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Ch 9&10

by: Holly Notetaker
Holly Notetaker

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Chapter 9 & 10 notes for biology
Class Notes
Biology, 101
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This 24 page Class Notes was uploaded by Holly Notetaker on Thursday September 1, 2016. The Class Notes belongs to at Southeastern Louisiana University taught by in Fall 2016. Since its upload, it has received 3 views. For similar materials see Biology in Science at Southeastern Louisiana University.


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Date Created: 09/01/16
Chromosome Overview DNA – deoxyribonucleic acid - composed of: 5-C sugar (deoxyribose), phosphate group, organic base - information encoded in DNA is organized into genes = segments of DNA that transmit information - as the cell prepares to divide, DNA strands coil into tight bundles called chromosomes = rod-shape structures that consist of a single DNA molecule {40%} and it proteins {60%} - only visible in this form These cells are diploid (2n) “two-fold, like” = a full set of chromosomes - these are body cells = somatic cells Some cells are haploid (n) “single, like” = a half set of chromosomes - haploid cells are called gamete (n) - unfertilized eggs or sperm/pollen - only has half the number of chromosomes - not complete - 2 haploid cells form a zygote (2n) = fertilized cell sister chromatids - identical to each other - each new cell has the same information - sister chromatids are attached at the centromere “center, part” Chromosomes come in pairs called homologous chromosomes “agreeing, corresponding” - look alike – same length and centromere location o 1 inherited from mom, 1 from dad - they code for the same traits - alleles = alter forms of a gene mitosis = division of somatic cells (body cells) in eukaryotes - identical clones of the mother cell for: growth, repair of dead cells and damaged tissue 1 meiosis = division to create sex cell in eukaryotes - reproduction of individual to create offspring autosomes (body chromosomes – same in both sexes) vs. sex chromosomes Patterns of Inheritance History: Early Humans wolves  dogs 100,000 years ago Native Americans corn  300 varieteis from 1 wild type selected breeding (monoculture) First Hypothesis: Pangenes - blood passes on trait (characteristics) Arstolte “blue-blood” Blending - traits from parents blend together red flower * white flower = pink flower Charles Darwin – Father of Evolution - tried to tie his theories of evolution with genetics o blending - didn’t take into account variation among species - didn’t know of Mendel’s work at the time Mendel, Pea Plants, and Inheritance Patterns Gregor Mendel – Father of Genetics 1860’s - Austrian monk - used math and science together for the first time - studied pea plants = very distinct traits (height, flower color, …) = can self and cross fertilize/pollinate them = fast generation rate = produce large numbers of offspring (high sample size) = work lost for 30-40 years, than resurfaced 2 Parts of the Flower: stamen – male part of flowering plants anther – pollen-bearing portion of stamen filament – stalk of the stamen pistil – female part (reproductive structure) stigma – where pollen adhere to the female part style – between stigma and ovary ovules in ovary – site of seed development As Viewed by Modern Genetics: gene = traits that can be passed from one generation to the next diploid (2n) = full set of chromosomes mutation = alters a gene’s molecular structure and its message about a trait hybrid = offspring that has inherited nonidentical alleles for the trait allele “parallel” = two copies of the same gene, alternate forms of a gene gene locus = the particular site where alleles occur on a homologous pair of chromosomes dominant allele = expressed allele, will mask the recessive allele (T) recessive allele = only expressed in the absence of the dominant allele (t) homozygous “same, yoke” = having the same allele for a particular gene, both alleles are alike (TT, tt) homozygous dominant = TT, both alleles dominant homozygous recessive = tt, both alleles recessive heterozygous “different, yoke” = having different alleles for a particular gene (Tt) 3 genotype “birth/origin/race; image/shape”= actual genetic material (TT, Tt, tt) phenotype “appear; image/shape” = physical expression of a trait (tall, short) true breeding – homozygous; self-fertilization yield offspring identical to self for a given trait wild type allele – the most comment form (genotype) or expression (phenotype) within a population mutant – a variant that arises when a gene undergoes a mutation Mendel’s Theory of Segregation Monohybrid