BIO 203 SDSU exam 3
after obtaining two heads from two tosses of a coin, the probablility of tossing the coin and obtaining a head is... 1/2 1/4 1/6 1/16 3/8
(1/2) x (1/2) =1/4
in the following cross, what is the probability of obtaining offspring that show all three dominant traits A_B_C_ ("_" indicates that the second allele can either be dominant or recessive without affecting the phenotype determined by the first dominant allele). AaBbcc x AabbCC 1. what is the probability that the offspring are A_B_C_? 2. what is the probability that the offspring of this cross will show at least 2 dominant traits?
1. (3/4) x (1/2) x (4/4) = 3/8 work~ Aa x Aa = AA, Aa, Aa, aa = 3/4 dominant Bb x bb = Bb, Bb, bb, bb = 1/2 dominant CC x cc = Cc, Cc, Cc, Cc = 4/4 dominant 2. You need to find the probability that at least two of these are true. We see that C will be dominant for all possible combinations, so all we need to find is the possibility that either A or B will be dominant. We have these cases 1. A dominant, b recessive 2. B dominant, a recessive 3. A, B dominant. The probability of dom. A and rec. b is 3/4 x 1/2 = 3/8 The probability of rec. a and dom. B is 1/4 x 1/2 = 1/8 The probability of dom. A and dom. B is 3/4 x 1/2 = 3/8 So the total probability is the sum of the three = 7/8.
anaphase 1
1. breakdown of cohesions (responsible for sister chromatid cohesion) 2. the homologs move toward opposite poles 3. sister chromatid cohesion persists at the centromere, causing the chromatids to move as a unit toward the same pole
anaphase II
1. breakdown of proteins that hold the sister chromatids together at the centromere allows the chromatids to separate. the chromatids move toward the opposite poles as individual chromosomes
prophase 1
1. chromosomes condense and homologs loosely pair along their lengths, aligned gene by gene 2. paired homologs physically connect to eachother along their lengths by a zipper-like structure (synaptonemal complex) = SYNAPSIS 3. CROSSING OVER-- a genetic rearrangement between non-sister chromatids involving the exchange of corresponding segments of DNA molecules (begins during pairing and synaptonemal complex formation and is complete when homologs are in synapsis) 4. synapsis has ended with the dis-assembly of the synaptonemal complex and chromosomes slightly move apart 5. each homologous pair has 1+ X-shaped regions called CHIASMATA which exists where the crossover occurred. ***it appears as a cross because sister chromatid cohesion still holds the two sister chromatids together 6. centrosome movement, spindle formation, nuclear envelope breakdown 7. microtubules from one pole attach to the other at the two kinetochores, move toward metaphase plate
telophase 1 and cytokinesis
1. in telophase 1 each half of the cell has a complete haploid set of duplicated chromosomes (each consisting of 2 sister chromatids, one or both chromatids include regions of nonsister chromatid DNA) 2. cytokinesis occurs simultaneously
telophase II and cytokinesis
1. nuclei form, the chromosomes being decondensing, cytokinesis occurs 2. meiotic division of one parent cell produces 4 daughter cells each with a haploid set of chromosomes 3. daughter cells are genetically distinct from one another and from parent cell
metaphase 1 (reductional division)
1. pairs of homologous chromosomes are now arranged at the metaphase plate with one chromosome in each pair facing each pole 2. both chromatids of one homolog are attached to kinetochore microtubules from one pole
three unique events that occur during meiosis I
1. synapsis and crossing over~ during prophase 1, duplicated homologs pair up, and the formation of the synaptonemal complex between them holds them in synapsis. crossing over also occurs during prophase 1. 2. homologous pairs at the metaphase plate~ at metaphase 1 of meiosis, chromosomes are positioned at the metaphase plate as pairs of homologs, rather than individual chromosomes, as in metaphase of mitosis 3. separation of homologs~ at anaphase 1 of meiosis, the duplicated chromosomes of each homologous pair move toward opposite poles, but the sister chromatids of each duplicated chromosome remain attached. in anaphase of mitosis, the sister chromatids separate
Chargaffs rules
1. the base composition varies between species 2. within a species, the number of A&T bases are equal and the number of G&C bases are equal
metaphase II (equational division)
1. the centrosomes are positioned at the metaphase plate 2. because of crossing over in meiosis I, the two sister chromatids of each chromosome are NOT genetically identical 3. kinetochores of sister chromatids are attacted to microtubules from opposite poles
the DNA content of a cell is measured in the G2 phase. after meiosis 1, the DNA content of one of the two cells produced would be equal to that of the G2 cell twice that of the G2 cell one half that of the G2 cell one fourth that of the G2 cell impossible to estimate due to independent assortment
1/2 that of the G2 cell
if both parents are carriers of a lethal recessive gene, the probability that their children will inherit and express the disorder is: 1/8 1/4 1/2 1/16 1/9
1/4
how many chromatids are present in metaphase 2 in a cell undergoing meiosis from an organism in which 2n=24 12 24 36 48 96
24
in sexually reproducing species with a diploid number of 8, how many different combinations of paternal and maternal chromosomes would be possible in the offspring? 8 16 64 256 512
256
if the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be ... 0.25x 0.5x x 2x 4x
2x
a cell with a diploid number of 6 could produce gametes with how many different combinations of maternal and paternal chromosomes? 6 8 12 64 128
8
the base height of the dingdong plant is 10cm. Four genes contribute to the height of the plant, and each dominant allele contributes 3cm to height. If you cross a 10cm plant (quadruply homozygous recessive) with a 34cm plant, how many phenotypic classes will there be in F2? 4 5 8 9 64
9
in a dihybrid cross of heterozygotes, what proportion of the offspring will be phenotypically dominant for both traits? 1/16 3/16 1/4 9/16 3/4
9/16
27. Based on the Chargaff's rules, in an analysis of the nucleotide composition of DNA, which of the following will be found? A) A + C = G + T B) A = C C) G + C = T + A D) A = G and C = T
A) A + C = G + T
After mixing a heat-killed, pathogenic strain of bacteria with a living, nonpathogenic strain, Griffith discovered that some of the living cells are now pathogenic. Which observation(s) would provide the best evidence that the ability to pathogenic is a heritable trait? A) Descendants of the living cells are also pathogenic. B) The pathogenicity of the living strain is especially strong. C) Protein passed from the heat-killed strain to the living strain. D) DNA passed from the heat-killed strain to the living strain. E) Both DNA and protein passed from the heat-killed strain to the living strain.
