IB Biology HL: Genetics Objectives

Outline the events of anaphase I and telophase/cytokinesis I in meiosis I.

-Anaphase I: homologous chromosomes are pulled to opposite poles of the cell -Telophase/Cytokinesis I: in some cell types, the nuclear membrane reforms; cytokinesis forms 2 daughter cells

Outline the events of anaphase II and telophase II in meiosis.

-Anaphase II: sister chromatids of the replicated chromosome are pulled to opposite poles -Telophase/Cytokinesis II: nuclear membrane forms around each set of chromosomes, which decondense; cytokinesis makes 4 haploid cells

Deduce inheritance patterns given a pedigree chart.

-Autosomal Dominant: appears equally in males and females in every generation -Autosomal Recessive: appears equally in males and females; can skip generations -X-Linked Recessive: more males are affected than females; mothers of affected sons are carriers

Define "autosome" and "sex chromosome".

-Autosome: any chromosome that is not a sex chromosome (in humans, #1-22) -Sex: a chromosome involved with determining sex (in humans, X and Y)

Define bivalent synapsis.

-Bivalent: the structure of a pair of homologous chromosomes physically attached at a chiasmata -Synapsis: the process of pairing homologous chromosomes during Prophase I

Outlline the effects of gene mutations in body cells and gamete cells.

-Body Cells: only affect the organism they occur in (not passed to offspring) -Gamete Cells: affect the egg and sperm and therefore the offspring

List mechanisms by which a species chromosome number can change.

-Chromosome Fusing: decreases number of chromosomes -Chromosome Splitting: increases number of chromosomes

State an example of a dominant allele and recessive allele found in pea plants.

-Color of pea pods: green = dominant, yellow = recessive -Flower color: purple = dominant, white = recessive

Compare continuous to discrete variation.

-Continuous: exists in traits for which multiple genes can interact for the distribution of phenotypes (height, skin color, etc.) -Discrete: has set groups of phenotypes (blood type is either A, B, AB, or O).

Contrast discrete with continuous variation.

-Discrete: individuals fall into 1 distinct category -Continuous: there is a range of measurements from 1 extreme to another (this is often due to polygenics, the combined effects of many genes, and environmental influences)

Define "dominant allele" and "recessive allele".

-Dominant Allele: an allele that shows if the individual is heterozygous or homozygous dominant -Recessive Allele: an allele that only shows it the individual is homozygous recessive

List example haploid cells.

-Egg -Sperm

Define "gamete" and "zygote".

-Gamete: a reproductive cell (egg or sperm) that fuses with another gamete during fertilization -Zygote: a diploid resulting from the fusion of 2 haploid gametes; the fertilized egg

State example human characteristics that are associated with polygenic inheritance.

-Height -Weight -Eye Color -Most Personality Traits

Describe the discovery of meiosis.

-Hertwig: observed one cell dividing to create 4 -VanBenedin: discovered chromosome movement during meiosis -Weismann: theorized how divisions could lead to daughter cells with only half the genetic information Overall, it was discovered by microscopic examination of dividing ger-line cells.

Determine possible allele combinations in gametes for crosses involving 2 genes.

-Homozygous Dominant -Homozygous Recessive -Heterozygous

Distinguish between a karyogram and a karyotype.

-Karyogram: graphical/photographic representation of a karyotype -Karyotype: characteristics of the chromosomes of an individual (number, type, and shape)

Compare divisions of meiosis I and meiosis II.

-Meiosis I: reduction division, 1 diploid to 2 haploid cells, chromosomes remain replicated (in the shape of an X), crossing over occurs -Meiosis II: Non-reductive division, chromatids separate, no crossing over, results in 4 haploid cells

Contrast meiosis I with meiosis II.

-Meiosis I: reduction in chromosome number (diploid to haploid), chromosomes remain replicated with sister chromatids, homologous chromosomes pair before separating into different daughter cells -Meiosis II: no further reduction in chromosome number (haploid to haploid), sister chromatids of a new replicated chromosome separate, no paring of homologous chromosomes

Define monohybrid, true breeding, hybrid, F1 and F2.

-Monohybrid: a genetic cross between 2 individuals, tracking 1 gene of interest -True Breeding: organisms bred to have a homozygous genotype -Hybrid: offspring resulting from the mating of 2 organisms of different breeds -F1: the first generation of a genetic cross (making F2 the offspring from the F1 cross)

Outline the events of prophase I and metaphase I in meiosis I.

