Term
| who first inferred the existence of genes? |
|
Definition
|
|
Term
| describe Griffith's experiment that first hinted that DNA was the genetic material. |
|
Definition
If S (smooth) type s. pneumoniae colonies infect a mouse, the mouse contracts pneumonia and dies. If R (rough) type s. pneumoniae colonies infect a mouse, the mouse remains healthy. If S cells are heat-killed, they do not cause disease. If living R cells are mixed with heat-killed S cells, they cause pneumonia and death in a mouse. Both R and S colonies can be isolated from the tissue of this dead mouse.
This experiment suggested that physical traits can be passed from one cell to another. (horizontally, not vertically) |
|
|
Term
| describe MacLeod and McCarty's experiment that helped prove that DNA was the genetic material. |
|
Definition
| If a culture of smooth s. pneumoniae cells (S) is heat-killed and then mixed with a live culture of R cells, R and a few S colonies will appear. This shows that transformation occurs. If protease or RNase is added to the heat-killed S cell extract, R and a few S colonies will still result. If DNase is added to the heat-killed S cell extract, only R colonies will appear. So, DNase prevents transformation, so the genetic material is degraded by DNase. |
|
|
Term
| describe Hershey and Chase's experiment that determined that DNA was the genetic material. |
|
Definition
| In one experiment, E coli cells are infected with a nonradioactive T2 phage and then grown in a medium containing radioactive P. In a separate experiment, E coli cells are infected with a nonradioactive T2 phage and grown in a medium containing radioactive S. In both cases, the phages reproduce and release labeled progeny phages. The radioactive P labeled DNA and the radioactive S labeled proteins. The progeny phages then infect nonradioactive cells. The phages reproduce and release progeny. The progeny phages of the first experiment have DNA labeled with radioactive P, while the progeny phages of the second experiment have no labeling. This experiment showed that radioactive P-labeled DNA is passed on to progeny, but S-labeled protein is not. |
|
|
Term
| describe the Meselson-Stahl experiment that proved that DNA is replicated semiconservatively. |
|
Definition
| DNA from E coli grown for many generations in a medium with 14N is extracted and centrifuged in cesium chloride. The DNA containing 14N is light, so a band appeared toward the top of the tube. Next, DNA from E coli grown for many generations in a medium with 15N is extracted and centrifuged in cesium chloride. The DNA containing 15N is heavier, to a band appears at the bottom of the tube. Next, the E coli from the 15N medium are transfered to a 14N medium and allowed to replicate only once. The DNA is extracted and centrifuged in cesium chloride. The new DNA all contain one strand from the parents containing 15N and one new strand containing 14N. Since this DNA is medium in weight, a band is seen in the center of the tube. Next, the 15N cells that are in the 14N medium are allowed to replicate a second time. The DNA is extracted and centrifuged in cesium chloride. Half of the duplex molecules will contain one strand with 15N and one strand with 14N, and the other half of the duplexes will contain two strands with 14N. Two bands will be seen, one at the top and one in the center. |
|
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Term
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Definition
| A genetic disease caused by a defective gene. An enzyme involved in the breakdown of phenylalanine is inactive, causing accumulation of Homogenistic acid. It turns black upon oxidation, so patients with this disease have black urine. |
|
|
Term
| what is the central dogma? |
|
Definition
| Nucleotide sequence in a DNA molecule--> transcription--> RNA--> translation--> AA sequence in a polypeptide chain |
|
|
Term
| what are the codons signaling STOP? |
|
Definition
|
|
Term
| What is the codon for START? |
|
Definition
|
|
Term
| why are mutant proteins inactive? |
|
Definition
| they have an altered structure leading to faster degradation |
|
|
Term
|
Definition
| single gene may affect multiple traits |
|
|
Term
|
Definition
| traits determined by multiple genes |
|
|
Term
|
Definition
| the effect of the environment on gene expression |
|
|
Term
| how many base pairs are in the human genome? |
|
Definition
|
|
Term
| how many base pairs per gene in humans? |
|
Definition
|
|
