* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download APDC Unit XI Meiosis
Ridge (biology) wikipedia , lookup
Population genetics wikipedia , lookup
Public health genomics wikipedia , lookup
Minimal genome wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Human genetic variation wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Point mutation wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Genome evolution wikipedia , lookup
Gene expression profiling wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Genetic engineering wikipedia , lookup
Gene expression programming wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Y chromosome wikipedia , lookup
History of genetic engineering wikipedia , lookup
Genomic imprinting wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Neocentromere wikipedia , lookup
X-inactivation wikipedia , lookup
Genome (book) wikipedia , lookup
Designer baby wikipedia , lookup
Unit XI: Meiosis & Inheritance Chapter 10 - Meiosis Chapter 36* - Reproduction (Parts of this will actually move to Unit 12) QUICK UNIT this time Test is soon! WHAT YOU NEED TO KNOW: • Terms associated with genetics problems: P, F1, F2, dominant, recessive, homozygous, heterozygous, phenotype, genotype. • How to derive the proper gametes when working a genetics problem. • The difference between an allele and a gene. • How to read a pedigree. Two Types of Reproduction • Asexual • One “parent” • All genes passed on “as is” • Very little genetic variation • Typically involves “just splitting” • Sexual • Two “parents” • Shuffling of gene combinations • Greater genetic variation • Typically involves meiosis • Sexual Reproduction • Why bother? Chromosome Terms • Homologous chromosomes • Carry same type of genes (though not necessarily same version of that gene) Ex: chromosome pair #1…both have gene for eye color in same spot…one codes for blue, other for brown • Sex chromosomes • Determine gender of offspring (Y determines) • In humans, X & Y (male XY; female XX) • Autosomes • The other chromosomes…in humans, #1-22 Human Karyotypes Map of homologous chromosome pairs Life Cycle Terms • Somatic cell – a regular body cell • Diploid (2n) has both sets of chromosomes • In humans, diploid = 46 chromosomes • Gamete – a reproductive cell • Haploid (1n) has one set of chromosomes • in humans, haploid = 23 chromosomes Human Life Cycle Events Fertilization – joining of sperm & egg Zygote – fertilized egg (diploid) Meiosis – production of haploid sex cells; occurs in ovaries & testes Other Life Cycles All share same alternation between fertilization and meiosis Animals – 2n dominates Fungi – 1n dominates Plants – alternation of generations How do we get to haploid? Meiosis is process to split chromosome # in half Result: 4 cells each with 1 of each type of chromosome Meiosis I – halves the chromosome # Meiosis II – reduces amount of DNA by half Meiosis I: Reduce to Haploid KEY TERM: Synapsis Homologous chromosomes pair up (prophase I) Meiosis I: Reduce to Haploid KEY TERM: Tetrad Group of 4 chromatids together during synapsis Meiosis I: Reduce to Haploid KEY TERM: Chiasma (chiasmata) Crossing of non-sister chromatids (see crossing over) Meiosis I: Reduce to Haploid Metaphase I: tetrads line up Anaphase I: homologous chromosomes separate Meiosis II: Reduce DNA Amount Works just like mitosis Mitosis vs Meiosis Mitosis vs Meiosis So Many Possibilities… The positioning of tetrads in metaphase determines variability of resulting gametes So Many Possibilities… • If diploid # is 4 chromosomes • 2 x 2 = 4 possible gametes • If diploid # is 6 chromosomes • 2 x 2 x 2 = 8 possible gametes • If diploid # is 46 chromosomes (like us!) • 2 x 2 x 2 x …x 2 = 8 million possible gametes And possibility after fertilization… 8 million x 8 million = 64 trillion possible individuals So Many Possibilities… Crossing over during meiosis I, nonsister chromatids of homologous chromosomes switch places Results in even more genetic variability Mendel and the Gene Idea Mendel’s Experiment Start with 2 purebred plants Cross-pollinate Allow to fertilize Plant resulting seeds to get F1 generation • P (parental) generation = true breeding plants • F1 (first filial) generation = offspring • F2 (second filial) generation = F1 offspring Results for F1 generation So where did the “white” go? Mendel allowed F1 plants to self-pollinate to see if they really had “lost” the white Results for F2 generation About ¾ were purple flower plants About ¼ made white flower plants Led to Law of Dominance: If both types present, one factor masks other Other traits… same results MENDEL’S PRINCIPLES 1. Alternate version of genes (alleles) cause variations in inherited characteristics among offspring. 