-Prophase I: replicated chromatin condense into chromosomes, homologous chromosomes pair up, crossing over between homologous non-sister chromatids occurs -Metaphase I: homologous pairs of chromosomes line up at the metaphase plate (independent assortment) after having been moved by microtubules

Outline the events of prophase II and metaphase II in meiosis II.

-Prophase II: nuclear membrane breaks down, chromosomes condense, spindle fibers form -Metaphase II: replicated chromosomes are moved by microtubules to the metaphase plate (the haploid cell makes it impossible for chromosomes to be paired)

Describe segregation of alleles and independent assortment of unlinked genes in meiosis.

-Segregation Example: One sperm gets an "A" and the other gets an "a" from a heterozygous male. -Independent Assortment Example: what happens to gene "a" has no affect on gene "b"

Compare sexual and asexual life cycles (the period of time that an organism passes through until producing offspring).

-Sexual: 2 parents, meiosis, results in genetic variation -Asexual: 1 parent, binary fission/mitosis

List the characteristics by which chromosomes are arranged on the karyogram.

-Size -Banding pattern -Centromere Position

Identify tetrad, bivalent, sister chromatids, and non-sister chromatids in diagrams of replicated chromosomes

-Tetrad: a pair of homologous chromosomes -Bivalent: a pair of joined homologous chromosomes (during crossing over) -Sister Chromatids: identical strands of DNA formed during replication interphase that are joined at the centromere -Non-Sister Chromatids: the chromatids of 2 homologous chromosomes

List effects of Huntington's disease on an affected individual.

-Uncontrolled movements -Decline in cognitive ability -Mood swings -Memory loss -Muscle damage

List 2 examples of genes with multiple alleles.

1) ABO Blood Groups 2) Eye Color

Outline 2 outcomes of the Human Genome Project.

1) Achieved the stated goals (see above) 2) Identified 3 million human genetic variations

Describe the 2 procedures for obtaining fetal cells for production of a karyotype.

1) Amniocentesis: a needle is inserted into the uterus to withdraw amniotic fluid (which contains cells from the fetus to be used in karyotyping) 2) Chorionic Villus Sampling: a tube is inserted into the uterus to remove a small sample of placenta

List 5 example genetic diseases.

1) Hemophilia 2) Red-Green Color Blindness 3) Huntington's Disease 4) Duchenne Muscular Distrophy 5) Cystic Fibrosis

List 3 biological research methods pioneered by Mendel.

1) Large number of replicates to demonstrate reliability of results 2) Repeats of whole experiments 3) Obtaining quantitative results, not just descriptions

List three events that occur in prophase I of meiosis.

1) Pairing of homologous chromosomes 2) Crossing Over 3) Condensation of chromosomes

State two factors that can increase the mutation rate.

1) Radiation 2) Chemicals

List 3 ways in which the types of chromosomes within a single cell are different.

1) Size/number of base pairs 2) Sequence of nitrogenous bases 3) Location of the centromere

State 2 consequences of chiasmata formation between non-sister chromatids.

1) Stabilizes bivalents during alignments on the metaphase plate. 2) Increases genetic variation by facilitating crossing over.

Outline 2 examples of environmental factors that can influence phenotypes.

1) Sun Exposure: stimulates the production of melanin, which is influenced by several genes 2) Diet and Exercise: influence hieght and weight (also polygenic)

State the two possible hypotheses of a statistical test.

1) There is no significance difference (accept Null Hypothesis) 2) There is a significant differences (reject Null Hypothesis)

State the minimum chromosome number in eukaryotes.

2.

State the number of genes in the human genome.

20,000-25,000 genes.

State the human haploid number.

23.

State the number of nuclear chromosome types in a human cell.

23.

State the human diploid number.

46.

Describe why it is not possible to be a carrier of a disease caused by a dominant allele.

A carrier has a heterozygous genotype, so they cannot show the disease phenotype if it is recessive. If the disease is due to a dominant allele, the individual will show the disease phenotype.

Describe the process of creating a karyogram.

A cell is "frozen" in metaphase by applying chemicals that disrupt the mitosis spindle. A hypotonic solution is then added; water enters the cell and bursts it to separate the chromosomes from one another. This allows them to be stained and seen under a microscope.

