GENERAL BIOLOGY I TEST IV

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1 GENERAL BIOLOGY I TEST IV R E V I E W The Academic Support Daytona State College (Science 65, Page 1 of 31)

2 TERMS TO KNOW Cell Cycle Interphase (G0, G1, S, G2) and mitosis An ordered sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two. The eukaryotic cell cycle is composed of interphase (including G1, S, and G2 subphases) and M phase (including mitosis and cytokinesis). Prophase Chromatin condenses into chromosomes, nuclear membrane dissolves. The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact. Metaphase Chromosomes line up along the center of the cell The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate. Anaphase Chromatids begin pulling apart The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell. Telophase Chromosomes move to opposite ends of the cell, nuclear membranes reform The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun. The Academic Support Daytona State College (Science 65, Page 2 of 31)

3 TERMS TO KNOW Cytokinesis Cleavage of the cell, involves cleavage furrow in animal cells and cell plate formation in plant cells The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II. Chromosome Tightly bundled DNA A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins. (A bacterial chromosome usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.) Chromatid One of a pair of duplicated chromosomes One of the longitudinal subunits of a replicated chromosome. Chromatin Loose DNA The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope. The Academic Support Daytona State College (Science 65, Page 3 of 31)

4 TERMS TO KNOW Karyotype The number and appearance of chromosomes in the nucleus of a eukaryotic cell. A display of the chromosome pairs of a cell arranged by size and shape. Karogram - A graph depicting all 23 pairs of chromosomes lined up in order from largest to smallest Haploid One complete set of chromosomes, i.e. 23 chromosomes in haploid human gametes Diploid Two complete sets of chromosomes, i.e. 23 pairs of chromosomes in somatic human cells Gamete Haploid reproductive cells A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote. The Academic Support Daytona State College (Science 65, Page 4 of 31)

5 TERMS TO KNOW Centromere Center of a chromosome In a duplicated chromosome, the region on each sister chromatid where they are most closely attached to each other by proteins that bind to specific DNA sequences; this close attachment causes a constriction in the condensed chromosome. (An uncondensed, unduplicated chromosome has a single centromere, identified by its DNA sequence.) Kinetochore Protein in the center of a chromosome where spindle fibers attach A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle. Homologous Chromosomes A pair of the same chromosomes, one from each parent, may have different versions of the same alleles A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism s father, the other from the mother. Also called homologs, or a homologous pair. Fission of Bacteria The method by which bacteria reproduce, doubling of chromosomes and splitting of one cell into two with no mitosis occurring. This takes place with out the formation of spindles. The Academic Support Daytona State College (Science 65, Page 5 of 31)

6 TERMS TO KNOW Autosomes autosome - A chromosome that is not directly involved in determining sex; not a sex chromosome. Sex Chromosomes sex chromosome - A chromosome responsible for determining the sex of an individual. Gametophyte Haploid organism that makes gametes via mitosis In organisms (plants and some algae) that have alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis. The haploid gametes unite and develop into sporophytes. Sporophyte Diploid organism that makes spores via meiosis In organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes. The sporophyte produces haploid spores by meiosis that develop into gametophytes. The Academic Support Daytona State College (Science 65, Page 6 of 31)

7 TERMS TO KNOW Recombination Increases genetic variation during meiosis I. Two types of recombination. Crossing over exchange of DNA between homologous chromosomes. Random separation (assortment/segregation) of homologous chromosomes. Independent assortment orientation of homologous pairs to poles is random. All possible combinations of gametes should be formed in equal frequency Formula for number of combinations is 2 n Gregor Mendel Proposed the existence of particulate unit factors (genes) are passed from generation to generation Proposed three postulates of inheritance Unit factors (alleles of genes) exist in pairs (in diploid) If an organism has two different alleles (heterozygous) then one is dominant and the other is recessive. One expresses phenotype in heterozygote, and the other is hidden in heterozygote The paired unit factors segregate independently during gamete formation (meiosis). Proposed that traits assort independently during gamete formation. Used true breeding strains of peas with seven characteristics, each characteristic had two contrasting traits. The Academic Support Daytona State College (Science 65, Page 7 of 31)

