Genetics Exam 2 EDITED

What are factorials?

(n! = n X n-1 X n-2 X...1)

What happens during prophase? draw early, middle, late

- Spindle fibers= the centromeres move to the poles of the dividing cell. The spindle fibers grow out of the centromeres and contact the chromosome via their kinetochore (found at the centromere). -Chromatin= condenses into visible chromosomes and migrates toward the equatorial plate (center of the dividing cell). Because the DNA was replicated in S phase, each chromosome now has two sister chromatids.By late prophase, you can often see two separate sister chromatids under the microscope -Nuclear envelope= this disintegrates. FURTHER DIVISION: a.) early prophase= chromosomes begin to condense. Centrosomes start to move to opposite poles of dividing cell. b.) late prophase (prometaphase)= -centrosomes have migrated to the poles. spindle fibers reaching in to bind chromosomes. -chromosomes are now condensed. -nuclear membrane has disappeared. picture= early prophase and late prophase (prometaphase). "eyes"= centrosomes.

what are the effects of a balanced translocation on phenotype?

-Abnormal phenotype: one or both breakpoints can fall inside a gene's sequence, resulting in the gene's sequence being broken into two parts, and the parts being separated from each other. Normal Phenotype: One or more genes have been moved, but the entire coding sequence and regulatory sequences have been moved and remain together

Describe/draw telophase (early, mid, late)

-centrosomes= The spindle fibers degenerate to some degree. -chromatids=sister chromatids are completely pulled apart towards the two poles during anaphase. there is no more movement that's needed. The chromatin decondenses. -nuclear membrane= Nuclear envelope reforms. New cell membrane material is synthesized so the two daughter cells are now separate functional cells There is cytokinesis. the cytoplasm and organelles are divided between the two daughter cells. physical process of cell division. picture= early-mid telophase. Nuclear membrane has not yet reformed. Chromatin is still somewhat condensed Cells only beginning to cleave apart, new cell membrane is not yet visible

draw/describe anaphase (early, mid, late)

-centrosomes=Centrosomes and spindle fibers still very visible chromatids=Sister chromatids separate and are pulled toward opposite poles. Each chromatid is now a chromosome -nuclear membrane= Nuclear envelope still disintegrated picture= middle anaphase.

How do you use two point dihybrid crosses to map genes?

-conduct dihybrid test cross as to determine what the gene combinations are. This gives you the key to understand the numbers. It allows one to see the distance between genes and also associate a label to it. 1.) whatever is 50cm means that they are recombinant. They assort independently. They are members of different linkage groups (so, a and b are each in a different linkage groups). 2.) if there are two groups below 50 cm then these tell us the distance between linkage groups (here, a and b are part of the same linkage group). 3.) focus on the gene groups bellow rf 50. These will be one linkage group and they will tell you the relative distances (remember, there can be rounding errors).

Why can inversion mess up children's phenotype?

-its like in a reciprocal translocation. in meiosis, when homologous chromosomes line up and put all sequences next to each other. if one has inversion, then chromosome has to form a loop. If there is a recombination breakpoint, the chromosomes end up exchanging unequal material 1.) two homologs exchange unequal info. One with deletion and one with duplication. 2.) can form a loop. Chromosomes can lose material from both the p and q arm, then form a ring An abnormal phenotype results because one or more portions or copies of one or more genes is lost

What does end of interphase look like? (draw, explain)

-spindle fibers= not yet organized -chromatin is decondensed and there is no discernible chromosomes in nucleus -nuclear membrane is intact

List the stages of meosis and describe each:

1.) End of interphase Centrosomes: Spindle fibers not yet organized. Chromatin: This is de-condensed. Nuclear Envelope: This is intact. * 2.) five stage of prophase I (similar to what happens in mitosis); the only difference is that recombination occurs during prometaphase I. * a.) Leptotene chromatin condenses. b.) Zygotene: chromatin condenses, homologous chromosomes pair up and partake in "synapsis" (aligning very close to each other) to form bivalents (2 chromosomes), which are tetrads (four chromatids). c.) Pachytene: chromatin condenses, synaptonemal complex develops between homologous chromosomes (i.e. the homologous chromosomes come into contact with each other at one or more places in each p and q arm). *Non-sister homologous chromatids (one from each member of the homologous chromosome pair) physically cross over at the points of contact and exchange material (i.e. recombination occurs)* d.) Diplotene—the two chromosomes in each bivalent begin to separate, but remain joined at the chiasma—i.e. the places where the crossing over took place e.) Diakinesis—chromatin condenses further, the two chromosomes in the bivalent separate farther apart, the two chromosomes now remain joined only at the ends *note* When authors use a prophase I/prometaphase I scheme, prometaphase I corresponds to the pachytene, diplotene and diakinesis stages. ANOTHER WAY TO VIEW PROPHASE I Early Prophase I -Centrosomes: centrosomes, beginning to move toward opposite poles of the dividing cell -Chromatids: Light blue squiggly figures in the nucleus are the chromosomes, which are beginning to condense -Nuclear Envelope: starts to disintegrates Late Prophase I -Centrosomes: Centrosomes have migrated to the poles. Spindle fibers are reaching in to bind the chromosomes Chromatids: Light blue chromosomes now obviously condensed Nuclear Envelope: This has disintegrated 3.)Metaphase I -Centrosomes: The bivalents are aligned in their tetrads along the equatorial plane. The spindle fibers grab the chromosomes by the kinetochores at their centromeres. Cell makes sense that every chromatid is bound by a spindle fiber. -Chromatids: -Nuclear Envelope: Late Metaphase I: -Centrosomes: Chromosomes are aligned at the equator. Spindle fibers are binding the chromosomes. -Chromatids: -Nuclear Envelope: Similar to mitosis. Big difference. Mitosis: all chromosomes are bivalent and are lined vertical. Meiosis: lined up in pairs vertically. Cells knows to differ these via sequences in chromosomes. 4.) Anaphase I: The enzyme separase degrades the cohesin that holds the two homologs together (but leaves the cohesin that is... holding the sister chromatids together at the centromere intact). The two chromosomes in each bivalent migrate apart from each other toward opposite poles of the dividing cell. Middle of anaphase I; Spindle fibers grab the chromosomes by connecting to the kinetochores at their centromeres and draw the chromosomes apart. The protein shugoshin protects the cohesin (at the centromeres only) from degredation by separase. This holds the sister chromatids together at their centromeres during anaphase I of meiosis, so they don't separate until anaphase II Shugoshin must be degraded during metaphase II, so the sister chromatids can separate during anaphase II 5.) Telophase I Centromere: chromosomes have migrated completely to opposite poles. Cytokinesis, aka cytoplasmic streaming—cytoplasm and organelles migrate into the two daughter cells Chromatid: Nuclear Envelope: Early-Mid Telophase I : Centromere: Chromatin: Chromatin is still somewhat condensed Nuclear Envelope: Nuclear membrane has not yet reformed Cells only beginning to cleave apart, new cell membrane is not yet visible *Interkinesis: Nuclear membrane reforms, spindle fibers degenerate, chromatin decondenses * *Reduction, division (reduction of number of chromosomes by half* *equatorial division, The second cell division is sometimes referred to as the equational division, because there is no change in the number of chromosomes per cell* 6.) Prophase II: Chromatin condenses, nuclear envelope degenerates, spindle fibers form 7.) Metaphase II: The chromosomes align at the equatorial plane, and the spindle fibers grab the chromosomes. Note that half the chromatids are recombinant chromatids, and half are nonrecombinant chromatids 8.) Anaphase II: The sister chromatids migrate apart from each other toward opposite poles of the dividing cell 9.) Telophase II: Nuclear membrane reforms, spindle fibers disappear, chromatin decondenses 10.)

