Study Guide Exam I (Ch 1-4)

I. Ch. 1 a. Model organisms (importance)b. Early theories of hereditary

transmissionc. Important people & their

contributionsi. Schwann and Schleiden

ii. Darwiniii. Mendeliv. Flemmingv. Weismann

vi. SuttonII. Ch. 2

a. Pro- vs eukaryoteb. Ploidyc. Chromosome structured. Cell cycle

i. Phasese. Mitosis

i. Phases & important eventsii. Spindle fibers

f. Meiosisi. Vs. mitosis

ii. Phases & important eventsiii. Crossing overiv. Genetic variabilityv. Unequal division

III. Ch. 3a. Mendel b. Definitionsc. Mendel experiments

i. Crossesii. Dominance

iii. Principle of segregationiv. Principle of Independent

assortmentd. Punnette. Phenotypic and Genotypic ratiosf. Branch diagramg. Probability

i. Multiplication ruleii. Addition rule

h. Chi-squarei. Pedigree Analysis

i. Identificationii. Determining genotypes

iii. Probabilities

IV. Ch. 4a. Allelesb. Symbolsc. Incomplete dominanced. Codominancee. Multiple allelesf. Lethal allelesg. Epistasish. Complementationi. Penetrance and Expressivityj. Temperature Effectk. Sex chromosomesl. Sex influenced/limitedm. Imprintingn. Cytoplasmic Inheritanceo. Maternal effect

CH1 Model genetic organisms are organisms used for the study of basic biological processes. An experimental organism conductive to efficiently conducted research whose genetics is intensively studied on the premise that the findings can be applied to other organisms. Important because you can use model genetic organisms to study human disease.

Early theories about heredity: Principles of heredity first demonstrated 10-12,000 years ago (domestication) Then artificial fertilization 2880 years ago (Assyrians) and also in Hindu writings 2000 years ago that suggested avoiding spouses with undesirable traits.

8000-1000BC-domestication of animals 5000 BC- plant cultivation 500BC-300BC- Aristotle 1856/1859- Darwin & Mendel

Pangenesis: idea on heredity was specific particles called gemmules carried information from the body to the reproductive organs which are passed to embryo at conception **very early concept**

Inheritance of acquired characteristics: Greeks proposed traits acquired in life incorporated into hereditary info and passed on. For example, a skilled artist would pass on art skills to offspring

Then 1665 Robert Hooke discovered the cell using a microscope…

Two early ideas:Preformationism: inside egg or sperm is a tiny very of an adult called a homunculus

Blending Inheritance: offspring are a blend of the parents

People: Schwann and Schleiden: Proposed the cell theory (1839) that stated cells are the basic unit of all living things and cells arise from preexisting cells.

Charles Darwin: Proposed the Theory of Evolution through natural selection and wrote On the Origin of Species (1856) that stated heredity was the fundamental of evolution

Gregor Mendel: Discovered the basic principles of heredity by crossing pea plants and analyzing patterns of transmission.

Walter Flemming: observed division of chromosomes (1879) and also figured out the heredity information was contained in the nucleus.

August Weismann: Cut off tails of mice for 22 generations and discovered the tail length of descendants did not change. He proposed Germ-plasm Theory that said cells of the reproductive system carry complete set of information

Sutton: proposed genes were on chromosomes in 1902

CH2Eu: “true” Pro: “pre” Karyote: “nucleus”

Bacteria DNA=spread throughout/ Eukaryote DNA= compact chromosomeA chromatin is DNA wrapped around histones (proteins that help organize DNA).Viruses are not cells because they can only reproduce inside a host cell (cannot survive alone).

Prokaryote Reproduction: BINARY FISSION1. Single circular chromosome in plasma membrane2. Chromosome replicates3. Two chromosomes separate4. Cell divides, each with an identical copy of original chromosome.

Happens very fast, 1 bacterium can divded into 10 billion in 10 hours.

Eukaryote Cell Division:Eukaryotes have 2 sets of chromosomes from sexual reproduction ( 1 from mom, 1 from dad =homologous pairs)

Homologous pairs of chromosomes are alike in structure, and carry genetic information for the same characters (genes). Humans have 23 homologous pairs

PloidyEukaryotes have 2 sets of genetic information= DIPLOID (2n) somatic cells 1 set= HAPLOID (n) This is in reproductive cells

Chromosome Structure: Kinetochore is essential for chromosomal movement

If shared centromere=1 chromosome. And you count chromosomes based on centromeres. (The centromere is necessary for cell division).

