase plate o For each chromosome, the kinetochores of the sister chromatids are attached to kinetochores microtubules coming from opposite poles

prophase

o The chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope o The nucleoli disappear o Each duplicated chromosome appears as two identical sister chromatids joined at their centromeres and in some species, all along their arms by cohesins (sister chromatid cohesion) o The mitosis spindle begins to form. It is composed of the centrosomes and the microtubules that extend from them. The radial arrays of shorter microtubles that extend from the centrosomes are called "asters" o The centrosomes move away from each other, propelled partly by the lengthening microtubules between them

nuclear pore complex

pores in the membrane that control what gets in and out of the cell

cohesins

protein that holds sister chromatids together and regulate cell division

primase

synthesizes an RNA primer at 5 prime end of leading strand and of each okazaki fragment of lagging strand

crossing over

when homologs exchange genetic information

Franklin, Gosling, and Wilkins

worked together, purified DNA to gather information on its 3D structure; work suggests that DNA is a double helic with antiparallel strands and 10 bases per helical turn

nucleolus

- a small dense spherical structure in the nucleus of a cell during interphase.

predict F1 and F2 genotypic and phenotypic ratios for monohybrid and dihybrid crosses when the traits for two independently assorting characters show recessive or dominant epistasis;

- Recessive: 9:4:3 - Dominant: 12:3:1

distinguish the gametophyte and the sporophyte generations during the sporic meiosis life cycle of a plant

- sporophyte: multicellular diploid stage o produces haploid cells called spores, doesn't fuse with another cell like a gamete but divides mitotically to produce the gametophyte - gametophyte: multicellular haploid generation

explain how Morgan's lab discovered a sex-linked gene for eye color in Drosophila;

- He realized that only the male fruit flies could have the phenotype of the white recessive allele until he did more crosses of siblings and found that females can have the trait too

describe the function of histone proteins (H1, H2A, H2B, H3, and H4), sliding clamps, and connecting protein;

- Histone proteins: help organize and package dna - Sliding clamps: the clamp protein binds DNA polymerase and prevents this enzyme from dissociating from the template DNA strand. - Connecting protein: connects DNA pol III to helicase

predict the consequences of leaving out (during DNA replication) one or more of the proteins listed

- If helicase was left out, the strands would not separate and DNA replication could not begin - If DNA ligase was left out, then the last connection could not be made so replication would stop with Okazaki fragment, but RNA would still be replaced with DNA if DNA pol I is still present - If DNA polymerase I was absent, then RNA nucleotides would not be removed and replaced with DNA so replication wouldn't continue

List and explain the simulates and differences between mitosis and meiosis and describe why the differences are important

- Meiosis results in 4 genetically different daughter cells, which is why we don't look exactly like our parents

explain the cause and consequences of a nondisjunction event during meiosis;

- Members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis II

compare and contrast (e.g., list the similarities and differences between) mitosis and meiosis

- Mitosis: o One division of the nucleus o End up with same amount of genetic info o No synapse of homologs o 2 daughter cells 2n to 2n 2c to 2c - Meiosis: o Two division of nucleus o End up with half the amount of genetic information o Synapse of homologs and crossing over occurs during prophase I o Results in 4 daughter cells that are genetically different --- recombination

predict the outcome of crosses involving (stable) nondisjunctions;

- One gamete receives two of the same type of chromosome and another gamete receives no copy - Downs syndrome is an example of nondisjunction of chromosome 21; one extra chromosome

explain the "telomere problem" and the function of telomerase.