Term
| what percent of the human genome codes for proteins? |
|
Definition
|
|
Term
| what percent of the human genome does not code for proteins? what does it code for instead? |
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Definition
| 96% codes for untranslated regions, introns, short repetitive sequences, pseudogenes, and function RNA (that don't encode protein) |
|
|
Term
| how many base pairs in the human genome are unique? |
|
Definition
|
|
Term
|
Definition
| any difference in DNA that is transmitted and can be tracked |
|
|
Term
| which bases in DNA are purines? |
|
Definition
|
|
Term
| which bases in DNA are pyrimidines? |
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| what are Chargaff's rules? |
|
Definition
| [A]=[T] [G]=[C] [purine]=[pyrimidine] |
|
|
Term
| describe the structure of the DNA double helix |
|
Definition
| right handed, B form, clockwise motion |
|
|
Term
| How many A are in one complete turn of one strand of DNA in a double helix? |
|
Definition
|
|
Term
| how many bases per turn per strand are there in a DNA double helix? |
|
Definition
|
|
Term
| describe the experiment that proved that DNA strands are antiparallel |
|
Definition
| the ratio of different dinucleotides was measured, and the concentration of 5'-AG-3' was equal to 5'-CT-3' rather that 5'-TC-3' |
|
|
Term
| what different motifs can DNA exist as? |
|
Definition
| hairpin, Z-DNA, triple helix |
|
|
Term
| what conditions are necessary for DNA to exist as ZDNA? |
|
Definition
| alternating G-C sequences, in alcohol or high salt content |
|
|
Term
| describe the structure of ZDNA |
|
Definition
| left handed. one turn spans 4.6 nm (rather than 3.4nm for BDNA) and comprises 12 base pairs. |
|
|
Term
| Three reasons why DNA is the genetic material |
|
Definition
| 1. replicated faithfully and accurately, inheritable 2. capacity to carry info (genetic code- 3 base code can be rearranged to form many proteins) 3. can undergo occasional mutations, genetic diversity (mutations are heritable, evolution is the slow accumulation of favorable mutations) |
|
|
Term
| what is the recognition site for EcoRI? |
|
Definition
|
|
Term
| how many base pairs are in the human genome? |
|
Definition
|
|
Term
| what factors affect the rate of movement of DNA fragments in electrophoresis gel? |
|
Definition
| aragose concentration, buffer composition, electrophoretic conditions |
|
|
Term
| what is ethidium bromide used for? |
|
Definition
| It binds to nucleic acid and fluoresces red-orange under UV light. (it only fluoresces when bound because of the increased hydrophobicity of the environment |
|
|
Term
| How is dentauration measured? |
|
Definition
| By absorbance at 260nm. ssDNA absorbs 37 times more than dsDNA |
|
|
Term
| describe the process of southern blotting |
|
Definition
| 1. DNA is cleaved and fragments are separated using electrophoresis. 2. DNA fragments are blotted onto nitrocellulose filter. Water absorbant paper must be on top of the filter to draw water out of the gel. 3. The filter is exposed to radioactive probe, which binds to the immobilized DNA fragments. 4. Filter is exposed to photographic film, and the film is developed |
|
|
Term
| what enzyme is involved in DNA synthesis? What does it do? |
|
Definition
| DNA polymerase adds nucleotides to the 3' end of a primer DNA. (releases pyrophosphate P-P group every time a new base is added) |
|
|
Term
|
Definition
| a restriction sequence with more than one variant |
|
|
Term
|
Definition
| single nucleotide polymorphism- A DNA marker in which a single nucleotide pair differs in the DNA sequence of homologous chromosomes, and in which each of the alternative sequences occurs relatively frequently. this can potentially lead to the gain or loss of a cutting site in DNA sequence, allowing it to be detected. |
|
|
Term
| how many SNPs are in the human genome? |
|
Definition
|
|
Term
| how common are SNPs in protein coding DNA sequences? |
|
Definition
|
|
Term
| how common are SNPs in non-coding DNA sequence? |
|
Definition
|
|
Term
|
Definition
| Restriction Fragment Length Polymorphism. It is a SNP that eliminates a restriction site |
|
|
Term
| what method is used to detect RFLPs? How? |
|
Definition
| Souther Blot is used because RFLPs change the number and size of DNA fragments produced by digestion with a restriction emzyme |
|
|
Term
|
Definition