What stages of meiosis does genetic diversity occur in humans?

1.) Recombination: prometaphase I or pachytene (recombination) 2.) Random Separation: random segregation: anaphase I of meiosis (when homologs are separated) or metaphase I of meiosis (when they line up).

What are the three most important "players" in M phase?

1.) centrosomes and spindle fibers 2.) chromatin 3.) nuclear membrane Always include these.

Steps to solve a LOD problem

1.) determine the number of LOD transmissions. 2.) calculate the probability of getting un-linked genes. It is 50%. If you have 13 offspring then you do (.5)^13. This makes use of the AND rule. This gives the odds of getting the unlinked outcomes. 3.) Calculate the p at several rfs and divide by the 50% value. Then take the log of this number and compare (these are LOD scores). The largest LOD score is the most likely genetic distance between two genes. Notice, we are using frequencies. It can go above 50%. You still use the rf. The photo shows the types of calculations that you should do. Finally, The most likely Rf, of the ones you tested, is Rf = 15%, where LOD = 1.49 The antilog of 1.49 = 30.9. Therefore, it is 30.9 times more likely that these genes are linked with Rf = 15% than they are unlinked USE THE ANTILOG to determine x likelihood

Go through M phase, explaining (and possibly drawing) what happens in each.

1.) end of interphase. -spindle fibers= not yet organized (are in centrosome). -chromatin is decondensed and there is no discernible chromosomes in nucleus -nuclear membrane is intact 2.) Prophase - Spindle fibers= the centrosomes move to the poles of the dividing cell. The spindle fibers grow out of the centrosomes and contact the chromosome via their kinetochore (found at the centromere). -Chromatin= condenses into visible chromosomes and migrates toward the equatorial plate (center of the dividing cell). Because the DNA was replicated in S phase, each chromosome now has two sister chromatids.By late prophase, you can often see two separate sister chromatids under the microscope -Nuclear envelope= this disintegrates a.) early prophase= chromosomes begin to condense. Centrosomes start to move to opposite poles of dividing cell. b.) late prophase (prometaphase)= -centrosomes have migrated to the poles. spindle fibers reaching in to bind chromosomes. -chromosomes are now condensed. -nuclear membrane has disappeared. 3.) Metaphase -centrosomes=spindle fibers are attached to eat chromatid. The cell goes through spindle-assembly checkpoint to be sure every chromatid has been bound by spindle. -chromatids= chromosomes are the most condensed and are aligned at equatorial plane. -nuclear membrane= still disintegrated 4.) anaphase -centrosomes=Centrosomes and spindle fibers still very visible -chromatids=Sister chromatids separate and are pulled toward opposite poles. Each chromatid is now a chromosome -nuclear membrane= Nuclear envelope still disintegrated 5.) telophase -centrosomes= The spindle fibers degenerate to some degree. -chromatids=sister chromatids are completely pulled apart towards the two poles during anaphase. there is no more movement that's needed. The chromatin decondenses. -nuclear membrane= Nuclear envelope reforms. There is cytokinesis. the cytoplasm and organelles are divided between the two daughter cells. physical process of cell separation. New cell membrane material is synthesized so the two daughter cells are now separate functional cells

What are the 4 possible things that can happen in meiosis? (three point cross)

1.) parent can pass down non-recombinant chromosome. 2.) single recombination between genes 3.) single recombination between other genes 4.) double recombination between above genes. 2-4 provides two possible allele combinations from parent, depending on which of the two chromosomes end up on the gamete.

What are the ways that humans create genetic diversity?

1.) recombination: When recombinant chromosomes are passed down some genetic material is from mother and some from father. If one took all the recombinant gametes of chromosome 1, then one would find that the recombination breakpoint is random. There can be different recombinant chromosome ones. 2. ) Random separation, there can be a various collection of chromosomes in gametes. There are many many possibilities.

How are monohybrid crosses useful to us?

1.) there must be two alleles of a particular gene (in the end, there was a dominant and recessive trait). 2.) one allele must be dominant and another must be recessive. (Why? the F2 generation can display two different phenotypes (the dominant and recessive trait), whereas the F1 generation displayed only one phenotype (the dominant one). 3.) For each gene, parent passes down one allele to each offspring (Because one F1 individual that has the dominant phenotypic trait can produce F2 offspring that have the dominant trait and F2 offspring that have the recessive trait, that parent must not only possess both alleles of the gene, but also be capable of passing only one allele of each gene to each offspring). This gave rise to Mendel's law of segregation (two alleles of a gene segregate apart from each other when an individual makes gametes). 4.) Each individual inherits one set of gene alleles from mother and one from father (if a parent passes one allele to each offspring, then it makes sense that the offspring will receive an allele from each parent).

What is turner syndrome?

45,X Female (because they have one X) Do not go through puberty normally (this patient is 16 years old) Some have mild cognitive deficits Many have webbed necks Chubby body type

draw out bridges hypothesis about the flies sexual determination system.