Telomere is for protection.

The “p” arm is the shorter arm (petite) The “q” arm is the larger arm

Cell Cycle

MPF= cyclin B + CDKG1= cell growth (4 chromosomes per cell, 4 DNA molecules) G0= arrested, non-dividing stage (still active ex: a happy liver cell that doesn’t divide often) Beyond the G1/S checkpoint, the cell is committed to divideS= DNA synthesis, cell actually starts replicating DNA (4 chromosomes per cell, 4 then 8 DNA molecules)G2: Preparing (4 chromosomes per cell, 8 DNA molecles)Beyond the G2/M checkpoint, the cell is ready to divide.Mitosis: Nuclear and cell divisionThe M or Spindle assembly checkpoint Cytokinesis

Cancer: loss of control over cells dividing. It is very important cells only divide when they are supposed to.

Of note: B-cell lymphoma can be caused by mutation in cyclinOverexpression of cyclin found in breast and esophageal cancer

Interphase: Cannot detect one chromosome from the other (cant see with light microscope)DNA synthesis G1, S, G2 occurREPLICATED

Mitosis (5 stages)- It is a small portion of overall cell cycle. 1 nuclear division, results in same # of chromosomes, yields genetically identical cells

Prophase: Chromosomes condense (DNA is already replicated in interphase)Mitotic spindle forms from centrosomes (poles)CHROMO CONDENSE, MITOTIC SPINDLE FORMS (4 chromosomes per cell, 8 DNA molecules)

Prometaphase: Nuclear envelope disappears Microtubules attach to chromatidsENVELOPE DISAPPEARS, MICROTUBLES ATTACH (4 chromo, 8 DNA)

Metaphase: Chromosomes arrange in a single plate called the metaphase plate (4 chromo 8 DNA)MIDDLE

Anaphase: Sister chromatids move toward opposite poles (after separation=chromosomes)Disjunction=separation of sister chromatids. Brief time of double chromosomes! (8 chromosomes 8 DNA)APART

Telophase: Chromosomes arrive at spindle polesNuclear membrane reforms (2 nuclei)Chromosomes disappear from viewChromosome count is normalEach cell now has a copy of all chromosomes (4 chromosomes per cell, 4 DNA molecules per cell)SEPARATION INTO TWO DIFFERENT CELLS

Cytokinesis: Splits the cytoplasm, organelles

How do chromosomes move?1. Depolymerization of tubulin at + end (microtubules shorten)2. Molecular motors

Some drugs specifically target spindle fibers and prevent them from building or removing. If the cell can’t move chromosomes because the spindle fibers don’t work, the cell stops.

-Spindle fibers not working could be a loss of chromosome or gain

Meiosis: CREATION OF GAMETES! 2 divisions, newly formed cell has ½ number of starting chromosomes, genetically variable cells

Prophase 1 is very important! Crossing over takes place!

Middle Prophase 1:Chromosomes condenseSpindle forms

Late Prophase 1Homologous chromosome pairSynapsis (Buddy system chromosome 1 from mom goes to chromosome 1 from dad) and forms a bivalent tetradCROSSING OVER OCCURS!

Chiasma: area of crossing over (stuck together and switch info) Nuclear membrane breaks down

Synapsis allows crossing over to take place. Does not happen between different chromosomes, only homologous chromosomes! Not sister chromatids (mitosis) if sister chromatids crossed over, nothing would happen because they are genetically identical.

Metaphase 1: Homologous pairs of chromosomes align along metaphase plateMicrotubules attach to one pair from each pole

Anaphase 1:Homologous pairs of chromosomes are separated

Telophase 1: Cytoplasm divides after chromosomes arrive at poles

Interkinesis: Nuclear membrane reforms and DNA relaxes

Meosis 2:

Prophase 2: Chromosomes re-condenseNuclear envelop breaks down

Metaphase 2:Chromosomes align on metaphase plateSpindle fibers move all to middle, each chromosomes own its own

Anaphase 2:Sister chromatids are pulled apart (now=chromosomes)Chromatids separate for brief moment of double

Telophase 2: Chromosomes arrive at spindle poleNuclear envelope reformsCytoplasm divides

Products:4 haploid (n) cells None have identical genetic makeup

Reason: crossing over yields sister chromatids that are not identicalRandom distribution of chromosomes (anaphase 1) 2n

Meiosis 1 and 2 occurs fairly normally in males (spermatogenesis), but in females (oogenesis) after meiosis 1, unequal cytokinesis occurs resulting in a polar body. After meiosis 2, unequal cytokinesis occurs again, resulting in the second polar body (neither of which are used). Females go from 1 diploid to 1 haploid and males go from 1 diploid to 4 haploid.