Inheritance monohybrid – crossing of one trait (characteristic) Tall * Short P 1“parental) (true-breeding) (true breeding) st All Tall F 11 filial – child) (self) Tall (3): Short (1) F 2offspring of F )1 In textbook, review the process of meiosis and apply to Mendel’s work. In textbook, review results of other traits in pea plants Law of Probability: - able to calculate the probable results of one-trait cross 4 Punnett Squares - probability of genetic inheritance - R. C. Punnett developed this method in 1900”s Monohybrid Crosses: practice doing them Pp * pp (P = purple flower; p = white flower) SS * ss (S = smooth seed shape; s = wrinkle) EE * Ea (E = free ear lobe; e –attached) on exam, you will need to figure out genotype and phenotypes Mendel’s Results Law of Dominance In the presence of the dominant allele, the recessive allele is NOT expressed Law of Segregation For every trait in an individual there are two factors (alleles), and they separate (meiosis) and are recombined randomly during inheritance. One-Trait Testcross – allows you to determine the unknown genotype of a parent (curly tail pig {CC, Cc}, straight tail pig {cc}) Mendel’s Theory of Independent Assortment Dihybrid Cross – crossing two traits Tall, Green Seed Pod * Short, Yellow Seed Pod P1 (true-breeding = TTGG) (true breeding = ttgg) ALL Tall F 1 Green (self - TtGg) Tall-Green (9): Tall-Yellow (3): Short-Green (3): Short-Yellow (3F 2 5 Dihybrid Problems: male genotype female genotype LLGG * llgg (L = long wing, l = short wing; G = gray body, g = black body) FOIL – allows you to figure out all possible combinations (male vs. female) F = first alleles on each genotype (LG vs. lg) O = outer alleles on each genotype (LG vs. lg) I = inner alleles on each genotype (LG vs. lg) L = last alleles on each genotype (LG vs. lg) male genotype female genotype LlGg * LlGg F = first alleles on each genotype (LG vs. LG) O = outer alleles on each genotype (Lg vs. Lg) I = inner alleles on each genotype (lG vs. lG) L = last alleles on each genotype (lg vs. lg) Law of Independent Assortment: Members of the one pair of factors segregate independently of members of another pair of factors. Therefore, all possible combinations of factors can occur in the gametes.  traits are NOT linked together  law of probability and Punnett Square · review meiosis again (where do the alleles come from ) Two-Trait Testcross: allows you to determine the unknown genotype of a parent with two traits long wing, gray fruit fly * short wing, black fruit fly (LLGG, LlGg) (llgg) 6 Impact of Crossing Over on Inheritance linkage groups = genes on the same chromosome that are inherited together - fruit flies = eye color, wing type, body color, leg length, and antennae type are all located on the same chromosome Patterns of Inheritance Beyond Mendel: - does not follow Mendel’s work because of: - variations in the dominant/recessive relationship - two alleles for one trait is too restrictive - some genes work together to bring about a phenotype co-dominance* = more than one dominate allele, so they can both be equally expressed ex.: blood type (A, B, AB, O) multiple alleles = more than two alleles for a single gene locus and there are more than two possible phenotypes among the offspring blood type*: Phenotype: Genotype: A AA, AO B BB, BO AB AB OO OO rabbit coat: C > cch > ch > cc (wild type) (Himalayan) (light grey) (albino) incomplete dominance = the dominate allele does NOT mask the recessive allele, but a new intermediate phenotype appears ex.: snapdragon - not “blending”  R1R1= red; R1R2= pink; R2R2= white - biochemical explanation 7 R R = red  produce full pigment 1 1 R 1 2 pink  produce half pigment R 2 2 white produce no pigment - alleles can code for a produce like pigment - human examples: hair texture (curly vs. wavy vs. straight); sickle cell disease; Tay-Sachs disease epistasis “on, standing” – part of polygenic inheritance = gene at one locus interferes with phenotypic expression of a gene at a different locus - sometimes a recessive pair of alleles at one site prevents the expression of a dominant allele at another site - both loci must have a functioning gene for the dominant phenotype to appear - in sweet peas: if one of the genes is hom. rec., then the result is a white flower regardless of the presence of the dom. allele (AAbb * aaBB) - in mammals, epistasis occurs with the blocking of pigments resulting in an albino individual - disorders in humans: cleft plate, clubfoot, diabetes, schizophrenia, cancers, some allergies - maybe some behavior disorders: alcoholism, phobias, suicide??? pleiotrophy “more, turning” = a single gene effects more than one trait - Marfan syndrome  lack of the protein