90% recombinant 10% nonrecombinant

If the rf is 50%, what is the ratio of the resulting allele combination? How about if the rf is lower than 50%?

9:3:3:1 If the rf is lower than 50%, there will not be all the allele combinations. in the picture, notice that there is no switch between the inner A, B, a, b. These possibilities arise more frequently than normal. They take away combinations from the 50% rf and put it to an atypical rf. In other words, there will be a mixture of outcomes.

What does recombination give to organisms?

A gamete can contain recombinated DNA. The individual inherited a chromosome with T and B from Dad, and with t and b from Mom. The individual may pass down the TB or tb combination, or may reshuffle the alleles and pass down either tB or Tb alleles (recombination). This gives us genetic diversity.

Is the wild-type allele a normal allele?

A number of these alleles will produce a normal level of proteins. The vast majority of the alleles will give an amount of protein that we can consider "normal." The wild type allele is simply the most common allele, which usually produces a normal amount of protein.

What are inversions and what types are there?

A segment of chromosome is inverted: Pericentric = If the inversion breakpoints lie on either side of the centromere Paracentric = If both breakpoints lie within the same chromosome arm (as seen in figure above) Inversions can be balanced or unbalanced. When the chromosome breaks to invert, it can break without losing DNA or with losing DNA. As before, An unbalanced inversion is more likely to produce an abnormal phenotype, because one or more portions or copies of one or more genes may be lost. In a balanced inversion, one or both breakpoints can fall inside a gene's sequence, resulting in the gene's sequence being broken into two parts, and the parts being separated from each other They can also cause the "position effect." For either a balanced or unbalanced reciprocal translocation there may be a position effect: Some genes (ex. clustered HOX genes) are lined up next to each other and expressed in a specific order; moving one away from the cluster may silence it Translocation can move a normally active gene close to a heterochromatic region, silencing the gene Remember, inversions may not cause problems for one's phenotype but can cause problems for one's offspring's phenotype.

Prophase II:

Chromatin condenses, nuclear envelope degenerates, spindle fibers form

Describe telophase I, meiosis (draw)

Centromere: chromosomes have migrated completely to opposite poles. Cytokinesis, aka cytoplasmic streaming—cytoplasm and organelles migrate into the two daughter cells Chromatid: Nuclear Envelope: Early-Mid Telophase I : Centromere: Chromatin: Chromatin is still somewhat condensed Nuclear Envelope: Nuclear membrane has not yet reformed Cells only beginning to cleave apart, new cell membrane is not yet visible

What does the end of interphase look like in meiosis?

Centrosomes: Spindle fibers not yet organized. Chromatin: This is de-condensed. Nuclear Envelope: This is intact.

What is metaphase I? meosis. draw early, middle, late

Centrosomes: The bivalents are aligned in their tetrads along the equatorial plane. The spindle fibers grab the chromosomes by the kinetochores at their centromeres. Cell makes sense that every chromatid is bound by a spindle fiber. -Chromatids: -Nuclear Envelope: Late Metaphase I: -Centrosomes: Chromosomes are aligned at the equator. Spindle fibers are binding the chromosomes. -Chromatids: -Nuclear Envelope: Similar to mitosis. Big difference. Mitosis: all chromosomes are bivalent and are lined vertical. Meiosis: lined up in pairs vertically. Cells knows to differ these via sequences in chromosomes.

What is a duplication? Name and portray the types.

Copied genetic code. ORIGINAL CODE: ABCDEFG NOT SIDE BY SIDE Displaced duplication—Not side by side A B-C D E F G D E Reverse duplication = inverted duplication A B-C D E F G E D SIDE BY SIDE: Tandem duplication= ABCDEFEFG segmental duplications: duplicated regions up to 100 kb (100,000 bp) in size (Approx. 4% of the human genome )

How do you use a monohybrid cross?

Crossing alleles to see what the future generation's allele combination will be.

What is the chi square used?

Mendel's assumption based on the equal frequency of alleles combos. It leads to 9:3:3:1. The Chi Square test is used to test whether the deviation from the predicted outcome is large enough to conclude that there was something wrong with your fundamental assumptions.

When chromosomes exchange pieces, what is one of the risks?

DNA can be lost. No DNA lost = balanced translocation DNA lost = unbalanced translocation Note that the two chromosomes often exchange different-sized pieces—this does not make the translocation unbalanced—the only thing that matters is whether any DNA is lost at the breakpoints

What happens during interphase before meiosis?

DNA is replicated during the S phase. There are two sister chromatids held together by cohesin. Separase will separate the two chromatids and by dissolving the cohesin, allowing the two homologous chromosomes to separate during anaphase I and the sister chromatids during anaphase II.

How does Mendel's work relate to sex-linked traits?

Mendel's assumptions work for autosomal genes but not sex chromosome-linked genes.

What does dominant and recessive mean?

Dominant: an allele that supersedes with its phenotype over all other alleles. an allele that will control the phenotype, in spite of the presence of another allele that would code for a different trait Recessive: An allele that will only control phenotype if the individual if the individual is homozygous for that particular allele.

Describe Michaelis' way to describe prophase I, draw

Early Prophase I -Centrosomes: centrosomes, beginning to move toward opposite poles of the dividing cell -Chromatids: Light blue squiggly figures in the nucleus are the chromosomes, which are beginning to condense -Nuclear Envelope: starts to disintegrates Late Prophase I -Centrosomes: Centrosomes have migrated to the poles. Spindle fibers are reaching in to bind the chromosomes Chromatids: Light blue chromosomes now obviously condensed Nuclear Envelope: This has disintegrated *notice, the last one is also known as prometaphase I* *When authors use a prophase I/prometaphase I scheme, prometaphase I corresponds to the pachytene, diplotene and diakinesis stages*

How do we use 9:3:3:1 to determine the relative distances of genes?

First, do a dihybrid cross and solve for the ratios and then compare. If it is 9:3:3:1, then the genes are pretty far apart. If it is divergent from 9:3:3:1, then the genes are close together. If it is wildly divergent from 9:3:3;1, then the genes are very close together.

How can you get one affected and three unaffected children for tay-sachs disease?