A) Descendants of the living cells are also pathogenic. & D) DNA passed from the heat-killed strain to the living strain.
Genes are the unit of inheritance. Which best represents the relationship between genes, chromosomes and chromatin? A) Genes are parts of DNA that code for proteins, this DNA wraps around specific proteins called histones to form chromatin, which condenses in the form of chromosomes during metaphase B) Chromatin wraps around genes to form chromosomes during metaphase, which are made up of histones C) Genes are parts of DNA that code for proteins, this DNA wraps around proteins called histones to form chromatin, which condenses in the form of chromosomes during interphase D) Chromosomes are non-condensed genes that are present in the cell only during interphase, and during metaphase, DNA wraps around specific proteins called histones to form chromatin
A) Genes are parts of DNA that code for proteins, this DNA wraps around specific proteins called histones to form chromatin, which condenses in the form of chromosomes during metaphase
Use the following list of choices for the following question: I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes separates the DNA strands during replication? A) I B) II C) III D) IV E) V
A) I
Independent assortment of chromosomes is a result of A) The random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I B) The random nature of the fertilization of ova by sperm C) The random distribution of the sister chromatids to the two daughter cells during anaphase II D) The relatively small degree of homology shared by the X and Y chromosomes E) None of the above
A) The random and independent way in which each pair of homologous
Which syndrome is characterized by the XO chromosome abnormality? A) Turner syndrome B) Trisomy X C) Down syndrome D) Klinefelter syndrome
A) Turner syndrome
Which of the following is known as a Philadelphia chromosome? A) a human chromosome 22 that has had a specific translocation B) an imprinted chromosome that always comes from the mother C) a chromosome found not in the nucleus but in mitochondria D) an animal chromosome found primarily in the mid-Atlantic area of the United States E) a human chromosome 9 that is found only in one type of cancer
A) a human chromosome 22 that has had a specific translocation
Mitochondria contain a small DNA genome that encodes several genes. They are always inherited from A) the mother. B) the father. C) both the mother and father. D) neither the mother or father.
A) the mother.
Possible genotypes for blood groups
AA, AO, BB, BO, AB, O
the calculation of offspring in a sexually reproducing species with a diploid number of 8includes only variation resulting from a)crossing over b)random fertilization c)independent assortment of chromosomes all of the above only b and c
B&C
Under the microscope you, see a triploid cell of Undergrauatis studentius, which contains three sets of chromosomes. Since in this species a diploid cell has 8 chromosomes, this triploid cell would be expected to have which of the following? A) 12 chromosomes in 6 pairs B) 12 chromosomes in 4 sets of 3 C) 12 chromosomes, each with three chromatids D) 4 chromosome pairs, and 4 unique chromosomes
B) 12 chromosomes in 4 sets of 3
Undergraduatis studentius cells have 60 nanograms of DNA during the G2 phase of their cell cycle (before meiosis). How much DNA would expect each resulting gamete to have during Metaphase I of meiosis? (in a 2n=8 organism) A) 20 nanograms B) 60 nanograms C) 30 nanograms D) 120 nanograms E) 15 nanograms
B) 60 nanograms
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work? A) Avery et al. have already concluded that this experiment showed inconclusive results. B) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins. C) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long. D) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive. E) There is no radioactive isotope of nitrogen.
B) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
Which of the following statements about DNA synthesis is true? A) As DNA polymerase moves along the template strand, each new nucleotide provides a 5' hydroxyl group for the next reaction to occur B) Primers are short sequences that allow the initiation of DNA synthesis. C) Nucleotides are added in a random fashion to single-stranded DNA. D) DNA polymerase adds dNTP monomers in the 3' to 5' direction.
B) Primers are short sequences that allow the initiation of DNA synthesis.
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are mosaic showing a mixture of red and white flower color. What does this say about the parental traits? A) Red is completely dominant. B) Red and white are codominant. C) Both red and white are pleiotropic. D) Red shows incomplete dominance over white.
B) Red and white are codominant.
What is meant by the description "antiparallel" regarding the strands that make up DNA? A) One strand contains only purines and the other contains only pyrimidines. B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. C) The twisting nature of DNA creates nonparallel strands. D) Base pairings create unequal spacing between the two DNA strands. E) One strand is positively charged and the other is negatively charged.
B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
What is the greatest benefit of having used a testcross? A) The homozygous parents are the only ones whose crossovers make a difference. B) The genotype of an individual with dominant phenotype can be determined. C) The homozygous recessive parents are obvious to the naked eye. D) All of the progeny will be heterozygous. E) The homozygous recessive parents will be unable to cross over.
B) The genotype of an individual with dominant phenotype can be determined.
How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced? A) Recombination did not occur in the cell during meiosis. B) The two genes are closely linked on the same chromosome. C) The testcross was improperly performed. D) The two genes are linked but on different chromosomes. E) Both of the characters are controlled by more than one gene.
B) The two genes are closely linked on the same chromosome.
How do we describe transformation in bacteria? A) the infection of cells by a phage DNA molecule B) assimilation of external DNA into a cell C) the type of semiconservative replication shown by DNA D) the creation of a strand of DNA from an RNA molecule E) the creation of a strand of RNA from a DNA molecule
B) assimilation of external DNA into a cell
It has been observed that the frequency of Down syndrome increases with the age of the mother. What is the source of the extra chromosome 21 in an individual with Down syndrome? A) duplication of the chromosome B) nondisjunction in either parent C) nondisjunction in the father only D) nondisjunction in the mother only E) It is impossible to detect with current technology.
