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EST 404 THE LIVING WORLD CHAPTER 11 NOTES CHAPTER 11 Genetics (pp. 349-373) 1 Factors responsible for character traits among living organisms A _____________________ _____________ is a physical, _________________ or physiological attribute that may vary from one _______________ to another within the same species. Examples: Eye colour ________________ 1.1 CHROMOSOMES An individual’s basic genetic information is found in the __________________ of its cells. The main component of the nucleus is ___________________ which is made up of a molecule of DNA (_____________________________ _________) combined with proteins. When a cell is about to divide, the chromatin contracts forming visible rods called ___________________. The number of chromosomes is _______________ in each animal species. In humans, a cell contains __________ chromosomes. The number of chromosomes DOES/DOES NOT determine the complexity of the organism. Chromosomes in a cell are classified according to: 1. ____________________ 2. ____________________________________ Chromosomes exist in matching _______________ (______________________ chromosomes). Humans have 46 chromosomes which form ______ homologous pairs. A _________________________ is an ordered representation of an individual’s chromosomes, obtained by grouping them in pairs according to size. 1 EST 404 THE LIVING WORLD CHAPTER 11 NOTES This is the karyotype of a human male. Note that in the ________ chromosomes the Y chromosome is smaller than the X. In females, the two sex chromosomes are the ___________. (XX). http://arnica.csustan.edu/Boty1050/Meiosis/human_karyotype.jpg 1.2 DNA AND GENES Each chromosome is made up of ____________. ___________ is referred to a ________________ _______________ because it is shaped like a twisting ladder. The chemical units which make up DNA are called ________________. Each ____________________ contains 3 chemical components: 1. _____________________________ 2. _____________________________ 3. _______________________________________:(A) ___________________, (T), ____________________, (G) _____________________, (C) ____________________ Alternating _____________ and phosphate groups make up the sides of the DNA ladder, while the ________________________ base pairs make up the “rungs”. Each nitrogenous base in DNA always pairs with its ______________________ base, according to the following pattern: Adenine always pairs with __________________________. (____-____ or ____-____) Cytosine always pairs with __________________________. (____-____ or ____-____) 2 EST 404 THE LIVING WORLD CHAPTER 11 NOTES A particular sequence of bases constitutes a ________________. Inside our cells, we have thousands of _______________ which provide instructions for making ____________________, which in turn determine traits, such as a person’s ________________, _________________________ or pointed _______________. A _____________ is a segment of DNA that contains information for making _____________________. Environment Extra – DNA mutations of environmental origin (p. 353) A ________________ is a change in the sequence of DNA nucleotides. Our cells have control mechanisms that counter most mutations. However, some mutations can cause _________________. Many mutations occur when cells divide as a result of errors during DNA replication. Others are caused by environmental agents, called __________________. Since mutations can cause cancer, these agents are also known as _______________________. Some carcinogens occur naturally in the environment (_______ rays or certain forms of ____________________). Other environmental agents are the result of human activities, such as nuclear waste, ____________________, some types of pesticides and certain industrial waste, such as ________ and other _____________ derivatives. 3 The discharge of these agents into the environment is highly regulated to protect life on earth. EST 404 THE LIVING WORLD CHAPTER 11 NOTES 1.3 PROTEINS A PROTEIN is a molecule that plays a specific role in the _______________________ of an organism and in the expression of its ___________________________________ _________________________. 11.6 EXAMPLES OF TASKS PERFORMED BY PROTEINS IN ORGANISMS TASK EXAMPLE _____________ is the protein that makes skin firm yet elastic. ______________________ is a protein that carries ____________ in the blood. _________________ are proteins that ________________ cell functions and _____________ messages in the body Example: __________________________________ _______________________ are proteins that protect us from disease. _________________________ are proteins that speed up biochemical reactions in the body. Examples:______________________________________ PROTEIN STRUCTURE Proteins are composed of one or more chains of ___________________ _____________. The sequence of ___________________ _____________ in a chain determines the _________________ of the protein. There are ________ different naturally occurring amino acids. The average protein contains __________ to __________ amino acids. 4 EST 404 THE LIVING WORLD CHAPTER 11 NOTES An AMINO ACID is a molecule that can _______________________ with other amino acids to form ________________________. Refer to APPENDIX 4 on p. 529 of your text book for the abbreviations and genetic code for each amino acid. 1.4 PROTEIN SYNTHESIS Cells have the ability to produce the _____________ they need. The genes containing the instructions for protein manufacture are inside the __________________. The process of protein synthesis is carried out by _______________________ (outside the nucleus on the ______). mRNA (________________________) carries the information from the __________ to the _______________________________. RNA and ______________ have similar structures with a few important differences and they are: 1. DNA is double-stranded while RNA is single-stranded. 