8 TERMS TO KNOW Allele Alternative forms of the same gene A single type of a gene, i.e. brown eye vs blue eye genes A variation of a gene or alternate form of a gene Any of the alternative versions of a gene that may produce distinguishable phenotypic effects. Genotype The genetic makeup of an individual. The combination of alleles of an organism. (Alleles of a gene; example AA, Aa, or aa.). The genetic makeup, or set of alleles, of an organism. Phenotype Composite of an organism s observable characteristics The observed characteristics. The observable physical and physiological traits of an organism, which are determined by its genetic makeup. Genotype + Environment Phenotype The Academic Support Daytona State College (Science 65, Page 8 of 31)

9 Genotype vs Phenotype The Academic Support Daytona State College (Science 65, Page 9 of 31)

10 Homozygous TERMS TO KNOW Having two of the same alleles for a specific trait (true breeding) When the alleles for a trait in an individual are the same. Example AA or aa Heterozygous Having two different alleles for a specific trait When the alleles for a trait in an individual are different. Example Aa Parental Generation The first set of parents crossed in which their genotype is the basis for predicting the genotype of their offspring, which in turn may be crossed. P generation - The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance; P stands for parental. F 1 Generation F 1 is the first cross of the parental generation, F 1 generation - The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross. F 2 Generations F 2 is a cross of the F1 generation F 2 generation -The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation. The Academic Support Daytona State College (Science 65, Page 10 of 31)

11 TERMS TO KNOW Dominant Allele that is always expressed if present dominant allele - An allele that is fully expressed in the phenotype of a heterozygote. Recessive Allele that is only expressed if homozygous for that allele recessive allele - An allele whose phenotypic effect is not observed in a heterozygote. Test Cross Dominant phenotype of unknown genotype being crossed with recessive phenotype to determine genotype Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype. Haploid Having a single set of chromosomes (n) Diploid Having two sets of chromosomes (2n) The Academic Support Daytona State College (Science 65, Page 11 of 31)

12 TERMS TO KNOW Complete dominance One allele is completely dominant over the other, and is always expressed if present The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable. Co-dominance Both alleles are completely expressed, i.e. AB blood type The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways. Incomplete dominance Both alleles are expressed, i.e. pink flowers being a cross of red and white The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele. Multiple alleles More than one allele exists, i.e. ABO blood types In a population of organisms, the presence of three or more alleles of the same gene. The Academic Support Daytona State College (Science 65, Page 12 of 31)

13 TERMS TO KNOW Monohybrid cross Monohybrid cross: Crossing of alleles for one trait A cross between two organisms that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant). Dihybrid cross A cross between two organisms that are each heterozygous for both of the characters being followed (or the self-pollination of a plant that is heterozygous for both characters). Dihybrid cross: Crossing of alleles for two traits Dependent assortment (like linked genes) vs. independent assortment Dependent assortment: Theory that alleles on the same chromosome are crossed together Independent assortment: Theory that alleles on the same chromosome are crossed separately Pleiotropy The ability of a single gene to have multiple effects. Polygenic Phenotype is determined by multiple genes polygenic inheritance - The transmission of a phenotypic trait whose expression depends on the additive effect of a number of genes. The Academic Support Daytona State College (Science 65, Page 13 of 31)

14 CONCEPT QUESTIONS MITOSIS: Be able to identify pictorial/symbolic representations of mitosis. Chromosomes condense during Pro phase; chromosomes are located in the equator during Meta phase, chromatids separate during Ana phase, chromosomes relax during Telo phase? Centrioles move to the poles during Pro phase of mitosis? The nuclear membrane disassembles during Pro phase, and reassembles during Telo phase and is absent in-between phases. How do spindle fibers move chromosomes during anaphase? In anaphase, spindle fibers pull sister chromatids toward the spindle poles. Spindle fibers not connected to chromatids lengthen and elongate the cell. Forming a cell plate Cytokinesis in plants is by and cytokinesis in animals is by. Forming a cleavage furrow Centrioles are found in Animals but not? higher level Plants If a cell had 10 chromatids in metaphase of mitosis, how many chromosomes are in each resulting nucleus? 5 The Academic Support Daytona State College (Science 65, Page 14 of 31)

15 CONCEPT QUESTIONS What is the life cycle of animals? Diploid with an extremely reduced haploid stage What is the life cycle (alternation of generation) of plants? Alternating haploid and diploid generations, sporophyte and gametophyte What are the differences between meiosis and mitosis? Meiosis forms haploid cells, Mitosis forms diploid cells Meiosis involves crossing over and shuffling of genes, mitosis makes two exact replicas Meiosis is a two stage process Meiosis 1 and Meiosis 2. What are the similarities between meiosis and mitosis? Both Meiosis and Mitosis go through the four phases; prophase, metaphase, anaphase, and telophase. The Academic Support Daytona State College (Science 65, Page 15 of 31)