B) nondisjunction in either parent
Which of the following represents the order of increasingly higher levels of organization of chromatin? A) nucleosome, looped domain, 30-nm chromatin fiber B) nucleosome, 30-nm chromatin fiber, looped domain C) looped domain, 30-nm chromatin fiber, nucleosome D) 30-nm chromatin fiber, nucleosome, looped domain E) looped domain, nucleosome, 30-nm chromatin fiber
B) nucleosome, 30-nm chromatin fiber, looped domain
Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this? A) codominance B) pleiotropy C) multiple alleles D) epistasis E) incomplete dominance
B) pleiotropy
4. Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that A) new mutations were frequently generated in the F2 progeny, "reinventing" traits that had been lost in the F1. B) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1. C) the traits were lost in the F1 due to dominance of the parental traits. D) members of the F1 generation had only one allele for each trait, but members of the F2 had two alleles for each trait. E) the mechanism controlling the appearance of traits was different between the F1 and the F2 plants
B) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
The presence of the Barr body is related to the A) presence of Down syndrome in girls. B) unusual pattern of coat color (black and orange mosaic fur) found in the calico cat. C) epistatic influence of the E/e gene on fur color in Labrador retrievers. D) a and c E) all of the above
B) unusual pattern of coat color (black and orange mosaic fur) found in the calico cat.
Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is incompletely dominant to white (r). The heterozygous condition results in pink (Rr) flower color. If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio (assuming the genes controlling height and flower color are on two different choromosomes)? A) 27:9:9:9:3:3:3:1 B)9:3:3:1 C) 6:3:3:2:1:1 D) 9:4:3 E) 1:2:1
C) 6:3:3:2:1:1
When you look at the organism (2n=8) after S-phase, before mitosis or meiosis occurs, how many chromosomes would you expect to see in its somatic cells? How many in its gametes (sex cells)? A) 8, 4 B) 16, 8 C) 8, 8 D) 16, 16 E) 4, 4
C) 8, 8
When you are looking at the gametes of Undergraduatis studentius under the microscope, you see chiasmata. This is indicative of what? A) Crossing over between two sister chromatids B) Condensation of the centrioles C) Crossing over between two homologous chromosomes D) Condensation of chromosomes E) Synthesis of DNA during S phase
C) Crossing over between two homologous chromosomes
Thomas Hunt Morgan used Drosophila melanogaster to provide evidence for the chromosomal theory of inheritance. What was that experiment? A) He mated female flies with normal wings to male flies with vestigial wings and showed that wing shape was linked to the inheritance of body shape. B) He mated females with gray bodies to males with black bodies and showed that body color was linked to the inheritance of the X chromosome. C) He mated females with red eyes to males with white eyes and showed that eye- color was linked to the inheritance of the X chromosome. D) none of the above.
C) He mated females with red eyes to males with white eyes and showed that eye-color was linked to the inheritance of the X chromosome.
The Hershey-Chase experiment demonstrated that DNA was the genetic material when A) T2 bacteriophage labeled with 35S were found to transfer the radioactivity to bacterial cells. B) pathogenic bacteria were found to transform non-pathogenic bacteria. C) T2 bacteriophage labeled with 32P were found to transfer the radioactivity to bacterial cells. D) non-pathogenic bacteria were found to transform pathogenic bacteria.
C) T2 bacteriophage labeled with 32P were found to transfer the radioactivity to bacterial cells.
according to medel's law of segregation... A) there is a 50% probability that a gamete will get a dominant allele B) gene pairs segregate independently of other genes in gamete formation C) allele pairs separate in gamete formation D the laws of probability determine gamete formation E) there is a 3:1 ratio in the F2 generation
C) allele pairs separate in gamete formation
Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication? A) topoisomerases, telomerases, polymerases B) nucleosome loosening, four dNTPs, four rNTPs C) double-stranded DNA, four kinds of dNTPs, primers, origins of replication D) ligase, primers, nucleases E) G-C rich regions, polymerases, chromosome nicks
C) double-stranded DNA, four kinds of dNTPs, primers, origins of replication
a multifactorial disorder a) can usually be traced to consanguineous mating b) is caused by recessively inherited lethal genes c) has both genetic and environmental causes d) has a collection of symptoms traceable to an epistatic gene e) is usually associated with quantitative traits
C) has both genetic and environmental causes
How many chromatids would you expect to see after S-phase, before mitosis or meiosis occurs, in somatic cells? How many in its gametes (sex cells)? (2n=8 organism) A) 8, 4 B) 16, 8 C) 8, 8 D) 16, 16 E) 4, 4
D) 16, 16
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred? A) A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell. B) No error occurred; these are normal gametes. C) A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell. D) A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
D) A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
Which of these is not true of sexual reproduction? A) It leads to an increase in variation in the offspring B) It is slower than asexual reproduction C) It requires two parents D) All multicellular organisms utilize only sexual reproduction E) In sexual reproduction, individuals transmit 50% of their genes to each of their offspring
D) All multicellular organisms utilize only sexual reproduction
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. The relationship between genes S and N is an example of A) Pleiotropy. B) Codominance C) Complete dominance D) Epistasis E) Incomplete dominance
D) Epistasis
How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes? A) It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity. B) It adds a single 5' cap structure that resists degradation by nucleases. C) It causes linear ends of the newly replicated DNA to circularize. How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes? D) It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication. E) It causes specific double-strand DNA breaks that result in blunt ends on both strands.
D) It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication.
Which of the following is an example of polygenic inheritance? A) white and purple flower color in peas B) pink flowers in snapdragons C) Huntington's disease in humans D) skin pigmentation in humans E) the ABO blood group in humans
D) skin pigmentation in humans
antiparallel DNA structure & synthesis
DNA polymerase can only add nucleotides to the free 3' end of a primer or growing DNA strand therefore, it elongates in the 5' to 3' direction*** leading strand--> continuous synthesis of new DNA elongation in 5' to 3' direction and only ONE primer is required for synthesis lagging strand---> in order to elongate the other new strand of DNA in the 5' to 3' direction, the DNA polymerase has to work in the direction away form the replication fork. synthesized discontinuously as a series of segments (Okazaki fragments) **DNA poymerase 1 replaces the rna nucleotides of the adjacent primer with DNA nucleotides, but it cannot join the final nucleotide to the first DNA nucleotide of the adjacent okazaki fragment DNA ligase = joins the sugar-phosphate backbones of all fragments to a continuous DNA strand
Undergraduatis studentius cells have 60 nanograms of DNA during the G2 phase of their cell cycle (before meiosis). How much DNA would you expect each resulting gamete to have after Telophase II of meiosis? (2n=8 organism) A) 20 nanograms B) 60 nanograms C) 30 nanograms D) 120 nanograms E) 15 nanograms
E) 15 nanograms
The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following? A) The formation of gametes in plants occurs by mitosis only. B) The diploid number of chromosomes in the pea plants was 7. C) All of the genes controlling the traits were located on the same chromosome. D) None of the traits obeyed the law of segregation. E) All of the genes controlling the traits behaved as if they were on different chromosomes.
