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SCIENCE 30 UNIT A: MAINTAINING HEALTH Chapter 2- Genetics Mrs. Steinbrenner Name: Chapter 2- Genetics 2.1- What is Genetics? Inside the cells of the body there is a ____________ with chromosomes. Chromosomes carry _____________, units of heredity. Each chromosome contains many different genes. Humans have ____ sets of chromosomes (46 in total). ____________comes from each parent. 1. Chromosomes Long, thin strands of DNA that are coiled around protein molecules for protection. Seen at cell division. _____ shape is created when copies attach at one point. 2. Genes A segment of DNA that codes for a ________ __________________. The ____________of the pattern codes for a specific trait (e.g.. Tongue rolling). Some genes are dominant (occur more often) and some are recessive. _____________ is the study of how parent genes determine the characteristics of the child. 3. Human Karyotype All of the chromosomes matched to their pair is a ____________________. 3 features are used to identify pairs: Length of chromosome (_______________= #1) Pattern of dark bands on chromosome. Position of centre connection (________________). The last 2 chromosomes are the sex chromosomes: 2 ‘x’ = _________________ 1 ‘x’ and 1 ‘y’ = ________________ 23 chromosomes from ___ is matched by 23 chromosomes from _____. ▪ Paired chromosomes are ________________ chromosomes ▪ homologous = same information ▪ Similar in ________________ __________________________ Genetic recombination explains diversity of people. 4. Role of Proteins Each gene makes a protein…these are used for/as: ___________________ (amylase- digestion). Structural (Keratin/ collagen). Transport ( cell membranes). Hormones (insulin). _____________________ (antibodies). Energy (Casein). Muscle contraction (Actin and myosin). 5. Chromosome replication The 2 ways that an exact copy of the DNA from the chromosome is created are: Mitosis (_________ reproduction). Meiosis (___________ reproduction) a) Mitosis Body cells (_____________________) divide by replicating all the parts and dividing into 2 identical cells (skin, hair, fingernails…). A copy of the DNA must be made before replication; each strand replicates and attaches at a centre point (______________). Original 2 strands of DNA (1 from each parent) = ____ strands (2 from each parent). 2 chromosomes line up at centre of cell (_____________) and are pulled apart. Cell membrane splits and 2 new “_________” cells are created. 2 “daughter” cell is ___________ to parent (both are diploid(____) cells = pair of homologous chromosomes). Plants undergo mitosis = asexual reproduction. b) Meiosis Reproductive cells (____________) are used to reproduce sexually. In humans = sperm (male) and egg (female). Create _____________ offspring. Starts the same as mitosis Cells reproduce chromosomes. Homologous chromosomes _______________________________ (Cross over). Crossing over creates completely new combinations of traits in next generation DNA material is exchanged between parent strands = ______________________. After crossing over, chromosomes align at equator, divide into 2 separate cells. Those 2 cells each divide into 2; ___ cells are produced, each with 23 chromosomes (___). Gametes (daughter cells) are ___________ cells because they have ½ the DNA of parent cell. Sexual reproduction allows us to maintain both genetic similarity & differences. Mitosis vs Meiosis Mitosis ___ division daughter cells genetically ________to parent cell produces 2 cells 2n ________ produces cells for growth & repair no crossing over Meiosis 2 divisions daughter cells genetically ___________from parent produces __________ 2n 1n produces ____________ crossing over 7. Fertilization The sperm and the egg (gametes) are each __________, the fertilized egg is ___________ and can reproduce through mitosis. This increases variation and allows for more than ______________ gene combinations. Crossing over improves the variation possible in the gametes; explains why 2 siblings look so different. 8. Selective Breeding Used to improve domestic varieties of plants and animals Plants: _________________________ • Sweet, full-kernel corn • Canola - can germinate and grow rapidly in colder climates Purebred or thoroughbred dogs and horses • _________________- in which similar phenotypes are selected for breeding New varieties of plants and animals can be developed by _____________________________. • Opposite to that of inbreeding • Blend desirable but different traits Corn : Hybrids tend to be more vigorous than either parent 9. Inheritance Ideas Prior to the 19th century, __________________ theory was prevalent- body parts developed from fully formed, tiny parts. Charles Darwin theorized evolution and the idea of inherited characteristics; there was no explanation for how this happened though! 3 a) Gregor Mendel: “ ______________________” Gregor (1822-1884) Mendel’s work with garden peas provided missing piece in theory of evolution by natural selection. Noticed that traits were not blended but instead one was ____________________. Cross-pollination: Transferring ______________ between genetically different plants. Mendel discovered that some traits were easy to recognize and studied these. Mendel’s Experiments Factors controlled traits of a plant = ____________. A trait can disappear in the 1st generation but reappear in_____of the second generation. Some genes were dominant Dominant allele – fully expressed physically; ___________________ ______________________. Other genes were recessive Recessive allele – completely masked physically by dominant gene. Mendel’s Laws 1. Inherited characteristics are controlled by genes that occur in pairs; each gamete receives 1 gene (_________________). 