First, start a punnett square to calculate the allele possibilities for one child. Then, use the or/and rules to calculate for the specific example. Four ways to get one affected and three unaffected children: Aff, Un, Un, Un = 1/4 X 3/4 X 3/4 X 3/4 = 27/256 Un, Aff, Un, Un = 3/4 X 1/4 X 3/4 X 3/4 = 27/256 Un, Un, Aff, Un = 3/4 X 3/4 X 1/4 X 3/4 = 27/256 Un, Un, Un, Aff = 3/4 X 3/4 X 3/4 X 1/4 = 27/256 Overall probability = 108/256 = 27/64

what is nondisjunction?

For any set of chromosomes, when the chromosomes do not split and stay together.

What can unbalanced and balanced translocations cause?

For either a balanced or unbalanced reciprocal translocation there may be a "position effect": Some genes (ex. clustered HOX genes) are lined up next to each other and expressed in a specific order; moving one away from the cluster may silence it Translocation can move a normally active gene close to a heterochromatic region, silencing the gene (tightening the gene).

What are the checks that occur in interphase?

G1= Phosphorylation of certain proteins, ex. the retinoblastoma (RB) protein. At the end of G1, the cell makes sure it has stockpiled all the enzymes it needs to replicate DNA before it goes into S phase G2= The cell must accumulate a certain level of a complex called the mitosis-promoting factor (MPF), and activate it by dephosphorylation, in order to enter the M phase. At the end of G2, the cell checks for DNA damage; the presence of DNA damage keeps the MPF inactive and halts the cell in G2. The cell also checks the length of the telomeres.The telomeres shorten every cell cycle, and telomere length is an indicator of cell age (more on this later)

What's the cell cycle?

G1= Stockpile nucleotides, ATP, enzymes to replicate DNA (know this) S: Replicate DNA G2: Synthesize microtubules and other proteins needed for cell division, stockpile ATP and enzymes for mitosis/meiosis. M: Mitosis or Meiosis * This cycle also has Go (if needed)* Go happens after G1 In this phase, the cell stops replicating and dividing. This is a "check point." The cell goes to Go if it senses that there aren't enough nutrients or growth factors to go through the cell cycle. This is a stable state during which cells usually maintain a constant size. They can remain in G0 for an extended length of time, even indefinitely, or they can reenter G1 and the active cell cycle. - if it cannot get repaired, it goes to apotosis.

What are the units of rf?

Genetic maps describe the distances between genes in terms of Rf Genetic map distance is expressed in map units (m.u.), aka centiMorgans (cM)—1 m.u. = 1 cM = 1% recombination

List all the mechanisms for sex determination

Grasshoppers: females have two Xs, males have one X--there is no "O" chromosome. Males are heterogametic—X-bearing sperm versus sperm with no sex chromosome Bees, Wasps, and Ants: No sex chromosomes. Females are diploid, males are haploid Some plants, some insects, some reptiles, some mammals: Females have XX, males have XY. Males are heterogametic--X-bearing sperm versus Y-bearing sperm birds, snakes, butterflies, some amphibians, and some fish: females have ZW, males have ZZ. Females are heterogametic—Z-bearing eggs versus W-bearing eggs fruit flies: genetic balance system.In Drosophila, sex is determined by the balance between the number of copies of certain X-linked genes versus certain autosomal genes, i.e the ratio between the number of X chromosomes and the number of haploid sets of autosomes (not total number of autosomes) Many Possibilities For The X:A Ratio Most flies have two sets of autosomes; some have three A fly may have up to four X chromosomes The Y chromosome does not determine sex. Females can have a Y chromosome.

What's the difference between the bee and grasshopper sex determination system?

Haplodiploidy is not the same thing as an XO sex-determination system. In Haplodiploidy, males receive one half of the chromosomes that female receive, including autosomes. In an XO sex-determination system, males and females receive an equal number of autosomes, but when it comes to sex chromosomes, females will receive two X chromosomes while males will receive only a single X chromosome

What is heterogametic and homogametic?

Heterogametic = produce two different types of gametes (i.e. X-bearing vs Y-bearing sperm Homogametic = all gametes have the same chromosome content

What does "homozygous" and "heterozygous" mean?

Homozygous: -the individual's two alleles for a particular gene are the same Heterozygous: The individual's two alleles for a particular gene are different.

What's the mneumonic to remember the stages of cell division?

I PP (on the) MAT C Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis https://www.youtube.com/watch?v=-PMXatafIXc

What difficulty do we have when trying to use rfs to map out genes?

If they do not give you the exact positions, you can organize the genes in many different ways. The problem that needs to be solved, thus, is finding the proper position of the genes relative to each other. The picture is an unavoidable situation (it is merely a mirror image). But, if not all the rf values are given, you can have more than just the mirror image. There can also be a rounding error. the numbers may not exactly match up (i.e. if you only did the AB and BC crosses to get these data, you might get 23-27 m.u. if you did the cross with the A and C genes themselves

What's the difference between spermatogenesis and oogenesis

Immediately after fertilization, the zygote/embryo undergoes several rounds of cleavage--cell division with no replication of cytoplasm and organelles The sperm has donated only its DNA and centrosome, so all the cytoplasm and organelles that are available to be divided among the newly created cells come from the egg In order to package as much cytoplasm and organelles into the egg as possible, during oogenesis, when the cell divides, almost all the cytoplasm and organelles migrate into one daughter cell The cell that gets the cytoplasm and organelles eventually becomes the egg; the other daughter cell is called a polar body—they usually die off **** oogenesis produces one viable egg. all the cytoplasm and organelles goes inside one egg. Born with the eggs she will have for the rest of her life. spermatogenesis produces four viable sperm. Happens throughout puberty. All the cytoplasm and eggs comes from mom and not dad. (about 8,000 cells needs to be outfitted with organelle and cytoplasm from the egg).

Why can we see two sister chromatids in prophase?

In S phase, the DNA replicated, so there is a duplicate of this DNA.

What happens during apoptosis?

In this process, a cell's DNA is degraded, its nucleus and cytoplasm shrink, and the cell undergoes phagocytosis by other cells without any leakage of its contents. It's called process called membrane blebbing

How many autosomes are there in the grasshopper sex determination system?

In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (X0), while females have two (XX). The zero (sometimes, the letter O) signifies the lack of a second X. Maternal gametes always contain an X chromosome, so the sex of the animals' offspring depends on whether a sex chromosome happens to be present in the male gamete. Its sperm normally contain either one X chromosome or no sex chromosomes at all. notice= there is an autosome where the O is.