Define "diploid".

A cell that has 2 complete sets of chromosomes (one from each parent).

Define "allele".

A different form of a specific gene that occupies the same locus on a chromosome.

Define "carrier" as related to genetic disorders.

A genetic carrier is an individual that has inherited a recessive allele but does not display the disease's symptoms because they have a dominant allele to mask it.

Define "gene".

A heritable factor that consists of a length of DNA and influences a specific characteristic.

Describe the relationship between the genetic cause of cystic fibrosis and the symptoms of the disease.

A mutation in the CFTR gene (which regulates movement of salt and water in the cell) causes the resulting protein to change in shape and therefore improperly function. This causes sticky mucus that clogs tubes in the lungs; symptoms include lung infections, wheezing, and a persistent cough.

Define "sequence" in relation to genes/genomes.

A sequence is the order of nitrogenous bases in a gene or genome; it is also the process of determining the order of these bases.

State the difference between alleles of the same gene.

Alleles of the same gene are different in their sequence of nucleotides, which can vary by a single base (known as single nucleotide polymorphism).

State a similarity between alleles of the same gene.

Alleles of the same gene occupy the same locus on a chromosome and have mostly the same nucleotide sequence.

Outline the possible combination of alleles in a diploid zygote for a gene with two alleles.

Although there are often multiple alleles for a gene in a population, any single individual can only have a maximum of 2 alleles of a gene (1 allele on each chromosome of a homologous pair). The zygote can either be homozygous dominant, heterozygous, or homozygous recessive.

Determine a DNA sequence from an electropherogram.

An electropherogram is the result of automated DNA sequencing. Well-defined, colored peaks are read from left to right to determine base order.

Outline the advancement in knowledge gained from the development of autoradiography techniques.

Autoradiography is used to produce an image of a radioactive substance. The technique is used in cellular/molecular biology to visualize structures. For example, it can allow for the visualization of the number of chromosomes, bands of DNA in electrophoresis, tissue samples, etc.

Outline the inheritance pattern of Huntington's disease.

Autosomal Dominant: not on a sex chromosome; requires only 1 mutated allele to show symptoms

Outline the inheritance pattern of cystic fibrosis.

Autosomal Recessive: not on a sex chromosome; requires 2 mutated alleles (one from each parent) to show symptoms

State an example of discrete variation.

Blood Groups (divided into either A, B, AB, or O)

Define "codominant alleles".

Both alleles are expressed equally; there is no masking of a recessive allele by a dominant one.

State 2 similarities and 2 differences between male and female gametes.

Both egg and sperm are haploid cells produced in meiosis, so they both have 1 allele of each gene. However, egg cells are much larger and do not have flagella like sperm do.

Explain why cytochrome oxidase 1 is often used to assess the differences in the base sequences of a gene between two species.

COXI is used to compare gene sequences between species because the gene is present in the majority of eukaryotic species. It has been sequenced for many species and is therefore accessible from genome databases.

Describe Cairn's technique for producing images of DNA molecules from E. Coli.

Cairn radioactively labeled DNA to produce images of the molecule, allowing for visualization and measuring of a length of DNA. DNA was then replicated with radioactive thymine, then covered with photographic film. The radioactivity exposed the film and led to an image of circular DNA.

Outline conclusions drawn from the images produced using Cairn's autoradiography technique.

Cairn was able to deduce that prokaryotic chromosomes are circular. The experiment also demonstrated that DNA replication occurred at the replication fork.

State that cells are haploid at the end of meiosis I.

Cells are haploid at the end of meiosis I after having been divided from a diploid.

Describe random orientation of chromosomes during meiosis I.

Chromosomes of a homologous pair orient at the metaphase plate during meiosis I at random, meaning that maternal or paternal chromosomes are equally likely to move to either pole.

State that crossing over occurs during prophase I.

Crossing over (the exchange of genetic material between non-sister chromatids of homologous chromosomes) occurs during prophase I.

Explain how crossing over between linked genes can lead to genetic recombinants.

Crossing over is the exchange of chromosome segments between non-sister chromatids, so it creates new recombinations of genes in the gametes that are not found in either parent. This makes for greater genetic diversity.

State that DNA is replicated in interphase before meiosis.

DNA is replicated in interphase before meiosis so that all chromosomes consist of 2 sister chromatids.

