Genetics Test Review - Loudoun County Public Schools

Genetics Test ReviewHeredity- 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 span2) Easy to grow3) Easily distinguishable traits4) Large number of offspring (sample number)5) Carry out both self and cross pollinationWhy Mendel?(5)1) Kept accurate written records2) Studied one trait at a time3) Conducted controlled experiments4) used a large sample number5) First to use statistics and probabilityKey Concepts Terminology (7)1) Dominant- A trait which expresses itself if even one dose of the gene is present2) Recessive- A trait which expresses itself only if two dose of the gene is present3) 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 Egg5) Phenotype- External appearance of a trait6) Genotype- Actual gene combination for a trait7) Allele- one form of a geneTypes of Cells1) Somatic Cells(Body cells)- Cells which are not directly involved in reproduction46 individual chromosomes per cell.23 pairs, 2(23) 462) Gametes(sex cells; sperm & egg)- Cells which are directly involved in reproduction23 Chromosomes per gametes ( sperm & egg)1 single set of chromosomesBiologyMr. Velázquez

Mendel’s Experiments-Height (T Tall t Short)Mendel used the term “Factor” instead of “Gene”P1-Parental Generation AKA First GenerationF1-First Filial AKA second generationF2-Second Filial AKA third generationP1 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 SquareGametesTtTTTTallTtTalltTtTallttShort1:2:1 Genotypic Ratio TT:Tt:tt3:1 Phenotypic Ratio Tall:ShortLaw of SegregationWhen F1 hybrids (heterozygous) are crossed with each other that that did not appear inthe F1 appears in 1/4 of the F2 (3/4 are Tall 1/4 are Short; all the F1 where Tall)BiologyMr. Velázquez

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 & enLaw of Independent AssortmentWhen two traits are studied at the same time, the inheritance of one trait isindependent of the second trait Exception-When genes for different traits are foundon the same chromosome they tend to be inherited togetherLinked GenesIncomplete Dominance-AKA Blending Inheritance-The hybrid does not resembleeither parent but instead is a blend of parental traits1)Four O’ Clocks(R Red Flowers W White Flowers)P1 RR x WWF1 RW- 100% PinkF2 1:2:1, Red: Pink: White, 25% Red 50% Pink 25% WhiteGametes RRRRRedWRWPinkBiologyMr. VelázquezWRWPinkWWWhite

2) Andalusian Fowl (B Black Feathers W White Feathers)Incomplete dominanceP1 BB x WWF1 BW-100% BlueF2 1:2:1, Black: Blue: White,25% Black 50% Blue 2% WhiteGametes BBBBBlackWBWBlueWBWBlueWWWhiteSickle Cell Disease (HbA-HemoglobinA Normal HbS-HemoglobinS AbnormalGametesHbAHbANormalHbSSickle CellTraitHbSSickle CellTraitSickle CellAnemiaSickle Cell Trait- Both types of cells, greater resistance to MalariaSickle Cell Anemia- Shortened Life span by approximately 50%Multiple AllelesThere are 3 or more different genes in the population but any individual has only 2genes/traitAlleles for Blood -IA; group A, IB; group B, i; Group OBlood GroupsPhenotype: AGenotype:IA IA, IAiAntigen:AAntibody:anti-bBiologyMr. VelázquezBIB IB, IBiBanti-aABIA I BA&BnoneOiiNoneanti-a/anti-b

Antigen- A foreign substance which stimulates the formation of antibodies(Red bloodcells)Antibodies- A substance formed in response to an antigen(plasma-liquid part ofblood)Blood groups are an exception to these definitions‘O’ blood is known as the universal donor‘AB’ blood is known as the universal recipientAgglutination Reaction-Caused by transfusions when the antibodies attack thetransfused bloodRH Factor(RH Positive( ) rh Negative(-)Blood typesA ,A-,B ,B-,AB ,AB-,O ,ORH DiseaseMother’s RH Factor NegativeFather’s PositiveFetus/Baby’s PositiveAntibodies from the mother attack the fetus if any blood from the baby leaked into themother, the second Fetus with Positive blood will be attacked if blood is leaked fromthe second fetus, the mother’s body remembers the foreign RH and antibodies arealready pre-created from first fetus, the second fetus may be injured or killed by theantibodies. After the first Baby is born a vaccine may be created to prevent thecreation of antibodies that may injure or kill the second fetus.Placenta- Provides O2 and nutrients to the fetus, carries away fetal wasteSex DeterminationSomatic Cells-46 chromosomes/cell (23 Pairs)44 Autosomes (22 Pairs)2 Sex Chromosomes (1 Pair)X chromosome-Female, Y Chromosome-MaleXX-Normal Female, XY-Normal MaleFemale to Male ratio should be the same however it is not;BiologyMr. Velázquez

