We begin our study with a brief history of how scientists discovered that DNA, and not protein, is the genetic material. Next, we'll look at the structure of DNA. In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize for unraveling its structure. Read Jim Watson's book, The Double Helix for the fascinating detective story about this discovery. We will then study DNA replication--the way that a DNA molecule doubles in preparation for cell division. Our last topic will be transcription and translation--how the DNA governs protein synthesis. This is the way that DNA governs the activity of the cell.
1. DNA History: Briefly describe Griffith's (1928) work. What is the significance of his work? Why is it in this chapter?
The genetic material directs all cellular activity. What is the genetic material? For a long time, biologists did not know. Whatever it is, it has to contain directions in a code. The two prime suspects in this mystery were proteins and DNA. Proteins are made of twenty different amino acids. DNA is made of four different nucleotides. If you were making a code, would you have one with twenty letters in the alphabet or four? Most biologists thought that proteins were the genetic material.
Griffith was a public health bacteriologist who was looking for a cure for pneumonia. He noticed that the bacteria that cause the disease had two forms, the R (rough appearance) strain and the S (smooth appearance) strain. He injected these into mice and found:
2. Copy the diagram of Hershey and Chase's work into your notebook. What was the importance of their work?
Hershey and Chase were studying how bacteriophages (viruses) attack and destroy bacteria. Viruses are made of only DNA (or RNA) and protein. The genetic material had to be one of these two. To find out, they grew some viruses in radioactive phosphorus and others in radioactive sulfur. DNA contains phosphorus, but proteins do not. Proteins contain sulfur, but DNA does not. Whichever was injected into the bacteria was the genetic material. After letting the bacteria grow with the radioactive viruses, they agitated the flasks and separated out the bacteria from the "shells" that were left outside the bacteria. They discovered that the DNA was injected into the bacteria. DNA is the genetic material.
3. DNA Structure: What is a nucleotide? What are its three parts? Draw one. What is a base? What are the four bases in DNA?
Nucleic acids, DNA and RNA, are made of nucleotides.
Each nucleotide has:
>MEMORY TIP< Remember: Automatic Transmission = Good Car (A/T, G/C)
4. Who discovered the structure of DNA? Nucleotides connect to form DNA or RNA. The DNA molecule is like a ladder with the rungs being base pairs and the rails being alternating sugars and bases. Below is a diagram of a section of a DNA molecule. Copy it into your notes. Compare this sketch with the ones in your text and to others that you might have available. Can you identify the nucleotides in this diagram? Each nucleotide is made up of three "linked circles." Draw a circle around one nucleotide. Then, fill each circle of the entire diagram with one of the following letters: D (deoxyribose sugar), P (phosphate), A (adenine), T (thymine), G(guanine), or C (cytosine.) Be sure to pair the bases correctly. James Watson and Francis Crick described the structure of the DNA molecule. They did not work in a vacuum but were helped by the following:
In 1962, James Watson, Francis Crick, and Maurice Wilkins won the Nobel Prize for Medicine or Physiology for their work on describing the DNA molecule.
In the image that I have drawn, the top row is filled in with, P, D, P, D, P, D, P, D, P, D. The second is any series of the four bases, A, T, G, and C. The third row is made up of the complimentary bases to the ones that you wrote in the second row. The bottom row is D, P, D, P, D, P, D, P, D, P. Can you recognize the nucleotides? Can you see the ladder structure?
5. DNA Replication: During which phase of the cell cycle does DNA replication take place? During DNA replication, the hydrogen bonds that connect the base pairs disconnect and the two "ladder halves" separate. New nucleotides, which are present in the nucleus, pair up with the "old halves" of the DNA molecule. When this process has been completed, two identical DNA molecules have been produced. Each of these is made of an "old" half and a "new" half. Study the drawing in your text and others that you might have available so that you understand this process.
For this question, create a diagram to show how DNA replication takes place. Use the three "linked circles" to show each nucleotide as was done in the previous question. It may take you some time to understand the process and to make the diagram. However, you can do it! When it is complete, then you can be confident of your understanding of DNA structure overall, and of DNA replication specifically.
New DNA is made in the S-phase of the cell cycle. We will talk about this process in class.
6. How is DNA packaged in the nucleus of a eukaryote? What is the relationship between a gene and a chromosome? For what do genes code?
You have between six and seven feet of DNA in every one of your cells. How is so much packaged into such a small place? The answer is that the DNA is wrapped around protein the way that a kite string is wrapped around a stick. (Actually, it is wrapped twice around a cluster of histone proteins. This wrapping is repeated a lot.) Then, this structure is coiled up several times. The end result is a lot of DNA packed in a small space. The resulting structures are chromosomes.
Genes are relatively small parts of a DNA molecule/chromosome. Genes control the "today" of the cell by controlling which proteins the cell makes.
7. RNA: What is RNA? Complete the chart on the following page
to show the difference between DNA and RNA:
| Characteristic | DNA | RNA |
| What sugar is present? | Deoxyribose | Ribose |
| What bases are present?
List all four. |
Adenine, Thymine,
Guanine, Cytosine |
Adenine, Uracil,
Guanine, Cytosine |
| How many strands are in the molecule? | Two | One |
8. What is the function of ribosomal RNA (rRNA)? Messenger RNA (mRNA)? Transfer RNA (tRNA)?
There are three types of RNA:
9. Protein Synthesis - Transcription: What is transcription? Define the term. In a prior question, I had you label the parts of the DNA diagram. Then, I had you "unzip" this DNA molecule to show how DNA replication occurs. Now, create a similar diagram (with three "linked circles" representing a nucleotide) to show how RNA is formed. "Unzip" a DNA molecule and add nucleotides to show how transcription occurs. Use R to identify ribose and use U to identify uracil. As with the question above, this is a tough concept. Yet you can do it!
The "central dogma" of biology is this: DNA is the genetic code. It codes for the production of RNA. RNA, in turn, codes for protein synthesis. Or:
DNA --(transcription/RNA synthesis)--> RNA --(translation/protein synthesis)--> Protein
Transcription is the process whereby RNA is made from DNA (all three types.) Both DNA and RNA are made of nucleotides. The DNA "unzips" to make RNA just as it does to make new DNA with a couple of exceptions: Only a small section (one gene) unzips to make the RNA. The base uracil (U) pairs with adenine (A) instead of thymine (T.) RNA is made along only one strand (the master strand) of the DNA. Multiple copies of RNA can be made from the same DNA strand. The DNA "zips back up" after the RNA is made.
We will talk more about this in class.
10. Protein Synthesis - Translation: What is a triplet? What is a codon? An anticodon? What is translation? Copy Figure 13.10 into your notes to show how the process of protein synthesis takes place.
Once mRNA is made, it moves out of the nucleus and into the cytoplasm. Remember from an earlier class that ribosomes are the sites of protein synthesis? The mRNA now moves through the ribosome to direct protein formation in the process called translation.
The DNA/RNA code is made of three letter (triplet) words. (Remember that there are four letters in this language, A, U, G, and C in the RNAs.) A codon is one three-letter "word" on the mRNA molecule. This codon will attract a tRNA with the corresponding anticodon. For example, if the codon on the mRNA has the code AUG, the anticodon on the tRNA will have the code UAC. This mRNA codes for the amino acid methionine. (The genetic code is given in your text.)
11. Mutations: What is a gene mutation? How are they important?
Occasionally, the sequence of DNA bases is changed. Mutagens are things that cause these changes. They may be energy types like UV and x-ray radiation, or matter like benzopyrene in tobacco smoke. If the genetic code is changed, a different protein will probably be produced. Sickle cell anemia is one example of this.
1. Before you begin your study of genetics, you will need to have a good understanding of the following: What are the functions of the nucleus? What is the genetic material? What is the structure of DNA found in eukaryotes? When does DNA replication take place in the cell cycle? What does the term diploid mean? What are homologous chromosomes?
The nucleus governs the "today" of the cell by directing protein synthesis and it governs the "tomorrow" of the cell by replicating. DNA is the genetic material. It is replicated in the S phase of the cell cycle. Diploid is a term referring to the presence of two copies of each chromosome in a cell. Haploid means having only one copy of each chromosome in a cell. The diploid chromosomes are called homologues. We got one of the pair from dear old mom and the other of the pair from dear old dad.
2. What is a gene? What is the relationship between a gene and a chromosome? What is the relationship between a gene and DNA? What is a gene locus?
A gene is a section of DNA in a chromosome that either codes for the production of a protein or acts as a "switch" to turn another gene on. Its specific location on the chromosome is called its locus. By the way, the Human Genome Project is a major research project whereby geneticists are trying to find the locus for EACH of the 50,000+ chromosomes in humans. Wow!
3. Define and give an example for each of the following terms: alleles, dominant, recessive, homozygous, heterozygous, genotype, phenotype. (Remember: Genotypes are letters and phenotypes are words. Remember: Humans are diploid. Every genotype that you write should have two letters for every gene.) Be sure that you clearly understand the concepts before you write your definitions. Then write your definitions so that your comprehension clearly shows.
To understand genetics, you need a thorough comprehension of these terms. Learn them well.
In a population, there are usually two or more forms of a gene. For instance, some people have dimples in their cheeks and others do not. These appearances are called phenotypes and are reflective of the person's genetic makeup or genotype. In the case of the "dimple" gene, there are only two forms or alleles for this gene. Having a dimple is dominant and is represented as "D." Not having a dimple is recessive and is represented as "d." Dominant means that if a person has at least one copy of the gene, they will show that phenotype (in this case, having a dimple.) But wait! How many copies of the gene do we have? Remember that term "diploid?" Humans are diploid. This means that each of our cells (with a few exceptions) has two copies of each chromosome and, therefore, two copies of each gene. There are three possible gene combinations (genotypes) for each person: DD, Dd, or dd. Homozygous means that the individual has two copies of the same allele. In this example, DD and dd are both homozygous individuals. To differentiate between them, we have to append the term dominant or recessive. So, DD is the homozygous dominant person and dd is the homozygous recessive person. Heterozygous means that the individual has two different alleles. In our example, Dd is the genotype of a heterozygous individual. There! Clear as mud. Actually, a lot of people have difficulty with genetics. I suggest that you reread this paragraph repeatedly.
4. Tanning readily (T) is dominant over forming freckles (t.) Write
the genotypes and phenotypes for individuals who are homozygous dominant,
heterozygous, and homozygous recessive. Write the same genotypes and phenotypes
for the dimple gene. Having a dimple in your cheek (D) is dominant over
not having a dimple in your cheek (d.)
| Description | Genotype | Phenotype |
| Homozygous dominant | TT | Tans |
| Heterozygous | Tt | Tans |
| Homozygous recessive | tt | Freckles |
| Homozygous dominant | DD | Dimple |
| Heterozygous | Dd | Dimple |
| Homozygous recessive | dd | No dimple |
5. Who was Gregor Mendel? Describe his work. What is Mendel's principle of segregation? When does it occur during meiosis?
See the [Meldelweb] page and the other [Genetics History] pages to learn more about Mendel.
The principle of segregation states that each individual carries a pair of genes for a trait (i.e., is diploid) and these pairs separate during gamete formation. This is how a single pair of genes is separated into the separate gametes.
When do homologues separate in meiosis? Anaphase I. (Note that if crossing over occurred, then these will separate during anaphase II.)
6. What is Mendel's principle of independent assortment? When does it occur in meiosis?
The principle of independent assortment states that when gametes form, the genes for one trait separate independently of the genes for a second trait. Humans have 46 chromosomes -- 22 pair of autosomes and one pair of sex chromosomes. Let's say that a person has the two alleles "A" and "a" on chromosome pair (homologues) number one. Let's say that they have alleles "B" and "b" on chromosome pair number two. These chromosomes line up along the center of the cell in metaphase I of meiosis. But, they line up at random. There is nothing in the cell to say that the dominants have to go to one of the cells and the recessives to the other. Likewise, there is nothing to say that all the maternal chromosomes have to line up along one side and the paternal chromosomes along the other. The chromosomes line up at (from a human point of view) random. The outcome is that the gametes could have the genotypes "AB" and "ab" -OR- they could have the combinations "Ab" and "aB." The way that they sort out in the gametes is random.
Again, when do the homologues separate? Anaphase I.
7. What is a monohybrid cross? A test cross? A dihybrid cross? Be able to solve genetics problems using a Punnett square.
A monohybrid cross is one where only one trait is being considered. An example would be Dd x Dd.
Consider this, If an individual shows a recessive trait, you know their genotype. If, however, they show the dominant trait, then they could be either homozygous dominant or they could be heterozygous. In a test cross, a dominant individual is crossed with a homozygous recessive one. This gives the genotype of the dominant individual. (This is not done for humans.)
How do we represent genes when we do genetic crosses? As you have seen in your text, we represent genotypes of individuals or gametes by a letter or sometimes, by a series of letters. (Remember: Genotypes are "letters.") We represent the dominant allele of a gene by a capital letter (e.g., D) and the recessive allele by a lowercase letter (d). (In this example, "D" will stand for a dimple in a person's cheek and "d" will stand for no dimple in their cheek.) Thus, a person who is homozygous dominant would be represented as DD and their phenotype would be "dimpled." (Remember: Phenotypes are words.) A person who is heterozygous has the genotype Dd and the phenotype "dimpled." A person who is homozygous recessive has a genotype of dd and a phenotype of "no dimple." Note that each is represented by two letters to show that they are diploid. (A haploid organism or a gamete would have only one letter such as "D." A triploid organism would have three letters, such as "DDD.")
The first step in doing genetic crosses is to determine the genotype(s) of the gametes (egg or sperm) that the individual can produce. Let us start with the simplest case where we consider only one gene. Remember that the purpose of meiosis is to reduce the number of chromosomes from the diploid to the haploid number. Consider a father who is homozygous recessive (dd.) How many gametes with different genotypes can he form? The answer is that he can only form one type: d. (Note that he may form many gametes, but this individual could not give a dominant allele for a dimple to his offspring.) (Similarly, the person who is homozygous dominant (DD) can only produce one gamete type: D.) Suppose that the mother is heterozygous (Dd.) How many gametes with different genotypes can she produce? The answer is two: D and d.
The second step in solving genetics problems is to set up a Punnett Square with the gametes that each parent can form placed along two adjoining edges of the Square. (See your text and the space below for examples. If you have difficulty with genetics problems, you might want to look at several other books as well.) For example, suppose again that the mother is Dd and can form two different gametes. We will need to draw a box that has room for her two gamete types along one outside edge. If the father is dd, he can produce only one gamete type and we need only one space along his side of the Punnett Square.
The third step is to show the offspring that are possible from the cross
between two individuals. The boxes inside the Punnett square represent
the genotype combinations that are possible in their offspring. Continuing
with our example, the father can only produce sperm cells with the "d"
gene. Write a "d" in each box to the right of his "d" gamete. If the mother
gives a gamete with a "D," this is shown by writing a "D" in the box below
her "D" gamete. If the mother gives a gamete with a "d," this is shown
by writing a "d" in the box below her "d" gamete. This is represented as:
| Mother's gametes | |||
|
|
|
||
| Father's gamete | d |
|
|
Once, we know how to set up a Punnett square for two genes, we can fill the gametes into the boxes as we did in the example given above.
The only other complication that you will need to handle when you solve genetics problems, is to know how to determine the genotype, when only the phenotype is given. For example, suppose that you were told that a person has no dimple. The only genotype that this person can have is "dd." If they had a "D" gene, they would have a dimple! Suppose that you are told that a person has a dimple. Can you determine their genotype? You could not because they could be either "DD" or "Dd." You would need more information to solve this problem.
To summarize, here are the steps to follow:
1. Given the genotypes listed below, list all possible gamete combinations that these cells could produce. (No Punnett square is needed.)
a. AA b. AaBB c. AaBbcc d. AabbCcDd
a. AA --> A
b. AaBB --> AB, aB
c. AaBbcc --> ABc, Abc, aBc, abc
d. AabbCcDd --> AbCD, AbCd, AbcD, abCD, Abcd, abCd, abcD, abcd
***** SHOW THE PUNNETT SQUARE FOR ALL CROSSES. *****
***** FOR ALL PROBLEMS BELOW, LABEL THE GENOTYPES AND PHENOTYPES FOR ALL INDIVIDUALS INCLUDING ALL POTENTIAL OFFSPRING. *****
2. In peas, T= tall plants and t= short plants. Y= green seeds and y= yellow seeds. Determine the offspring possible for each of the following crosses:
a. TT x tt b. Tt x Tt c. TtYy x TtYy d. TtYy x ttyy
a. TT x tt --> Offspring are all Tt (tall) b. Tt x Tt --> 1 TT (tall): 2 Tt (tall): 1 tt (short) c. TtYy x TtYy --> 9 T_Y_) (tall, green): 3 T_yy (tall, yellow): 3 ttY_ (short, green): 1 ttyy (short, yellow) d. TtYy x ttyy --> 1 T_Y_) (tall, green): 1 T_yy (tall, yellow): 1 ttY_ (short, green): 1 ttyy (short, yellow)
3. A heterozygous tall pea plant is crossed with a short plant. What fraction of the offspring will be tall? Short?
The parents are Tt and tt. ½ = 50% will be Tt (tall) and ½ = 50% will be short.
4. Your instructor suffers from a rare recessive mutation that causes him to grade too hard(h). He has married a person who is homozygous dominant for this trait. What fraction of his children will suffer from this affliction?
I am hh (but not really) and my wife is HH (but not really.) In this fictitious scenario, all of my kiddos are Hh which is an "easy grader" phenotype. (Rats!)
5. In humans, having a cleft chin is dominant over no cleft chin. A man who has a cleft chin (although his mother did not) marries a woman who does not have a cleft chin. What fraction of their children will have cleft chins?
The man is Cc and the woman is cc. 50% of their children will be Cc (cleft) and 50% will be cc (no cleft.)
6. A= very; a= not very; W= funny; w= boring. Show the cross between two people who are aaWw and Aaww.
Offspring would be 1 AaWw (very funny): 1 aaWw (not very funny): 1 Aaww (very boring): 1 aaww (not very boring)
7. Show the cross between a heterozygous tall, heterozygous green plant and a heterozygous tall, yellow seeded plant. Heterozygous tall heterozygous green = TtYy Heterozygous tall, yellow = Tt yy
Offspring are: 3 T_Y_ (tall, green): 3 T_yy (tall, yellow): 1 ttY_ (short, green): 1 ttyy (short, yellow)
1. What is a karyotype? Explain, in general terms, how a karyotype is prepared. What are autosomes? What are sex chromosomes?
A karyotype is a graphical representation of the chromosomes of an individual. To prepare a karyotype, cells are taken from blood, bone marrow, amniocentesis, or general tissue. These cells are allowed to divide in a culture in an incubator. A chemical is added to prevent spindle formation during mitosis. Some of the culture is drawn out with a medicine dropper, and is dropped from a height of a foot or so onto a microscope slide. As the cells hit the slide, they "splat" out. The slide is examined under the microscope. In the "old days," people would photograph the cell, cut the chromosomes out, and paste them on the karyotype. Now, there is some slick software that allows a geneticist to "point and click" with a mouse to line the chromosomes up.
When we look at human karyotypes, we see 46 chromosomes -- 22 pairs (homologues) of autosomes (non sex chromosomes) and one pair of sex chromosomes.
2. What is a pedigree? Be able to read and interpret pedigrees.
A pedigree shows the history of a family and shows the individuals who have a particular trait. With a pedigree, geneticists can tell if a trait is autosomal dominant, recessive, or sex linked.
3. Chromosome Number Changes: What is nondisjunction? What are monosomy and trisomy?
In nondisjunction, homologous chromosomes do not separate in meiosis. The result is that one parent gives either two copies of a chromosome (or chromosomes) to an offspring or the parent gives no copy of that chromosome (or chromosomes.) The result is a child with only one copy of a given chromosome (monosomy) or a child with three copies of a chromosome (trisomy.)
With only one exception, a baby cannot survive if it lacks a chromosome (monosomy.) There are only a few cases where offspring can survive with extra chromosomes. Forty five percent (45%) of all miscarriages have abnormal chromosome numbers.
4. What is Down's syndrome? What are its symptoms? What are its causes?
Symptoms of Down's syndrome include mental deficiencies and a short, stocky body. Down's syndrome is caused by having three copies of chromosome 21 instead of two.
Edward's syndrome is caused by three copies of chromosome 18. These babies have multiple congenital defects and usually do not live for more that a few months.
5. What abnormalities can take place in the sex chromosomes? What are the symptoms of Kleinfelter's syndrome and Turner's syndrome?
A person with Kleinfelter's syndrome is XXY. (A person is male if they have a Y chromosome.) These people are almost always sterile, have undersized sex organs, and may develop secondary sexual characteristics of females. This happens in 1/800 males born.
A person with Turner's syndrome is XO. (This is the one case where humans can develop with a missing chromosome.) These women are variable phenotypically. They usually do not mature as women. This occurs in 1/3000 girls born.
Why does God allow genetic abnormalities to occur in the sex chromosomes? Folks, we live in a fallen world.
6. Chromosome Structure Changes: What is a deletion? Give an example of a disease that is inherited in this manner. Describe cri-du-chat syndrome. What is duplication? What is inversion? What is translocation? What is a translocation carrier? Give an example of a disease that is inherited in this manner.
The changes discussed above alter whole chromosome numbers and can be observed in the karyotype. Changes can also occur within a chromosome. Depending on the severity, some of these can be seen in the karyotype. This question discusses these changes.
Consider a chromosome with the genes in the following order: A B C D E.
Deletion is a loss of part of a chromosome. After deletion, the example given above could look like: A B E. Cri-du-chat is an example of a genetic disease caused by deletion of part of the short arm of chromosome 5. The name is from the French transliterated, "cry of the cat" and this describes the cry of babies with this disorder. They are also mentally retarded.
In duplication, a section of DNA is repeated. An example would be: A B C D B C D E.
A chromosome section is reversed in inversion. Thus, A D C B E.
In translocation, a section of one chromosome (or an entire chromosome) is attached to another chromosome. While most of Down's syndrome is caused by nondisjuntion, some is due to translocation of chromosome 21. A person with a 21, a 14/21 (or 15/21), and a 14 is a translocation carrier. They do not have Down's syndrome, but may pass it to their offspring if they donate a 21, and a 14/21 (or 15/21.) The second parent would give a 14 and a 21 and the baby would end up with three 21's. This situation can be observed on a karyotype.
7. Gene Changes: How are autosomal recessive traits inherited? Phenylketonuria is inherited in this matter. Describe it. Look on a container of a substance that contains Nutrasweet. Do you see the warning to people with phenylketonuria? Copy that warning into your notes.
The changes that we are discussing now are called inborn errors of metabolism. They cannot be seen in a karyotype but affect our physiology. In the genetics lesson, we discussed dimpled cheeks and the ability to tan. These genes are inherited as simple dominant and recessive traits. While having a dimple or not is really no big deal, there are genetic traits that are inherited in this manner and that are much more serious. One such disease is phenylketonuria. People with this disease (pp) cannot make an enzyme to break down excess amounts of the amino acid phenylalanine. People who are PP or Pp can make the enzyme. As this amino acid accumulates, it interferes with brain development and babies with this disease become mentally retarded. Roughly 1/15,000 infants are homozygous recessive.
A simple test can tell is a baby has phenylketonuria. A few days after birth, the baby's heel is pricked and a sample of blood is drawn for the test. If the baby has the disease, he is put on a low phenylalanine diet. (Nutrasweet is high in this amino acid. My soda can says, "Phenylketonurics: Contains phenylalanine.") In doing this, a major cause of mental retardation has been prevented. By the way, do you have any idea who was involved in the research to test this low-phenylalanine diet? James Dobson.
8. How are autosomal dominant traits inherited? Give an example of a disease that is inherited in this manner. Describe Huntington's disorder.
Autosomal dominant traits are governed as "regular" dominant traits. The difference is that they are harmful. Huntington's disorder is one such disease. This disorder destroys brain cells causing involuntary movement, mental disturbance, and death. Symptoms usually show up in mid-life, after people may have had children. If a person is heterozygous for this trait, they will, on average, pass it onto one half of their children before they realize that they have the disease.
9. How are X-linked traits inherited? Why are these traits more common in males than in females? Describe hemophilia?
The sex chromosomes determine our gender. However, there are other genes on the X-chromosome such as those for color-blindness, male pattern baldness, and hemophilia. Women have two X chromosomes and men have an X and a Y. Representing hemophilia as "h," women can be XHXH, XHXh, or XhXh. The first two phenotypes would be normal (although the second is a carrier) and the third would have hemophilia. Men can be XHY or XhY. The first male is normal and the second has hemophilia. You see, if a woman has a sex-linked recessive gene, she has a second gene that may "cover it up." If a man has a sex-linked recessive trait, he has no second gene to cover it up and will show the harmful phenotype.
Last revision: 1/22/09