Genetics. the of an organism. The traits of that organism can then be passed on to, on

Transcription

1 Genetics DNA contains the genetic code for the production of. A gene is a segment of DNA, which consists of enough bases to code for many different proteins. The specific proteins produced by a gene determine the of an organism. The traits of that organism can then be passed on to, on by their offspring. The study of the inheritance of traits is called. Who is Gregor Mendel? Mendel can be called the of genetics because he developed the principles of genetics that we still use today! Mendel s most significant work was the research and experiments that he conducted by studying. These experiments helped him explain how were passed from one generation to the next. Where are these genes? Each gene controls something different, and it has a specific location on a DNA molecule. A DNA molecule that is coiled up is called a, which may have more than a thousand genes on it. Your chromosomes are in the of the cell. Each species of organism have a different number of chromosomes. Every chromosome carries genes for different traits. Humans have chromosomes in a somatic cell (body cell) and in a gamete (sex cell). In body cells chromosomes exist in. The pictures below are of a. This is a picture of a test that shows human chromosomes that have been cut out and arranged in their pairs.

2 Who cares about the pairs? Mendel s research showed that there are two factors that control a trait. He concluded that at the end of, when the gametes are produced, each reproductive cell contains only one factor of each pair. When the gametes combine during, the offspring will have the two factors controlling each specific trait. One chromosome is from the mom and the other chromosome of the pair is from the dad. Because the pair of factors is separated, or segregated during meiosis, Mendel named this the Law of. Humans have pairs of chromosomes in every cell. One piece of information that can be found by investigating a karyotype is the of the baby. The first 22 pairs of a male and a female are the same; they are called or body chromosomes. The 23 rd pair isn t really a pair so it is labeled differently. This last pair is considered to be the. These chromosomes determine the sex of the organism. They also carry for other characteristics. The sex chromosome of the female is the chromosome. A human female has two X chromosomes in every body cell. The sex chromosome only found in males is the chromosome. A human male has one chromosome and one chromosome in every body cell. What is the sex of person A? how do you know?. What is the sex of person B? how do you know?.

3 Are more chromosomes better? It would be easy to think that having an extra chromosome or two would make a superhuman, but this in not the case. Extra chromosomes, damaged chromosomes and missing chromosomes almost always cause. A karyotype can be used to detect some genetic disorders that may occur in a developing baby, or. Doctors will use cells taken from a developing baby to check that the baby has the correct number of chromosomes. This is done by a procedure called. If there are too many, too few chromosomes, or damaged chromosomes, then that means that there must have been a mistake in when the are formed. If the number of chromosomes is wrong then the did not separate correctly during the phase of Meiosis called. This mistake in tetrad separation is called. If an egg is fertilized under conditions like these, it is very likely that the mother will miscarry or the baby will die in the first year. If the baby is born, it will have a genetic abnormality. How many extra chromosomes there are and which pair has extra chromosomes determine what genetic disorder the baby will have and how severe it is. What could happen to the baby? Here are some of the possible disorders that are caused by these types of mistakes. Read the descriptions and fill in the chart below. Cri Du Chat Syndrome: This disorder results in severe mental and physical retardation. The affected individuals make catlike cries, hence the name cri du chat, which is French for Cry of the cat. A missing portion of chromosome five determines it; the amount of the chromosome that is missing determines how severe the effects are. Down Syndrome: Non-disjunction in the 21 st pair of chromosomes in one of the gametes brings an extra 21 st chromosome. This results in mental retardation. A person born with this genetic disorder has very serious physical and mental disabilities. They may have small, round heads, shorter bodies and almond shaped eyes. They are more susceptible to diseases and have a shorter life expectancy. This is found in about 3 of every 2000 births. Klinefelter Syndrome: The sperm gives a Y chromosome and non-disjunction in the egg gives two X chromosomes- OR normal egg gives an X chromosome and non-disjunction in the sperm gives an X and a Y chromosome. The presence of the Y chromosome makes this person a male. A person with this karyotype has internal male sex organs, but they are underdeveloped and they are unable to produce sperm. They also develop a few feminine characteristics, such as enlarged breasts. They have above-average height (usually over 6 ft tall) and below- normal intelligence; they may even be mentally retarded. Turner Syndrome: The sperm gives an X chromosome and non-disjunction in the egg results in an egg with no sex chromosome- OR there is a normal egg that gives an X chromosome and non-disjunction occurs in sperm and it gives no sex chromosome. This baby will be a female, but her ovaries will not develop and she will be unable to have children. She will not mature sexually, and she will have minimal physical maturity. Her mental abilities will also be inhibited, which means she will have low intelligence.

