FTCE SAE Biology Preparation Course

1. FTCE SAE Biology Preparation Course Instructor Valerie Ruwe vruwe@browardschools.com

2. Session Norms • No side bars • Work on assigned materials only • Keep phone on vibrate only • If a call must be taken please leave the room to do so

3. Session Agenda • Session I: Pre-Test, Competencies 1 & 2 • Session II: Competencies 3,4 • Session III: Competencies 5,6 • Session IV: Competencies 7,8 • Session V: Competencies 9,10

4. 5. Knowledge of genetic principles, processes, and applications 12 % • Evaluate the relationships between the structure and function of DNA. • Identify and sequence the principal events in DNA replication. • Identify and sequence the principal events of protein synthesis. • Distinguish between the various functions of DNA and RNA. • Distinguish between the regulatory systems for prokaryotic and eukaryotic protein synthesis. • Evaluate the appropriate application of DNA manipulation techniques (e.g., gene splicing, recombinant DNA, gene identification, PCR technique).

5. 5. Knowledge of genetic principles, processes, and applications 12 % • Predict the effects of environmental and other influences on gene structure and expression (e.g., viruses, oncogenes, carcinogenic agents, mutagenic agents). • Analyze the processes and products of meiosis (e.g., gametogenesisin male and female vertebrates; plant, animal and fungi meiosis) in representative examples from various kingdoms. • Differentiate between classical laws of inheritance, their relationship to chromosomes, and related terminology. • Analyze applications of probability and chi-square analysis in genetics. • Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomal linkage, multiple alleles, polygenic inheritance). • Identify the causes of genetic disorders (e.g., point mutation, nondisjunction, translocation, deletion, insertion, inversion, duplication). • Identify the effect of a mutation in a DNA sequence on the products of protein synthesis.

6. Evaluate the relationships between the structure and function of DNA • 5-carbonpentose sugar (deoxyribose) • a phosphate attached at the #5 carbon of the sugar • an organic or nitrogenousbase – a nitrogen containing ring structure – attached at the #1 carbon of the sugar. • the phosphates and sugars form the backbone of the DNA strand.  • Hydrogen bonds form between the nitrogenous bases of each strand of DNA forming a structure that resembles a ladder;  the nitrogenous bases are the rungs of the ladder and the sugars and phosphates form the sides of the ladder.  • The sides of the ladder run in an antiparallel configuration; the sugar-phosphate bonds are laid down in a 5’ to 3’ configuration – a phosphate is bonded to a #5 carbon followed by another phosphate bonded to the #3 carbon which joins the nucleotide to the #5 carbon of the next sugar in the backbone.  The opposite side of the double helix is reversed – the phosphate is bonded to the #3 carbon first. • The amount of A= T & amount of C= G

7. Evaluate the relationships between the structure and function of DNA • Prokaryotic DNA • Single Circular Chromosome • Contain Less • Contains only EXONS (expressed sequences) • No proteins • Smaller circular plasmid DNA • Can be exchanged • Transformation • Transduction • Conjugation

8. Evaluate the relationships between the structure and function of DNA • Eukaryotic DNA • Chromosomes with sister chromatid attached at centromere visible during mitosis • DNA wrapped around histones • Contains only EXONS (expressed sequences) • Chromatin is uncoiled when genes are being transcribed

9. Identify and sequence the principal events in DNA replication. • DNA is copied by a process called DNA replication. • During semi conservative replication the 2 strands of DNA separate and 2 new complementary strands are synthesized. • Helicaseis an enzyme that unzips the double-stranded DNA helix. • Primase is an enzyme which produces an RNA primer needed to get the process of DNA replication started.Muchlike you put on a coat of primer before adding paint to a wall, an RNA primer must be placed on the DNA before new DNA bases can be made or synthesized. • DNA polymerase III is an enzyme which adds the new, complementary bases (A, T, C, G) to the growing DNA strand in the proper 5' to 3' direction (5'-->3'). • DNA polymerase I is a proof-reading enzyme that corrects any "mistakes" made when the DNA is being copied. • Ligaseis an enzyme that acts like molecular tape, linking or joining the new DNA bases together. • Lagging-strand replication is discontinuous, with short Okazaki fragments being formed that are later linked together.