E) All of the genes controlling the traits behaved as if they were on different chromosomes.
In which of the following phases of the meiotic cell cycle would a cell be considered haploid? A) Metaphase I B) Metaphase II C) Telophase II D) A and B E) B and C
E) B and C
Three genes (A, B, and C) at three loci are being mapped in a particular species. Each gene has two alleles, one of which results in a phenotype that is markedly different from the wild type. The unusual allele of gene A is inherited with the unusual allele of gene B or C about 50% of the time. However, the unusual alleles of genes B and C are inherited together 14.4% of the time. Which of the following describes what is happening? A) The three genes are linked. B) Gene A is located 14.4 map units from genes B and C. C) Gene A is linked but genes B and C are not. D) The three genes are showing independent assortment. E) Gene A is assorting independently of genes B and C, which are linked.
E) Gene A is assorting independently of genes B and C, which are linked.
Which of the following best represents the change in chromosome number during the stages of meiosis? A) The number of chromosomes stays the same during Meiosis I and Meiosis II B) The number of chromosomes doubles during Meiosis I and decreases by half during Meiosis II C) The number of chromosomes stays the same during Meiosis I and decreases by half during Meiosis II D) The number of chromosomes doubles during Meiosis I and stays the same during Meiosis II E) The number of chromosomes decreases by half during Meiosis I and stays the same during Meiosis II
E) The number of chromosomes decreases by half during Meiosis I and stays the same during Meiosis II
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? A) XnXn and XNY B) XNXN and XnY C) XnXn and XnY D) XNXN and XNY E) XNXn and XNY
E) XNXn and XNY
Skin color in a certain species of fish is inherited via a single gene with four different alleles. One fish of this type has alleles 1 and 3 (S 1 S 3) and its mate has alleles 2 and 4 (S 2 S 4). If each allele confers a unit of color darkness such that S 1 has one unit, S 2 has two units, and so on, then what proportion of their offspring would be expected to have five units of color? A) 1/5 B) 0 C) ¼ D) 1/8 E) ½
E) ½
possible matching problems ___1. codominance a) true-breeding variety ___2. homozygous b) cross between 2 hybrids ___3. heterozygous c) cross that involves 2 . different gene pairs ___4. phenotype d) cross with homozygous . recessive to determine . . genotype of unknown ___5. polygenic e) physical characteristics . . of an individual ___6. pleiotropy f) genotype with 2 different . . alleles ___7. epistasis g) genotype with multiple . . . alleles for same locus ___8. testcross h) one gene influences the . . expression for another gene ___9. dihybrid cross i) both alleles are fully . . . . . expressed in heterozygote __10. incomplete dominance j) single gene with multiple . . phenotypic effects k) heterozygote intermediate . between homozygous . phenotypes L) 2+ genes with additive affect on phenotype
I 1. codominance ~ both alleles are fully expressed in heterozygote A 2. homozygous ~ true breeding variety F 3. heterozygous ~ genotype with 2 different alleles E 4. phenotype ~ physical characteristics of an individual L 5. polygenic ~ 2+ alleles with additive affect on phenotype J 6. pleiotropy ~ single gene with multiple phenotypic effects H 7. epistasis ~ one gene influences the expression of another gene D 8. testcross ~ cross with hoomozygous recessive to determine theunknown genotype C 9. dihybrid cross ~ cross that involves 2 different gene pairs K 10. incomplete dominance ~ heterozygote intermediate between homozygous phenotypes
mitosis VS meiosis
MITOSIS: 1. DNA REPLICATION ~ mitosis: occurs during the interphase before mitosis begins ~meiosis: occurs during the interphase before meiosis begins 2. NUMBER OF DIVISIONS ~mitosis: one, including prophase, metaphase, anaphase, and telophase ~meiosis: two, each including prophase, metaphase, anaphase, and telophase 3. SYNAPSIS OF HOMOLOGOUS CHROMOSOMES ~mitosis: does not occur ~meiosis: occurs during prophase 1 along with crossing over between nonsister chromatids; resulting chiasmata holding pairs together due to sister chromatid cohesion 4. # OF DAUGHTER CELLS AND GENETIC COMPOSITION ~mitosis: two, each dipoloid (2n) and genetically identical to parent cell ~meiosis: four, each haploid (n), containing half as many chromosomes as the parent cell and from each other 5. ROLE IN ANIMAL BODY ~mitosis: enables multicellular adult to arise from zygote, produces cells for growth, repair and in some species asexual reproduction ~meiosis: produces gametes, reduces number of chromosomes by half and introduces genetic variability among gametes (population)
law of segregation
Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete an organism inherits 2 copies of a gene, one from each parent the two alleles for a heritable character segregate during gamete formation and end up in different gametes his experiment with purple and white pea plants is what made him make this law. he realized that no white was in the f1 but there was one white in the f2. 3:1 ratio. decided traits can be recessive or dominant derived from experiments where he only followed ONE character
prophase II
NO REPLICATION BETWEEN MEIOSIS 1 AND 2 1. spindle apparatus forms, move toward metaphase plate
parental types (unlinked genes)
Offspring with a phenotype that matches one of the parental phenotypes. b/c the offspring have new combinations they are called recombinant types when 50% are recombinant then there is a 50% frequency of recombination ~~~ observed for any 2 genes on different chromosomes so the basis of recombination is random independent assortment during metaphase 1 of meiosis
sister chromatid cohesion
The name of the attachment of two sister chromatids (two copies of one chromosome). Protein complexes (cohesins) are responsible for this, they adhere two sister chromatids together. together the sister chromatids make up one duplicated chromosome
norm of reaction (multifactorial)
The range of phenotypes produced by a single genotype, due to environmental influences. nature vs nurture a genotype generally is not associated with a rigidly defined phenotype, rather with a range of phenotypic possibilities due to environmental influences multifactorial~ many factors genetic and environment collectively influence phenotype ex) hydrangea flowers that have the same genetic variety range in color depending on the acidity and aluminum content in soil
the probability of tossing three coins simultaneously and obtaining two heads and one tail is... 1/2 3/4 1/8 1/16 3/8