2. _____________________________________________________________________ 3. _____________________________________________________________________ _____________________________________________________________________ Two types of RNA are involved in protein synthesis: _____________________ (mRNA) which acts as a _________________ for carrying instructions about the gene to the ribosome. __________________ (tRNA) which transfers the ________________ _____________ in the cell’s cytoplasm to the ribosomes in order to make proteins. 5 http://en.wikipedia.org/wiki/File:Ciliate_telomerase_RNA.JPG EST 404 THE LIVING WORLD CHAPTER 11 NOTES THE FOUR STEPS OF PROTEIN SYNTHESIS (See Figure 11.10 (pp. 358-59) 1. TRANSCRIPTION OF __________ INTO ___________ The genetic information of the _______ is copied to the _____ RNA. 2. ATTACHMENT OF THE ______________ TO THE ________________________ __________ leaves the nucleus and attaches itself to a _________________________. The ribosome slides over the mRNA reading the codons (groups of ______ nucleotides). When it comes across ____________, protein synthesis begins. (________ = Start codon) 3. TRANSLATION OF ___________ INTO A _______________________ As the ribosome reads the nucleotide triplets one after the other, __________________ ______________ are brought to the chain by ____ RNA. The ___________________ _______________ link together and the ____ RNA is released. 4. END OF PROTEIN SYNTHESIS: When the ribosome reads _______, _______, or _______, the amino acid chain is COMPLETE. The protein is _____________________ from the ribosome and then it folds up and goes to work! For better understanding, refer to the PowerPoint on Protein Synthesis posted in FC. Click on this link to see an animation of protein synthesis: http://www.columbia.edu/cu/biology/courses/c2005/images/animtransln.gif 6 EST 404 THE LIVING WORLD CHAPTER 11 NOTES 2 Principles of Heredity Children’s frequent resemblance to their parents is a well-know phenomenon. But why do some children have blue eyes when both their parents have brown eyes? The answer lies in a phenomenon called _______________________. _______________________ is the transmission of parents’ __________________ ______________ to their offspring. A character trait is considered _________________________ when it can be passed on from the _________________________ to their ______________________. Examples: ____________________________ Dwarfism ____________________________ Alzheimer’s disease ____________________________ Heart disease 2.1 CROSSBREEDING The scientist ____________________ ____________________ was the first to understand how ____________________ ________________ are passed on from one generation to the next through ____________________ ______________________________. He used ___________ plants because they can _____________ - ________________________, thus creating a _______________ line. A ________________ line is a group of individuals of the ________________ species, which, for a __________________ character trait, produces only offspring with the ___________ trait, ___________________ variation. He chose to study the ________________ of their blossoms because it is a trait that “breeds _____________”. To understand how this trait was passed down from one generation to the next, he _______________ - _____________ the plants. 7 EST 404 THE LIVING WORLD CHAPTER 11 NOTES ______________________________ is the exchange of __________________ between two _______________________ individuals during _____________________ reproduction. What did Mendel do to make sure that self-pollination was impossible? ______________________________________________________________________________ He fertilized the purple flowers with the pollen from white flowers and observed that all the pea plants obtained by this cross-pollination were plants with ___________________ plants. (What the heck?) The plants he created from this cross-pollination are called ___________________. A ___________________ is an individual obtained by the _______________________ of two genetically ________________________ individuals. To continue his research, Mendel left the hybrids to reproduce with on another for ____________ generations. A GENERATION is a group of individuals descended from ________________ __________________. Mendel observed that the white flowers reappeared in the _______________ generation with one-quarter of all the flowers being ___________________ and three-quarters being ______________. Mendel assumed that _______________ contain information that is passed down from one generation to the next. http://www.brown.edu/Courses/BI0032/gentherp/genIB2.html 8 EST 404 THE LIVING WORLD CHAPTER 11 NOTES 2.2 THE PRESENCE OF ALLELES Mendel didn’t know about chromosomes and genes, but he understood that some type of information factor, which he called a _______________________ __________________, must be responsible for the expression of character traits in living organisms. This ______________________ ____________________ is now known as a ______________. It’s possible to have different versions of a particular trait, such as flower colour, eye colour, etc. because of the presence of ________________________. An __________________ is a possible form of a ______________. Different __________________ have different __________________________ sequences. HOMOZYGOUS AND HETEROZYGOUS On one your chromosomes from your father, there a gene for eye color and on the matching chromosome from your mother, there is also a gene for eye colour. Since these genes can carry different alleles (brown, blue, etc.), it is possible for you to carry __________ distinct alleles for the ______________ character trait. When both alleles for a given character trait are identical in an individual, it is said to be _______________________________ for the trait. When both alleles for a given character trait are different in an individual, it is said to be _______________________________ for the trait. A __________________________ is an individual with two identical alleles for a given character trait. A __________________________ is an individual with two different alleles for a given character trait. http://www.csulb.edu/~kmacd/361-6-Ch2.htm 9 EST 404 THE LIVING WORLD CHAPTER 11 NOTES DOMINANT AND RECESSIVE ALLELES A DOMINANT ALLELE is an allele that is ______________________ when an individual carries two _______________________ alleles for a given gene. An allele is said to be “expressed” when it affects how an organism __________________ or _____________________. An individual carrying the dominant allele expresses the ____________________ character trait and can therefore be either ___________________________ or __________________________ dominant (see image at bottom of previous page). A RECESSIVE ALLELE is an allele that is _________ ___________________ ___ when an individual carries two _______________________ alleles for a given gene. For a recessive allele to be expressed in an individual, the two alleles for the particular trait must be ______________________. The individual is then said to be __________________________ ________________________ or to carry a recessive trait. (ex. __________ eyes, albinism, white flowers on a pea plant, etc.) Class activity on Dominant and Recessive Traits http://faculty.virginia.edu/teach-present-bio/GeneticsWorksheet.html List of Human Traits (dominant and recessive) http://faculty.southwest.tn.edu/jiwilliams/Human_Traits.htm 2.3 GENOTYPES AND PHENOTYPES Due to the phenomenon of dominance and recessivity in alleles, all of an individual’s alleles may not be expressed, meaning that they do not affect the individual, but the individual carries them nonetheless. (ex. You have brown eyes, but may carry the gene for __________ eyes.) A _____________________________ is an individual’s genetic inheritance. It describes all of an individual’s ________________________ for specific ____________________. When describing an individual’s genotype each allele is represented by a _________________. 10 EST 404 THE LIVING WORLD CHAPTER 11 NOTES Dominant alleles are represented with ______________________ letters and the corresponding recessive allele is represented with the ____________________________ form of the __________________ letter. A _____________________________ is the way in which a genotype expresses itself. It describes the ___________________________ or ____________________ of the individual for one or more character traits. HEREDITARY CHARCTER TRAITS IN PEAS, AS STUDIED BY MENDEL Character trait Genotypes Flower colour Phenotypes Purple flowers White flowers Seed colour YY or Yy yy Seed shape Round shape Wrinkled shape Stem length LL or Ll ll 2.4 THE LAW OF SEGREGATION OF ALLELES Gametes (_____________ and __________________) are formed through a phenomenon of cell division called ______________________. Each gamete contains only ________________ the chromosomes normally present in the cells of the organism and thus only ____________ chromosome from each pair and consequently only ____________ allele instead of __________. When organisms mate, their offspring get half their chromosomes from the _________________ and half from the ___________________. So why don’t offspring half resemble the father and half resemble the mother? ______________________________________________________________________________ The law states that two alleles for a particular character trait _____________________when gametes are formed. 11 EST 404 THE LIVING WORLD CHAPTER 11 NOTES Homozygous individuals produce gametes that all have _______________________ allele. In heterozygous individuals, ______ percent of the gametes carry the ____________________ allele and ______ percent carry the _______________________ allele. 2.5 DETERMINING POSSIBLE GENOTYPES AND THEIR PROBABILITY During reproduction, gametes join at random; so many different combinations of _____________ are possible. To determine all the genotypes that could occur during gamete fusion and evaluate the probability of each occurrence, a scientist devised a grid called a _____________________ ______________________. STEPS IN COMPLETING A _______________________ ___________________ 1. Determine the ________________________ of each parent. 2. Find all possible _________________________ for the gametes of each parent and write them in circles. 3. Place the possible gametes from one parent at the ____________ of the Punnett square, and all possible gametes from the other parent, on the _______________ side of the same grid. 4. Indicate, inside the Punnett square, all the possible gamete combinations; enter the resulting ____________________________ and _____________________________. Example showing what happens when a heterozygous brown- eyed (Bb)person mates with a homozygous blue-eyed (bb) person. 