Genetics booklet 1.pdf - Mrs Stovel

Genetics (^• Genetics is the study of heredity• Heredity is the study of how traits are passed from parents to their offspring• To understand heredity, one needs to understand how sexual. reproduction andmeiosis worksSexual reproduction involves the fusion of 2 different cells to make a new cellthat then grows into the new organism. The cells that fuse are called sex cells orgametes or eggs and sperm. Eggs and sperms carry parental traits and the fusionof them produces an offspring with a combination of both parental traits-Meiosis is one of the two main types of cell division. Understanding meiosishelps to explain how the sex cells acquire the traits that they carry.To fully understand meiosis, it is easier to first learn, or review the process ofmitosis, the other main type of cell division.• Mitosis occurs in all living things. It is cell division that produces 2 cells fromone parent cell. The 2 new cells are identical to each other and to the parent cellthat divided. The chromosome number in the 2 new cells is the same as it wasin the parent cell. Mitosis is how tissues grow or are repaired or replaced. Thereare 6 phases.• Meiosis only occurs in sexually reproducing organisms, including animals,plants and many other types of living things. It is cell division that produces 4cells from one parent cell. The 4 new cells are not identical to one another, norare they identical to the parent cell that divided. The chromosome number in thenew cells (called gametes) is one half the number of the chromosomes that werein the parent cell. In animals, meiosis only occurs in ovaries of females andtestes of males. There are 12 phases.• There are similarities and differences between the 2 types of cell division thatwe will examine in detail.• To learn about cell division, we must first learn about a structure called thechromosome.

Chromosomes• Made up of the chemical called DNA (Deoxyribonucleic Acid)• Located in the nucleus of all eukaryotic cells. Contain units called genes• Can exist as 2 different forms:Single, unduplicated or duplicated• When a chromosome exists as a duplicated chromosome, its legs are called "sisterchromatids" or just "chromatids":r ^; ► 11.c.-. Z a(rti^ovna ['iC^S• When a duplicated chromosome exists by itself, it can also be called a "dyad" (because itconsists of 2 chromatids)• Dyads exist during prophase through telophase of Mitosis as well as during prophase IIthrough telophase II of Meiosis !• When a duplicated chromosome exists as a pair, it can also be called a "tetrad" (because itconsists of 4 chromatids)• Tetrads exist only during metaphase I of Meiosis• Homologous chromosomes are chromosomes which are the same size and which carry thesame types of genes. For example, a homologous pair of chromosomes may both carry genesfor eye color at the same spot and for hair color at the same spot. The genes however maycode for different alternatives of the the trait and so homo. Chromos. May not be geneticallyidentical. /Y 9 F--- a ye co [Qr.. ka;r GO 1 or-During meiosis, homo. chromos. may touch each other. This is called "synapsis" (becausethe process closes the gap between the chromosomes, and a gap can also be called asynapse).• Some times, during synapsis, the chromatids may "cross over". If crossing over occurs,sometimes the legs of the chromatids may break off and then re-join in a different way. Newversions of chromosomes may be produced.• The point where the chromatid legs touch each other is called the "chiasmata".

-1m . Gr_-t4 TIc -Chapter 7 - MeiosisReview.el IPages 155-169 (fe +e ck)co r P. 13$-1J}-c ''1 QChromosomesCentr iol esSpindlesMitosis - definition and general idea of phases-- inter-, pro--, meta-, ana-, and telo-phasesCytokinesisSexual reproduction (vs. asexual)gameteszygoteNew; .Meiosis - definitionhaploid vs. diploid p.170 (7.153 e)Homologous Chr omosomes p. 171 Cip. \ s;- 9)Genetic Recombination what is it? p.171 ( S^t3)a) independant assortment p 174 and fig. 7.24( p. I foo) (E- 7.2-k) (0u e )b) crossing over p 176 and f ig. 7. 25B.( t, t +60 (. 2 1Meiosis stages - p 173 fig 7.23^,S $) (7. ?-D)Explain the heading on p,170 "Meiosis -- a reshuffling and1.5(,4) reduction of chromosomes"Other Terms tetrad, dyad, kinetochore, maternal vs. paternalchromosomes, centromere, chromatid, SYY1 ctpS/S,GhraSrn^* DNA rcpt- cctl"ion.