4 Karyotype Sex Disorder

5 What is the probability of having a boy or a girl? Many times in genetics, we can figure out how likely it is that a parent will pass something on to their children. To do this we use a tool called a. This is a way to show what all of the possible combinations are from the egg and sperm and how it is for those combinations to occur. The end product of meiosis produces egg in a woman and sperm in a man. Gametes have the number of chromosomes that any body cell has. The gametes, then will only have one of the sex chromosomes that are in any body cell. What are the possible sex chromosomes that a woman can give? or What are the possible sex chromosomes that a man can give? or An example of an empty Punnett Square is below. Follow the steps provided to determine how likely it is to have a boy or girl. 1. The sides of a Punnett Square are for what the gametes could have. In this case, we are investigating sex chromosomes. Write in the sex chromosomes that the mother can give on the top and those from the father on the side. 2. Copy the letters from the top of the square into each of the boxes below it. 3. Copy the letters from the sides of the square into each of the boxes next to it. 4. Each of the boxes now shows a possible combination of the egg and sperm. Within all 4 boxes is every possible combination of these two parents. What are the possible combinations? How many times does each occur? How likely is it for any woman and man to have a boy child? How likely is it for any woman and man to have a girl child? If a woman has a baby boy, what are the chances of her having another baby boy? Explain.

6 How do certain traits get passed on? Non-sex chromosomes are called. Every cell of an organism that has been produced by sexual reproduction has two copies of each autosome. The offspring receives one copy of each autosome from each. The two autosomes of the pair are called chromosomes. Homologous chromosomes are the same size and shape and carry genes for the same trait. The picture below is a pair of homologous human autosomes. The different types of genes that are possible for a trait are called. Every trait that an organism has is determined by at least two alleles. If a trait is controlled by more than two alleles, it is said to have. Alleles are represented by a letter. Capital letters represent alleles and lower case letters represent alleles. The trait for a dominant allele will show up over a trait for a. The genes of an organism make up its. To represent this, we write the alleles. The genotype of this person for this trait is. Both of these alleles are. If both of the alleles are the same, for example two dominant (GG) or two recessive(gg), the genotype is called. If the alleles are different (Gg) the genotype is said to be, or a carrier of the recessive gene. This person s genotype is. The way that an organism looks is called its. If B represents the trait for brown eyes, and b represents the trait for blue eyes, what is the phenotype of this person?

7 List the genotypes of each of the plants: List the phenotypes of each of the plants: Describe the genotype of each of the plants using the following terms: Homozygous, Heterozygous If it is Homozygous, write whether it is Dominant or Recessive What are the possible genotypes and phenotypes of the offspring of plants 1 and 3? - Start by completing this Punnett Square. Possible genotypes Possible phenotypes

8 Follow the directions provided. To fill in the chart, you will have to make some Punnett Squares. Use the space at the bottom of the page to make them.

9 Name: Date: Period: Punnett Square Problems Write the possible genotypes and the genotypic ratios below each Punnett Square. Use Punnett Squares to help you predict the genotypes and phenotypes resulting from each of the given crosses.

10 Cross Yellow (YY) peas Genotype s of parents Phenotypes of Parents Punnett Square Genotypi c Ratios Phenoty pic Ratios X Green (yy) peas Yellow (Yy) peas X Green (yy) peas Yellow (Yy) peas X Yellow (Yy) peas Yellow (YY) peas X Yellow (YY) peas Yellow (YY) peas X Green (yy) peas

11 Are all genes either dominant or recessive to determine traits? Certain traits like freckles or dimples are caused by dominant alleles. Only one parent has to have the recessive allele, because there only needs to be dominant gene for the trait to show. Set up a Punnett Square below to show what kind of alleles the parents must have to have a child with more than five fingers per hand. Five digits per hand is a recessive trait. Explain how this shows what the parents genotypes must be. Some traits are neither totally nor totally. In this case, we cannot tell which gene is dominant over the other. This situation is called. If there is one dominant and one recessive gene, then only the gene is seen. Incomplete dominance will not show either trait. In incomplete dominance, the phenotype of the organism is a mixture of both of the genes. Because both of the traits are dominant, both alleles are written as capital letters. Try these examples.

12 When there are two dominant genes, and neither trait is shown because the phenotype is a mixture of the two dominant traits, this is called. There are other cases, in which both traits show because they are both dominant. This is called. Sickle-cell anemia is a dangerous, usually fatal genetic disorder. Red blood cells carry through your body. The shape of sickle red blood cells is different from the disk-like shape of normal red blood cells. The sickle cells are unable to carry enough oxygen to body parts. Their shape also makes it difficult for them to move through blood vessels, which causes. R is the gene for round cell shape and R is the gene for sickle cell shape. Put checkmarks in the table to show the shape of cells for persons with the genes listed. What are the genotypes from the chart above? 1.) 2.) 3.) What are the phenotypes shown in the chart above? 1.) 2.) 3.) When genes are codominant, what do you notice about the phenotype of the organism? Human blood type genes are also codominant as well as dominant. Complete the chart with the possible genes that a person with each of the following blood types could have. Blood Type A B O AB Possible genes Or Or What blood type genes are dominant to other blood type genes? How do you know? What blood type genes are codominant with each other? How do you know? What possible blood types could a child have if the parents blood types were A and B?

