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Research Biology Genetics Genetics Class Notes 2017 Heredity- The passage of traits from one generation to another. Gregor Mendel-Father of genetics, conducted breeding experiments with pea plants, university education, was a monk. Why pea plants? (5) 1) Short generation span 2) Easy to grow 3) Easily distinguishable traits 4) Large number of offspring (sample number) 5) Carry out both self and cross pollination Why Mendel? (5) 1) Kept accurate written records 2) Studied one trait at a time 3) Conducted controlled experiments 4) used a large sample number 5) First to use statistics and probability Key Concepts Terminology (7) 1) Dominant- A trait which expresses itself if even one dose of the gene is present 2) Recessive- A trait which expresses itself only if two dose of the gene is present 3) Homozygous- Both genes for the trait are the same (BB, bb) 4) Heterozygous- The two genes for the trait are different (Bb) Homo- Same Hetero- Different Zygote- Fertilized Egg 5) Phenotype- External appearance of a trait 6) Genotype- Actual gene combination for a trait 7) Allele- one form of a gene Types of Cells 1) Somatic Cells(Body cells)- Cells which are not directly involved in reproduction 46 individual chromosomes per cell. 23 pairs, 2(23) = 46 2) Gametes(sex cells; sperm & egg)- Cells which are directly involved in reproduction 23 Chromosomes per gametes ( sperm & egg) 1 single set of chromosomes Mr. Luis A. Velázquez Research Biology Genetics Mendel’s Experiments-Height (T=Tall t =Short) Mendel used the term “Factor” instead of “Gene” P1-Parental Generation AKA First Generation F1-First Filial AKA second generation F2-Second Filial AKA third generation P1 TT x tt (Homozygous Tall~TT~Crossed with Homozygous Short~tt) F1 Tt-100% (All of the offspring was Tall) F2 3:1, Tall: Short, 75% Tall 25% Short (25% Homozygous Tall~TT,50% Heterozygous Tall~Tt, 25% Homozygous Short~tt) Punnit Square Gametes T t T TT Tall Tt Tall t Tt Tall tt Short 1:2:1 Genotypic Ratio TT:Tt:tt 3:1 Phenotypic Ratio Tall:Short Law of Segregation When F1 hybrids (heterozygous) are crossed with each other that that did not appear in the F1 appears in 1/4 of the F2 (3/4 are Tall 1/4 are Short; all the F1 where Tall) Mr. Luis A. Velázquez Research Biology Genetics Multi-Trait Crossing-Height(T=Tall t =Short)& Seed Color(Y=Yellow y =Green) P1 TTYY x ttyy (Pure Tall & Yellow crossed with Pure Short & Green) F1 TtYy x TtYy (100% Tall & Yellow) F2 9:3:3:1, Tall & Yellow: Tall & Green: Short & Yellow: Short & Green Alleles (Gametes) Gametes TY Ty tY ty TY TTYY Tall Yellow TTYy Tall Yellow TtYY Tall Yellow TtYy Tall Yellow Ty TTYy Tall Yellow TTyy Tall Green TtYy Tall Yellow Ttyy Tall Green tY TtYY Tall Yellow TtYy Tall Yellow ttYY Short Yellow ttYy Short Yellow ty TtYy Tall Yellow Ttyy Tall Green ttYy Short Yellow ttyy Short Green Law of Independent Assortment When two traits are studied at the same time, the inheritance of one trait is independent of the second trait Exception-When genes for different traits are found on the same chromosome they tend to be inherited together Linked Genes Incomplete Dominance-AKA Blending Inheritance-The hybrid does not resemble either parent but instead is a blend of parental traits 1)Four O’ Clocks(R=Red Flowers W=White Flowers) P1 RR x WW F1 RW- 100% Pink F2 1:2:1, Red: Pink: White, 25% Red 50% Pink 25% White Gametes R R RR Red W RW Pink Mr. Luis A. Velázquez W RW Pink WW White Research Biology Genetics 2) Andalusian Fowl (B=Black Feathers W=White Feathers) Incomplete dominance P1 BB x WW F1 BW-100% Blue F2 1:2:1, Black: Blue: White,25% Black 50% Blue 2% White Gametes B B BB Black W BW Blue W BW Blue WW White Sickle Cell Disease (HbA-HemoglobinA=Normal HbS-HemoglobinS=Abnormal Gametes HbA HbA Normal HbS Sickle Cell Trait HbS Sickle Cell Trait Sickle Cell Anemia Sickle Cell Trait- Both types of cells, greater resistance to Malaria Sickle Cell Anemia- Shortened Life span by approximately 50% Multiple Alleles There are 3 or more different genes in the population but any individual has only 2 genes/trait Alleles for Blood -IA; group A, IB; group B, i; Group O Blood Groups Phenotype: A Genotype: IA IA, IAi Antigen: A Antibody: anti-b Mr. Luis A. Velázquez B IB IB, IBi B anti-a AB IA I B A&B none O ii None anti-a/anti-b Research Biology Genetics Antigen- A foreign substance which stimulates the formation of antibodies (Red blood cells) Antibodies- A substance formed in response to an antigen (plasma-liquid part of blood) Blood groups are an exception to these definitions ‘O’ blood is known as the universal donor ‘AB’ blood is known as the universal recipient Agglutination Reaction-Caused by transfusions when the antibodies attack the transfused blood RH Factor(RH=Positive(+) = Negative(-) Blood types A+,A-,B+,B-,AB+,AB-,O+,ORH Disease Mother’s RH Factor Negative Father’s Positive Fetus/Baby’s Positive Antibodies from the mother attack the fetus if any blood from the baby leaked into the mother, the second Fetus with Positive blood will be attacked if blood is leaked from the second fetus, the mother’s body remembers the foreign RH and antibodies are already pre-created from first fetus, the second fetus may be injured or killed by the antibodies. After the first Baby is born a vaccine may be created to prevent the creation of antibodies that may injure or kill the second fetus. Placenta- Provides O2 and nutrients to the fetus, carries away fetal waste Sex Determination Somatic Cells-46 chromosomes/cell (23 Pairs) 44 Autosomes (22 Pairs) 2 Sex Chromosomes (1 Pair) X chromosome-Female, Y Chromosome-Male XX-Normal Female, XY-Normal Male Mr. Luis A. Velázquez X Y X XX XY X XX XY Research Biology Genetics Female to Male ratio should be the same however it is not; 106 Males:100 FemalesThe Y chromosome is smaller and lighter in weight then the X chromosome. Y sperm can swim slightly faster then the X sperm so more Y sperm will reach the egg. There is a somewhat better chance that the Y sperm will fertilize the egg. Twins 1) Fraternal-Two eggs each of which is fertilized by its own sperm 2) Identical-One egg is fertilized by one sperm then the zygote divides and each zygote matures by itself. Variations in Sex Chromosomes Sexual Syndromes Pair 23 Males or Females only 1)XO-Female-45 chromosomes per somatic cell; 44 autosomes 1 sex chromosome AKATurners Syndrome-sexually immature Female. 2)XXY-Male-47 chromosomes per somatic cell; 44 autosomes 3 sex chromosomes AKA Klinefelter’s Syndrome-sexually immature Male. 3)XXX-Female-47 chromosomes per somatic cell; 44 autosomes 3 sex chromosomes AKA Super Females. 4)XYY-47 chromosomes per somatic cell; 44 autosomes 3 sex chromosomes AKASuper Males also known as Jacobs syndrome. 5)XXYY-48 chromosomes per somatic cell; 44 autosomes 4 sex chromosomes. Autosomal Syndromes seen in both genders Male and Female 6)XX/XY+21 Down 47 chromosomes somatic cell; 45 autosomes 2 sex Trisomy 21 7)XX/XY+18 Edwards 47 chromosomes somatic cell 45 autosomes 2 sex Trisomy 18 8)XX/XY +13 Patau 47 chromosomes somatic cell 45 autosomes 2 sex Trisomy 13 9)XX/XY d-5 Cri du chat 46 chromosomes per somatic cell 44 autosomes 2 sex Pair 5 deletion Mr. Luis A. Velázquez Research Biology Genetics Normal Gamete Formation Crossing over is the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes during sexual reproduction. Happen during prophase I This will guarantee that all gametes are different. Abnormal Gamete Formation Non-Disjunction- Failure of chromosome pairs to separate during Gamete formation (Same diagram as previous page until the last stage) Autosomal Non-Disjunction Down’s Syndrome AKA Trisomy 21 & Mongolism (incorrectly called Mongolism because of appearance) 47 Chromosomes/ Somatic Cell-45 Autosomes 2 Sex Chromosomes Mental retardation, Short, Overweight, Round face, Poor muscular coordination, Tip of the tongue protrudes, Shortened life span, Simian Crease -Line crease across the length of both hands. Called Trisomy 21 because there are three 21st Chromosomes instead of the normal pair (2) Mr. Luis A. Velázquez Research Biology Genetics Amniocentesis-A technique in which amniotic fluid and embryonic cells are retrieved and analyzed for genetic defects. Cells are cultured and examined microscopically to find the point of cell division A photo of the chromosomes is taken which is called a Karyotype-A photo of the chromosomes arranged in pairs. Sex Linkage(sex linked traits) - The genes for these traits are found only on the X chromosome, There are NO genes for this trait on the Y chromosome Color-blindness (C-Normal color vision c-color blindness) Females-Has XX therefore 2 genes Males-Has XY therefore 1 gene (on the X chromosome) CC-Normal Color Vision CY-Normal Color Vision Cc-Carrier(Normal color vision but has the Cannot be a carrier gene to pass on) cc-Color-blind cY-Color-blind Gametes C c Mother CC-Normal Color Vision Cc-Carrier -Females C CY-Normal Color Vision cY-Color-blind -Males Y Father Hemophilia-A condition in which the blood doesn’t clot and continues to bleed caused by the body not synthesizing factor VIII(8)-a step in the process of blood clotting H-Normal Clotting h-Hemophilia Female HH-Normal Hh-Carrier hh-Hemophilia Male HY-Normal hY-Hemophilia There have been virtually no cases(but still some) of Hemophilia in a Female because it is a rare gene and most people die at an early age from it. Genetics and Environment 1)Green Color in Plants-(C-Chlorophyl production c-No chlorophyl production) CC- Green Cc- Green cc-White (dead) 2)Baldness in Humans-(B-Bald b-Hair) Female Genotype Male A minimal level of testosterone Hair BB Bald is needed to activate the dominant Hair Bb Bald gene for baldness in Humans Hair bb Hair Mr. Luis A. Velázquez