2. Principal of dominance- 1 gene masks the effect of the other. 1. Dominant trait = ____________ 2. _______________ trait = lowercase letter 3. Individuals ______________ genes from parents. 4.______________ inheritance of traits to offspring- not linked to other traits. 2.2- Inheritance Inherited traits are passed on to offspring via genes. __________________________ _______________ traits are created by the environment; not genes. Scars, ability to speak languages… a) Alleles An _______________ form of a gene responsible for a trait (e.g. Tongue rolling). Individuals have __ alleles for every trait located on chromosomes. When the chromosomes separate during meiosis, __ allele is passed to each gamete. Dominance Theory 2 alleles: ______________________________. Dominant alleles are able to mask recessive alleles; result in a dominant trait. Recessive traits are coded only when an offspring receives ___________________. Genetic Terms Homozygous: two identical copies of an allele (eg. pp or PP) (“pure”). Can be homozygous _____________________ Heterozygous: ___________________copies of an allele (eg. pP) (“hybrid/carrier”). Genotype: the___________ that an individual has. Phenotype: the observable ___________ of an individual. b) Punnett Squares If alleles are known, it is possible to predict the ________________. Punnett squares are used to simplify the process. 3 steps to use: Draw a____________and label each row with alleles of the ____________. Fill in the squares with the genotype. Determine the _____________of the offspring with each genotype. Phenotype vs. Genotype Genotype needs to be described as: _____________________________________ Phenotypic ratios are usually expressed as: 4 c) Blood Type Controlled by 3 alleles: A, B, O. Produce 4 genotypes: A, AB, B, O. O is _____________; individual needs to be homozygous for type. A and B are __________________; both can be expressed at the same time. d) Gender determination Mother has only _____ chromosomes; all eggs have an X chromosome. Father determines the gender of the baby; ________ chance for either gender. e) Sex linked traits Traits that are coded by genes located on ______ chromosomes (X or Y). Traits that are controlled by genes on the other 22 chromosomes are ___________. Use a Punnett square with sex chromosomes and the gene (___________________). Color blindness is an X linked trait; males need only 1 recessive allele to be colorblind, women need 2. 2.3- DNA Deoxyribose Nucleic Acid- DNA Is a _____________shape (2 strands twisted); looks like a spiral staircase. Composed of ___________ = phosphate, sugar (deoxyribose), 1 Nitrogen base. a) Structure DNA most often described as a double helix • Closely resembles a twisted ladder Sugar and phosphate molecules form “______________” of ladder N bases form rungs • N bases from one spine of ladder are connected with N bases from other by means of _______________. Nitrogen Bases There are 4 Nitrogen bases: Adenine (A) Guanine (G) Thymine (T) Cytosine (C) When 2 Nitrogen bases join (using a Hydrogen bond) they form a ____________. Only certain bases bond, due to chemical structures: ___________; ______________ b) Base pair bonding DNA molecule has 1 base strand and 1 _________________ base strand. 2 strands form the ladder, with the bonded pairs becoming the ‘rungs’. What is the complementary strand to: ATTGCCGATGC _________________________ c) DNA Structure Determination 5 • Franklin collected x-ray diffraction data (early 1950s) that indicated 2 periodicities for DNA: 3.4 Å and 34 Å. • Watson and Crick proposed a 3-D model accounting for the data. • Proportion of nitrogen bases varies from species to species • # adenine molecules = # thymine • # guanine molecules = # cytosine • N bases were arranged in___________ • Watson and Crick developed a 3 - D model of DNA molecule d) Histones DNA from 1 cell is 2 meters long; it is coiled and wrapped around ______________ __________called histones. Used to reduce the needed space in nucleus. e) Replication of DNA __________ is only molecule known that is capable of duplicating itself (replication) • Helps explain how 1 cell can divide into 2 identical cells During replication, weak H bonds are broken • 2 edges of the ladder seem to “__________" ▪ Parent strands are conserved. • Each parent strand acts as a template to which ________________________ in cell can attach • Nucleotides attach themselves at their __________: adenine (A) with thymine (T), and cytosine (C) with guanine (G). • Enzymes,_____________, fuse free nucleotides together in complementary chain of DNA Free-floating nucleotides in cells are derived from the food one eats. ____ new strands of DNA are formed into the double helix. f) The genetic code With only 4 bases, billions of genes can be coded. Proteins are made from specific _______ __________________ called genes. A protein is a chain of amino acids (1 of 20 building blocks of proteins); each amino acid is coded by ____ bases together = DNA triplet code. 64 possible codes but only ____ are used for amino acids in the human body. g) Making Proteins DNA can’t leave nucleus (too large) so messenger RNA (________) come and carry it to the ribosome. RNA does not have T but instead has ____________ The ________( 3 bases) codes for an amino acid; these are joined together in the ribosome. Start and Stop codons mRNA takes DNA to __________ and tells them what protein to make. Always code from the 5’ end to the 3’ end. To start or stop, a specific codon is used: Start = Initiator codon (_____). Stop = _______ codon (TAA, TAG, TGA). h) Protein versatility Proteins are variable because they are made using specific amino acids; some can even ______________and reverse when finished. The body creates a protein for every need: Enzymes (polymerase). Structural ( body cells). _________________________ Storage (Hemoglobin). 