Which organisms rely on environment for sex determination?

In turtles, crocodiles and alligators, temperature determines sex In turtles, warm temperatures produce females, cooler temperatures produce males In alligators, the reverse is true

What is interkinesis?

Interkinesis--Nuclear membrane reforms, spindle fibers degenerate, chromatin decondenses

How can a Robertsonian translocation mess up phenotype of offspring?

It can cause down syndrome: It may also have two centromeres, but the cell only recognizes one of them when it comes time for the spindle fiber apparatus to recognize chromosomes for the purposes of pulling one set of chromosomes into each daughter cell during anaphase of meiosis I When the cell divides during meiosis I, the Robertsonian translocation is treated as if it was a single chromosome; the gamete that gets the Robertsonian translocation does not realize it has obtained a copy of the second chromosome as well The gamete pulls in a second copy of that chromosome, making the gamete disomic (possessing two copies) for that chromosome So, one with a Robertsonian translocation has an OK phenotype because it has two functioning chromosomes. During meiosis, the body sees it as one and it creates a trisomic child. 14-21 (common robersonian translocation and also is where down syndrome occurs).

What's a monohybrid test cross?

It helps determine the allele nature of an individual. For example, we can have an individual that displays dominant allele for a particular gene. But, we don't know exactly what the allele is. It can be AA or Aa. Based on the results of the test cross, we can determine what the allele composition is.

Why is rf 50%? Why is this the max?

It is based on Mendel's assumption. Ideally, two will be recombinant and two nonrecombinant. So 50% will recombinant. But, this can diverge. Sometimes there will be less than 50% recombinant. If the breakage point happens sometimes above or below the genes, then you will have an rf that is lower than 50% rf.

what could a possible cause of nondisjunction be?

It is believed that a reduced ability to recombine during prometaphase I leads to an increased frequency of nondisjunction

What does "allele" mean? How many alleles are there total?

It is one of the two copies of a gene that an individual has. A gene can have various alleles of a gene.

What does genetic linkage mean? What's the rf?

It means that AB are so close together that there will be no recombination breaks between them. The rf between them is said to be 0% (aB or bA never appear. AB and ab are linked to each other). The rf between A and C or a and c is 50% (they are far enough apart that they will always recombinant).

How does double recombination show us the order of the genes?

It tells us which gene is in the middle. When there is double recombination, the gene in the middle switches partners. So, the genes on the end, the alleles are still the same. When Dr. M gives us the genotypes, it might seem that a certain recombination is double recombination. But, the only way this can be confirmed is if we look at the numbers. The pair with the lowest frequency will be the one with double recombination. This is what we base double recombination on. So, after we look at the frequency and realize it is the lowest, we can look at the gene that is switched. This represents the center allele.

How many DNA molecules and chromosomes are there throughout mitosis?

Make sure that in stage 2 of meiosis, you draw two cells. How many chromosomes are there (per cell)? Remember, in mitosis, if you start with diploid, then you end with diploid. in meiosis, you start off with 2 diploid and make 4 haploid.

What's the difference between mitosis and meosis

Meiosis: only oongonia (female reproductive cells) and spermatogonia (male reproductive cell). Mitosis: all other cells Meiosis: produce four haploid daughter cells (one set of chromosomes per cell). Mitosis: two diploid daughter cells (two sets of chromosomes per cell). Meiosis: it has recombination. this allows a child to inherit.

What are the assumptions that lead to a 9:3:3:1?

Mendel assumed that the AB, Ab, aB and ab allele combinations would appear equally often in the two parents' gametes after every meiosis Mendel also assumed that the gametes with the AB, Ab, aB and ab allele combinations would be equally likely to create viable offspring

Explain the sex-determining system used in Bees, Wasps, and Ants

No sex chromosomes. Females are diploid, males are haploid Unfertilized eggs develop into haploid males whose genomes are derived solely and completely from their mother The female decides whether there will be fertilization or not (she has a pouch that stores the genetic material). For every gene, the son has one of the two alleles the mother possesses Females produce haploid eggs by meiosis, males produce haploid sperm by mitosis Fertilized eggs develop into diploid females, who have half their genes from their mother and half from their father. Punnett square does not apply to males (it doesn't have the second allele).

Telophase II

Nuclear membrane reforms, spindle fibers disappear, chromatin decondenses

How do you use a dihybrid test cross? You have an individual with a dominant trait for character A and a dominant trait for character B. Is the individual homozygous or heterozygous for the dominant allele?

Possible genotypes: AABB or AABb or AaBB or AaBb Cross with aabb. *know how to do the reverse dihybrid. AKA, you are given the ratios and you need to do the reverse* 1:01 (shan)* know this.

How does one set up a punnett square?

Put the possible allele combinations on one side of the punnett square and the other possible allele combinations on the other side of the punnett square (this can be two parents). Then, cross the combinations within the box and see what the result is. This is the F2 generation possibilities. An important part is to pinpoint the possible allele combinations.

What is TDF?

Testis Determining Factor. This is what develops male features to arise due to the Y region (SRY (sex determining region)

What significance does the SRY gene have?

The X and Y sex chromosomes can recombine like autosomes but only at the ends (called pseudoautosomal regions). Below this on the Y chromosome is the TDF (Testis determining factor) or SRY (sex determining region), which is what causes the male features to arise. If too much information is exchanged, then someone might exchange some SRY region. This can get translocated to the X chromosome. If a sperm develops with the SRY region on the X chromosome, then the child will develop as a male (even though he has two X chromosomes). Conversely, If the sperm that makes the child contains the Y that has lost the SRY gene, the child will develop as a female, despite having a Y chromosome.

What is Robertsonian translocation?

The acrocentric chromosomes 13, 14, 15, 21 and 22 form Robertsonian translocations. A Robertsonian translocation is considered a single chromosome, so the karyotype of a male with a Robertsonian translocation involving chromosomes 13 and 14 is written as 45,XY,rob t(13q;14q) or 45,XY,t(13:14)(q11;q11) If you have 5 Robertsonian translocations, and don't lose all of the p arm material from all those acrocentric chroms, it is possible for you to be phenotypically normal yet have 41 chromosomes

What is the consequence of independent assortment?

The allele do not tell us what the other alleles are like. Whether a sperm/egg cell contains a T allele or a t allele tells you nothing about which B/b allele that gamete has. So, if you have a T allele, you can either have it paired with a B or b allele.