10. Identify and sequence the principal events in DNA replication. • Origins of replication • Single origin for bacterial chromosome • Many origins for eukaryotic chromosomes • Replication forks • Prokaryotes have circular DNA, thus this is not a problem • Eukaryotic cells have special nucleotide sequences called telomeres at their ends • Telomeres do not contain genes • Telomeres consist of multiple repeats of one short nucleotide sequence • Example is TTAGGG for humans • Telomeres protect genes from being eroded by successive rounds of replication • Telomeres also prevent cell from recognizing the ends as damaged

11. Distinguish between the various functions of DNA and RNA. • Central Dogma of Biology • DNA>RNA>Protein

12. Distinguish between the various functions of DNA and RNA. • mRNA (messenger RNA) - carries genetic information from the nucleus to the cytoplasm • tRNA(transfer RNA) - brings amino acids to ribosomes during protein synthesis • rRNA(ribosomal RNA) - guides the translation of mRNA into a protein

13. Identify and sequence the principal events of protein synthesis. • .Transcription Before the synthesis of a protein begins, the corresponding RNA molecule is produced by RNA transcription. • One strand of the DNA double helix is used as a template by the RNA polymerase to synthesize a messenger RNA (mRNA). • This mRNA migrates from the nucleus to the cytoplasm. • During this step, mRNA goes through different types of maturation including one called splicing when the non-coding sequences are eliminated. • The coding mRNA sequence can be described as a unit of three nucleotides called a codon.

14. Identify and sequence the principal events of protein synthesis. • Translation • The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA. • The ribosome proceeds to the elongation phase of protein synthesis. • During this stage, complexes, composed of an amino acid linked to tRNA, sequentially bind to the appropriate codon in mRNA by forming complementary base pairs with the tRNAanticodon. • The ribosome moves from codon to codon along the mRNA. Amino acids are added one by one, translated into polypeptidic sequences dictated by DNA and represented by mRNA. • At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome.

15. Identify and sequence the principal events of protein synthesis.. • The sequence of a eukaryotic protein-coding gene is typically not colinear with the translated mRNA; that is, the transcript of the gene is a molecule that must be processed to remove extra sequences (introns) before it is translated into the polypeptide. • Most eukaryotic protein-coding genes contain segments called introns, which break up the amino acid coding sequence into segments called exons. • The transcript of these genes is the pre-mRNA (precursor-mRNA). • The pre-mRNA is processed in the nucleus to remove the introns and splice the exons together into a translatable mRNA. That mRNA exits the nucleus and is translated in the cytoplasm.

16. Distinguish between the regulatory systems for prokaryotic and eukaryotic protein synthesis. • Prokaryotic Control Gene Expression by Operon • Lac Operon is inducible • The lacoperon is a DNA sequence that governs the production of proteins and enzymes for transporting and metabolizing lactose in bacteria such as E. coli. • In the absence of lactose, the lac repressor substance binds to the operator (a part of the DNA sequence), inhibiting the production of three proteins. • Lactose, however, represses/inhibits the repressor, allowing the enzymes to be produced. • When the mRNA of the lacoperon is transcribed, a polycistronic mRNA, three proteins will be produced by ribosomes: β-galactosidase, lactose permease and transacetylase.

17. Identify and sequence the principal events of protein synthesis.. • Prokaryotic Control Gene Expression by Operon • TrypOperon is repressible • trpoperon is normally transcribed • When tryptophan is present, it binds with the trp repressor, triggering an allosteric change • The trp repressor with bound tryptophan binds to the operator, shutting off transcription of the trpoperon • ·Tryptophan is a corepressor

18. Identify and sequence the principal events of protein synthesis.. • Eukaryotic Control • Chromatin Remodelling The region of the chromosome must be opened up in order for eznymes and transcription factors to access the gene • Transcription Control  The most common type of genetic regulation • Turning on and off of mRNA formation • Post-Transcriptional Control Regulation of the processing of a pre-mRNA into a mature mRNA • Translational Control Regulation of the rate of Initiation • Post-Tranlational Control (protein activity control) Regulation of the modification of an immature or inactive protein to form an active protein