| randomly amplified polymorphic DNA. PCR is done with a pair of short (8-10) primers that hybridize to many places in a genome by chance. Occasionally, 2 primers hybridize to complementary strands near each other, generating a PCR product. then, a type of DNA marker is identified by a band in gel. *No prior knowledge of DNA sequence is needed |
|
|
Term
|
Definition
| Amplified fragment length polymorphism. DNA is cut with restriction enzymes and an adapter DNA (linkers) containing primer hybridization sequence is ligated to the sticky ends. Then it is amplified with PCR, leading to different sized products. If needed, the addition of extra nucleotides to the hybridization end of the adapter can reduce the number of PCR products generated. |
|
|
Term
| when is AFLP more useful that RAPD? |
|
Definition
| when analyzing large genomes because RAPD will result in too many bands to analyze |
|
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Term
|
Definition
| Simple tandem repeat polymorphism. the number of copies of short repeated sequences at particular loci may differ between animals |
|
|
Term
|
Definition
| simple sequence length polymorphisms. 2-9 bp repeatss (microsatellite) |
|
|
Term
|
Definition
| variable number of tandem repeats. 10-60 bp repeats (minisatellite) |
|
|
Term
| what are the uses of STRP |
|
Definition
| useful for DNA fingerprinting and for identification of individuals and assessing genetic relatedness in a population |
|
|
Term
| how many genes are estimated to be in the human genome? how many are known? |
|
Definition
| 25-40,000 estimated genes. only 8,000 are known |
|
|
Term
| how can disease genes be mapped? |
|
Definition
| DNA markers that are close to the disease gene tend to be inherited with the disease gene. So, DNA markers that are genetically linked to the disease gene are used to identify the chromosomal location of the disease gene. (Genetic mapping) |
|
|
Term
| define transmission genetics |
|
Definition
| the study of inherited traits |
|
|
Term
| define mendelian genetics |
|
Definition
| how traits are passed from parents to offspring |
|
|
Term
| what is the molecular basis of the wrinkled seat coat mutation in peas? how does this allow it to be identified in elecrophoresis gel? |
|
Definition
| A transposable element is inserted into the wild type smooth seed coat SBEI gene. So, the mutant gene is heavier than the wild type gene, and it will not travel as far in electrophoretic gel. |
|
|
Term
| what is the principle of segregation? |
|
Definition
| in the formation of gametes, the paired hereditary determinants separate in such a way that each gamete is equally likely to contain either member of the pair. |
|
|
Term
| what factors determine the 3:1 ratio of filial phenotypes from a homozygous dominant parent and a homozygous recessive parent? |
|
Definition
| segregation, random union of gametes, dominance |
|
|
Term
| how did mendel verify segregation? |
|
Definition
| He bred SS and ss parents, producing 1/4 s phenotype and 3/4 S phenotype. the s phenotype peas bred true. the S phenotype peas also reproduced, and 1/3 of its offspring had only S phenotype seeds, and 2/3 of its offspring had both S and s phenotypes in a 3:1 ratio. |
|
|
Term
| what factors determine the 3:1 ratio of filial phenotypes from a homozygous dominant parent and a homozygous recessive parent? |
|
Definition
| segregation, random union of gametes, dominance |
|
|
Term
| how did mendel verify segregation? |
|
Definition
| He bred SS and ss parents, producing 1/4 s phenotype and 3/4 S phenotype. the s phenotype peas bred true. the S phenotype peas also reproduced, and 1/3 of its offspring had only S phenotype seeds, and 2/3 of its offspring had both S and s phenotypes in a 3:1 ratio. |
|
|
Term
| what is the law of independent assortment? |
|
Definition
| segregation of the members of any pair of alleles is independent of the segregation of other pairs in the formation of reproductive cells. |
|
|
Term
| what is a testcross? what are they used for? |
|
Definition
| a testcross is a cross between an organism that is heterozygous and an organism that is homozygous for the recessive allele . The phenotypes of the progeny reveal the relative frequencies of the gametes produced by the heterozygous parents because the recessive parent contributes only the recessive allele. |
|
|
Term
|
Definition
| hybrid organisms are crossed with one of the parental genotypes (test cross is a type of back cross) |
|
|
Term
| how can the genotype or phenotype frequency be easily determined if there are three or more genes? |