2.4- Mutations and Genetic Diseases 6 Mutation = ______________ in the sequence of bases in the DNA. Most occur naturally or due to radiation exposure. Each change is carried to next generation and _________________________. Mutations increase variability and lead to _________________ (beneficial and harmful). a) Mechanism of Mutation Mutagenic agents can cause mutations: ________________________________. Dangerous for pregnant women in 1st trimester. Carcinogens are mutagens that are known to cause _____________ (uncontrolled cell growth): Xrays, cigarette smoke, pesticides… Mutations usually occur in chromosomal regions where they do not affect the protein; body can ______________ some mutations. Some mutations cause gene to stop working or alter function. Beneficial mutations Mutations can allow for adaptation to the environment; _______________________, camouflage coloring, etc. Allows for more chances to breed = more offspring with adaptation. Genetic inheritance is the key to ________ _____________________. b) Types of mutations There are 2 types of mutations: ________________ (substitution of 1 base for another). ____________ mutations (deleting/adding a base during replication). c) Passing on Mutations If a mutation is in an sex cell (sperm or egg); the mutation is passed to ___________. These diseases are genetic; the mutation is present in every cell of the offspring. In most cases a parent is a carrier and the mutated gene is ______________ to the healthy gene of the other parent. ___ chance of having disease, ½ of carrier and ¼ healthy. d) Genetic Diseases Each disease occurs because of a mutation on ___ of the chromosomes in the parent. Can be caused by recessive or dominant genes. 4 common diseases are: Cystic Fibrosis (CF) _____________________ Huntington disease ____________________ Cystic Fibrosis: chromosome __, autosomal recessive, 1:2500 affected in Canada. Huntington’s: chromosome ___, autosomal dominant, 1:10 000 affected in Canada. Hemophilia: X chromosome, sex-linked recessive, 1:10 000 (higher % ___________). 7 Sickle cell anemia: chromosome 11, autosomal recessive, higher ______________ individuals (link to malaria). e) Pedigree Charts A genetic family tree; used to predict the _________________ of the individual. Used to trace genetic diseases. Uses specific symbols: Female = ____________ Male = square Line between male and female = have children. Shaded = _________________ Partly shaded = carrier for disease. Roman numerals = new generation. g) Super bugs! Antibiotic resistant bacteria have adapted and mutated so they are ________________________. Every time the bacteria is exposed to an antibiotic, more become resistant- pass on to the new bacteria. Bacteria reproduce asexually but can exchange material via _________________________. Transformation: Bacteria incorporate ______ ____________ into self. Plasmid: self-replicating ____________ piece of DNA that is transferred between bacteria. Plasmid may have the bacterial resistance gene and ______________ to all other bacteria. Promotes resistance in all strains of bacteria. 8 2.5- Genetic Technologies Used to identify, treat and prevent hereditary disease; develop medicine, solve crimes and identify individuals. ______________ issues arise with this new technology. a) DNA fingerprinting In ________, DNA matching was used to identify a rapist-murderer in England In the same year, a rapist in Florida, was convicted on the basis of genetic evidence DNA fingerprinting test was developed by ______ ________________________. • Particular segments of DNA are unique arrangements of nitrogen bases • Only _______________________share same N base arrangements in these sections • DNA segment is taken from semen found in rape victim. Compared with DNA segment taken from a blood sample of suspect • DNA samples are transferred to a _______________. DNA are tagged with a radioactive probe that identifies unique segments of DNA chain • Nylon sheet is then placed against an X-ray film • Black bands appear where probes have attached to segments used to establish identity • A ____________ is then made from film and used to compare samples b) Transgenics Genes from 1 species are transferred and spliced into the________ of another species. Results in a genetically modified organism (_____). Used to create food, medicine or materials that will improve results. Crops with naturally producing pesticides. Bacteria that can produce insulin. Pig organs that are closely related to humans. c) Gene Therapy Using genes to treat or _______ a disease. Using an _______________ to deliver needed gene to individual’s cells. Uses enzymes to cut healthy DNA into pieces---isolate needed ________-- insert into a plasmid--transfer to bacteria. ________________________= DNA with genes from 2 or more organisms. Used to treat Cystic Fibrosis and Diabetes. Cured the “bubble baby” by injecting bone marrow cells with an altered virus that produced ____________ _____________. 9