19. Evaluate the appropriate application of DNA manipulation techniques (e.g., gene splicing, recombinant DNA, gene identification, PCR technique). • Gene splicing is just what it sounds like: cutting the DNA of a gene to add base pairs. • Chemicals called restriction enzymes act as the scissors to cut the DNA. • Once it finds that sequence in a strand of DNA, it attacks it and splits the base pairs apart, leaving single helix strands at the end of two double helixes. • Scientists are then free to add any genetic sequences they wish into the broken chain and, afterwards, the chain is repaired (as a longer chain with the added DNA) with another enzyme called ligase. • Hence, any form of genetic material can be spliced together; bacteria and chicken DNA can, and have been, combined • Recombinant DNA contains DNA from two different organisms.

20. Evaluate the appropriate application of DNA manipulation techniques (e.g., gene splicing, recombinant DNA, gene identification, PCR technique). • Recombinant DNA technology has extensive applications in developing pharmaceuticals. • The first drug created using recombinant DNA was human insulin. • To make the recombinant DNA, the insulin gene is cut from human DNA with restriction enzymes. • The DNA is then placed in a vector, such as a plasmid, and another enzyme, DNA ligase, seals the plasmid containing the insulin gene. • The plasmid is placed into another bacterial cell and this new cell produces multiple copies of the gene, called clones, when it divides. • The host bacterial cell also expresses the gene product, in this case insulin. • This technology is possible because the genetic code is universal. DNA functions in the same way, whether in a human cell or a bacterial cell.

21. Evaluate the appropriate application of DNA manipulation techniques (e.g., gene splicing, recombinant DNA, gene identification, PCR technique). • Southern blotting is a technique for detecting specific DNA fragments in a complex mixture. • It has been applied to detect Restriction Fragment Length Polymorphism (RFLP) and Variable Number of Tandem Repeat Polymorphism (VNTR).  The latter is the basis of DNA fingerprinting. • Polymorphism refers to the DNA sequence variation between individuals of a species. • If the sequence variation occurs at the restriction sites, it could result in RFLP.  • The most well known example is the RFLP due to bglobin gene mutation. 

22. Evaluate the appropriate application of DNA manipulation techniques (e.g., gene splicing, recombinant DNA, gene identification, PCR technique). • The purpose of a PCR (Polymerase Chain Reaction) is to make a huge number of copies of a gene. This is necessary to have enough starting template for sequencing.

23. Predict the effects of environmental and other influences on gene structure and expression (e.g., viruses, oncogenes, carcinogenic agents, mutagenic agents). • In the last few years, gene-therapy has focused the attention of the scientific community since it could be an efficient new way to cure several major human diseases such as cancer, AIDS, cystic fibrosis, anaemia or progeria. • The concept of gene therapy is the substitution in the cell nucleus of abnormal genes causing diseases by normal healthy DNA sequences. • The main challenge in gene therapy is the design of specific carriers, which allow efficient delivery of the healthy genes in the cell (transfection). • Such carriers should be able to transport DNA in the bloodstream, to cross efficiently cell membranes and to free the genetic material near the cell nucleus. • Typically, viral systems are the most effective carriers for gene delivery. Viral systems can selectively target cells and usually possess a very high transfection efficiency, leading to high gene expression rates. However, viral carriers can also be very toxic for the human body. Moreover, their isolation from biological sources and their processing are very expensive

24. Predict the effects of environmental and other influences on gene structure and expression (e.g., viruses, oncogenes, carcinogenic agents, mutagenic agents). • Cancer results from the breakdown of the controls that regulate cells. • These controls all originate from the genetic plans in a cell's DNA. • Therefore, a mistake or change in a cell's DNA code would cause problems with the cell's control system. • A mutation is a change in the normal DNA code. A mutation can be spontaneous or caused by outside factors. Mutations can have large effects on the cell or no effect at all. • A mutagen is a substance or agent that induces heritable change in cells or organisms. • A carcinogen is a substance that induces unregulated growth processes in cells or tissues of multicellular animals, leading to cancer. • Although mutagen and carcinogen are not synonymous terms, the ability of a substance to induce mutations and its ability to induce cancer are strongly correlated. • Mutagenesis refers to processes that result in genetic change, and carcinogenesis (the processes of tumor development) may result from mutagenic events