|
Definition
| multiply the frequency of each trait separately. ie. if a filial population is 50% WW and 50% ww, and 25%, GG and 75% gg, the frequency of WWGG is (1/2)x(1/4)=(1/8) |
|
|
Term
| during which phase of meiosis does independent assortment occur? what happens during this phase? |
|
Definition
| metaphase I- non-homologous chromosomes line up randomly at the metaphase plate |
|
|
Term
| during which phase of meiosis does segregation occur? what happens during this phase? |
|
Definition
| anaphase I- physical separation of homologous chromosomes to opposite poles of the spindle |
|
|
Term
| define penetrance (of a genetic disorder) |
|
Definition
| the proportion of individuals with the at-risk genotype who actually expresses the trait |
|
|
Term
| why are molecular markers important for pedigree analysis? |
|
Definition
| 1. most genetic diseases are rare, so there are only a small number of families that can be analyzed. 2. many genes of interest are recessive, so they aren't detected in heterozygotes. 3. the number of offsprings in human families are small, so segregation is difficult to detect. 4. it is hard to perform a testcross or backcross on humans |
|
|
Term
| what does it mean when codominance of alleles is seen (in elecrophoresis)? |
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Definition
| there is no masking of one allele by another allele for DNA markers, so both genotypes are seen in elecrophoresis |
|
|
Term
| a homozygous blue flower and a homozygous white flower are crossed. what color will the offspring be if blue and what have incomplete dominance? codominance? |
|
Definition
| if they have incomplete dominance, the flowers would be light blue (a mix of blue and white) if they have codominance, the flower will contain both blue parts and white parts |
|
|
Term
| what type of antibodies are present in the serum of A, B, O, and AB blood types? |
|
Definition
| A- antibodies against B. B-antibodies against A. AB- no antibodies. O-antibodies against A and B |
|
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Term
| Blood type O had antibodies against A and B. What happens when type O is donated to a person with A, B or AB blood? |
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Definition
| the donor antibodies are acceptable because they are rapidly diluted to prevent clumping and blocking of blood vessels, which can lead to shock and death |
|
|
Term
|
Definition
| gene interaction that perturbs the normal mendelian ratio |
|
|
Term
| describe recessive epistasis in the coat color of labradors |
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Definition
| alleles are Bb and Ee. Yellow labs are homozygous for the recessive e allele, no matter what the B/b genes are. Chocolate labs are homozygous for bb. But, if the genotype is bbee, the lab is yellow because ee masks the B and b alleles. All black labs have one B allele and one E allele. |
|
|
Term
| describe the effect of the H gene in blood groups |
|
Definition
| The H gene codes for the enzyme fucosyltransferase. If the H gene is not present (hh), A or B enzymes are useless, so the blood type will always be O |
|
|
Term
| how can two parents with blood type O produce a child with blood type A or B? |
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Definition
| If one of the parents is homozygous recessive for the H gene, even if they have the gene for A or B, they will be type O. If the other parent is type O, but homozygous dominant for the H gene, they will also be type O. The children will all be heterozygous for the H gene, and if the child inherits A or B from the hh parent, they will have blood type A or B |
|
|
Term
| what is a genetic complementation test? |
|
Definition
| a test that allows one to determine if two mutations with the same phenotype are in the same gene or in two different genes. (ie, cross white flower mutant 1 with mutant 2, producing only white flowers. this indicates noncomplementation, so mutations 1 and 2 are defects in the same gene. cross white flower mutant 1 with mutant 3, producing only purple wild type flowers. this indicates complementation, so mutations 1 and 3 are defects in different genes) |
|
|
Term
| what is the molecular explanation of genetic complementation? (use mutant white and wild type purple examples) |
|
Definition