- Only occurs in linear DNA (eukaryotes) o The telomere problem is that as DNA replication continues it results in shorter and shorter daughter molecules, the ends of the chromosomes (telomere) shorten o telomeres become shorter during every round of replication - Not every cell has telomerase - Telomerase extends the ends of chromosomes Remember that telomeres are the ends of chromosomes

compare and contrast mitosis and cytokinesis in animal cells and plant cells;

- Plant cells don't pinch in telophase, so they form a cell plate - Animal cells form a cleavage furrow

compare and contrast MTOCs in animal cells and plant cells;

- animal cells also have centrioles associated with the MTOC: a complex called the centrosome. Animal cells each have a centrosome and lysosomes, whereas plant cells do not

explain the use of a test cross in Mendelian genetics

- Take a homozygous recessive organism to test for an unknown genotype

state Mendel's two "laws" and distinguish between them as to when they need to be evoked and when they are "realized" during meiosis

- The law of independent assortment: two or more genes assort independently- that is, each pair of alleles segregates independently of any other pair of alleles- during gamete formation o Realized during Anaphase I - The law of segregation: during the production of gametes the two copies of each hereditary factor segregate so that offspring acquire one factor from each parent.

Describe the relationships between homologous chromosomes, nonhomologous chromosomes, and sister chromatids

- The sister chromatids are identical strands of DNA. During mitosis, the sister chromatids are separated and during meiosis homologous chromosomes pair up. Carry same genes in same loci but can have different alleles because one half is from the female and one half from the male (maternal and paternal) - Homologous Chromosomes: Homologous chromosomes refer to a pair of chromosomes having the same gene sequences, each derived from one parent. - Non-Homologous Chromosomes: Non-homologous chromosomes are chromosomes that do not belong to the same pair. - Homologous Chromosomes: Homologous chromosomes pair during meiosis 1. - Non-Homologous Chromosomes: Non-homologous chromosomes do not pair during meiosis 1 - Homologous Chromosomes: The parts of the homologous chromosomes can be exchanged during recombination. - Non-Homologous Chromosomes: The parts of non-homologous chromosomes can be exchanged during translocations.

distinguish between parental chromosomes and recombinant chromosomes during meiosis

- The true breeding parents are the parental type and then anything else is a recombinant -The larger the recombination frequency, the farther away they are from the parental chromosomes

distinguish among X-Y, Z-W, X-0, and haplo-diploid systems of sex determination;

- X-Y: sex is determined by male sperm - Z-W: egg determines the sex of the offspring - X-0: sex determined by sperm - Haplo-diploid system: females are diploid, males are haploid

explain what a linkage group is

- a set of genes at different loci on the same chromosome that except for crossing-over tend to act as a single pair of genes in meiosis instead of undergoing independent assortment

kinetochore microtubules

- a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle; the microtubules bind to the kinetochore and as these attach to sister chromatids they are pulling on duplicated chromosomes in opposite directions until they end up on the metaphase plate

centrosome

- a structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles

spindle apparatus

- consists of spindle fibers, motor proteins, chromosomes, and, in some cells, structures called asters; Spindle fibers are a part of the spindle apparatus, which moves chromosomes during mitosis and meiosis to ensure that each daughter cell gets the correct number of chromosomes; forms during cell division to separate sister chromatids between daughter cells.

nuclear lamina

- dense network inside the nucleus which provides support and regulates cellular events

Avery, Macleod and McCarty

- discovered that DNA is the transforming principle, although many weren't convinced; chemically isolated griffiths transforming principle

chromatids

- each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA; one-half of two identical copies of a replicated chromosome. During cell division, the identical copies are joined together at the region of the chromosome called the centromere. Joined chromatids are known as sister chromatids

chromosome arm

- either of the two segments of the chromosome separated by the centromere

centromere

- in a duplicated chromosome, the region on each sister chromatid where it is most closely attached to its sister chromatid by proteins that bind to the centromeric DNA. Other proteins condense the chromatin in that region, so it appears as a narrow waist on the duplicated chromosome. (an unduplicated chromosome has a single centromere, identified by the proteins bound there)

represent the state of the DNA at various stages of meiosis using the conventions of the symbol n and the symbol c;

- interphase: 2n, 2c to 2n, 4c (twice as much DNA because it has been replicated) - Meiosis I: 1n, 2c - Meiosis II: 1n, 1c

DNA ligase

- joins 3 prime end of DNA that replaces primer to rest of leading strand and joins okazaki fragments of lagging strand

List and explain the difference of mitosis in plants and animals

- main difference is how they form the daughter cells during cytokinesis. During that stage, animal cells form furrow or cleavage that gives way to formation of daughter cells. ... During telophase, plant cells phragmoplast forms in the center of the cell.

draw and label (each 5' end, each 3' end, template strand, leading strand, lagging strand, RNA primer, Okazaki fragment, continuous replication, discontinuous replication) a figure showing DNA replication in a prokaryote or eukaryote

- reads from 5 prime to 3 prime end ONLY - leading strand: Along one template strand, DNA polymerase III can synthesize a complementary strand continuously by elongating the new DNA in the mandatory 5′ S 3′ direction. DNA pol III remains in the replication fork on that template strand and continuously adds nucleotides to the new complementary strand as the fork progresses. The DNA strand made by this mechanism is called the leading strand - lagging strand: To elongate the other new strand of DNA in the mandatory 5′ S 3′ direction, DNA pol III must work along the other template strand in the direction away from the replication fork. The DNA strand elongating in this direction is called the lagging strand. In contrast to the leading strand, which elongates continuously, the lagging strand is synthesized discontinuously, as a series of segments. - Okazaki fragments: segments of the lagging strand

cell plate

- structure found inside the dividing cells of terrestrial plants and some algae. It develops in the middle plane of the cell separating two daughter cells during cell division

explain the differences among a gamete, a spore, and a zygote;

- the difference between a "spore" and a "gamete" is that a spore will germinate and develop into a sporeling, while a gamete needs to combine with another gamete to form a zygote before developing further. - zygote is a fertilized egg cell while spore is a reproductive particle, usually a single cell

nuclear envelop

- two lipid bilayer which surround the nucleus

DNA polymerase III

- using parental DNA as a template, synthesizes new DNA strand by covalently adding nucleotides to the 3 prime end of a pre-existing DNA strand or RNA primer

morgan

- white eyed fruit fly, wild type; flies were better to test genetics than peas because you could produce several generation within a short period of time, they are easily sexed and you can control reproduction--- his research led to the discovery of linked genes

replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

cell wall

A rigid structure that surrounds the cell membrane and provides support to the cell

Meselson and Stahl

Proved that DNA replicates in a semiconservative fashion, confirming Watson and Crick's hypothesis. Cultured bacteria in a medium containing heavy nitrogen (15N) and then a medium containing light nitrogen (14N); after extracting the DNA, they demonstrated that the replicated DNA consisted of one heavy strand and one light strand 2 bands- one with only 14N (light) and 1 with 1/2 light and 1/2 heavy

single stranded binding protein

binds to and stabilizes single-stranded DNA until it can be used as a template, without this DNA strands would join back together so it keeps the parental strands from rejoining

anaphase

o Anaphase is the shortest stage of mitosis, often lasting only a few minutes o Anaphase begins when the cohesion proteins are cleaved. This allows the two sister chromatids of each pair to part suddenly. Each chromatid thus becomes an independent chromosome o The two new daughter chromosomes begin moving toward opposite ends of the cell as their kinetochore microtubules shorten. Because these microtubules are attached at the centromere region, the centromeres are pulled ahead of the arm. o The cell elongates as the nonkinetochore microtubules lengthen o By the end of anaphase, the two ends of the cell have equivalent-and complete- collections of chromosomes