What does independent assortment mean?

The alleles do not influence each other in regards to which goes on to be in a gamete. Each allele has an equal probability of going inside a gamete (regardless to whether it is dominant or recessive). This means that, for two genes with two alleles each (alleles A/a and B/b), there are four possible combinations you might see in a gamete--AB, Ab, aB and ab Mendel assumed that these allele combinations will appear equally often in the individual's gametes

What are the checks that occur in metaphase?

The cell checks each chromosome so that it is properly aligned. at the equatorial plane and that each centromere has been contacted by spindle fiber. If the chromosomes/spindles have not aligned properly, this inhibits activation of the MPF and halts the cell in mitosis. depends on tension generated at the kinetochore as the two conjoined chromatids are pulled in opposite directions by the spindle fibers

Metaphase II

The chromosomes align at the equatorial plane, and the spindle fibers grab the chromosomes. Note that half the chromatids are recombinant chromatids, and half are nonrecombinant chromatids

What happens in the Go phase?

This happens right after G1 In this phase, the cell stops replicating and dividing. This is a "check point." The cell goes to Go if it senses that there aren't enough nutrients or growth factors to go through the cell cycle. This is a stable state during which cells usually maintain a constant size. They can remain in G0 for an extended length of time, even indefinitely, or they can reenter G1 and the active cell cycle. - if it cannot get repaired, it goes to apotosis.

What influences the rf?

The distance of two genes to each other. The closer they are to each other, the lower the rf (lower than 50%). This is because they display more linkage qualities. The farther they are from each other, the higher the rf (the more likely the rf is 50%). This is because they display less linkage qualities and are more likely to separate cleanly. Different chromosomes have different rfs between genes that may lie the same distance from each other. different people (male vs. female, different ethnicities) also have different rfs, even if the same genes are the same distance apart. The distance in regards to the location in reference to the centromere or telomere can also change the rf (even if the distance is the same). So, if the genes are near the centromere, then it will be a lower rf than if the genes were near the telomere. So the same distance will have different rfs.

Describe/draw anaphase I meosis

The enzyme separase degrades the cohesin that holds the two homologs together (but leaves the cohesin that is... holding the sister chromatids together at the centromere intact). The two chromosomes in each bivalent migrate apart from each other toward opposite poles of the dividing cell. Middle of anaphase I; Spindle fibers grab the chromosomes by connecting to the kinetochores at their centromeres and draw the chromosomes apart. The protein shugoshin protects the cohesin (at the centromeres only) from degredation by separase. This holds the sister chromatids together at their centromeres during anaphase I of meiosis, so they don't separate until anaphase II Shugoshin must be degraded during metaphase II, so the sister chromatids can separate during anaphase II

What are the generations that arise in genetic offspring? name and describe.

The first two organism that mate, the parents= P Parent's offspring= F1 F1's offspring= F2

What's prometaphase I?

This is a contested category within meiosis. Several other textbooks do, so you may see other sources in which there is a separate phase described called Prometaphase I.

What is shugoshin?

The protein shugoshin protects the cohesin (at the centromeres only) from degredation by separase. This holds the sister chromatids together at their centromeres during anaphase I of meiosis, so they don't separate until anaphase II. What does this do? Protects the cohesin at the centromere through stage I of meisos. This is why the spindle fibers pull, they pull apart the homologs and not the sister chromatids. Then in anaphase II, shugoshin gets degraded, separates and the cohesion breaks down, thus allowing the sister chromatids to separate. This is what allows for the unique separation of meiosis.

What is equatorial division?

The second cell division is sometimes referred to as the equational division, because there is no change in the number of chromosomes per cell.

Anaphase II

The sister chromatids migrate apart from each other toward opposite poles of the dividing cell Shugoshin dissolved, so sister chromatids can separate due to the dissolving of cohesion.

What problem did morgan's experiment face?

There were some offspring that did not follow his theory. Morgan considered all his F1s to have red eyes, but he noticed a very small number of white-eyed males in his original F1 generation He kept seeing white-eyed males and females—they were rare, but too frequent to be due to new random mutations

When the rf is 50%, what does this mean? What are the possible chromosomes in the gamete?

There will be two recombination chromosomes and two non-recombination. So it is 25% each. This is true even if there is a 50% rf, which means that the recombination breakpoint always falls in between the genes.

What is a punnett square?

This allows us to see what the genotype will be for a particular combination of alleles.

What does rf 50% mean for the nature of the chromosomes?

This doesn't mean they are on different chromosomes. They can be on the same chromosome, just sufficiently far apart from each other. They can be on different chromosomes, but also on the same chromosome. Max value of 50% means that two of the chromosomes are recombinant and two of them are non-recombinant.

How do we use binomial expansion to calculate the probability of a number of affected.

This equation tells us how many are affected out of a total amount. First calculate the probability of one child being affected and unaffected. Then apply it to this binomial equation.

What is an autosome?

This is a numbered chromosome (1-22).

What does "true-breeding" and "pure-breeding" mean?

This term pertains to a situation when all an individual's offspring have the same trait, which suggests that the individual is homozygous for the alleles that code for that character.

How do you calculate the probability of a set of independent events occurring? Ex: The probability of getting 3 heads in a row when flipping a coin

Use the "and" rule. 1/2 probability to get a head on any single flip 1/2 X 1/2 X 1/2 = 1/8 you take the probabilities of the individual events and multiply them together

In monohybrid test crosses, why do we use a parent that is homozygous recessive?

We are trying to get the phenotype of the offspring to show us what the genotype of the one parent us. But we have to make sure the other parent doesn't influence phenotype. The phenotype is going to be strictly determined by the target parent. Based on the results of the test cross, we can correlate the test cross results to what the offspring composition is. If all of the offspring is dominant then we know the individual is AA. If half of the offspring is dominant and the other half is recessive, then we know the individual is Aa.

What is a wild type and variant allele, and how do we denote this?

Wild-type allele= the allele that is the most common allele found in nature. Variant-type allele= the allele that is divergent from the wild-type allele for that particular gene. Wild-type allele= "Allele+" or just "+."

What is Klinefelter Syndrome?

XXY develops as a male. Due to a transfer of the SRY region. Male (because they have a Y) Secondary sexual development is somewhat female Gynecomastia (male breasts) Very low sex drive Sterile

How does blindness transfer in h umans?