State the usual cause of one allele being dominant over another.

Dominant alleles code for a functioning protein, while recessive alleles code for a non-functioning protein.

Describe the pattern of inheritance for sex linked genes.

Dominant alleles typically code for normal conditions while recessive alleles code for a disorder. Because men only have 1 X-Chromosome, genes on the X are expressed in their phenotype. In females, a recessive allele can be masked by a dominant on the other X-Chromosome.

Describe the use of a karyogram to diagnose Down Syndrome.

Down Syndrome is caused by a nondisjunction of Chromosome 21, resulting in 3 of these chromosomes.

Describe random orientation and independent assortment.

During metaphase I of meiosis, the way chromosomes align at the plate is random, meaning that in anaphase I, either chromosome (maternal or paternal) can end up at either pole or daughter cell. This is called random assortment. The way a pair is facing is independent of the other homologous pairs, generating independent assortment. Random orientation occurs within a homologous pair, while independent assortment occurs between homologous pairs.

Outline the process and result of crossing over.

During prophase I, homologous chromosomes exchange pieces of non-sister chromatids, resulting in new combinations of genes (recombinant chromosomes).

Use correct notation to show alleles of linked genes.

Each horizontal line represents a chromosome (2 in each diploid cell) while the letters represent genes and alleles.

Describe the relationship between the genome size of a species and the species complexity in structure, physiology, and behavior.

Eukaryotes generally have larger genomes, but size does not correlate with complexity. The larger the genome size, the more base pairs the sequence of DNA contains. The physiology of an organism has little to no effect (no greater phenotypic complexity). More than genome size, behavior is dependent on outside influences from the environment.

Describe the relationship between the number of genes in a species and the species complexity in structure, physiology, and behavior.

Eukaryotes generally have more genes than prokaryotes, and therefore are more complex in each regard. However, within plants and animals, there is little correlation between complexity and the number of genes.

Describe the structure of eukaryotic DNA and associated histone proteins during interphase (chromatin).

Eukaryotic DNA is linear and associated with histone proteins in a structure called the nucleosome. During interphase, the DNA is not supercoiled into chromosomes but is in a looser form called chromatin.

Determine the sex of an individual given a karyogram.

Examine the last pair of chromosomes to see if there are two X chromosomes, or an X and a Y.

Outline the formation of diploid cell from two haploid gametes.

Gametes (egg and sperm) are haploid with one complete set of chromosomes. When the gametes fuse during fertilization, the 2 sets of chromosomes combine to create a diploid zygote.

Explain how meiosis leads to genetic variation in gametes.

Genetic variation (variation/differences in the DNA sequences) is caused by crossing over and random orientation.

State an advantage of being diploid.

Having 2 copies of each chromosome means an individual would have 2 copies of each gene that the chromosome contains. Therefore, if one carries a detrimental allele of a gene, there is a second copy that could counter the negative effects.

State an example of continuous variation.

Height

Describe the cause and effect of hemophilia.

Hemophilia is caused by a mutated allele of the F8 gene that codes for a protein necessary for the blood clotting process. Without proper clotting, excessive bleeding typically occurs.

Using the correct notation, outline an example of codominant alleles.

I^A = allele coding for Type A glycoproteins I^B = allele coding for Type B glycoproteins

Explain sickle cell anemia as an example of a genetic disease caused by codominant alleles.

If a person has one copy of the sickle cell allele, 1/2 of their blood cells will be misshapen. In this way, the alleles are codominant since both normal and sickle shapes are seen.

Draw a conclusion of significance by comparing the calculated and critical chi-square values.

If the calculated chi-square value is greater than the P-Value provided, then there is a significant differences and the Null Hypothesis can be rejected.

Compare meiosis II with mitosis.

In both, sister chromatids separate and move to different poles. -Meiosis II: haploid cell in metaphase II, creates gametes -Mitosis: diploid cell in metaphase, creates daughter cells

Outline the role of fertilization as a source of genetic variation.

In fertilization, any sperm can fuse with any egg; the zygote therefore has a unique genetic identity.

Describe difficulties in microscopic examination of dividing cells.

In this process, cells had to first be preserved before viewing. This killed the cells and prevented meiosis from being observed in action, along with the behavior of the chromosomes.

Explain why the chromosome number of a species does not indicate the number of genes in the species.