| When two white mutants that do not complement each other are crossed, they produce white flowers. Both parents had a nonfunctional gene product causing the white color, and the offspring inherited a nonfunctional copy from each parent. When two white mutants that DO complement each other are crossed, they produce wild type purple flowers. Each parent had a defect in a different gene. The offspring inherited defective gene A and normal gene B from one parent, and normal gene A and defective gene B from the other. Since the offspring had one copy of both normal genes, it had the wildtype color |
|
|
Term
| what is the molecular explanation of genetic complementation? (use mutant white and wild type purple examples) |
|
Definition
| When two white mutants that do not complement each other are crossed, they produce white flowers. Both parents had a nonfunctional gene product causing the white color, and the offspring inherited a nonfunctional copy from each parent. When two white mutants that DO complement each other are crossed, they produce wild type purple flowers. Each parent had a defect in a different gene. The offspring inherited defective gene A and normal gene B from one parent, and normal gene A and defective gene B from the other. Since the offspring had one copy of both normal genes, it had the wildtype color |
|
|
Term
| what are the various stages in the condensation of DNA? |
|
Definition
| DNA duplex--> nucleosome fiber--> chromatin fiber--> coiled chromatin fiber--> coiled coil--> metaphase chromatid |
|
|
Term
|
Definition
| compact, heavily staining chromosome regions rich in satellite DNA and low in gene content |
|
|
Term
|
Definition
| less condensed chromosome regions high in genecontent |
|
|
Term
|
Definition
| highly repeated non-coding DNA sequences |
|
|
Term
| define metacentric chromosomes |
|
Definition
| a pair of sister chromatids attached by a centromere in the center |
|
|
Term
| define acrocentric chromosomes |
|
Definition
| sister chromatids that are connected by an off-centered centromere |
|
|
Term
| what are the four stages of cell division? |
|
Definition
| G1 (pre-DNA synthesis), S (DNA synthesis), G2 (post-DNA synthesis), M (mitosis) |
|
|
Term
| What do the two checkpoints of cell division ensure? |
|
Definition
| G1/S- sufficient time from previous mitosis/sufficient size of cell. G2/M- DNA replication and repair is complete before beginning mitosis |
|
|
Term
| What happens during each stage of mitosis? |
|
Definition
| Prophase- Chromosomes condense and become visible. centrosomes move apart toward opposite poles and generate new microtubules. nucleoli begin to disappear. Prometaphase-nuclear envelope breaks down, microtubules from the centrosome invade the nucleus. sister chromosomes attach to microtubules from opposite centrosomes. Metaphase- chromosomes line up at the metaphase plate in the center of the cell with sister chromatids facing opposite poles. Anaphase- sister chromatids separate and each one is pulled to opposite poles of the cell. Telophase- nuclear membranes and nucleoli re-form, spindle fibers disappear, chromosomes uncoil and become a tangle of chromatin. Cytokinesis- cytoplasm divides |
|
|
Term
| what is the primary difference between cytokinesis in an animal cell and in a plant cell. |
|
Definition
| Animal cells form a cleavage furrow and a contractile ring. Plant cells form a cell plate |
|
|
Term
| checkpoints help prevent three types of genomic instability. what are they? |
|
Definition
| 1. chromosome aberrations/rearrangements 2. aneuploidy- loss or gain of a chromosome 3. changes in ploidy (2n to 4n) |
|
|
Term
| What are the phases of prophase I? |
|
Definition
| 1. Leptotene (thin thread)- chromosome condensation. 2. Zygotene (paired thread)- pairing (synapsis) of homologous chromosomes= bivalent 3.pachytene (thick thread)- crossing over between homologous chromosomes 4. diplotene (double thread)- chromosome repulsion. %. diakinesis (moving apart)- maximum chromosome contraction |
|
|
Term
| What happens during Metaphase I, Anaphase I, Telophase I, and Interkinesis in meiosis? |
|
Definition
| Metaphase I- tetrads line up along the metaphase plate. each chromosome of a homologous pair attaches to fibers from opposite poles, sister chromatids attach to fibers from the same pole. Anaphase I- the centromere does not divide (unlike mitosis), the chiasmata migrate off chromatid ends, homologous chromosomes move to opposite poles. Telophase I- the nuclear envelope re-forms Interkinesis- similar to interphase but with no chromosomal duplication |
|
|
Term
| what happens during each phase of meiosis II? |
|
Definition
| Prophase II- chromosomes condense, centrioles move toward the poles, the nuclear envelope breaks down. Metaphase II- chromosomes align at the metaphase plate. sister chromatids attach to spindle fibers from opposite poles. Anaphase II- centromeres divide and sister chromatids move to opposite poles. Telophase II- chromosomes begin to uncoil, nuclear envelopes and nucleoli re-form (cytokinesis- cytoplasm divides) |
|
|
Term
| how many different gametes are possible in a human, without recombination |
|
Definition
|
|
Term
| what phase are primary oocytes in in the fetal ovary? When do they come out of it? |
|
Definition
| Arrested in the diplotene stage of meiosis I. Every month one primary oocyte ovulates and completes meiosis I and proceeds until metaphase of meiosis II. If fertilized, the ovum will quickly complete meiosis II to form a diploid zygote. |
|
|
Term
| what is a cause of asymmetrical meiosis? |
|
Definition
| the long interval before completion of meiosis I and II may contribute to meiotic segregational errors with maternal age (ie. trisomy 21) |
|
|
Term
| what causes hybrid sterility? (ie in a mule) |
|
Definition
| when chromosome cannot pair during meiosis I and consequently segregate improperly. (ie. only the first 13 chromosomes are homologous between a donkey and a horse) |
|
|
Term
| What experiment first proved that genes are part of chromosomes? |
|
Definition
| Thomas morgan and fruit flies- analyzed patterns of transmission of the sex chromosomes. Males are genetically haploid for most genes on the X chromosome, which results in unique pattern of X-linked inheritance |
|
|
Term
| define homogametic and heterogametic |
|
Definition
| females are homogametic because they only produce X gametes. males are heterogametic because they produce X and Y gametes |
|
|
Term
|
Definition
| a meiosis error when chomosomes fail to separate properly during anaphase I or II, resulting in unbalanced chromosome segregation, such that one cell receives both copies of the chromosome pair |
|
|
Term
| what is the chromosome theory? |
|
Definition
| the idea that genes are physically located within chromosomes |
|
|
Term
| what are sex-limited traits? |
|
Definition
| mutations in genes that can influence only the phenotype of the sex that expresses the affected structures of processes (only expressed in one sex and not the other) ie. penis mutation |
|
|
Term
| what are sex-influenced traits? |
|
Definition
| a trait that shows up in both sexes, but expression differs in each sex. ie. patterned baldness |
|
|
Term
| describe the difference between cis and trans and the frequency of recombination of each. |
|
Definition
| trans configuration is when two mutant alleles are in opposite chromosomes. cis configuration is when two mutant alleles are in the same chromosome. Recombination between linked genes takes place with the same frequency whether the alleles of the genes are in the cis or trans configuration; it is the same no matter how the alleles are arranged |
|
|
Term
|
Definition
| two chromosomes are said to be syntenic if they are on the same chromosome, regardless if they show independent assortment or linkage |
|
|
Term
| what is the chi-square test for linkage used for? |
|
Definition
| tests for an equal number (1:1 ratio) of recombinant vs nonrecombinant progeny. |
|
|
Term
| how is the frequency of recombination (r) calculated? |
|
Definition
| number of recombinants/ number of progeny |
|
|
Term
| what does it mean when genes have a recombinant frequency less than 50%? equal to 50%? |
|
Definition
| Less than 50%- genes are linked. Equal to 50%- genes are unlinked, and are either on nonhomologous chromosomes, or are located far apart on the same chromosome. |
|
|
Term
| what is a genetic/linkage/chromosomal map? |
|
Definition
| linear order of genes along a chromosome with the distances between adjacent genes proportional to the frequency of recombination between them |
|
|
Term
| what is a map unit? how does this relate to the percent of cross-overs? |
|
Definition
| 1 map unit equals 1% recombination. 1% recombination equals 2% crossover because one cross-over results in two recombinant chromatids (among 50 cells, if only 2 chromosomes are recombinant, the frequency of crossing over is 1/50, and the frequency of recombination is 2/200) |
|
|
Term
| what is the important distinction between map units and recombination frequency relating to double crossing-over? |