Meiosis results in haploid spores in plants

CH3

Mendel: “Father of Genetics” Likely he read Darwin’s book At first, people did not understand Mendel’s work

Mendel’s pea plants were an excellent choice because:1. Choice of subjects- easy to grow, fast, produces many offspring2. Had genetically pure stocks of different types of peas3. Avoided characters that exhibited variation4. Used “experimental approach”

Gene: a genetic factor (region of DNA) that helps determine a characteristicAllele: one of two or more alternate forms of a geneLocus: specific place on a chromosome occupied by an alleleGenotype: set of alleles that an individual possessesHeterozygote: An individual possessing two different alleles at a locusHomozygote: An individual possessing two of the same alleles at a locusPhenotype (trait): The appearance or manifestation of a character (genotype + environment)Character or characteristic: an attribute or feature

ONLY GENOTYPE IS INHERITED

Mendel’s Crosses:Monohybrid Cross: parents differ in a single characteristic

Reciprocal Cross: cross in the other direction that shows the sex of the parents did not have an impact

Every time Mendel did a study it looked like the F1 wasn’t affected, but then he got this 3:1 ratio in the F2 generation, proving the first parent did contribute.He concluded:

1. Unit factors in pairs- each trait has 2 different unit factors that result in the different traits, that give 3 possible combinations (AA, Aa, aa)

2. Dominance vs. Recessiveness: traits that were observed in F1=dominant and those that disappeared were recessive

3. Segregation: two alleles separate when gametes are formed- one allele to each gamete- upon fusion at fertilization, zygote get one allele from both male and female parent, separate but equal.

a. Mendel’s first Law: Principle of Segregation (Everyone has 2 alleles that separate into random gametes)- each individual diploid organism (2n) possesses two alleles for any particular characteristic. Two alleles segregate into gametes, and this occurs randomly and in equal proportions.

Dominant capital letter: RR can only produce gametes that have Rrr can only produce gametes that are rRR crossed with rr will all be Rr (F1 generation)F1 can produce gametes with R and r

F1 crossed with F1 (Rr and Rr)

Will yield a 1:2:1 RR, Rr, rR, and rr3 possible phenotypes (3:1)

Backcross: cross the F1 generation to make sure the results match what you think is happening

Punnett square is a quick way to figure out to genotype and phenotypic ratio

Test cross: Cross individual of unknown genotype with homozygous recessiveIf TT F1 will = Tt (Tall)If Tt F1 will = Tt (tall) and tt (short) in a 1:1 ratio

Dihybrid crosses: crosses of organisms that differ in two characteristics-Combining multiple variables-Got a 9:3:3:1 ratio

Mendel’s second law: Principle of Independent Assortment (alleles separate independently) Alleles at different loci separate independently of one another

*Note characters must be located on different chromosomes! (as assortment is related to chromosome separation at Anaphase 1)

Multiplication Rule:

“AND” multiply the fraction of what you are looking for

Branch Diagram: obtain both genotypic and phenotypic ratios

Sutton: Discovered that homologous pairs of chromosomes consist of one maternal and one paternal

Addition Rule: probability that one of two or more mutually exclusive events will occur

If you observe ratios different from what we expect: use Chi square testUsed to determine the probability that the difference between the observed and the expected value is due to chance

IF P> .05 Differences likely caused by chance (random)IF P < .05 chance is not responsible and a significant difference exists

(Observed-expected) 2 Expected

Df= n-1 where n is the number of phenotypes

Pedigrees:

If two unaffected people have an affected child, it is autosomal recessive If cousins marry cousins= very likely to have a lot of affected people

Autosomal dominant: every affected person has an affected parent

Appears equally in males and femalesUnaffected people do not transmit to offspring

Each child is an independent event

CH4

Allele- different forms of same geneLoss-of-function mutation- not making like supposed to, or just not enough (ex pigments supposed to be black but looks gray)Null allele- complete loss of function (no pigment at all)Gain-of-function mutation- allele making more then supposed to or making it at the wrong time (supposed to make gray but not makes more pigment then supposed to and you end up black)Neutral mutation- changed the gene to a different allele but have no impact on how it works (doesn’t change phenotypically but genetically) Gene interaction- sometimes a single phenotype that multiple genes have an affect on