Cytokinesis

o The division of the cytoplasm is usually well under way by late telophase, so the two daughter cells appear shortly after the end of mitosis. o In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two

prometaphase

o The nuclear envelope fragments o The microtubules extending from each centrosome can now invade the nuclear area o The chromosomes have become even more condensed o A kinetochore, a specialized protein structure, has now formed at the centromere of each chromatid (thus, two per chromosome) o Some of the microtubules attach to the kinetochores, becoming "kinetochore mictrotubules" which jerk the chromosome back and forth o Nonkinetochore mictrotubules interact with those from the opposite pole of the spindle, lengthening the cell

telophase

o Two daughter nuclei form in the cell. Nuclear envelopes arise from the fragments of the parents cells nuclear envelope and other portions of the endomembrane system o Nucleoli reappear o The chromosomes become less condensed o Any remaining spindle microtubules are depolymerized o Mitosis, the division of one nucleus into two genetically identical nuclei, is now complete

metaphase I

o all the tetrads line on the metaphase plate, microtubules are in the process of connecting to the kinetochore of the homologous chromosomes o pairs of homologous chromosomes are now arranged at the metaphase plate, with one chromosome of each pair facing each pole o Both chromatids of one homolog are attached to kinetochore microtubules from one pole; the chromatids of the other homolog are attached to microtubules from the opposite pole

anaphase I

o the homologues separate from one another o breakdown of proteins that are responsible for sister chromatid cohesion along chromatid arms allows homologs to separate o the homologs move toward opposite poles, guided by the spindle apparatus o sister chromatid cohesion persists at the centromere, causing chromatids to move as a unit toward the same pole

metaphase II

o the microtubules connect to the kinetochore of the sister chromatids which are lined up on the metaphase plate o the chromosomes are positioned at the metaphase plate as in mitosis o because of the crossing over in meiosis I, the two sister chromatids of each chromosome are not genetically identical o the kinetochores of sister chromatids are attached to microtubules extending from opposite poles

prophase II

o the nuclear envelope fragments again, centrosome duplicated again o a spindle apparatus forms o in late prophase II, chromosomes, each still composed of two chromatids associated at the centromere, are moved by microtubules toward the metaphase II plate

prophase I

o the nuclear envelope fragments and the DNA condenses, the homologous chromosomes synapse to form a tetrad (a piece of the DNA from one homologue is exchanged with the other homologue) o chromosomes condense progressively o during early prophase I, each chromosome pairs with its homolog, aligned gene by gene, and crossing over occurs: the DNA molecules of nonsister chromatids are broken (by proteins) and are rejoined to eachother o each homologous pair has one or more X shaped region called a chiasmata where crossovers have occurred o later in prophase I, microtubules from one pole or the other attach to the kinetochores, one at the centromere of each homolog. (the two kinetochores on the sister chromatids of a homolog are linked together by proteins and act as a single kinetochore). Microtubules move the homologous pairs toward the metaphase plate

anaphase II

o the sister chromatids are pulled apart o Breakdown of proteins holding the sister chromatids together at the centromere allows the chromatids to separate. The chromatids move toward opposite poles as individual chromosomes

Telophase I and Cytokinesis (Meiosis)

o varies from species to species, sometimes they skip this step and just go in to Meiosis II o When telophase I begins, each half of the cell has a complete haploid set of duplicated chromosomes. Each chromosome is composed of two sister chromatids; one or both chromatids include regions of nonsister chromatid DNA o Cytokinesis (division of the cytoplasm) usually occurs simultaneously with telophase I, forming two haploid daughter cells o In animal cells, a cleavage furrow forms. In plant cells, a cell plate forms o In some species, chromosomes decondense and nuclear envelopes form o No chromosome duplication occurs between Meiosis I and II

spindle fiber

one of the microtubules that extend across a dividing eukaryotic cell; assists in the movement of chromosomes; filaments that form the mitotic spindle in cell division, i.e. mitosis and meiosis. They are chiefly involved in moving and segregating the chromosomes during nuclear division, made up of microtubules

shugoshin

protein that protects cohesins at the centromere during meiosis I

centromere

region where the chromosome duplicates

nuclear envelope

regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryotic cells. It contains a large number of different proteins that have been implicated in chromatin organization and gene regulation.

nucleoplasm

similar to the cytoplasm but in the nucleus

chromosome

structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes

telomere

the ends of the chromosome

origin of replication

where everything starts; short stretches of DNA that have a specific sequence of nucleotides

chiasma

where the crossing over is occurring (becomes visible)