|
Definition
| map units measure how much crossing over actually takes place between the genes. recombination frequency is how much recombination is actually observed in an experiment. So, double crossovers that do not yield recombinant gametes contribute to mu, but not to r. mu is frequently underestimated when it is set equal to observed r |
|
|
Term
| when does crossing over occur in meiosis? |
|
Definition
| in the four strand stage, after the chromosomes have duplicated |
|
|
Term
| why are attached X chromosomes in flies useful for studying X linked inheritance? |
|
Definition
| the X-linked gene is passed from father to son to grandson, which is the opposite of the usual X-linked inheritance, so the attached-X is useful to study X-linked mutations |
|
|
Term
| to produce a homozygous chromosome from a heterozygous, when must crossing over take place? |
|
Definition
| at the 4-strand stage of meiosis, after the chromosome has been duplicated |
|
|
Term
| what is unique about fungi haploid cells? |
|
Definition
| all four spores are in a single ascus. -direct representation of their genotype -no complications from domination |
|
|
Term
| Differentiate between the parental ditype, non-parental ditype, and tetratype in yeast gametes. |
|
Definition
Parental ditype is a tetrad type containing two different genotypes, both of which are parental.(ie. AaBb x aabb-->AaBb and aabb)
Non-parental ditype is a spore arrangement that containts the two recombinant-type ascospores. (Ie, AABB X aabb-->AaBb and AaBb);
Tetratype is a tetrad containing four different genotypes, two parental and two recombinants, resulting from crossing over. |
|
|
Term
| when two genes are on different chromosomes, what kinds of tetrads can be generated? |
|
Definition
| parental ditype (same as parents), nonparental ditype (not the same as parents), tetratype (two parental ditypes and two nonparental ditypes) |
|
|
Term
| What does it mean when the number of PD genotypes of progeny equals the number or NPD genotypes of the progeny? What if PD>> NPD? |
|
Definition
| the two gene markers are unlinked. if PD>>NPD, the genes are linked |
|
|
Term
| how is the recombination frequency calculated? |
|
Definition
| RF= [ (NPD+1/2T) / total tetrads } x100 |
|
|
Term
| how do we know from analyzing tetrads that recombination occurs at the 4 strand stage? |
|
Definition
| If recombination occur before chromosomes duplicated, the crossover event would yield 4 recombinant chromatids, ie. NPD>>T. But, we really see T>>NPD. The very low number of NPDs established that the recombination occurs after the chromosomes have replicated. ie. 1/4th of rare double crossovers |
|
|
Term
| if a double crossover occurs between two genetic markers, how can the crossover be detected? |
|
Definition
| by using a third genetic marker whose gene is part of the fragment that recombined |
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Term
| what is chromosome interference? |
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Definition
| crossing over in one region reduces the probability of a second crossing-over in a nearby region. |
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Term
| how is the coefficient of coincidence calculated? |
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Definition
| observed number of double recombinants/ expected number |
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Term
| how is interference calculated? |
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Definition
| 1- (coefficient of coincidence) |
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Term
| why is the length of heterochromatin misrepresented in a genetic map? |
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Definition
| very little recombination takes place in heterochromatin, so it occupies a small distance on a genetic map, although it actually occupies a large distance on a physical map |
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Term
| how does the frequency of mitotic combination compare to the frequency or meiotic combination? |
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Definition
| 1000 fold higher in meiosis |
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Term
| what causes mitotic recombination? |
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Definition
| mistakes in chromosome replication or exposure to radiation |
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