12 EST 404 THE LIVING WORLD CHAPTER 11 NOTES 2.6 THE LAW OF INDEPENDENT ASSORTMENT OF CHARCTER TRAITS To predict the genotype or phenotype of offspring when considering more than one character trait, you must complete a 4 × 4 Punnett square. This is known as a dihybrid cross. Example: A female guinea pig with the genotype BbSs (black short hair) is crossed with a male guinea pig whose genotype is bbSs (brown short hair). NOTE: Black hair (B) is dominant and brown hair (b) is recessive Short hair (S) is dominant and long hair (s) is recessive What are the chances that these two guinea pigs with produce a guinea pig with brown long hair? ______________ 3 Cloning There are two natural methods of reproduction: __________________ and _________________. The offspring produced by sexual reproduction are genetically _______________________ because it inherits a __________________ combination of genes from ______________ parents. The offspring produced by asexual reproduction are genetically ___________________ to their single parent. They are ____________________. 13 EST 404 THE LIVING WORLD CHAPTER 11 NOTES _________________________ is the reproduction of an individual, _____________ of that individual or one of its __________________ in order to obtain an extra _______________. 3.1 NATURAL CLONING When cloning occurs in nature, ______________________ any human intervention, it is called _______________________ _________________________. It produces genetically _______________________ individuals through ________________________ reproduction. EXAMPLES OF NATURAL CLONING Form of asexual reproduction Description A new individual forms from a _________________________ ________________________ that eventually detached itself from the ___________________. Example: Hydra Specific to plants, roots called __________________ develop from branches in contact with the ground. If the stolon ________________________ detached itself from the parent plant, it becomes a ___________ individual. Example: Mangrove trees Specific to plants, a new individual is formed from a ________________________ ________________________ ________________________ section of the plant (other than its __________________), which falls to the ground and roots itself. http://img2.allposters.com/images/PTGPOD/OSOSF00002234-001-FB.jpg 14 EST 404 THE LIVING WORLD CHAPTER 11 NOTES 3.2 ARTIFICIAL PLANT CLONING Layering and cutting techniques have been used by humans for centuries. People often take a ____________________ from a plant and put it in water until ________________ grow. Then they can transfer the new plant to a ______________. This type of cloning is considered artificial because _____________________ are involved. Artificial plant cloning allows ___________________ and ____________________ to obtain identical copies of individual plants with _______________________ characteristics. Read the ENVIROMENT EXTRA “Farmer’s fields or pharmaceutical factories?” on p. 370 What is molecular farming? _____________________________________________________________________________ _____________________________________________________________________________ Click on this link to learn about “Golden Rice” - rice that was genetically modified to produce beta-carotene to prevent millions of children in Africa and South East Asia from dying from Vitamin A deficiency (VAD). http://en.wikipedia.org/wiki/Golden_rice 3.3 ARTIFICIAL ANIMAL CLONING Animals that reproduce ________________________ cannot be cloned naturally. Mammals can be cloned artificially using the following technique: 1. A ________________ is removed from the individual to be ______________________. 2. An ________________ (egg) is taken from another individual and its ___________________ (thus DNA) is removed. 3. The __________________ and the “enucleated” ____________________ are combined creating an _____________________ with the same genetic material as the ______________________ individual. 15 EST 404 THE LIVING WORLD CHAPTER 11 NOTES 4. The embryo is __________________________ into the uterus of a ______________________ mother. The embryo grows and develops until the _________________________ gives birth to a clone of the _________________________ individual. Click on this link to read about the ewe Dolly (July 5, 1996 – February 14, 2003) who was the first animal to be cloned from an adult somatic cell, using the process of nuclear transfer. http://www.bootstrike.com/Genetics/Cloning/dolly_the_sheep.html 3.4 HUMAN CLONING Human cloning may take one of two forms: _______________________________ cloning _______________________________ cloning The purpose of ______________________________ cloning would be to produce babies that are genetically identical to the people being cloned. (Currently ________________________ in Canada and many other countries) The purpose of ____________________________ cloning would be to obtain tissues (ex. skin for burn victims) or _____________________ that are genetically identical to those of a person in need of a __________________________ or graft. The benefit of this type of cloning is that the risk of rejection of such tissues or organs by the individual is _____________. 3.5 MOLECULAR CLONING Many illnesses, such as cystic fibrosis, are due to _____________________ genes. In order to find a cure, scientists need to study such genes more closely so they clone the ______________ so that they can obtain multiple ____________________. This is called ________________________ cloning (also ____________ or _____________ cloning.) END OF CHAPTER 11 16