2. For each character, every organism inherits one allele from each parent. 3. If 2 alleles are different, the dominant allele will be fully expressed; the recessive allele will have no noticeable effect on offspring’s appearance. 4. Law of Segregation: the 2 alleles for each character separate during gamete formation. Law of Segregation • Alternate versions of genes (alleles) account for variation in inherited traits • For each trait, an organism inherits 2 alleles (one from each parent) • Law of Segregation: Can only pass on ONE of these to gametes – why? • When in meiosis does this occur? Law of Segregation Mathematically proven through both generations Remember Punnett squares? What do the letters on outside represent? Letters on inside? dominant (P), recessive (p) • homozygous = 2 same alleles (PP or pp) • heterozygous = 2 different alleles (Pp) Mendel’s Other Law • Remember metaphase I…what controls how those tetrads align themselves? • Are the genes on one chromosome “linked” to the ones on other chromosomes? • So, are they inherited independently of each other…or linked to each other? Phenotype: expressed physical traits Genotype: genetic make-up Law of Independent Assortment • Assuming the genes are on different chromosomes, they are inherited independently of each other… • (Ex: just because you got your Mom’s freckles does not mean you inherited her widow’s peak) • Occurs due to random alignment of tetrads in metaphase I Punnett Square • Device for predicting offspring from a cross • Example: Pp x Pp (P=purple, p=white) Genotypic Ratio: Phenotypic Ratio: Testcross: determine if dominant trait is homozygous or heterozygous by crossing with recessive (pp) Law of Independent Assortment • What happens if you test 2 traits at the same time? (dihybrid cross) • Monohybrid will have typical 3:1 results • Ex: YY x yy Yy x Yy ¾ yellow, ¼ green • What if you cross purebred yellow-round with purebred green-wrinkled? • Will traits “stick” to each other? • Will traits “split up” from each other? Law of Independent Assortment Alleles segregate (and passed on) separately from each other What if the genes are on the SAME chromosome? • Monohybrid cross: study 1 character • eg. flower color • Dihybrid cross: study 2 characters • eg. flower color & seed shape Dihybrid Cross • Example: AaBb x AaBb The laws of probability govern Mendelian inheritance • Rule of Multiplication: • probability that 2+ independent events will occur together in a specific combination multiply probabilities of each event • Ex. 1: probability of throwing 2 sixes • 1/6 x 1/6 = 1/36 • Ex. 2: probability of having 5 boys in a row • ½ x ½ x ½ x ½ x ½ = 1/32 • Ex. 3: If cross AABbCc x AaBbCc, probability of offspring with AaBbcc is: • Answer: ½ x ½ x ¼ = 1/16 The laws of probability govern Mendelian inheritance • Rule of Addition: • Probability that 2+ mutually exclusive events will occur add together individual probabilities • Ex. 1: chances of throwing a die that will land on 4 or 5? • 1/6 + 1/6 = 1/3 Segregation of alleles and fertilization as chance events Extending Mendelian Genetics The relationship between genotype and phenotype is rarely simple Complete Dominance: heterozygote and homozygote for dominant allele are indistinguishable • Eg. YY or Yy = yellow seed Incomplete Dominance: F1 hybrids have appearance that is between that of 2 parents • Eg. red x white = pink flowers Codominance: phenotype of both alleles is expressed • Eg. red hair x white hairs = roan horses Multiple Alleles: gene has 2+ alleles • Eg. human ABO blood groups • Alleles = IA, IB, i • IA,IB = Codominant Blood Typing Phenotype (Blood Group) Genotype(s) Type A IAIA or IAi Type B IBIB or IBi Type AB IA IB Type O ii Blood Transfusions • Blood transfusions must match blood type • Mixing of foreign blood clumping death • Rh factor: protein found on RBC’s (Rh+ = has protein, Rh- = no protein) Blood Typing Problem: • A man who is heterozygous with type A blood marries a woman who is homozygous with type B blood. What possible blood types might their children have? Polygenic Inheritance: the effect of 2 or more genes acting upon a single phenotypic character (eg. skin color, height) Nature and Nurture: both genetic and environmental factors influence phenotype Hydrangea flowers vary in shade and intensity of color depending on acidity and aluminum content of the soil. Mendelian Inheritance in Humans Pedigree: diagram that shows the relationship between parents/offspring across 2+ generations Woman = Man = Trait expressed: Pedigree Analysis Genetic Disorders Autosomal Recessive • • • • Cystic fibrosis (CF) Tay-Sachs disease Sickle-cell disease Phenylketonuria (PKU) Autosomal Dominant • Huntington’s disease (HD) • Lethal dominant allele Animal Reproduction • Both asexual & sexual reproduction in animals (some do both) • Asexual reproduction may include… • Budding – new individuals grow off of a part of adult • Fragmentation (& regeneration) – body breaks into parts & all of them can grow into adults • Advantages *best in stable environments* • Don’t need partner (good for isolated or nonmotile) • Multitudes of offspring in short time (colonize quickly) Reproductive Cycles & Patterns • Most animals have reproductive cycles WHY? • allows for conserving energy & reproducing at optimal times • Controlled by variety of hormonal & environmental cues Such as…? - temp, day-length, rainfall, etc - Ex: light pineal gland melatonin pituitary gonads Reproductive Cycles & Patterns • Parthenogenesis – egg develops into adult • Ex: Daphnia – asexual when conditions good, sexual when under stress conditions…why? Reproductive Cycles & Patterns • Parthenogenesis – egg develops into adult • Ex: whiptail lizards…lost “maleness”, but still use sex act to stimulate egg/offspring production; alternate between “male behavior” and “female behavior” • What evolutionary advantage? Reproductive Cycles & Patterns • Hermaphroditism – • Has both male & female parts • Sequential hermaphoriditism • Selective advantage? Reproductive Mechanisms • Internal Fertilization • Fewer zygotes, more care • External fertilization • More zygotes, less care Complex Reproductive Structures Human Male • Structures • Check out the pic…testes most important! • Hormone Patterns • FSH & LH • Stimulate testes to act • Testosterone • Make sperm • Secondary sex characteristics Spermatogenesis vs Oogenesis • 4 sperm cells • 1 egg cell (& 3 polar bodies) • Production starts at puberty, • Production before birth, but lasts much longer arrested until puberty • Sperm must be modified • Egg cell keeps most of the before viable (tails, organelles & cytoplasm… VERY acrosomes, etc) LARGE Complex Reproductive Structures • Human Female • Structures • Ovaries! • Hormone Patterns • FSH • Stimulates follicle • LH • Stimulates ovulation • Estrogen • Sex characteristics; ovaries • Progesterone • Get uterus ready Animal Development • Epigenesis • Determined by genome & egg’s organization of cytoplasm • Fertilization • Acrosome action: “hat” drops off enzyme to eat thru • Cortical reaction: Ca+ released; changes membrane charge • Activation of egg…fertilization Animal Development • Cleavage • Mitosis…but cells do not separate Animal Development Gastrulation Infolding; forms 3-layered embryo How do they know how to do this? Animal Development • Organogenesis • • • • Folds and splits and clusters Ecto = nervous Meso = muscles & bones Endo = linings Animal Development • Morphogenesis • Changes in cell shape, position, and adhesion The End Warm-Up 1. What is the pattern of inheritance of the trait (shaded square/circle) shown in the pedigree? 1. How many chromosomes are in a human cell that is: a) Diploid? c) Monosomic? b) Triploid? d) Trisomic? THE CHROMOSOMAL BASIS OF INHERITANCE What you must know: • How the chromosome theory of inheritance connects the physical movement of chromosomes in meiosis to Mendel’s laws of inheritance. • The unique pattern of inheritance in sex-linked genes. • How alteration of chromosome number or structurally altered chromosomes (deletions, duplications, etc.) can cause genetic disorders. • How genetic imprinting and inheritance of mitochondrial DNA are exceptions to standard Mendelian inheritance. Chromosome theory of inheritance: • Genes have specific locations (loci) on chromosomes • Chromosomes segregate and assort independently Chromosomes tagged to reveal a specific gene (yellow). Thomas Hunt Morgan • Drosophila melanogaster – fruit fly • Fast breeding, 4 prs. chromosomes (XX/XY) • Sex-linked gene: located on X or Y chromosome • Red-eyes = wild-type; white-eyes = mutant • Specific gene carried on specific chromosome Sex determination varies between animals Sex-linked genes • Sex-linked gene on X or Y • Females (XX), male (XY) • Eggs = X, sperm = X or Y • Fathers pass X-linked genes to daughters, but not sons • Males express recessive trait on the single X (hemizygous) • Females can be affected or carrier Transmission of sex-linked recessive traits Sex-linked disorders • Colorblindness • Duchenne muscular dystrophy • Hemophilia X-Inactivation Barr body = inactive X chromosome; regulate gene dosage in females during embryonic development • • Cats: allele for fur color is on X Only female cats can be tortoiseshell or calico. Human development • Y chromosome required for development of testes • Embryo gonads indifferent at 2 months • SRY gene: sex-determining region of Y • Codes for protein that regulates other genes Genetic Recombination: production of offspring with new combo of genes from parents • If offspring look like parents parental types • If different from parents recombinants • If results do not follow Mendel’s Law of Independent Assortment, then the genes are probably linked Linked genes: located on same chromosome and tend to be inherited together during cell division Crossing over: explains why some linked genes get separated during meiosis • the further apart 2 genes on same chromosome, the higher the probability of crossing over and the higher the recombination frequency Calculating recombination frequency Linkage Map: genetic map that is based on % of cross-over events • 1 map unit = 1% recombination frequency • Express relative distances along chromosome • 50% recombination = far apart on same chromosome or on 2 different chromosomes Exceptions to Mendelian Inheritance Genomic Imprinting • Genomic imprinting: phenotypic effect of gene depends on whether from M or F parent • Methylation: silence genes by adding methyl groups to DNA Non-Nuclear DNA • Some genes located in organelles • Mitochondria, chloroplasts, plastids • Contain small circular DNA • Mitochondria = maternal inheritance (eggs) Variegated (striped or spotted) leaves result from mutations in pigment genes in plastids, which generally are inherited from the maternal parent. Genetic Testing Reasons for Genetic Tests: • Diagnostic testing (genetic disorders) • Presymptomatic & predictive testing • Carrier testing (before having children) • Pharmacogenetics (medication & dosage) • Prenatal testing • Newborn screening • Preimplantation testing (embryos) Prenatal Testing • May be used on a fetus to detect genetic disorders • Amniocentesis: remove amniotic fluid around fetus to culture for karyotype • Chorionic villus sampling: insert narrow tube in cervix to extract sample of placenta with fetal cells for karyotype Nondisjunction: chromosomes fail to separate properly in Meiosis I or Meiosis II Karyotyping can detect nondisjunctions. Down Syndrome = Trisomy 21 Nondisjunction Klinefelter Syndrome: 47XYY, 47XXY Nondisjunction Turner Syndrome = 45XO Chromosomal Mutations Chromosomal Mutations Nondisjunction • Aneuploidy: incorrect # chromosomes • Monosomy (1 copy) or Trisomy (3 copies) • Polyploidy: 2+ complete sets of chromosomes; 3n or 4n • Rare in animals, frequent in plants A tetraploid mammal. Scientists think this species may have arisen when an ancestor doubled its chromosome # by errors in mitosis or meiosis. Review Questions 1. What is the pattern of inheritance of the trait (shaded square/circle) shown in the pedigree? 