106 Males:100 Females-The Y chromosome is smaller and lighter in weight then theX chromosome. Y sperm can swim slightly faster then the X sperm so more Y spermwill reach the egg. There is a somewhat better chance that the Y sperm will fertilizethe egg.Twins1) Fraternal-Two eggs each of which is fertilized by its own sperm2) Identical-One egg is fertilized by one sperm then the zygote divides and eachzygote matures by itself.Variations in Sex Chromosomes1)XO-Female-45 chromosomes per somatic cell; 44 autosomes 1 sex chromosomeAKATurners Syndrome-sexually immature Female.2)XXY-Male-47 chromosomes per somatic cell; 44 autosomes 3 sex chromosomesAKA Klinefelter’s Syndrome-sexually immature Male.3)XXX-Female-47 chromosomes per somatic cell; 44 autosomes 3 sex chromosomesAKA Super Females.XYY-Male-47 chromosomes per somatic cell; 44 autosomes 3 sex chromosomesAKASuper Males also known as Jacobs syndrome.XXYY-Male-48 chromosomes per somatic cell; 44 autosomes 4 sex chromosomes.BiologyMr. Velázquez

Normal Gamete FormationAbnormal Gamete FormationNon-Disjunction- Failure of chromosome pairs to separate during Gamete formation(Same diagram as previous page until the last stage)Autosomal Non-DisjunctionDown’s Syndrome AKA Trisomy 21 & Mongolism(incorrectly called Mongolism because of “oriental” appearance)47 Chromosomes/ Somatic Cell-45 Autosomes 2 Sex ChromosomesMental retardation, Short, Overweight, Round face, “Oriental” appearance, Poor muscularcoordination, Tip of the tongue protrudes, Shortened life span, Simian Crease -Line crease acrossthe length of both hands. Called Trisomy 21 because there are three 21st Chromosomes insteadof the normal pair (2)BiologyMr. Velázquez

Amniocentesis-A technique in which amniotic fluid and embryonic cells are retrieved andanalyzed for genetic defects.Cells are cultured and examined microscopically to find the point of cell divisionA photo of the chromosomes is taken which is called a Karyotype-A photo of the chromosomesarranged in pairs.Sex Linkage(sex linked traits) - The genes for these traits are found only on the Xchromosome, There are NO genes for this trait on the Y chromosomeColor-blindness (C-Normal color vision c-color blindness)Females-Has XX therefore 2 genesMales-Has XY therefore 1 gene (on the Xchromosome)CC-Normal Color VisionCY-Normal Color VisionCc-Carrier(Normal color vision but has the Cannot be a carriergene to pass ormal Color Vision Cc-Carrier-FemalesCCY-Normal Color Vision cY-Color-blind-MalesYFatherHemophilia-A condition in which the blood doesn’t clot and continues to bleed caused by thebody not synthesizing factor VIII(8)-a step in the process of blood clottingH-Normal Clotting MaleHY-NormalhY-HemophiliaThere have been virtually no cases(but still some) of Hemophilia in a Female because it is a raregene and most people die at an early age from it.Genetics and Environment1)Green Color in Plants-(C-Chlorophyl production c-No chlorophyl production)CC- GreenCc- Greencc-White (dead)2)Baldness in Humans-(B-Bald b-Hair)FemaleGenotype Male A minimal level of testosteroneHairBBBald is needed to activate the dominantHairBbBald gene for baldness in HumansHairbbHairBiologyMr. Velázquez

Genetics Test Review 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)