25. Predict the effects of environmental and other influences on gene structure and expression (e.g., viruses, oncogenes, carcinogenic agents, mutagenic agents). • Cancer genes are specific parts of DNA that when mutated, can lead to cancer. Cancer genes can be divided into two major categories: oncogenes and tumor suppressor genes. In normal cells, these two types of genes work together to regulate cell division. • Oncogenes are genes that usually produce positive signals that promote cell division. When mutated, these genes become permanently "turned on," causing cancer cells to continuously divide out of control. A defective oncogene is analogous to a car with the gas pedal stuck in the "on" position. It will move forward whether you push the pedal or not and can't be stopped. • Tumor suppressor genes are genes that usually produce negative signals that tell cells not to divide. When mutated, these genes become permanently "turned off," allowing cancer cells to divide even when they are not supposed to. A defective tumor suppressor gene is like a car with a broken brake system. You won't be able to stop the car when it is moving.

26. Analyze the processes and products of meiosis (e.g., gametogenesisin male and female vertebrates; plant, animal and fungi meiosis) in representative examples from various kingdoms. • Meiosis reduces chromosome number from diploid to haploid: a closer look • Meiosis and sexual reproduction significantly contribute to genetic variation among offspring. • Meiosis includes steps that closely resemble corresponding steps in mitosis. • Like mitosis, meiosis is preceded by replication of the chromosomes. • Meiosis differs from mitosis in that this single replication is followed by two consecutive cell divisions: Meiosis I and Meiosis II. • These cell divisions produce four daughter cells instead of two as in mitosis. • The resulting daughter cells have half the number of chromosomes as the original cell; whereas, daughter cells of mitosis have the same number of chromosomes as the parent cell.

27. Sources of Genetic Variation • Independent Assortment • Anaphase I • Homologues separate and are moved towards the poles by the spindle apparatus. • Sister chromatids remain attached at their centromeres and move as a unit towards the same pole, while the homologue moves towards the opposite pole. • This differs from mitosis during which chromosomes line up individually on the metaphase plate (rather than in pairs) and sister chromatids are moved apart towards opposite poles of the cell. Crossing Over • Prophase I • Synapsisoccurs. • During this process, homologous chromosomes come together as pairs. • .Since each chromosome has two chromatids, each homologous pair in synapsis appears as a complex of four chromatids or a tetrad. • In each tetrad, sister chromatids of the same chromosome are attached at their centromeres. • Nonsisterchromatids are linked by X-shaped chiasmata, sites where homologous strand exchange or crossing-over occurs. • Random Fertilization

28. Analyze the processes and products of meiosis (e.g., gametogenesisin male and female vertebrates; plant, animal and fungi meiosis) in representative examples from various kingdoms. • Animal: In animals, including humans, gametes are the only haploid cells. Meiosis occurs during gamete production. The resulting gametes undergo no further cell division before fertilization. • Fertilization produces a diploid zygote that divides by mitosis to produce a diploid multicellular animal. • Fungi and Some Protists: In many fungi and some protists, the only diploid stage is the zygote. Meiosis occurs immediately after the zygote forms. • Resulting haploid cells divide by mitosis to produce a haploid multicellular organism. • Gametes are produced by mitosis from the already haploid organism. • Plants and Some Algae: Plants and some species of algae alternate between multicellular haploid and diploid generations. This type of life cycle is called an alternation of generations. • The multicellular diploid stage is called a sporophyte, or spore-producing plant. Meiosis in this stage produces haploid cells called spores. • Haploid spores divide mitotically to generate a multicellular haploid stage called a gametophyte, or gamete-producing plant. • Haploid gametophytes produce gametes by mitosis. • Fertilization produces a diploid zygote which develops into the next sporophyte generation.

29. Analyze the processes and products of meiosis (e.g., gametogenesisin male and female vertebrates; plant, animal and fungi meiosis) in representative examples from various kingdoms.