fibrillin results = tall and thin with long arms, legs, fingers = nearsighted with a weak aorta ex. Abraham Lincoln Human Chromosomes Sex Chromosomes = determine the sex of the individual (XX = female/ XY= male) 8 - males determine the sex of the offspring by either donating an X coupled with the female X (XX) or a Y coupled with the female X (XY) - sex chromosomes also carry alleles for other traits - sex-linked refers to traits carried on the X chromosome - Y chromosome carries very few genes - autosomes (nonsex chromosomes) - the same between the sexes What is karyotyping? karyotype = a preparation of an individual’s metaphase chromosomes, sorted out by length, shape, centromere location, and other defining features * read about this - abnormal chromosomes (structure or number) can be detected by comparing it to a standard karyotype for the species Making a Karyotype of Human Chromosomes take cell sample induce mitosis artificially (place in solution to stimulate growth, then division) add colchicines (spend mitosis at metaphase when chromosomes are most condensed)  centrifuge to isolate metaphase cells  place in hypotonic solution (osmosis – makes cells swell)  cells fixed and stained for microscope  photographed  cut out and organized by size and shape Special Karyotypes - fluorescent dyes are used to bind with specific chromosomes for identification of abnormalities, Philadelphia chromosomes Examples of Autosomal Inheritance Patterns Examples of Autosomal Inheritance Patterns: - autosomal dominant means that homozygous dominant or heterozygous genotypes express the disorder 9 - autosomal recessive means that homozygous recessive genotypes express the disorder Autosomal Dominant Inheritance: achondroplasia – also calthd dwarfism affecting growth of long bones; gene located on 4 chromosome. AA – results in death before they can reproduce Aa – results in dwarfism (Aa parents can produce AA, Aa, aa offspring) aa – results in “normal” features (most population is this) Huntington disease – neurological disorder resulting in degeneration of brain cells; caused by mutated copy of gene on 4 chromosome affecting protein producing huntingtin which has too many glutamines in the brain Autosomal Recessive Disorders: - individuals have homozygous recessive - both parents are carries (heterozygous) Galactosemia – does not produce an enzyme to digest milk products - results in a toxic build up which can lead to other health issues and death, if left untreated - reduce symptoms when put on an exclusive dairy-free diet early neurobiological disorders - depression, schizophrenia, or bipolar disease linked to chromosomal mutations Tay-Sachs Disease* – affects seen in Jewish people, lack of enzyme hexosaminidase A (Hex A); results in a build up of glycosphingolipid in lysosomes, individuals tend to die by age 3-4. 10 Cystic Fibrosis* (CF) – affects Caucasians; chloride ion channel does not function correctly; results are mucus builds up; individuals in the past died as infants, today medication has prolonged life into their 30’s. Phenylketonuria (PKU) – lack enzyme needed for normal metabolism of the amino acid phenylalanine; results in a phenylketone accumulates in the urine; can be controlled by diet until individual develops enough to control it; otherwise can cause severe mental retardation; doctors recommend staying on diet for life. Sickle Cell Disease* – affects seen in African Americans; blood cells are sickle shaped resulting in poor oxygen flow in the body; evolved from environmental pressures for malaria (see textbook) SS – homozygous dominant = can die from malaria (big problem in Africa) Ss – heterozygous = protection from malaria and sickle cell ss – homozygous recessive = has sickle cell, dies - large population is heterozygous since homo. dom./rec. tends to result in death of individual * Many of the above diseases are found in a particular race or religious group because people tend to marry like individuals resulting in these genetic diseases continuing within those populations Too Young, Too Old Hutchinson-Gilford disease - autosomal mutation which accelerates the aging process - believed to be a spontaneous mutation effecting lamin A, a protein responsible for organizing the nucleus - early death (late teens) due to heart attack/stroke Sex Determineation in Humans - autosome = body chromosomes; not sex chromosome - humans - 22 autosomes (1-22); 1 sex chromosome (23 ) rd XX = female XY = male 11 Sex Determination in Humans - female gamete one X chromosome - male gamete  half carry the X chromosome, other half Y chromosome one X from mom, one X from dad = XX daughter one X from mom, one Y from dad = XY son - Y chromosome carries 255 