13 Name: Date: Period: Baby Mix Up Four newborn babies are born in the hospital at the same time. Clumsy Clara the nurse ran in to attach a wristband with each child s name on it, but she dropped the wristbands and they got out of order. She looked took the charts with the blood types of all four babies and their parents. Please help her figure out which baby belongs to which family. The baby s blood types are luckily all different. There is one baby with each: Baby A = blood type A Baby B = blood type B Baby C = blood type AB Baby D = blood type O The parents blood types are as follows: The Gonzalez = blood types O and O The Johnsons = blood types O and A The Rogers = blood types AB and B The Smiths = blood types O and AB Show your Punnett Squares below. Baby A is a. Baby C is a. Baby B is a. Baby D is a.

14 Are some traits more common in boys than girls? Like autosomes, the sex chromosomes also carry genes for certain traits. The figure below shows some of the traits that are controlled by the on the sex chromosomes. Label the sex chromosomes either male or female. How many genes determine whether or not a female has dry skin? How many genes determine whether or not a male has dry skin? The Y chromosome does not have ALL of the same traits that the X chromosome has. In autosomes, recessive genes must be present for the recessive trait to show. This is different in sex chromosomes. One X-linked trait shown above is color blindness. Because this trait is on an X-Chromosome, we write X c for recessive or X C for dominant. The dominant trait is normal color vision and the recessive trait is red-green color blindness. In order for a female to have the disease, she must have the genotype. In order for a male to have this disease, he must have the genotype.

15 Let s investigate muscular dystrophy, another recessive X- linked disorder that weakens and destroys muscle tissue. You are a genetic counselor and you have to tell these couples how likely it is that they will have children with this disorder. Figure out the probability using Punnett squares- be sure to show your work! Remember- THERE IS NO GENE ON THE Y CHROMOSOME. 1.) Healthy father and homozygous dominant mother. 2.) Father with MD and heterozygous mother 3.) Healthy father and mother with MD 4.) Healthy father and heterozygous mother 5.) Father with MD and mother with MD 6.) Father with MD and homozygous dominant mother. Couple # 1. Punnett square Genotypic ratios Phenotypic ratios Who has a greater risk of having a recessive X- linked genetic disorder, a male or female? Why?

16 How do we know if we could pass a trait to our children? When Mendel did his studies on genetics, he cross-pollinated different pea plants. If he had a Yellow (YY) pea plant and a green (yy) plant that he knew were homozygous, he could use them to find out the genotype of a yellow pea plant. Since a yellow pea plant could have a genotype of or, how could he figure out the genotype of a yellow pea plant? The study of human inheritance is different, we can t do test- cross and as many experiments as we can with plants or small animals. When geneticists mate fruit flies, they control which ones mate with others. We cannot do this with humans. The study of human genetics depends a lot on the study of family history of disorders and traits. A is a diagram, which shows how a particular trait is passed through a family from one to the next. Some of the symbols that are used in a pedigree chart are: Pedigree I traces the dimples trait through three generations of a family. 1. What do the Roman Numerals stand for? 2. How is marriage and mating symbolized in a pedigree? 3. How are children symbolized? 4. What do the numbers stand for? 5. The genes for dimples are on autosomes. Are dimples a dominant or recessive trait? How can you tell?

17 Although Jane and Joe Smith have dimples, their daughter, Clarissa, does not. Joe s dad has dimples, but his mother and sister, Grace does not. Jane s dad, Mr. Renaldo, her brother Jorge, and her sister, Emily does not have dimples, but her mother does. 6. Write the name of each person in the pedigree below. I-1. I-2. I-3. I-4. II-2. II-3. II-4. II-5. II-1. III-3. Analyze the pedigree below that traces cystic fibrosis, a recessive autosomal disorder. How many generations does this pedigree represent? What does it mean if the shape is half colored in? Is the gene for cystic fibrosis dominant or recessive? How can you tell? Write in the genotypes of the family members in the pedigree. Who married a homozygous dominant person? In which generation does the first case of cystic fibrosis appear? Who was born with it? What are the chances that IV-10 will have an affected baby if she marries a homozygous dominant man?

18

19 If every gamete has half of the chromosomes, why are siblings so different? Mendel s research also demonstrated that offspring could get one trait without necessarily getting another. He concluded that the alleles for different traits are not necessarily connected. The Law of Independent Assortment states that factors for different characteristics are distributed to gametes. The phase of Meiosis when crossing over occurs is called this changes the assortment of alleles that every gamete contains. How likely is it for a person to have TWO TRAITS? So far, we have only done crosses for one trait at a time. For instance whether or not the child will be able to roll its tongue. This is called a cross. What if someone was interested in finding out how likely it was for their child to have two traits like brown hair and brown eyes? We would have to do a Punnett Square for all of the possible outcomes. This gets a little more complex. A cross with two traits is called a cross and a cross for three traits is called a tri-hybrid cross. Let s say we mate a pair of hamsters. What are the possible genotypes and phenotypes of the following crosses? Black fur (B) is dominant over brown fur (b). Short fur (A) is dominant over long fur (a). Rough coat (R) is dominant over smooth coat (r). Heterozygous black and heterozygous short fur X heterozygous black and heterozygous short fur Genotypes of Parents: X Gamete Possibilities: Punnett Square: X Genotype & Phenotype Ratios: