Topic 7: Genetics and Variation PDF

Official (Closed) - Non Sensitive Topic 7: Genetics and Variation Fundamentals of Biology, PFP, LSCT, Ngee Ann 1...

Official (Closed) - Non Sensitive Topic 7: Genetics and Variation Fundamentals of Biology, PFP, LSCT, Ngee Ann 1 Polytechnic  Official (Closed) - Non Sensitive Genetics: what is it? What is genetics? “Genetics is the study of heredity, the process in which a parent passes certain genes onto their children.” What does that mean? Children inherit their biological parents’ genes that express specific traits, such as some physical characteristics, natural talents, and genetic disorders. Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol ytechnic 2  Official (Closed) - Non Sensitive Human Genome Most human cells contain 46 chromosomes: 2 sex chromosomes (X,Y): XY – in males. XX – in females. 22 pairs of chromosomes named autosomes. http://www.sketchite.com/duchenne-muscular-dystrophy- chromosome-karyotype/ Fundamentals of Biology, PFP, LSCT, Ngee Ann bW9udGV3ZXN0b24qY29tfEJpb2xvZ3l8QmlvfGh1bWFuKmPolytechnic 3 dpZg_bW9udGV3ZXN0b24qY29tfEJpb2xvZ3l8Sm9uYXMzK  Official (Closed) - Non Sensitive Genetic Concepts Gene – a gene is a segment of DNA located in a specific site on a specific chromosome that contains information for producing a particular protein. Chromatin – a thread-like structure of DNA (nucleic acids and proteins) that carries genes Chromosome – condensed form of chromatin DNA – deoxyribonucleic acid. Contains the genetic instructions specifying the biological development of all cellular forms of life Fundamentals of Biology, PFP, LSCT, Ngee Ann http://blog.targethealth.com/dna-key-to- Polytechnic 4 personalized-medicine/  Official (Closed) - Non Sensitive Eukaryotic Chromosomes DNA is packaged up tightly into structures called chromosomes DNA, chromosomes and gene expression. (n.d.). Retrieved January 5, 2016, from Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 5 http://sciencelearn.org.nz/Contexts/Uniquely-Me/Sc ytechnic ience-Ideas-and-Concepts/DNA-chromosomes-and-  Official (Closed) - Non Sensitive Chromosome Structure In diploid cells: Locus – location of a gene on the chromosome. Allele – a variant form of a gene Individuals with two copies of the same allele of a gene are homozygous for that trait. Individuals with different alleles of a gene are heterozygous for that trait. Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 6 ttp://slideplayer.com/slide/4894109/ ytechnic  Official (Closed) - Non Sensitive Dominant vs. Recessive Alleles are dominant or recessive, meaning: A dominant allele is expressed even if it is paired with a recessive allele. A recessive allele is only visible when paired with another recessive allele. Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 7 ytechnic  Official (Closed) - Non Sensitive Dominant vs. Recessive Example: The allele for brown eyes is dominant, while the allele for blue eyes is recessive. Brown Brown eyes eyes Blue Variation and inheritance. (n.d.). Retrieved January 17, 2016, from eyes Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 8 http://www.bbc.co.uk/schools/gcsebitesize/science/ocytechnic r_gateway/understanding_organisms/  Official (Closed) - Non Sensitive Dominant vs. Recessive The dominant allele is usually designated a capital letter, whereas the recessive allele is designated a lowercase letter. Homozyg Heterozyg Homozygo ous ous (Bb) us dominant recessive https:// ytechnic (BB) Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol (bb) 9 mendeliangenetics.wordpress.com/  Official (Closed) - Non Sensitive Genotypes vs Phenotypes A genotype is the precise set of alleles an individual possesses for a given trait / traits. It tells us whether the individual is homozygous or heterozygous for a given gene. A phenotype is the observable physical trait(s) of an individual. E.g. hair color, weight, or the presence or absence of a disease. Fundamentals of Biology, PFP, LSCT, Ngee Ann Polytechnic 10  Official (Closed) - Non Sensitive Genotypes Phenotypes (example) phenotypes genotypes https:// Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 11 ytechnic mendeliangenetics.wordpress.com/  Official (Closed) - Non Sensitive Gregor Mendel Born in 1822 in Czechoslovakia Became a monk at a monastery in 1843 Taught biology and had interests in statistics Also studied at the University of Vienna Fundamentals of Biology, PFP, LSCT, Ngee Ann 12 Polytechnic ttps://en.wikipedia.org/wiki/Gregor_Mendel  Official (Closed) - Non Sensitive Mendel continued After returning to the monastery he continued to teach and worked in the garden. Between 1856 and 1863 he grew and tested over 28,000 pea plants https://www.mun.ca/biology/ Fundamentals of Biology, PFP, LSCT, Ngee Ann 13 Polytechnic scarr/Mendels_Garden.html  Official (Closed) - Non Sensitive Mendel’s Peas Why peas? Easy to grow. Easily identifiable traits Can work with large numbers of samples http://www.slideshare.net/jrohara/ Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 14 ytechnic geneticsstudent2007-presentation  Official (Closed) - Non Sensitive Mendel’s experiments He studied one characteristic at a time. He chose 2 contrasting pure breed parent plants (P generation) He cross-pollinated the two plants, collected the seeds and planted them. The hybrid offspring are called the F1 generation. He then allowed the F1 generation to self-pollinate. The offspring of this group are called the F2 Note the ratio of 3:1 generation. https://www.boundless.com/biology/ textbooks/boundless-biology-textbook/ Fundamentals of Biology, PFP, LSCT, Ngee Ann mendel-s-experiments-and-heredity-12/ 15 Polytechnic patterns-of-inheritance-95/phenotypes-  Official (Closed) - Non Sensitive ndel examined seven traits and always got th same results. Interpretation: e F1 always showed only one of the two paren traits, and always the same trait. e trait that “disappeared” in the F1 generat reappeared in about 25% of the F2’s traits did not blend, but remained unchange from one generation to another Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 16 ytechnic  Official (Closed) - Non Sensitive Mendel’s conclusions: Traits are not always expressed. Alleles that are always expressed are called dominant alleles Alleles that are not expressed if a dominant allele is present are called recessive alleles Fundamentals of Biology, PFP, LSCT, Ngee Ann 17 Polytechnic  Official (Closed) - Non Sensitive Mendel’s Laws 1. the Law of Dominance 2. the Law of Segregation 3. the Law of Independent Assortment https://upload.wikimedia.org/wikipedia/commons/b/ba/  Official (Closed) - Non Sensitive 1. Law of Dominance In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype. Tt (Tal https://www.khanacademy.org/science/biology/classical-genetics/mendelian--genetics/a/  Official (Closed) - Non Sensitive Law of Dominance P T x tt T T T t t F1All tall T T T T t t t t https://www.khanacademy.org/science/biology/classical-genetics/mendelian--genetics/a/  Official (Closed) - Non Sensitive 2. Law of segregation Law of segregation Two members of a gene pair segregate from each other into the gametes, so half the gametes carry one member of the pair and the other half carry the other member of the pair. Parent Bb Gamet Gamet e e B b https://en.wikipedia.org/wiki/ Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 21 ytechnic Mendelian_inheritance  Official (Closed) - Non Sensitive http://genetics-and-dna.weebly.com/ Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 22 ytechnic homozygous-heterozygous-genotypes-  Official (Closed) - Non Sensitive Punnett square A Punnett square is a diagram used to predict the genetic makeup of the offspring of individuals of particular genotypes. Gametes are placed above and to the left of the square. Offspring are placed in the square. Capital letters (Y) represent dominant alleles. Lower case letters (y) represent recessive alleles. Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 23 ytechnic  Official (Closed) - Non Sensitive Example 1: Goodenough, J., & McGuire, B. (2011). Genetics and Human Inheritance. In Biology of Humans. Concepts, Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 24 applications and issues (4th ed., pp. ytechnic 420-421). Benjamin Cummings.  Official (Closed) - Non Sensitive Example 2: Goodenough, J., & McGuire, B. (2011). Genetics and Human Inheritance. In Biology of Humans. Concepts, Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 25 applications and issues (4th ed., pp. ytechnic 420-421). Benjamin Cummings.  Official (Closed) - Non Sensitive Try it yourself Predict the genotype & phenotype of the offspring: Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 26 ytechnic  Official (Closed) - Non Sensitive What if you are studying more than 1 trait? Monohybrid Cross - crossing parents who differ in only one trait (AA with aa) Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee) Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 27 ytechnic  Official (Closed) - Non Sensitive 3. Law of independent assortment Law of independent assortment Different gene pairs assort independently in gamete formation..This “law” is true only in some cases Gene Gene pairs pairs on on SEPARATE SEPARATE CHROMOSOMES CHROMOSOMES assort assort independently independently at at meiosis. meiosis. Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 28 ytechnic  Official (Closed) - Non Sensitive Independent assortment Alleles separate independentl y during the formation of gametes. https://www.mansfieldct.org/Schools/ Fundamentals of Biology, PFP, LSCT, Ngee Ann 29 Polytechnic MMS/staff/hand/gen2genegametes.htm  Official (Closed) - Non Sensitive Chromosomes Moved at Random into Forming Gametes Starr, C., & McMillan, B. (2014). Human Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 30 ytechnic biology (10th ed.). Belmont, CA:  Official (Closed) - Non Sensitive YYR R Source: Boundless. “Mendel's Law of Independent Assortment.” Boundless Biology. Boundless, 08 Jan. 2016. Retrieved 17 Jan. 2016 from https://www.boundless.co m/biology/textbooks/boundless- biology-textbook/mendel-s- experiments-and-heredity-12/ laws-of-inheritance-96/mendel- s-law-of-independent- assortment-422-11649/ Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 31 ytechnic  Official (Closed) - Non Sensitive 21. In guinea pigs, black (B) is dominant to white (b). Short hair (S) is dominant to long hair (s). The genes for colour and hair length are located on different chromosomes. In the parental generation, pure (homozygous) black, short-haired pigs are crossed to white, long-haired pigs. In the F2 generation, in what proportion would we expect the following phenotypes / genotypes? Please match. BBss Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 32 ytechnic  Official (Closed) - Non Sensitive Some exceptions to Mendel’s principles: Some alleles are neither dominant nor recessive. Many traits are controlled by more than one gene (polygenic traits) Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 33 ytechnic  Official (Closed) - Non Sensitive Incomplete dominance F1 hybrids have a phenotype somewhere in between the phenotypes of the two parents. Incomplete dominance in snapdragon color. http://greatneck.k12.ny.us/GNPS/SHS/ dept/science/krauz/ Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 34 ytechnic regents_bio_lecture_notes/notes%20as  Official (Closed) - Non Sensitive Multiple allele inheritance When three or more alleles of a given gene exist E.g. human ABO blood group Controlled by 3 alleles: IA, IB and i. IA and IB are codominant. Both IA and IB are dominant over i. Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 35 ytechnic  Official (Closed) - Non Sensitive Mowshowitz, D., & Chasin, L. (n.d.). Lecture 21. Retrieved January 17, 2016, from http://www.columbia.edu/cu/biology/courses/c2005/lec tures/lec21_10.html Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 36 ytechnic  Official (Closed) - Non Sensitive https://socratic.org/questions/why-can-t-a- person-with-blood-type-a-safely-receive-a- Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 37 ytechnic transfusion-of-blood-type-  Official (Closed) - Non Sensitive Question Show the possible blood groups of the offspring if: a) The father has blood group AB and the mother has blood group O b) The father has blood group A (IA, i) and the mother has blood group B (IB, i) Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 38 ytechnic  Official (Closed) - Non Sensitive Sex-linked inheritance Sex-linked genes – carried on the X chromosome. The Y chromosome does not carry these genes because it is shorter E.g. of sex-linked traits are: haemophilia (condition in which the blood cannot clot normally) colour blindness (condition in which a person cannot distinguish certain colours) Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 39 ytechnic  Official (Closed) - Non Sensitive Colour blindness Is caused by a recessive allele on the X chromosome Key : B is the dominant allele for normal colour vision b is the recessive allele for colour blindness XBXB ( normal female), XBY (normal male) XbXb ( colour blind female), XbY (colour blind male) XBXb ( carrier female) Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 40 ytechnic  Official (Closed) - Non Sensitive Question Show how colour blindness is inherited if: a) A colour blind man marries a normal vision woman b) A normal vision man marries a colour blind woman Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 41 ytechnic  Official (Closed) - Non Sensitive Hemophilia is a sex-linked trait where XH gives normal blood clotting and is dominant to the hemophilia allele Xh. a. Give the genotypes of 1) a woman with normal blood clotting whose father had hemophilia 2) a normal man whose father had hemophilia. b. What is the probability that a mating between these two individuals (in a. above) will produce a child, regardless of sex, that has hemophilia? Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 42 ytechnic  Official (Closed) - Non Sensitive c. If this couple has a daughter, what is the probability that the daughter will be a carrier of the hemophilia trait? d. What is the probability a daughter would have hemophilia? e. If this couple has a son, what is the probability he will have hemophilia? Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 43 ytechnic  Official (Closed) - Non Sensitive Examples of traits inherited environment both Earlobe shape scars Intelligence Eye colour language Body mass Nose shape height Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 44 ytechnic  Official (Closed) - Non Sensitive 8 riations may be inherited or acquir nherited variations result from the activity of genes hey are genetically controlled enetically controlled variations cannot be altered For example, hair colour, skin colour*, blood group, finger prints and sex cannot be changed naturally *excluding the effect of tanning Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 45 ytechnic  Official (Closed) - Non Sensitive The Environment Can Affect Phenotypes Height Diet low in protein Disease or injury that prevents the normal release of growth hormone Skin color Tanning Good lifestyle choices May limit the chances that a harmful gene(s) will be expressed Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 46 ytechnic  Official (Closed) - Non Sensitive 14 Discontinuous variation You either have these conditions or you do not. There are no intermediate states A single gene gives the characteristic. Always inherited Discontinuous variations are entirely genetically controlled They cannot be altered by external conditions. Genetic defects such as colour blindness, albinism, dwarfism, sickle cell anaemia are all genetically controlled Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol ytechnic 47  Continuous Official (Closed) - Non Sensitive variation Continuous variation describes the situation in which there are a great many intermediates between the extremes Either many genes are involved in that characteristic Or the genes are operating with environmental effects too Height Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 48 ytechnic ttp://slideplayer.com/slide/9720471/  Official (Closed) - Non Sensitive https://www.pinterest.com/pin/ Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 49 146015212896672796/ ytechnic  Official (Closed) - Non Sensitive Eye Color Is Just One of Many Human Polygenic Traits Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 50 ytechnic ttp://slideplayer.com/slide/4894109/  Official (Closed) - Non Sensitive Thank you! Fundamentals of Biology, PFP, LSCT, Ngee Ann Pol 51 ytechnic