[ (1/2) x (1/2) x (1/2)] = 1/8 [ (1/2) x (1/2) x (1/2)] = 1/8 [ (1/2) x (1/2) x (1/2)] = 1/8 (1/8) + (1/8) + (1/8) = *3/8*
replication fork
a Y-shaped region where the parental strands of DNA are being unwould (each end of a replication bubble)
transformation
a change in genotype and phenotype due to the assimilation of external DNA by a cell transforming agent was DNA
barr body
a condensed inactive X in each cell of a female -- random and independent inactivation happens when a methyl group (CH3) attaches to one of the nitrogenous bases of DNA nucleotides female mammals inherit two X chromosomes but one becomes inactive during embryonic development~ so cells of male and females have the same amount (one copy) of most x-linked genes barr bodies are reactivated in the cells that give rise to eggs
huntingtons disease
a degenerative disease of the nervous system caused by a lethal dominant allele that has no obvious phenotypic effect until the individual is 35 to 45 years old
pedigree
a families history for a particular trait -- in a family tree form *helps to calculate the probability that a future child will have a particular genotype and phenotype
in most fungi and some protests a zygote is the only haploid stage gametes are formed by meiosis the multicellular organism is haploid the gametophyte generation produces gametes by mitosis reproduction is exclusively asexual
a multicellular organism is haploid
what is a karyotype
a pictorial display of an individuals chromosomes
Philadelphia chromosome
a shortened chromosome produced when a large portion of chromosome 22 is exchanged with a small fragment from a tip of chromosome 9 can cause cancer (CML)
asexual reproduction:
a single individual that is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes--- exact copies of parents genome in offspring (clone) done by single celled eukaryotes
a cell that has 22 autosomes and a Y chromosome would be a sperm a male somatic cell a male ovum
a sperm
mosaic b/c inactive X
after an x chromosome is inactivated in a particular cell, all mitotic descendants of the cell have the same inactive x if a female is heterozygous for a sex-linked trait, about half her cells will express one allele and the others will express the alternate allele
meiosis
after the chromosomes duplicate in inter-phase, the diploid cell divides TWICE, yielding four haploid daughter cells
somatic cells
all cells of the body (except gametes) have 46 chromosomes
dispersive model of replication
all four strands of DNA following replication have a mixture of old and new dna
during the first meiotic division (meiosis 1), homologous chromosomes separate the chromosome number becomes haploid crossing over between nonsister chromatids occurs paternal and maternal chromosomes randomly assort all of the above
all of the above
diploid cell:
any cell with a 2 chromosome set (2n) humans have a diploid number of 2n= 46 drosophila has a diploid number 2n=8 dogs have diploid number 2n=78
carriers of a genetic disorder are indicated by solid symbols on a family pedigree are involved in consanguineous matings will produce children with the disease are heterozygotes of the gene that can cause the disorder have a homozygous recessive genotype
are heterozygotes of the gene that can cause the disorder
sex chromosomes
are two distinct chromosomes (X and Y) that determine gender most genes are carried on the X chromosome and do not have counterparts on the Y 23 chromosomes from each parent that make up a total of 46 in our somatic cells
Griffiths study on 2 strains of bacteria
attempting to develop a vaccine for pneumonia he had 2 strains of bacterium: one pathogenic, one nonpathogenic when he injected the mouse with living pathogenic cells the mouse died when he injected the mouse with living nonpathogenic cell the mouse lived when injected with heat killed pathogenic cells, the mouse lived when injected with a mixture of heat killed pathogenic cells and living nonpathogenic cells, the mouse died concluded that a chemical in the dead pathogenic cells caused a heritable change in the living nonpathogenic cells ~transformation
the F2 generation a) has a phenotype of 3:1 b) is the result of the self-fertilization or crossing of F1 individuals c) can be used to determine the genotype of individuals with the dominant phenotype d) has a phenotypic ratio that equals its genotypic ratio e) has 16 different genotypic possibilities
b) is the result of the self-fertilization or crossing of F1 individuals
crossing over genetic variation
b/c of independent assortment we each produces a collection of gametes differing in their combinations of chromosomes from our parents crossing over produces RECOMBINANT chromosomes (individual chromosomes that carry DNA derived from 2 different parents). ***in meiosis 1 humans average of 1 to 3 crossover events happen depending on the size of chromosomes and position of centromeres
random fertilization genetic variation
because there are so many chromosome combinations due to independent assortment (2^n), the fusion of a male and female gamete will produce a zygote with any of about 7 trillion diploid combinations
which of the following describes why or how recombinant chromosomes add to genetic variability? a)they are formed as a result of random fertilization when two sets of chromosomes combine in a zygote b)they are the result of mutations that change alleles c)they randmoly orient during metaphase 2 and the d)nonequivalent sister chromatids separate in anaphase 2 genetic material from 2 parents is combined on the same chromosome e)both c and d are true
both C&D are true
DNA polymerase & synthesis
catalyze the synthesis of new DNA by adding nucleotides to a preexisting chain require: a primer and a DNA template strand for nucleotides to line up each nucleotide added to DNA strand comes from a nucleoside triphosphate (chemically reactive). as each monomer joins the growing side of the DNA strand, 2 phosphate molecules are lost as pyrophosphate (which is coupled exergonic reaction that drives the polymerization reaction) ecoli: DNA polymerase III and DNA polymerase I eukaryotes: 11 different DNA polymerases
telomerase
catalyzes the lengthening of telomeres in eukaryotic germ cells in order to restore their original length and preserve essential genes in the gametes
thymine dimers
cause the DNA to buckle and interfere with DNA replication due to sun damage and must be repaired or can cause skin cancer
sickle cell disease
caused by a substituation of a single amino acid in the hemoglobin protein of the red blood cells; in homozygous individuals, all hemoglobin is sickle celled oxygen content runs low and cells is an abnormal rod shape that can accumulate in small blood vessels it is said that evolution hasnt gotten rid of this because heterozygotes might be more resistant to maleria