1. How many chromosomes are in a human cell that is: a) Diploid? c) Monosomic? b) Triploid? d) Trisomic? Chi-Square Analysis Practice • Two true-breeding Drosophila are crossed: a normal-winged, red-eyed female and a miniature-winged, vermillion-eyed male. The F1 offspring all have normal wings and red eyes. When the F1 offspring are crossed with miniature-winged, vermillion-eyed flies, the following offspring resulted: • 233 normal wing, red eye • 247 miniature wing, vermillion eye • 7 normal wing, vermillion eye • 13 miniature wing, red eye • What type of conclusions can you draw from this experiment? Explain your answer. Definitions: Closing Questions • Sex-linked gene 1. A white-eyed female fruit-fly is mated with a redeyed male. What genotypes and phenotypes do you • Barr body predict for the offspring? • SRY gene 2. Neither Tim nor Rhoda has Duchenne muscular • Linked dystrophy (X-linked recessive disorder), but their genes firstborn son has it. What is the probability their 2nd • Linkage child will have it? map 3. Colorblindness is a sex-linked recessive trait. A colorblind male and a female with normal vision have a son who is colorblind. What are the parents’ genotypes? Closing questions 1. What is a Barr body? 2. How are linkage maps constructed? (See your textbook) 3. What does a frequency of recombination of 50% indicate? Fake Quiz! • PURPOSE: • Take note of what you know and what you do not know! • You do NOT need to write full sentences – use short, quick phrases Fake Quiz! • 1. What was Mendel’s basic experiment? What was result of F1 (first set of offspring)? Why? • What was result of F2? Why? • 2. Which is better – sexual or asexual reproduction? Defend! (What defense would you have for the opposite choice?) • 3. What are the events of G1,S,G2? What are the events of Pro I? Meta I? Ana I? Why is meiosis II even needed? Fake Quiz! • 4. Identify 3 processes/events that contribute to genetic variation. For each, describe what it means and when it happens. • 5. What does the law of independent assortment state? When do these events happen? • 6. What does the law of segregation state? When do these events happen? FRQ - Unit X: Meiosis & Reproduction • 35. -- 3 points maximum (4 available) – • NOTE: if it says “TWO”, only the first two mentioned are eligible for grading – be careful! • A) 2 maximum • 1 – copy DNA, make sister chromatids, etc • 2 – sisters pulled apart (not homologous chroms!) • 3 – sisters align (in preparation for pulling apart) • 4 – cell/cytoplasm/CM actually splits into 2 • 5 – chromatin coils to chromosomes (easier to pull) FRQ - Unit X: Meiosis & Reproduction • 35. -- 3 points maximum (4 available) – • NOTE: Must state both parts – FOLLOW THROUGH! • B) 2 maximum • 1 – # divisions (1 vs 2) OR # resulting cells (2 vs 4) • 2 – ploidy of daughter cells (haploid vs diploid) • 3 – crossing over (yes vs no) • 4 – hom-chrom separate/ind.assort/synapsis (Y vs N) FRQ - Unit X: Meiosis & Reproduction • 36. -- 3 points maximum – • NOTE: if it says “TWO”, only the first two mentioned are eligible for grading – be careful! • A) 2 maximum B) 1 maximum • 1 – faster - genetic • 2 – more offspring overall variation!!! • 3 – less overall energy • 4 – no mate required • 5 – no gonads/meiosis • 6 – 100% genes passed on FRQ - Unit X: Meiosis & Reproduction • 37. -- 4 points maximum – • NOTE: for parth, must address mate issue! • A) 2 maximum • 1 – DEFINE adult forms from non-fertilized egg • 2 – SEL ADV no mate required • Less energy • Less time • No limitation due to lack of available mates FRQ - Unit X: Meiosis & Reproduction • 37. -- 4 points maximum – • NOTE: follow through…why are there more babies? • B) 2 maximum • 1 – DEFINE orgs with both male & female gonads • 2 – SEL ADV more babies because both fertilized OR no need for mate because can self-fertilize MC - Unit X: Meiosis & Reproduction • Most Missed MC • 9 – A - Did you draw it? • After S, have 4 double-stand chroms = 8 strands DNA • After meiosis, have 2 chroms (1/2), and 2 DNA strands (1/4) • 1 – B – Segregation = when the hom-chroms split • Happens during meiosis MC - Unit X: Meiosis & Reproduction • Most Missed MC • 24 – D – If on same chrom, would not ind-assort • Because not linked, must take into account all possibilities • 11 – C – What happened here? • Meiosis daughter cells NOT same as parents (are haploid) • 17 – D – 22 pairs+XX = 46 is somatic, not gamete • Female = XX