It is possible to have one large chromosome with many genes, or many smaller chromosomes with fewer amounts of genes each. Likewise, it is possible to have larger chromosomes with relatively few genes or smaller ones that are full of genes.

Describe what makes genes "linked".

Linked genes do not independently assort because they are located near each other on the same chromosome. The genes therefore travel together in meiosis and alleles of the gene will end up at the same gamete.

Use computer software tools to create an alignment of the gene sequences between different species.

Look for similarities/differences between sequences of different species that can be easily identified by the arrangement of the alignment, particularly in base pairs.

Outline why Mendel's success is attributed to his use of pea plants.

Mendel's use of pea plants allowed him to easily observe distinguishable characteristics. The peas were also able to reproduce quickly, allowing for many generations to be examined. Finally, the reproduction could be controlled, so Mendel knew exactly which 2 parent plants were being mated.

Describe the trends and discrepancies that led Morgan to propose the idea of linked genes.

Morgan crossed a red-eyed female with a white-eyed male. All offspring ended up red-eyed, displaying a trend that suggested red was dominant. He then crossed two of the red-eyed offspring together, leading to a discrepancy because all F2 offspring that had white eyes were male.

Describe the trends and discrepancies that led Morgan to propose the idea of linked genes.

Morgan observed the results of genetic crosses in fruit flies, and they did not match Mendel's expected laws. He developed the idea of linked genes to explain these results.

Outline Thomas Morgan's elucidation of sex linked genes with Drosophila.

Morgan studied that flies normally have red eyes, but his experiment contained a mutant male with white eyes. When mated with a red-eyed female, all offspring were red-eyed (displaying red-eye dominance). Only males had white eyes, suggesting that white is carried on the X-chromosome.

Describe how Morgan discovered a relationship between eye color and sex in Drosophila.

Morgan studied the genetics of the fruit fly, Drosophila. He noticed that results of genetic crosses did not match the expected outcome stated by Mendel's Law of Independent Assortment. He developed the idea of genes being linked on chromosomes to explain this observation.

Explain why most genetic diseases are rare in a population.

Most of these diseases are caused by alleles that are rare in the population. The chance of inheriting 1 allele for an autosomal dominant disease is 50% if the heterozygous parent is diseased. For autosomal recessive, the individual must inherit 2 copies of a rare allele (1 from each parent).

Use NCBI to search for COX1 sequences for different species.

NCBI allows for the use of the Basic Local Alignment Search Tool that can search for genes or protein sequences in the database.

State the source of new alleles of a gene.

New alleles (versions) of a gene are formed by mutations in the DNA sequence of the gene.

Define non-disjunction.

Non-disjunction is the failure of a homologous chromosome pair or sister chromatids to separate normally in meiosis or mitosis.

State the result of non-disjunction.

Non-disjunction results in an abnormal number of chromosomes in daughter cells.

State that normal distribution of variation is often the result of polygenic inheritance.

Normal distribution of variation is often the result of polygenic inheritance.

Describe a base substitution mutation.

One base is replaced with another, which may cause a change in the protein, have no effect on the protein, or cause an incomplete/non-functioning protein to form.

Outline inheritance patterns of genetic diseases caused by dominant alleles.

Only one copy of the disease allele is neede for the individual to express the disease phenotype. If the parent is homozygous dominant, there is 100% chance that the offspring will inherit the allele. With a heterozygous dominant allele, there is a 50% chance.

State that chromosome number and type is a distinguishing characteristic of a species.

Organisms with differing numbers of chromosomes are not likely to interbreed, while all members of a species will have the same number to distinguish their species in particular.

Outline the use of Pascal's triangle to determined phenotype frequencies that result from polygenic crosses.

Pascal's triangle displays the ratio of possible outcomes in polygenic inheritance.

Describe the structure/function of plasmid DNA.

Plasmids are circular, double-stranded DNA molecules that are distinct from chromosomal DNA. They have accessory genes that encode various functions of the host cell.

Explain polygenic inheritance using an example of a 2 gene cross with codominant alleles.

Polygenic characteristics are determined by many genes; between all of them, each dominant allele contributes to the phenotype.

Outline the effects of radiation exposure after nuclear exposure at Hiroshima and Chernobyl.

Radioactivity can permanently damage DNA and burn cells. Many developed cancer after these events as a result. Others suffered hair loss, internal bleeding, and vomiting; symptoms emerged both immediately after the occurrences, and years later.