which of the following would NOT be considered a haploid cell a daughter cell after meiosis 2 gamete daughter cell after mitosis in gametophyte generation of a plant cell in prophase 1 cell in prophase 2
cell in prophase 1
chromatin
complex of DNA and protein that fits into the nucleus through an elaborate multilevel system of packing
watson and crick
confirmed that dna was helical in shape b/c rosalind franklins x-ray crystallography double helix model with sugar phosphate backbone was good because then the hydrophobic bases were in the interior and the negatively charged phosphates were on the outside antiparallel~ subunits are in opposite directions each base has chemical side groups that can form hydrogen bonds with its partner: 2 h-bonds between A&T, 3 between G&C
monohybrid cross
cross between heterozygotes determined this b/c law of independent assortment when he followed 2 characters at the same time (vs 1 for the law of segregation)
nuclease
cuts out segments of the strand containing the damage (DNA cutting enzyme) -- the resulting gap is filled in with nucleotides using the undamaged strand as a template repair system is called the nucleotide excision repair
you think that two alleles for coat color in mice show incomplete dominance. what is the best ans simplest cross to perform in order to support your hypothesis? a) a testcross of a homozygous recessive mouse with a mouse of unknown genotype b) a cross of F1 mice to look for a 1:2:1 ratio in the offspring c) a reciprocal cross in which the sex of the mice of each coat color is reversed d) a cross of 2 true-breeding mice of different colors to look for an intermediate phenotype in F1 e) a cross of F1 mice to look for a 9:7 ratio in the offspring
d) a cross of 2 true-breeding mice of different colors to look for an intermediate phenotype in F1
A mother with type B blood has 2 children, one with type A blood and one with type O blood. Her husband has type O blood. which of the following could you conclude from this information? a) the husband could not have fathered either child b) the husband could have fathered both children c) the husband much be the father of the child with the O type blood and could be the father of the type A child d) the husband could be the father of the child with the type O blood but not the father of the type A child e) neither the mother nor the husband could be the biological parent of the type child.
d) the husband could be the father of the child with the type O blood but not the father of the type A child
alterations of chromosome structure
deletions and duplications are likely to occur during meiosis in crossing over when nonsister chromatids exchange nonequal sized segments of DNA. product: one chromosome with a deletion, one with duplication in reciprocal translocations the segments are exchanged between nonhomologous chromosomes and inversersions, the balance of genes is not abnormal ~ can alter genes expression and be influenced by its location among neighboring genes
nucleoid
dense region of DNA in bacterium -- not bound by a membrane
proof reading and repairing DNA
during DNA replication, DNA polymerases proofread each nucleotide against its template. if one is incorrectly paired, the polymerase removes it mismatch repairs~~ when other enzymes remove and replace incorrectly paired nucleotides that have resulted from replication erros (not seen by DNA polymerase) DNA is constantly exposed to harmful chemical and physical agents (smoke/x-rays) so it is always being corrected even after replication usually corrected before they become permanent mutations through successive replications
ecoli replication vs eukaryotic
ecoli ~the parental strands separate at the origin, forming a replication bubble with two forks. replication proceeds in both directions until the forks meet on the other side. resulting in 2 daughter cells eukaryotic~ has a few thousand replication origins, multiple replication bubbles for and eventually fuse to speed up the copying of DNA. replicates in both directions
helicase
enzymes that untwist the double helix at the replication forks, separating the two parental strands and making them available as template strands
quantitative characters
ex) multiple characters that affect something like skin color indicates polygenic inheritance~ the addition of 2+ genes on a single phenotypic character **different than pleiotropy b/c in pleiotropy only one gene effects several characters)**
the restoration of the diploid chromosome number after halving in meiosis is due to synapsis fertilization mitosis dna replication chiasmata
fertilization
Morgan's experiment on drosophila
flies have lots of advantages (should know this b/c lab report) ~wildtypes + red eyes he mated a white male with a red female but only males showed the white eyes ~ discovered sex-linked traits supports theory of inheritance b/c it shows that a specific gene is carried on a specific chromosome
a cell in G2 before meiosis compared with one of the four cells produced by that meiotic division has twice as much DNA and twice as many chromosomes four times as much DNA and twice as many chromosomes four times as much DNA and four times as many chromosomes half as much DNA but the same number of chromosomes half as much DNA and half as many chromosomes
four times as much DNA and twice as many chromosomes
haploid cells
gametes that contain a single set of chromosomes (n) in humans n=23 --> which contains 22 autosomes plus a single sex chromosome an unfertilized egg contains an X and a sperm may contain and X or Y
sex-linked genes
gene located on either sex chromosome
independent assortment of chromosomes genetic variation
generates genetic variation through the random orientation of pairs of homologous chromosomes at metaphase of meiosis 1. ~at metaphase 1 the homologous pairs (one maternal, one paternal) are situated at the metaphase plate. each pair (either its maternal OR paternal homolog) move closer to a given pole *****50% chance that a particular daughter cell of meiosis 1 will get either the maternal OR paternal chromosome ~DEFINITION~ each pair of homologous chromosomes is positioned independently of the other pairs at metaphase 1. so each daughter cell represents one outcome of all possible combinations of maternal and paternal chromosomes. **4 possible arrangements: 2 for the first pair times the 2 for the second pair the number of possible combinations when chromosomes sort independently is 2^n, where n is the haploid number of the organism ex) humans(n=23) so its n^23
law of independent assortment only applies to....