16 LIFE CYCLE OF A FERN EXAMPLE OF ALTERNATION OF GENERATIONS The Academic Support Daytona State College (Science 65, Page 16 of 31)

17 LIFE CYCLE OF A MOSS EXAMPLE OF ALTERNATION OF GENERATIONS The Academic Support Daytona State College (Science 65, Page 17 of 31)

18 LIFE CYCLE OF AN ANIMAL The Academic Support Daytona State College (Science 65, Page 18 of 31)

19 CONCEPT QUESTIONS If there are 100 chromosomes before meiosis, how many are there after meiosis? 50 If there are 100 chromosomes before mitosis, how many are there after mitosis? 100 If a cell has two pair of homologous chromosomes before mitosis (after S phase), then how many chromatids does it have? 8 If a cell has two pair of homologous chromosomes before meiosis (after S phase), then how many chromatids does it have? 8 The Academic Support Daytona State College (Science 65, Page 19 of 31)

20 PUNNETT SQUARES P p P p The Academic Support Daytona State College (Science 65, Page 20 of 31)

21 PUNNETT SQUARES P p P PP Pp p Pp pp The Academic Support Daytona State College (Science 65, Page 21 of 31)

22 PUNNETT SQUARES I A I B i i The Academic Support Daytona State College (Science 65, Page 22 of 31)

23 PUNNETT SQUARES I A I B i I A i I B i i I A i I B i The Academic Support Daytona State College (Science 65, Page 23 of 31)

24 Dihybrid Cross: a cross that shows the possible offspring for two traits Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth In this example, we will cross a heterozygous individual with another heterozygous individual. Their genotypes will be: BbRr x BbRr The Academic Support Daytona State College (Science 65, Page 24 of 31)

25 Dihybrid Cross BbRr x BbRr First, you must find ALL possible gametes that can be made from each parent. Remember, each gamete must have one B and one R. The Academic Support Daytona State College (Science 65, Page 25 of 31)

26 Dihybrid Cross BbRr x BbRr Possible gametes: BR Br br br Next, arrange all possible gametes for one parent along the top of your Punnett Square, and all possible gametes for the other parent down the side of your Punnett Square The Academic Support Daytona State College (Science 65, Page 26 of 31)

27 Dihybrid Crosses: a cross that shows the possible offspring for two traits BbRr x BbRr Fur Color: B: Black b: White BR BR Br br br Coat Texture: R: Rough r: Smooth Br Then, find the possible genotypes of the offspring br br The Academic Support Daytona State College (Science 65, Page 27 of 31)

28 Dihybrid Crosses: a cross that shows the possible offspring for two traits BbRr x BbRr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth BR Br br BR Br br br BBRR BBRr BbRR BbRr BBRr BBrr BbRr Bbrr BbRR BbRr bbrr bbrr br BbRr Bbrr bbrr bbrr The Academic Support Daytona State College (Science 65, Page 28 of 31)

29 How many of the offspring would have a black, rough coat? How many of the offspring would have a black, smooth coat? How many of the offspring would have a white, rough coat? How many of the offspring would have a white, smooth coat? BR Br br br BR Br br br BBRR BBRr BbRR BbRr BBRr BBrr BbRr Bbrr BbRR BbRr bbrr bbrr BbRr Bbrr bbrr bbrr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth The Academic Support Daytona State College (Science 65, Page 29 of 31)

30 How many of the offspring would have black, rough coat? How many of the offspring would have a black, smooth coat? How many of the offspring would have a white, rough coat? How many of the offspring would have a white, smooth coat? Phenotypic Ratio 9:3:3:1 BR Br br br BR Br br br BBRR BBRr BbRR BbRr BBRr BBrr BbRr Bbrr BbRR BbRr bbrr bbrr BbRr Bbrr bbrr bbrr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth The Academic Support Daytona State College (Science 65, Page 30 of 31)

31 Questions Prepared by K. Martin (Peer Tutor) & D. Leonard (Learning Specialist) The Academic Support Daytona State College The Academic Support Daytona State College (Science 65, Page 31 of 31)