Describe the cause and effect of red-green color blindness.

Red-green colorblindness is caused by a sex-linked recessive allele of a gene coding for the protein ops in, which is sensitive to particular wavelengths of light. The mutated allele causes red-green color vision defects.

State the difference between independent assortment of genes and segregation of alleles.

Segregation refers to alleles of the same genes separating into different gametes, while independent assortment occurs when different genes located on different chromosomes move independently from one another.

Outline information that can be determined given gene sequence alignment data.

Sequence alignment data can be used to measure evolutionary relationships between species. The more similar 2 sequences are, the more closely related the 2 species.

Define sex linkage.

Sex linkage occurs with genes located on the sex chromosomes. The gene's expression, inheritance pattern, and effect on the phenotype differ between males and females.

Explain why the typical number of chromosomes in a species is always an even number.

Sexual reproduction requires an even number of chromosomes. Each parent gives one set of chromosomes, resulting in an even number in the offspring.

State a similarity and difference found between pairs of homologous chromosomes.

Similarity: same genes at the same locus, same base pair length Difference: separate origin (either maternal or paternal), different alleles of genes

Explain inheritance patterns of red-green color blindness.

Since it is X-Linked Recessive, males only need 1 mutated allele while females need 2 mutated alleles in order to express the color blindness phenotype.

Explain the inheritance patterns of hemophilia.

Since it is X-Linked Recessive, males only need 1 mutated allele while females need 2 mutated alleles in order to express the hemophilia phenotype.

Describe the attachment of spindle microtubules to chromosomes during meiosis I.

Spindle microtubules are long protein fibers that attach chromosomes to the poles of the cell. In meiosis I, the homologous chromosomes of a pair are each attached to different poles. The way the chromosom pairs align (and therefore the pole to which they attach) is random.

Describe the role of statistical tests in deciding whether an actual result is a close fit to a predicted result.

Statistical tests allow for the determination of the probability of a discrepancy between the observed (actual) and expected values. Essentially, they determine the chance of getting observed results given the expected.

Define the degrees of freedom and critical value for chi-square tests.

Subtract 1 from the total number of possible phenotypes and find the corresponding P-Value.

Describe ABO blood groups as an example of complete dominance and codominance.

The ABO blood groups are determined by a single gene: I. However, it has 3 alleles (I^A, I^B, and i). The former are typically dominant over i, but they are codominant to each other and are therefore expressed in a heterozygous individual.

Explain the relationship between parental age and chances of non-disjunction.

The age of the parent (usually the mother) is positively associated; higher rates of non-disjunction are associated with older age

State the outcome of allele segregation during meiosis.

The alleles of each gene separate into different haploid nuclei during meiosis.

Outline the technological improvements that have sped the DNA sequencing process.

The automatization of the process with computer tools has greatly increased efficiency; in DNA sequencing, a computer can deduce the base sequence by reading fluorescent markers that indicate the type of nitrogenous base.

Explain why chromatin DNA in interphase is said to look like "beads on a string".

The basic unit of chromatin is the nucleosome, connected by sections of linker DNA.

Define "haploid".

The cell/organism contains only 1 set of chromosomes, so there are no chromosome pairs.

Explain why meiosis I is a reductive division.

The chromosome number begins as diploid (2 of each chromosome type) and becomes a haploid at the end of meiosis, reducing the chromosome number.

State the difference in amino acid sequences in transcription of normal and mutated Hb mRNA. Outline the consequences of the Hb mutation on the impacted individual.

The codon GAG found in normal Hb genes mutates to GTG, resulting in a different mRNA codon. This in turn results in the hemoglobin of the individual being altered (to Hemoglobin S instead of A). The blood cells therefore become sickle-shaped and cannot transport oxygen efficiently.

Given a diploid number, outline the movement and structure of DNA through the stages of meiosis.

The diploid number is consistent with the first division (2n=8) at cytokinesis/telophase, where it becomes a haploid (n=4).

State the cause of Sickle Cell Anemia, including the name of differences in the Hb alleles.

The disease is caused by a mutation called HBB, containing the blueprint for cells to make hemoglobin (which binds to/releases O2). The mutation changes an amino acid in hemoglobin's beta chain, causing hemoglobin proteins to stick together/form stiff fibers that distort the shape of red blood cells.