genes (allele pairs) located on different chromosomes (chromosomes that are NOT homologous).. or very very far apart on the same chromosome
linked genes
genes located near each other on the same chromosome tend to be inherited together in genetic crosses different than sex-linked b/c it involves 2+ genes, not 1
sturtevant's observations/hypothesis
genetic map~ordered list of the genetic loci along a particular chromosome hypothesized that the percent of recombinant offspring (recombination frequency) depends on the distance between genes on the chromosome the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency
homologous chromosomes have identical genes have genes for the same traits at the same loci are found in gametes separate in meiosis 2 have all of the same above characteristics
have genes for the same traits at the same loci
topoisomerase
helps relieve the strain caused by the untwisting of the double helix at the replication fork by breaking, swiveling, and rejoining DNA strands
genes are
hereditary units that are inherited from our parents
dihybrids
heterozygotes for two characters being followed
aneuploidy~ trisomic
if a chromosome is present in triplicate in the zygote ex) down syndrome
linked genes (crossing over)
if the parental types have a frequency greater than 50% then the genes are linked about 17% however are recombinants crossing over ~~~> process that occasionally breaks the physical connection between specific alleles of genes on the same chromosome which accounts for recombination of linked genes. happens in prophase 1 of meiosis -----so the end portions of nonsister chromatids trade places each time a crossover occurs -----increases genetic variation
heterochromatin
interphase chromatin that is visible as irregular clumps with a light microscope largely inaccesable to the machinery in the cell responsible for transcribing the genetic info coded for DNA
duchenne muscular dystrophy
is a progressive weakening of the muscles and loss of coordination sex linked to x chromosome
Tay-Sachs disease
is an inherited disorder in humans where the brain cells of a child cannot metabolize certain lipids because an enzyme doesnt work properly.. lipids accumulate in the brain and the kid has seizures, blindness, and degeneration of motor and mental performance **only children who are homozygous for this allele have the disease, which makes it recessive organismal level: allele is recessive biochemical level: homozygous chromosomes show incomplete dominance molecular level: normal allele and tay-sachs allele are codominant
the term "dominant" is used because
it is SEEN in the phenotype not because it suppresses the recessive allele
background on mendel (idk if this is relevant at all but it was in the book so...yeah)
left his monastery and went to study physics and chemistry at the university of vienna physicist christian Doppler encouraged his students to learn science through experimentation and trained mendel to use mathematics to help explain natural phenomena botanist franz Unger aroused mendels interest in the causes of variation in plants
locus (loci)...
location of a gene along the length of a chromosome
euchromatin
loose packing of DNA that is accessible to the DNA machinery for transcription
cytogenic maps
maps which locate genes with respect to chromosomal features, such as stained bands linear order of genes is identical in all the maps, but the spacing between genes is not
nondisjunction
members of a pair of homologous chromosomes do not move apart properly during meiosis 1 or the sister chromatids fail to separate during meiosis 2 when it happens in meiosis 1 it results with : two n+1 and two n-1 in meiosis 2: one n+1, one n-1, and two n
chromosome theory of inheritance
mendelian genes have a specific loci along chromosomes and it is the chromosomes that undergo segregation and independent assortment Sutton & Boveri
alleles
mendels name for alternative versions of genes that account for variations in inherited characters in a somatic cell, the two chromosomes may have identical or different alleles on a given loci
which phase of meiosis is most directly related to the law of independent assortment? prophase 1 prophase 2 metaphase 1 metaphase 2 anaphase 2
metaphase I
DNA is located in
mitochondria and chloroplasts and nucleus mitochondrial DNA is inherited from your mother
what life cycle change is found in plants but not animals? gamete zygote multicellular diploid multicellular haploid unicellular diploid
multicellular haploid
evolutionary significance of genetic variation in populations
natural selection results in the accumulation of genetic variations favored by the environment (Darwin's evolution). as the environment changes, the population may survive if in each generation at least some of its members can cope effectively with the new conditions mutations are original source of different alleles which are mixed and matched during meiosis asexual reproduction in a stable environment is more adventagious b/c ensures perpetuation of successful combinations of alleles
what are autosomes sex chromosomes chromosomes that occur singly chromosomal abnormalities that result in genetic defects chromosomes found in mitochondria and chloroplasts none of the above
none of the above
deletion mutation
occurs when a chromosomal fragment is lost so it is missing genes.
addition rule
probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities
asexual reproduction of a diploid organism would be impossible involve meiosis produce identical offspring show variation among sibling offspring involve spores produced by meiosis
produce identical offspring
a synaptonemal complex would be found during prophase 1 of meiosis fertilization or sengamy of gametes metaphase 2 of meiosis prophase of mitosis anaphase 1 of meiosis
prophase 1 of meiosis
genetic variation
provides raw material for natural selection mutations crossing over independent assortment law of segregation random fertilization
which of the following is NOT a source of genetic variation in sexually reproducing organisms crossing over replication of DNA during the S phase before meiosis 1 independent assortment of chromosomes random fertilization mutation
replication of DNA during the S phase before meiosis 1
gametes
reproductive cells that transmit genes from one generation to the next
histones
responsible for the first level of DNA packing in chromatin total mass of histone in chomatin equals the mass of DNA H2A, H2B, H3, H4
hemophilia
sex linked gene recessive absence of one of more of the proteins required for blood clotting (basically cannot stop bleeding)
problems in DNA replication
since DNA polymerase can only add nucleotides to the 3' end of a preexisting nucleotide, there is no way to complete the 5' ends of the daughter strands even though okazaki fragments can be started by an RNA primer, once the primer is removed the DNA cannot be replaced SO repeated rounds of replication produce shorter and shorter DNA molecules with uneven (staggered) ends
meiosis 2 is similar to mitosis because sister chromatids separate homologous chromosomes separate DNA replication precedes the division they both take the same amount of time haploid cells are produced
sister chromatids separate
telomeres
special nucleotide sequences at the ends of eukaryotic DNA molecules protects genes of linear eukaryotic chromosomes from being eroded away during successive rounds of replication --do not contain genes--consists of repetitions of one short sequence human telomere= TTAGGG
origins of replication
specific sites where the replication of a DNA molecule beings ~short stretches of DNA having a specific sequence of nucleotides
primase
synthesizes the RNA primer for DNA replication by starting a complementary RNA chain from a single RNA nucleotide, adding RNA nucleotides one at a time, using the parental strand as a template
which of the following human diseases is inherited as a simple recessive trait? Tay-sachs disease cancer diabetes Alzheimers cardiovascular disease
tay-sachs
true breeding
term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate
hybridization
the act of mixing different species or varieties of animals or plants and thus to produce hybrids p generation, f1, f2....