genes - Y chromosome has SRY gene – this determines sex - Y – triggers the formation of testes (male gonads) - X chromosome carries 1,141 genes - X chromosome has no SRY gene, less testosterone - forms ovaries (female reproductive organs) - responsible for other sexual differences (body fat, hair) - responsible for nonsexual difference as well like blood- clotting What Mendel Didn’t Know: X-Linked Inheritance X-linked Alleles = traits on the X chromosomes, Y chromosome is blank for these alleles (sex-linked) - fruit flies have same sex chromosome pattern as humans (Thomas Hunt Morgan) - 8 chromosomes – 3 pairs autosomes, 1 pair sex chromosomes - female mates only once, lays hundreds of eggs, short generation R R X R =rred-eyed female X X = red-eyed female X X = white-eyed female X Y = red-eyed male r X Y = white-eyed male - be able to figure out fruit fly genetic problems for exam 12 Examples of X-Linked Inheritance Patterns Human X-Linked Disorders - genetic results found in humans due to the X chromosome - Y chromosomes tends to be absent of traits - disorders are linked the female hemophilia – absence of the clotting factor VIII (hemophilia A) or IX (hemophilia B); called the “bleeders” disease because blood does not clot or clots slowly; biotechnology products are used for treatment; pedigree chart from European royalty (marriages between close relatives) color blindness – three light receptor cone cells in the human eye (1 controlled by autosome chromosomes; 2 by X-chromosomes); some males are color blind due to the recessive allele passed from grandfather (color blind) to daughter (carrier) to son (color blind) muscular dystrophy (DMD) – wasting away of muscles leading to an early death; results from the absence of the protein dystrophin; gene therapy is being used to treat this disorder with some success fragile X syndrome – base triplet repeats in a gene on the X chromosomes (Huntington disease and others) Human Genetic Analysis * read through this material for understanding polydactyly – extra fingers, toes, or both (see pedigree)  Genghis Khan? = Y chromosome pedigrees = constructed of both parents to predict inheritable disorders carriers – do not express the disorder, but can pass it to their offspring syndrome – a specific set of symptoms Genes and the Environment environment Influence 13 = environment effect phenotype (fur changes color – fox, rabbit) - submerged in H O 2an effect the morphology (shape) of plants - in rabbits, temperature can trigger the activation of enzymes which effect coat color  tyrosinase h - Himalyayhn rabbits are homozygous for the c allele - c is heat sensitive - warm temperatures will not produce the darker color, coats appear lighter  allows animals to survive varying seasons - temperature can affect the color of flowers, sex of alligators - humans  transport protein effects the movement of serotonin across the membrane resulting in some humans not handling stress well Complex Variations in Traits polygenetic inheritance “many, producing”(inheritance of multiple alleles) = one trait is governed by several genes occupying different loci on the same homologous pair of chromosomes or on different homologous pairs of chromosomes - dominant allele contributes to phenotype, recessive does not wheat seeds: - pure recessive cross with pure dominant - result is equally intermediate which is crossed - result is 7 phenotypic expressions (various degrees) - bell shaped curve - other factors contribute like the environment and nutrition level of individuals - human examples: hair color; height; skin color; eye color 14 Meiosis and Sexual Reproduction asexual – organisms simply copy their DNA and split its contents - change can occur through mutation - bacteria, archaea, and single-celled eukaryotics sexual – requires two parents, exchange of genetic material - conjugation – exchange of genetic material with a sex pilus between bacteria cells (beginning process of sexual reproduction) o started 3.5 billion years ago  1.5 billion years ago o allows some asexual organisms to exchange genetic info Introducing Alleles and What Meiosis Does Halving the Chromosome Number meiosis = “less, act or process of” - nuclear division that reduces the chromosome # from 2n to n o gametes (egg, sperm/pollen) - 2 gametes fuse to form a zygote (2n) o sexual reproduction - without meiosis, the chromosome # will double with each generation Chromosomes come in pairs called homologous chromosomes “agreeing, corresponding” - look alike – same length and centromere location o 1 inherited from mom, 1 from dad  humans have 23 different chromosomes (46 chromosomes total)  crawfish have 100 different chromosomes (200 total chromosomes) - they