30. Analyze the processes and products of meiosis (e.g., gametogenesisin male and female vertebrates; plant, animal and fungi meiosis) in representative examples from various kingdoms. • Meiosis occurs in the gametangia. • •  Gametangium = an organ that produces gametes • •  In animals, the gametangia are the ovaries in females which produce eggs and the the testes in males which produce sperm. • Meiosis is part of gametogenesis, the formation of gametes. • Following meiosis, haploid cells undergo changes in their structure so as to form specialized reproductive cells called gametes. • Spermatogenesis (sperm-formation) occurs in the testes of males while oogenesis (egg-formation) occurs in the ovaries of females.

31. Analyze the processes and products of meiosis (e.g., gametogenesisin male and female vertebrates; plant, animal and fungi meiosis) in representative examples from various kingdoms. • Moccursin sporangia (organs that make spores), producing haploid spores. • • A spore develops into a haploid stage called the gametophyte ("gamete-plant") which produces gametes. • •  After fertilization, a zygote develops into a diploid stage called the sporophyte ("spore-plant") which produces spores. • •  So there is an alternation of two multicellular stages: sporophyte (2n) and gametophyte (n).

32. Analyze the processes and products of Differentiate between classical laws of inheritance, their relationship to chromosomes, and related terminology • Mendel's first law, stating that allele pairs separate during gamete formation, and then randomly re-form pairs during the fusion of gametes at fertilization. • As long as they are unlinked

33. Analyze the processes and products of Differentiate between classical laws of inheritance, their relationship to chromosomes, and related terminology • Trait - any characteristic that can be passed from parent to offspring • Heredity - passing of traits from parent to offspring • Genetics - study of heredity • Alleles - two forms of a gene (dominant & recessive) • Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R) • Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r) • Genotype - gene combination for a trait (e.g. RR, Rr, rr) • Phenotype - the physical feature resulting from a genotype (e.g. tall, short) • Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or Rr); also called pure  • Heterozygous genotype - gene combination of one dominant & one recessive allele    (e.g. Rr); also called hybrid • Monohybrid cross - cross involving a single trait • Dihybrid cross - cross involving two traits • Punnett Square - used to solve genetics problems

34. Analyze the processes and products of Differentiate between classical laws of inheritance, their relationship to chromosomes, and related terminology • Mendel's first law, stating that allele pairs separate during gamete formation, and then randomly re-form pairs during the fusion of gametes at fertilization. • As long as they are unlinked • Mendel demonstrated that an organism inherits an allele from each of its two parents — this is the law of segregation. • The phenotypes of mothers and fathers often appear to blend in their offspring, and consequently most students of heredity before Mendel thought that inheritance involved some sort of blending of genes.

35. Analyze the processes and products of Differentiate between classical laws of inheritance, their relationship to chromosomes, and related terminology • Mendel's Second Law • Also known as the principle of independent assortment • Mendel's Second Law holds that genes are inherited independently of each other. • Mendelism is an atomistic theory of heredity. • Not only are there discrete genes that encode discrete proteins, but also the genes are preserved during development and passed on unaltered to the next generation.

36. Analyze the processes and products of Differentiate between classical laws of inheritance, their relationship to chromosomes, and related terminology

37. Analyze applications of probability and chi-square analysis in genetics.

38. Analyze applications of probability and chi-square analysis in genetics. • Goodness of fit tests • •  You can use a goodness of fit test (like the chi-square test) to find out how close results like those in the examples are to the expected outcomes. • •  This kind of analysis is used to test a hypothesis. • •  You can't prove the hypothesis is right or wrong. • •  You can only say how likely the hypothesis is to be correct. • •  You actually determine if the observed results are consistent with the expected results. • •  Based on the analysis, you accept or reject your hypothesis.

39. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. • This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of inheritance. • Since humans have many more genes on the X than the Y, there are many more X-linked traits than Y-linked traits. • In mammals, the female is the homozygous sex, with two X chromosomes (XX), while the male is heterozygous, with one X and one Y chromosome (XY). Genes on the X or Y chromosome are called sex linked genes. • In birds, the opposite is true: the male is the homozygous sex, having two Z chromosomes (ZZ), and the female (hen) is heterozygous, having one Z and one W chromosome (ZW).

40. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Sex influenced: These traits are expressed to some degree in both sexes, but are differentially affected by sex hormones. Examples include amount of body hair, muscle mass, and male pattern balding. • Sex-limited inheritance is where an allele on an autosomal gene cannot be expressed because the individual is the wrong sex. For example, a gene governing breast size is only expressed in females, whereas a gene for beard growth is only expressed in males. • Both Auotsomal alleles

41. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Incomplete Dominance • The heterozygous condition results in an intermediate (third) blended phenotype. • A capital letter is used to represent one allele and the same capital letter prime represents the other allele

42. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • You will not always have one recessive and one dominant allelle; sometimes, there might be two or more that arec dominant. • Take the example of blood group, where A and B are dominant to O, and A and B are codominant. This means that if you have the genotype AO or BO then your blood type will be A or B, but having AB means you have both A and B blood group, and the only way to have blood group O is to have the genotype OO.

43. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Epistasis: gene at one locus affects outcome at another locus • e.g., color of labrador retrievers • melanin production: B=more melanin • b=less melanin • melanin deposition: E=deposit melanin in fur • e=don't deposit in fur

44. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Peliotropy: one gene multiple effects

45. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Polygenic traits are traits that are controlled by several different genes. • Usually these traits exist on a continuum of expression. • For example consider height; there are not just two types of height but instead normal height exists on a fairly large continum of about 12 inches

46. Analyze various patterns of inheritance (e.g., sex-linked, sex-influenced, sex-limited, incomplete dominance, autosomallinkage, multiple alleles, polygenic inheritance). • Polygenic traits are traits that are controlled by several different genes. • Usually these traits exist on a continuum of expression. • For example consider height; there are not just two types of height but instead normal height exists on a fairly large continum of about 12 inches

47. Identify the causes of genetic disorders (e.g., point mutation, nondisjunction, translocation, deletion, insertion, inversion, duplication) • point mutation, or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. • The term point mutation also includes insertions or deletions of a single base pair. • A point mutant is an individual that is affected by a point mutation.

48. Identify the causes of genetic disorders (e.g., point mutation, nondisjunction, translocation, deletion, insertion, inversion, duplication) • A chromosome anomaly, abnormality or aberration reflects an atypical number of chromosomes or a structural abnormality in one or more chromosomes. • A karyotype refers to a full set of chromosomes from an individual which can be compared to a "normal" karyotype for the species via genetic testing. • A chromosome anomaly may be detected or confirmed in this manner. Chromosome anomalies usually occur when there is an error in cell division following meiosis or mitosis. • There are many types of chromosome anomalies. They can be organized into two basic groups, numerical and structural anomalies.

49. Identify the causes of genetic disorders (e.g., point mutation, nondisjunction, translocation, deletion, insertion, inversion, duplication) • Nondisjunction ("not coming apart") is the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2. • This could arise from a failure of homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. • The result of this error is a cell with an imbalance of chromosomes. Such a cell is said to be aneuploid. • Loss of a single chromosome (2n-1), in which the daughter cell(s) with the defect will have one chromosome missing from one of its pairs, is referred to as a monosomy. • Gaining a single chromosome, in which the daughter cell(s) with the defect will have one chromosome in addition to its pairs is referred to as a trisomy.

50. Identify the effect of a mutation in a DNA sequence on the products of protein synthesis • Deletion and insertion mutations also have distinct effects on the coding capabilities of genes (Figure 14.12). • If the number of deleted or inserted nucleotides is three or a multiple of three then one or more codons are removed or added, the resulting loss or gain of amino acids having varying effects on the function of the encoded protein. • Deletions or insertions of this type are often inconsequential but will have an impact if, for example, amino acids involved in an enzyme's active site are lost, or if an insertion disrupts an important secondary structure in the protein. • On the other hand, if the number of deleted or inserted nucleotides is not three or a multiple of three then a frameshift results, all of the codons downstream of the mutation being taken from a different reading frame from that used in the unmutated gene. • This usually has a significant effect on the protein function, because a greater or lesser part of the mutated polypeptide has a completely different sequence to the normal polypeptide.