X-linkage- what happens when a gene is on a sex chromosome (X)

Wild type= majority +Mutant= minority -

Incomplete Dominance: Purple fruit x White fruit= Violet fruit“blending”

Codominance: produce both alleles and both alleles are presentPhenotype of heterozygote includes the phenotypes of both homo ex: sickle cell

Dominance: Phenotype of hetero is same phenotype of homo

Incomplete dominance: phenotype of hetero is intermediate (range) of two phenotypes

Cuenot: Showed Mendel’s principles applied to animals

Pleitrophy: one gene that impacts several aspects of the overall phenotypeDominant lethal= one copy causes death

Recessive epistasis: ee in dogs

Dominant epistasis: The dominant allele inhibits A to B conversion. You have know way to know to see what is going on in y locus.

Hypostatic- gene that is hidden

Complementation: We want to know if alleles are on the same lociGet three true breeding and cross- determine which allele is dominant and which is recessiveIf mutations are in different genes: we would expect to get a wild type on chromo 1 and b mutant on chromo 2, since they are all recessive to wild type, we have wild type of a and b even though

we have two mutations for each gene. Now we will get a wildtype phenotype: complement each other

If mutation in same gene: chromo 1 has two mutant copies and chromo 2 has 2 wild types, we do not get complementation bc we have two mutants on chromosome 1

Mutated in both copies of gene 1=mutationWt on each chromosome=complementation

Penetrance: % of individuals having a particular genotype that express the expected phenotype (there or not there)Incomplete penetrance: Genotype does not always produce the expected phenotypeExpressivity: degree to which a character is expressed (all have some but in different amounts)*Environmental factors can alter the effect of a gene: temperature effect, nutritional effect, and imprinting*

Norm of reaction- range of phenotypes produced by a genotype in different environments

SEX CHROMOSOMES:Mom gives an X to every child, Dad gives X (daughters) or Y (sons) Y-chromosomes are a little different than X

Morgan explained sex linked inheritance (some traits were associated with one sex or the other) in fruit fliesThe traits were not randomly distributed between the sexes. Females would have all red and males would have ½ red and ½ white

He did a reciprocal cross (white eye female with red eye male) and all males had white and all females had red Now it wasn’t dependent on sex, it depends which parent starts with a certain phenotype X linked If it is located on the X chromosome, the males will have it Females will be carriers

In pedigrees, if the affected father does not pass it to his son, but the daughters are carriers, it is an X linked trait. (if it skips a generation it is through a female) If mom is a carrier and dad is affected, daughters have a 50/50 chance of getting the disease. Shows up quickly in makes because they cannot be carriers

X linked recessive: Hemophilia “royal disease” all affected are male, carriers are female

X linked dominant: DO NOT SKIP GENERATION (will show up with just one copy) affected males pass to all daughters, not sons. Heterozygous females pass trait to half of their sons and half of their daughters. Females are NOT carriers, when they have the allele, they show it.

Y linked traits only appear in males: dad always passes it to son, not daughters. Does not skip because every male has to receive that y chromosome

Sex Influences Characteristics: determined by autosomal genes, but express differently in males and females. Ex: Bb beard=dominant in males, recessive in females Baldness is sex-influenced: mom does have input; males just need 1 allele females require two, however, may just be thinning in females

Sex Limiting Characteristics: determined by autosomal gene. But expressed only in one sex. If it is only expressed in males, no matter what the genotype is for a female, it will be hidden.

Genomic Imprinting: occurs with autosomal genes- males and females contribute equal number of genes- but expression is affected by parental origin

Genes are “marked” during gamete formation as being from mom or dad, and do not use it. Created haploid mice and depending on which genome the mice had, different thing went wrong in the early stages. Conclusion: you need both genomes

PWS: example of imprinting- small AS: uncontrollable movements- Same deletion, different affectsImprinting does not affect all genes

Epigenetics: genome modifications that cause functional differences but do not change the nucleotide sequence

Cytoplasmic Inheritance: zygote inherits nuclear genes from both parents, but most (all) cytoplasmic genes come from the motherEgg is huge, and sperm is small

All affected females pass it to ALL children both male and femaleMales do not pass trait to children

Genetic Maternal Effect: Phenotype is determined by genotype of the mother! Genes are inherited from both parents, but offspring’s phenotype is determines by genotype of mother.