code for the same traits - alleles = alter forms of a gene - genes = sequences of chromosomal DNA 1 mitosis = division of somatic cells (body cells) in eukaryotes - identical clones of the mother meiosis = division to create sex cell in eukaryotes germ cells = immature reproductive cells MEIOSIS - cell division to create sex cells (gametes) - mother cell (2n) splits to form 4 daugther cells (n) o 2 nuclear divisions  diploid (2N) to haploid (N) Meiosis I o 2n  n o homologous chromosomes pair up – synapsis “united, joined together” during meiosis 1, prophase I o homologous chromosomes are pulled apart  each new cell has only 1 of the 2 o cytokineisis takes place resulting in 2 daughter n cell Meiosis II o n  n o sister chromatids are pulled apart o cytokinesis takes place resulting in 4 daughter n cells  each cell contains one chromatid Visual Tour of Meiosis Phases of Meiosis I (2n) 4 parts: Prophase I - chromosomes completely condense - homologous chromosomes come together = synapsis - crossing-over occurs (sister chromatids – no longer identical) - spindles begin to form as centrosomes migrate away from each other - nucleus fragments and disappears 2 Metaphase I - homologous chromosomes line-up in the middle of the cell - independent assortment - attached to the spindle at the centromere Anaphase I - homologous chromosomes pulled apart to opposite ends of the cell Telophase Itwo daughter cells are (n) - nucleus reforms - spindles disappear - cytokinesis takes place (cell division) - each cell has half the # of chromosomes = haploid Interkinesis - between mitotic division (no DNA duplication) MEOISIS II: (n) Prophase II - sister chromatids completely condense - spindles begin to form - nucleus fragments and disappears Metaphase II - sister chromatids line-up in the middle of the cell - attached to the spindle at the centromere Anaphase II - sister chromatids pulled apart to opposite ends of the cell Telophase II - nucleus reforms around the one chromatid - spindles disappear - cytokinesis takes place (cell division) 3 - four haploid daughter cells (n) Now, what happens to the gametes? - fertilization or death How Meiosis Introduces Variations in Traits Genetic Variation (3 ways) - meiosis keeps chromosome numbers the same from one generation to the next - this also allows for genetic variation among the species through genetic recombination o each new daughter cell is genetically different than the mother cell  compared to asexual reproduction depend on mutations to change in their genetic code o this insure variation among species, so they can better survive in a changing environment o 2-ways for genetic recombination: 1) crossing-over of nonsister chromatids = an exchange of genetic material between nonsister chromaids of a bivalent - occurs during Meiosis I – Prophase I - within the gamete itself 2) independent assortment of homologous chromosome = homologous chromosomes separate independently and randomly from each other o occurs during Meiosis I – Metaphase I o they do not line-up in the middle of the metaphase plate in any specific order 4 o when new daughter cells form, they contain a mixture of chromosomes from each parent  increase possible combinations  within the gamete itself 3) Fertilization 2 gametes (n) creating a zygote (2n) this greatly increases genetic variation by the introduction of a new and different set of chromosomes Mitosis and Meiosis – An Ancestral Connection? Mitosis Meiosis DNA replication only once DNA replication only once 1 nuclear division 2 nuclear divisions 2n  2n 2n  n  n mother cell  2 daughter cells mother cell  4 daughter cells identical daughter cells genetically different daughter cells (crossing over & independent assortment) separate sister chromatids separate homologous chromosomes, separate sister chromatids growth and repair (somatic cells) reproduction (gametes) Heritable Changes in Chromosome Structure Chromosomal Mutation (change) = permanent changes in genes or chromosomes that can be passed to offspring if they occur in cells that become gametes - increase gamete variation along with crossing over and independent assortment - changes in chromosomal number - changes in chromosomal structure Changes in Chromosome Structure - some changes can be detected, some not 5 - various agents in the environment, such as radiation, certain organic chemicals, or even viruses, can cause chromosomes to break - damaged chromosomes can repair themselves chromosomal mutation = results when repairs are not made properly Types of Mutation: duplication = 2 copies of the same gene - can cause neural problems and physical abnormalities deletion = lacks a set of genes - William’s syndrome - chromosome 7 results is pixie-like features, wide mouth, small chin, good verbal and musical skills; lacks production of the protein elastin (premature aging of skin) - cri du chat (cat’s cry) syndrome - small head, mentally retarded, facial abnormalities - larynx is abnormal = cat’s cry inversion = gene fragments switched around translocation = fragments of genes join the wrong chromosomes - 5% of time occurs between chromosomes 14 and 21 - Down’s syndrome not related to mother’s age; but in family of either parent - changes between chromosome 2 and 20 - Alagille syndrome results in abnormal facial abnormalities and internal organs and severe itching 6 - some cancers are linked to translocation on chromosome 22 and 9 or on chromosomes 8 and 14 - some mutations can cause spontaneous abortions - some mutations result in the death quickly after birth - or a shortened life span (CF) - some mutations benefit the species allowing change to occur which benefits species in a changing environment Heritable Changes in the Chromosome Number Changes in Chromosome Number aneuploidy: - more or less than the normal number of chromosomes - can be lethal for offspring monosomy (one) – a diploid cell missing 1 chromosome; 2n - 1 nondisjuction (ex: monosomy and trisomy) = occur during meiosis I if members of a homologous pair fail to separate, and during meiosis II if the daughter chromosomes go into the same daughter cell trisomy (three) – a diploid cell with an extra chromosome; 2n + 1 Trisomy 21 = Down syndrome women: extra 21 chromosome – Down syndrome under 30 = 1 out of every 1,500 babies 30-35 = 1 out of every 750 babies over 45 = 1 out of every 16 - gene that causes the characteristics is called Gart gene polyploidy “many, fold” = more than two sets of chromosomes triploids – 3n tetraploids – 4n pentaploids – 5n - not seen in animals, because it tends to be lethal - evolutionary mechanism in plants - 47% of flowering plants are polyploidy 7 (wheat, corn, cotton, sugarcane, fruits) - hybridization = two different species cross - chromosomes double to have matching pairs - in some animals, offspring are usually sterile (horse/donkey = mule) Changes in Sex Chromosome Number: - abnormal number of either the X or Y chromosome - result of nondisjunction in oogenesis or spermatogenesis in the gametes Turner Sydrome – XO; has 1 sex chromosome, missing 1; females with under developed sex organs; can lead normal life Poly-X Females – more than 2 XX (XXX, XXXX) “super females”; tall, thin, slow learners; more than 3X are taller and severely retarded Klinefelter Syndrome – XXY or more X; males; underdeveloped sex organs; slow learners; can lead normal life Jacobs Syndrome – XYY, more than 2 Y’s; nondisjunction during spermatogenesis; males are taller, bad acne, speech and reading problems - geneticist tried to link extra Y chromosomes to crimes, not founded From Gametes to Offspring life cycle – all the reproductive events that occur from one generation to the next similar generation - in plants, there are two adults stages  one 2n (sporophyte), one n (gametophyte) sporophyte = a spore-producing vegetative body of a plant or multicelled alga that grows by mitotic cell divisions from a zygote 8 spore = n reproductive cell that is not a gamete and does not take part in fertilization gametophyte = n multicelled body in which n gametes form during the life cycle of plants and some algae - in animals, adults are always 2n who produce gametes (gametogenesis) during meiosis for reproduction o spermatogenesis “seed, producing”  occurs in males through meiosis (sperm) o oogenesis “egg, producing”  occurs in females through meisois (eggs)  combine the two to produce a zygote  grows through mitosis The Human Life Cycle - Spermatogenesis in Humans o occurs in the testes of males nd  1st spermatocytes (46 chromosomes)  2 spermatocysts (23 sister chromatids)  2 spermatocyts (23 sister chromatids)  spermatids (one chromatid) spermatids will mature to form sperm - Oogenesis in Humans o occurs in the ovaries of females  1st oocytes (46 chromosomes)  2 cells (23 sister chromatids) 2 oocyte “egg, cell” o starts meiosis II, stops during metaphase II o ovulation allows cell to leave ovary o sperm will activate meiosis completion o meiosis is only complete in females after fertilization 9 polar body – might divide, may not o discards unnecessary chromosomes o production of 1 egg and 2-3 polar bodies o cytoplasm supply goes to the 1 egg fertilization – restores chromosomal number by combining gametes from the male and female - variation within each gamete due to crossing-over and independent assortment - fertilization increase variation 10


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