Xc is dominant.

bees, and wasps. Do they need a punnett square?

no. female is diplod. male is haploid. no sex chromosomes.

What's the difference between chromosomes, chromatids, and alleles?

a chromosome (when duplicated) is made up of two sister chromatids, the chromatids are made up of bundled DNA. when a chromosome is not duplicated it is simply one chromatid an allele is a sequence of genes that is located on a specific part of a specific chromosome.. this sequence (allele) is the code for a specific trait

What does "trait" mean?

a specific form of the character, for example yellow flowers

What are the stages in prophase I?

a.) Leptotene chromatin condenses. b.) Zygotene: chromatin condenses, homologous chromosomes pair up and partake in "synapsis" (aligning very close to each other) to form bivalents (2 chromosomes), which are tetrads (four chromatids). c.) Pachytene: chromatin condenses, synaptonemal complex develops between homologous chromosomes (i.e. the homologous chromosomes come into contact with each other at one or more places in each p and q arm). *Non-sister homologous chromatids (one from each member of the homologous chromosome pair) physically cross over at the points of contact and exchange material (i.e. recombination occurs)* d.) Diplotene—the two chromosomes in each bivalent begin to separate, but remain joined at the chiasma—i.e. the places where the crossing over took place e.) Diakinesis—chromatin condenses further, the two chromosomes in the bivalent separate farther apart, the two chromosomes now remain joined only at the ends *note* When authors use a prophase I/prometaphase I scheme, prometaphase I corresponds to the pachytene, diplotene and diakinesis stages.

what are the effects of an unbalanced translocation on phenotype?

abnormal phenotype (usually): Parts of the genetic code are lost, thus permanently altering the expression of these genes. normal phenotype: This is possible, but less likely because parts of the genetic code have been lost.

What does hemizygous mean?

an individual possess only one copy of the chromosome. So there is no other copy of that chromosome. Thus, there is only one copy of the gene.

What does "character" mean?

an observable feature, such as flower color

What do the sister chromatids become chromosomes?

anaphase

What's the difference between the "and" and "or" rule?

and rule= There is only one way that this could happen. or rule= A number of different ways this can happen.

What's the difference between autopolyploidy and allopolyploidy?

auto: at least one extra set of chromosomes from same species. allo: from two related species that their gametes can fuse (donkey and horse).

What's the different between an autosome and sex chromosome?

autosome= pertains to the numbered chromosomes. sex chromosome= pertains to the chromosomes that determine sex (in humans X and Y).

What can balanced reciprocal translocations cause? Can unbalanced do this? Draw out the balanced reciprocal translocation gamete possibilities. Which is worse and better?

balanced reciprocal translocations can cause unbalanced gametes. It's worse to completely miss a gene (in this case, these genes are just replicas of genes already preexisting) than to have mixed up genes but maintaining all these genes Unbalanced ones cannot because they cannot reciprocate (there will be pieces missing). (remember, affect pertains to whether functional genes are cut out not amount of genes cut out).

What's a cis and trans genotype?

cis= coupling; trans= repulsion

What happens if there is x inactivation on an x recessive allele in females?

females have a 50/50 pattern of inactivation. half from dad half from mom. So 50% of cells are saved and 50% are suffering. If the xinactivation causes 90% inactivation of affected allele, then only 10% will be suffering from mutation. If only 10% is inactivated, then 90% will suffer and 10% will be saved. If this mutation is dominant and it is x inactivated, then it is saved from this mutation more. The woman is still affected but not as affected.

Describe the fruitfly genetic balancing system

fruit flies: genetic balance system.In Drosophila, sex is determined by the balance between the number of copies of certain X-linked genes versus certain autosomal genes, i.e the ratio between the number of X chromosomes and the number of haploid sets of autosomes (not total number of autosomes) Many Possibilities For The X:A Ratio Most flies have two sets of autosomes; some have three A fly may have up to four X chromosomes The Y chromosome does not determine sex. Females can have a Y chromosome.

What's happening in early, mid, late metaphase?

generally, metaphase is when -centrosomes=spindle fibers are attached to each chromatid. The cell goes through spindle-assembly checkpoint to be sure every chromatid has been bound by spindle. -chromatids= chromosomes are the most condensed and are aligned at equatorial plane. -nuclear membrane= still disintegrated picture: late metaphase. when is metaphase over? when all chromosomes are lined up at equator and is contacted properly by spindle fibers.

What does genotype and phenotype mean?

genotype: the actual genes of an organism; the specific alleles held by an individual. phenotype: the physical display of the genes in question. the observable characteristics of the individual, both overtly visible characteristics (ex. hair color) and those that cannot be seen (ex. blood sugar level).

What is in interphase?

has G1 (Go if needed), S, G2

How does linkage relate to rf?

if two genes are linked, then the rf is 0%. But you can have two linked genes (two alleles) among another gene that is not linked. So the rf between the two linked genes and the other gene could range between 0%-50%.

Will the recombination breakpoint always be the same? give the rfs too

no. sometimes it falls between two genes (rf 50%) sometimes it falls above or below two genes (rf <50%). During recombination the rf will be between 0% and 50%

What's the limitation of rf mapping?

if you have two genes that have an rf of 50% (50 cM), then it is not mappable. This is because 50% goes to infinitum in distance. rfs don't take into account double crossing over. There could have a double crossover which would make it seem that nothing happened. The rf is often an underestimated. There is crossing over that happens that is not reflected in phenotype (there is more at 55:00).

how does the 9:3:3:1 ratio help map out the relative positions of genes?

in order for this to be true (the 9:3:3:1 ratio), each of the 16 possible allele combinations must appear at equal frequency. These gametes must also appear at equal frequency. This is not necessarily true. The gametes will not appear at equal frequencies.

What is nonreciprocal translocation?

inserting one part of a chromosome into another one.

What's in-between meiosis I and II?

inter-kinesis. This is a resting period.

What can cause the position effect?

inversions, translocation.

What benefit can deletions have?

it can help us map out diseases. Problem: As researchers go through the process of finding the genes that are responsible for a disease, they often have periods where they have the location of the gene narrowed down to a portion of the chromosome, but the region is big enough to contain a large number of genes They need to narrow the region down some, before they start looking for the gene Solution: You try to find people who have deletions in that region Some will have the disease, and some will not Both help narrow down the location of the disease-causing mutation Scientists look at the region that is deleted in some people and not deleted in other patient.