Describe the arrangement of prokaryotic DNA (nucleoid and plasmid).

The genome is composed of a single, double-stranded DNA molecule in the form of a circle. This is contained in the nucleoid region of the cell. Plasmids are separate from chromosomal DNA and replicate independently.

State the size in base pairs of the human genome.

The human genome is composed of 3.2 billion base pairs within the 23 chromosome pairs and mitochondrial DNA.

Define "chiasmata".

The location at which 2 homologous non-sister chromatids exchange genetic material during crossing over.

State the number of chromosome combinations possible due to random orientation is 2^n.

The number of chromosome combinations possible due to random orientation is 2^n.

Explain the reason why the outcomes of genetic crosses do not usually correspond exactly with predicted outcomes.

The outcomes do not usually match what was predicted because there is most always an element of chance in the segregation of alleles in fertilization.

Define "gene locus".

The position on a chromosome where a gene is located.

State the aim of the Human Genome Project.

The project aimed to determine the sequence of the 3.2 billion base pairs and identify the location of the 20,000-25,000 genes.

Explain why meiosis must occur as part of a sexual life cycle.

The sexual life cycle combines genetic information from 2 parents. To maintain the correct number of chromosomes in the offspring, the parents must undergo meiosis to create gametes with half of the genetic information.

Define the term "naked" in relation to prokaryotic DNA.

The term denotes that the DNA is not associated with any histone.

Define "genome".

The whole of the genetic information of an organism.

Describe the experiment of Bateson and Punnett that led to results that did not support Mendel's law of independent assortment.

They crossed long pollen (LL) purple flowers (PP) with round pollen (ll) and red flowers (pp). The expected outcome was a 9:3:3:1 ratio, but they instead found many L_P_ and llpp, with few L_pp or llP_. They therefore recognized a discrepancy between expected and observed.

Explain why genetic diseases usually appear unexpectedly in population.

This occurs because the disease is usually caused by a recessive allele that has been masked by a dominant ones. If 2 carriers (with no disease symptoms) mate, there is a 1/4 chance of an offspring with the disease.

Describe Mendel's pea plant experiment.

Through selective breeding, he discovered certain traits in offspring without blending of the parent characteristics. He observed the traits of flower color, position, stem length, seed color, and more. This led him to conclude that genetic "units" of inheritance are passed from parent to offspring, and genes for 2 different characteristics are inherited separately.

Use the df and critical chi-square value to determine if there is a significant difference between observed and expected results of a dihybrid cross.

To find degrees of freedom, subtract 1 from the total number of phenotype possibilities. Locate the corresponding P-Value; if it is smaller than the calculated chi-square value, then there is a significant difference between the observed and expected dihybrid cross results.

Describe the cause and symptoms of Down Syndrome.

Trisomy 21 (an extra chromosome 21) results in physical and cognitive impairments that vary depending on the individual.

Define "homologous chromosome".

Two chromosomes (one of maternal origin, and one of paternal origin).

Search NCBI or OMIM for a given gene.

Use the 6-digit numbering system to link the entries to autosomal loci or phenotypes.

Determine the gene locus, abbreviated gene name, and description of the gene.

Using the 6-digit numerical code, determine the autosomal loci or phenotypes depending on what each number correlates to.

Determine the predicted genotype and phenotype ratios of F1 and F2 offspring of dihybrid crosses.

When two heterozygous F1 individuals are combined, the expected ratio will be 9:3:3:1.

Outline the possible combination of alleles in a diploid zygote for a gene with 3 alleles.

Within a diploid individual, genes can have a maximum of 2 alleles. For example, in the ABO blood typing, the 3 common alleles are I^A, I^B, and i. This means the possible outcomes are I^AI^A, I^BI^B, I^AI^B, I^Bi, I^Ai, and ii.

Outline the structure and function of the two human sex chromosomes.

X: larger of the two, with 156 million base pairs and 1805 genes Y: smaller of the two, with 57 million base pairs and 460 genes; if the Y-Chromosome is present, this means the organism is male

Outline gender determination by sex chromosomes.

XX = female; XY = male The male parent determines the sex by either passing on an X-chromosome or a Y-chromosome.

Use correct notation for sex linked genes.

X^R = red X^w = white Y = no subscript because the gene is not on this chromosome