map units
the distance between genes on a chromosome one map unit = 1% recombination frequency does not correspond to actual physical distance between genes
a 1:1 phenotypic ratio in a testcross indicated that the alleles are dominant one parent must have been homozygous recessive the dominant phenotype parent was a heterozygote the alleles segregated independently the alleles are codominant
the dominant phenotype parent was a heterozygote
fertilization & zygote
the fusion of two gametes which results in a fertilized egg with two haploid sets of chromosomes from both parents that restore the diploid conditions of somatic cells gametes are the only cells in the human body are NOT produced by mitosis
in the alternation of generations found in plants, the sporophyte generation produces spores by mitosis the gametophyte generation produced gametes by mitosis the zygote will develop into a sporophyte generation by meiosis spores develop into the haploid sporophyte generation the gametophyte generation produces spores by meiosis
the gametophyte generation produces gametes by mitosis
primer
the initial nucleotide chain that is produced during DNA synthesis is actually a short stretch of **RNA** ==== primer (5-10 nucleotides long) primer is synthesized by primase new DNA strand will start from the 3' end of the RNA primer
cystic fibrosis
the normal allele for this gene codes for a membrane protein that functions in the transport of chloride ions between certain cells and the extracellular fluid. these chloride transport channels are defective or absent in the plasma membranes of children who are homozygous recessive for the gene leads to pleiotropic effects like poor absorption of nutrients from the intestines, etc
epistasis
the phenotypic expression of a gene at one locus can alter that of a gene at a second locus ex) the lab dogs with black brown and yellow colors mating heterozygous for both genes get 9:3:3:1 ratio and follow independent assortment
DNA replication
the process by which a DNA molecule is copied, and how cells repair their DNA
genetic recombination
the production of offspring with combinations of traits that differ from those found in either parent
genetics is
the scientific study of heredity and hereditary variation
why mendel chose to work with peas
they are available in many varieties ~character: heritable feature that varies among individuals (ex color) ~trait: each variant for a character (purple/white colors) short generation time large number of offspring from each mating could strictly control the mating between plants he only tracked characters that occurred in two distinct forms
single strand binding proteins
they bind to the unpaired DNA strands(after helicase separates parent strands) to keep them from re-pairing
Meselson and Stahl -- DNA replication experiment
they cultured e. coli for several generations in a medium containing nucleotide precursors labeled with a heavy isotope nitrogen-15. then they transferred bacteria to a medium with only nitrogen-14. a sample was taken after DNA replicated once, another take after DNA replicated again. they extracted the DNA from the bacteria in the samples and centrifuged each DNA sample to separate DNA of different densities results~~~ 1st replication produced a solid band of a hybrid (which eliminated the conservative model). then the 2nd replication produced both light and hybrid DNA which supported the semi-conservative model
which of the following is NOT true of homologous chromosomes they behave independently in mitosis they synapse during the S phase of meiosis they travel together to the metaphase plate in prometaphase of meiosis 1 each parent contributes one set of homologous chromosomes is indicated by the presence of chiasmata
they synapse during the S phase of meiosis
multiplication rule
to determine probability we need to multiply the probability of one event by the probability of another (individual probabilities) segregation is like flipping a coin -- the outcome of any particular toss is unaffected by what has happened on the previous trials (independent)
down syndrome
trisomy 21. extra chromosome 21 (3n)
codominance
two alleles each affect the phenotype in separate, distinguishable ways different from incomplete dominance b/c the phenotype is not intermediate between the two dominant alleles. so both phenotypes are exhibited
homologous chromosomes:
two chromosomes composing a pair that have the same length, centromere position, and staining patterm each control the same inherited characters
nucleosome
unfolded chromatin that resembles beads each "bead" is the basic unit of DNA packing... the string is linker DNA N-terminus= amino acid end of each histone extends outward from the nucleosome H1 is involved in the interactions of the histone tails for tighter packing looped domains-- loops that are attached to the chromosome scaffold made up of proteins (scaffold is rich in topoisomerase)
Hershey/Chase DNA experiment
used radioactive sulfur-35 and phosphorus-32 to trace the fates of protein and DNA or t2 phages that infected bacterial cells of ecoli the sulfur tagged the phage protein. and phosphorus tagged DNA concluded that DNA is genetic material and proteins are not b/c the radioactive phage proteins stayed in the liquid and the radioactive dna formed a pellet inside the cells. ***dna entered host cell and the phage did not** 1. mixed radioactively labeled phages with bacteria. phages infected cells 2. agitated the mixture in a blender to free phage parts outside the cell 3. centrifuged so bacteria formed a pellet at the bottom; free phages remained suspended in liquid. measured radioactivity in pellet and liquids
genomic imprinting
variation in phenotype depending on whether an allele is inherited from the male or female parent (most imprinted genes are on autosomes, unlike sex linked ones) aka traits that depend on which parents allele is inherited occurs during gamete formation.. results in the silencing of a particular allele of certain genes consists of methyl (CH3) groups that are added to cytosine nucleotides of an allele ---- methylization can activate or silence genes
bacteriophages
viruses that infect bacteria in order to produce more viruses. does this by taking over the cells metabolic machinery virus= dna enclosed by a protective coat
translocation mutation
when a chromosomal fragment joins to a nonhomologous chromosome
inversion mutation
when a chromosomal fragment reattaches to the original chromosome but in the reverse orientation
duplication mutation
when a deleted fragment from another chromosome attaches as an extra segment to a sister chromatid
semi-conservative model
when a double helix replicates each of the two daughter molecules will only have one old strand, one from the parental molecule and one new strand
aneuploidy
when either of the gametes resulting from a nondisjunction unite with a normal one during fertilization then the zygote will have an abnormal number of a particular chromosome if a nondisjunction error takes place early in the embryonic development then the condition will be passed along to all cells by mitosis
aneuploidy~ monosomic
when fertilization involving a gamete with no copy of a chromosome will lead to a missing chromosome in zygote (2n-1)
pleiotropy
when genes have multiple phenotypic effects in humans it causes ~ cystic fibrosis, sickle cell anemia
incomplete dominance
when neither allele in a heterozygote is completely dominant... so they have a phenotype somewhere in between the parental phenotypes 2 heterozygotes mate ex) red snapdragon + white snapdragon = pink snapdragon
polyploidy
when organisms have more than 2 complete sets of chromosomes in all somatic cells mostly in plants appear nearly normal in appearance compared to aneuploidy
complete dominance
when phenotypes of the heterozygote and the dodminant homozygote are indistinguishable
conservative model of replication
when the two parental strands somehow come back together after the process
if the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be 2x. Then the DNA content of a single cell at metaphase of meiosis II would be... 0.25x 0.5x x 2x 4x
x