Why is nondisjunction a problem for people? and in what context?

it is a problem because it leads too much or too little DNA. In the context of a woman's biological clock. The older she gets, the more likely she is to have nondisjunction.

Under Mendel's assumptions, what is the percentage of recombination for

it's 50% for one version and 50% over the other version. Each gamete is 25%

Where is the centromere located? What are the types of chromosomes? Which ones do humans not have?

middle of the chromosome Humans do not have telocentric chromosome.

What are polycentric chromosomes? What is the consequence of this?

multiple centromeres. The spindle fibers attach to the multiple centromeres. This could lead to shredding.

What's the difference between a mutation and disorder?

mutation= you can inherit a mutation that can cause a disorder. You inherit a mutation that creates a disorder.

Do we always get the 9:3:3:1 ? What does this tell us?

no. We do not always get the 9:3:3:1 ratio. If it diverges from this, then we can determine the relative distance of the genes.

What are autosomes?

numbered chromosomes; sex chromosomes = X and Y in many organisms, Z and W in others

How do you set up a three point cross to map genes?

once you get the F1 heterozygous gametes, you cross it with homozygous gametes and see what the result is. List all the F2 possibilities as to have a key. This allows the phenotype of the offspring to reflect the genotype of the parent. It is a test area.

What are tumor suppressors?

prevent cancers from growing. A cyclic dependent kinase phosphorylates the proteins. The tumor suppressors bind to these proteins, preventing the phosphorylation. This causes apoptosis.

When does recombination occur? In what way? what are the effects? What's an allele?

prometaphase or pachytene When you draw recombination, make sure you draw it happening to both arms. Gene Allele: For any given gene, there are many different versions of that specific gene sequence in a human population. Each sequence is called an allele. Some versions produce higher proteins. There can be different regulatory sequences. If an individual has one allele rather than another, then this individual could result in a different phenotype (example: big B for brown, little b= brown). It depends what the kid gets from mom and dad. There are four possible sperm combinations. Recombination can influence what alleles end up in child. The phenotype can change because the allele can change.

What is M phase divided into?

prophase, prometaphase, metaphase, anaphase, telophase (this is where cytokinesis occurs. This means that the organelles and cytoplasm are divided between two daughter cells).

What is reduction, division ?

reduction of number of chromosomes by half

By what means do the sister chromatids separate? when does this happen?

separase.There is cohesin that holds the two sister chromatids together at the centromere until the enzyme (separase) degrades this cohesin. This allows the sister chromatids to separate. when? end of metaphase—beginning of anaphase Once this separation occurs, the sister chromatids can effectively separate during anaphase. The sister chromatids are helped with the motor protein dynenin. This is what physically pulls the sister chromatids apart. Dynein sits on two spindle fibers and pulls on two spindle fibers that are connected to chromosomes

What did Mendel assume?

that the breakpoint will be in between the genes. There will always be four possible allele combination in gametes and they will appear at equal frequencies.

What is a sex chromosome?

the X and Y chromosome.

What's the fundamental assumption of gene maps?

the closer two genes lie, the smaller the rf between them.

What are pseudoautosomal regions?

the ends of the chromosome that recombine.

What physically separates the sister chromatids?

the motor protein dynenin. Dynein sits on two spindle fibers and pulls on two spindle fibers that are connected to chromosomes

How does one count the amount of chromosomes at a particular cell phase?

the number of centromeres= number of chromosomes. When there are two sister chromatids, it's one chromosome but two DNA molecules. G1=4 S=4 G2=4 Prometaphase=4 Metaphase=4 Anaphase=8 Telophase/cytokinesis=4

Why do Robertsonian translocations allow the phenotype to stay the same sometimes?

the p arm (which is removed) is not that rich with important DNA material. It can be made up else where. The p arms of your acrocentric chromosomes each contain hundreds of copies of the ribosomal RNA gene, but that's all. Material is lost from one or both p arms, but there are so many copies of the rRNA gene in your other acrocentric chromosomes that you can afford to lose some

What happens if the frequency of a certain recombination is 90%?

the rf is still 50%. it cannot go over this.

What practical usage do rf values allow for?

they allow for the mapping of genes. Physical maps describe the distances between genes in basepairs (b.p.). The fundamental assumption that allows for this is that the closer that genes lie, the lower the rf value.

What's the cause of duplication?

they can cause new genes. Genes that make proteins that are essential for the life or health of an individual are often not free to mutate—there is natural selection against mutations that render the protein nonfunctional, or change its function.

What purpose do reciprocal crosses play?

they confirm certain dihybrid crosses. It reverses the sexes that one see for particular phenotypic trait. It then allows one to see whether a certain phenotype is connected to a sex chromosome.

What is a locus?

this is a specific place in the DNA molecule and it varies in length. It is nothing more than a place.

What's the method for noting genotypes?

top of two lines= one chromosome bottom of two lines= second chromosome

What is reciprocal translocation?

two chromosomes exchange parts of its self with each other. notice: you can trade very different size pieces

How do you calculate the probability of a set of mutually exclusive events occurring? Ex:The probability of getting three children of the same sex

use the "or" rule. In order to calculate the probability of a set of mutually exclusive events occurring, you take the probabilities of the individual events and add them together—Note that you first calculate the probability of each individual event using the AND rule p(3 girls) = 1/2 X 1/2 X 1/2 = 1/8 (AND rule) p(3 boys) = 1/2 X 1/2 X 1/2 = 1/8 (AND rule) p(3 girls OR 3 boys) = 1/8 + 1/8 = 2/8 = 1/4 (OR rule)

How do you use a branch diagram to solve for probability?

use the and rule.

When you do a monohybrid test cross, what question is one asking? How does the outcome of the test cross answer one's question?

what is the genotype of the parent that has the dominant phenotypic trait. Just say the result of the test crosses.

When is metaphase over?

when all chromosomes are lined up at equator and is contacted properly by spindle fibers.

what do we need to take into account when determining what effect a particular translocation will have?

will rearrangement mess up my phenotype or children's phenotype. Some rearrangements does not mess up my phenotype but can mess up phenotype of children.

How do you do a dihybrid test cross?

you cross a heterozygous pairing to a homozygous recessive pairing (the homozygous pairing allows for an analysis of the heterozygous pairing without interference).