Rules of Heredity1. A hereditary trait is governed by a sequence of DNA called a GENE. ( some virusescontain RNA, therefore their genes are encoded in RNA sequences)2. Genes reside on chromosomes.3. The gene for each trait can exist in two or more alternative forms called ALLELES.a. ALLELES help to determine the organism's:i) the external appearanceii) biochemical functioningiii) patterns of behavior4. Most higher organisms have two copies of each gene in every body cell. Body cells arecalled SOMATIC CELLS and are said to be DIPLOID in chromosome number.5. Homologous Chromosomes are two chromosomes that are similar in:a) sizeb) shapec) genetic content6. A HOMOZYGOTE has two identical alleles (copies) of the gene.A HETEROZYGOTE has two different alleles (copies) of the gene.7. A heterozygote may have visible traits dictated by only one of the alleles, called theDOMINANT ALLELE.The HIDDEN ALLELE i s called the RECESSIVE ALLELE8. The PHENOTYPE is the way an organism looks and functions.The GENOTYPE is an organism's genetic makeup and is represented by symbols.9. Pairs of alleles SEPARATE-----SEGREGATE during egg and sperm formation-MEIOSIS- resulting in sex cells ( gametes) each having one copy of a gene in it. Such a cell is said tobe HAPLOID or MONOPLOID in chromosome number.10. According to the principle of INDEPENDENT ASSORTMENT, genes ondifferent chromosomes ASSORT into gametes INDEPENDENTLY of each other.11. LINKED GENES lie on the SAME CHROMOSOME and tent to be packaged intogametes together.12. Occasionally, two genes on the same chromosome may become separated owing to anexchange of alleles between that chromosome and its homologous partner in a processcalled, RECOMBINATION---CROSSING OVER.

NameDateCASeyt us *UK+%ooI6.60 ,ti Diagram 21 MitosistI^at etc-k c,-„ re sCopyright is 1984 by Addison- Wesley Publishing Company, Inc.Biology

Name DateUse- '/ouLc- b ea kAwod 41^f-W Diagram 22 MeiosisBiology Copyright Qc 1984 by Addison- Wesley Publishing Company, Inc.

02,001 LIFE SCIENCES ON FILECONTINUITYCell division 02.001A Mitosis4 Daughter cellsB Meiosis4a Diploid. identical to parental cellb Haploid. not identical to parental cell9 Diploid parental cell with one pair of homologous 5 Second meiotic divisionchromosomes6 Haploid gametes2 Chromosomes duplicate to form pairs of chromatids3 Cell division3s Mitotic division3b First rnetotic division

Background for understanding Genetic VariationRECALL the process of mitosis'inter phaseprophasele^_VIPmetaphaseanaphasetelephasecytokinesis02 identicle diploid daughtor cellsThe process of MEIOSIS is what allows for variations betweenmembers of the same species. This kind of cell divisionproduces 4 non-i.denticle haploid sex-cells. Meiosis occurswhen the cell that is dividing has its' DNA double duringinterphase I but not during the second interphase. Alsoduring MEIOSIS, the formation of tetrads due to the pairing'of HOMOLOGOUS (similar shapes and sizes) chromosomes results(during metaphase I). This allows for more variations ifCROSSING OVER occurs.Sep: cells must have only 1/2 of the species' chromosome # sothat when they unite to form a zygote, the originalchromosome is restored. (and not doubled).When 2 sex cells (each haploid) unite to form a diploidzygote, there are 2 sets of each chromosome - one set ismaternal (from the mother) and the ether is paternal.When this zygote grows and developer into an adult, theadult will also meioti€-ally produce haploid gametes. Thegametes that it produces can contain either maternal orpaternal chromosomes or a combination of both.(AV

^ N t . VA k, ^A t 1(0RANDOM ASSORTMENT OE MATERNAL (BLACK) 1\N PATERNAL (WHITE) CHROMOSOMESfURINC MEIOSIS IN AN ORc NISM WITH A DI PLOID 1TT1MBF;'R OP 0(2n=6)If the maternal chromosomes align themselves on one side of thequator and the paternal chromosomes on the other, the gametes wouldbe the same (necflecting cross, over) as those they received from theirparents. "BUT" A six others are equally likely.

02.008 LIFE SCIENCES ON FILE `"CONTINUITYCrossing over and genetic variation 02,008A No crossing over8 Sing le crossing overC Double crossing over1 Homologouschromosomes2 Chromatids3 Alleles4 Centromere5 Chiasma5 Chiasmata7 Chromosome variationin the four haploidgametes

Mitosis and Meiosis Compared1. (a) One of the diagrams on the left represents the metaphase stage of mitosis and theother diagram, the metaphase stage of meiosis. On the line below each diagram, name thetype of cell division which is shown.(b) Draw the appropriate number of chromosomes of each color (black or white) in theblank cells that are to the right of the original (parent) cell which is on the left.2. Underline the correct choice in each of the following sentences.(a)The gametes produced by meiosis are (haploid cells, homologous pairs, diploid cells)(b) In the two successive cell divisions of meiosis, the chromosomes replicatethemselves (once, twice, not at all)(c) Crossing over, which results in an exchange of material between homologouschromosomes, occurs during (interphase, replication, synapsis)

Crossing Over in Meiosis1. (a) Diagram .shows a cell with a single pair of homologous chromosomeslying alongside one another. What processin meiosissdoes this represent?or also known as(b) In the diagram, what do letters A,B,C,a,b,c represent?2. What g tc je in meiosis is shown in diagram II?3. Assuming that the four cells in diagram IV are the products of meiosis of theoriginal cell, draw the chromosome as they appear during reduction division.4. Underline the correct choice in each of the following sentences.(a) The four cells in diagram IV are called (a tetrad, haploid gametes,contrasting gametes)(b) In the stage of meiosis shown in diagram II, there is an exchange of(homologous chromosomes, haploid gametes, genetic material)(c) The zygote which results from fertilization is a (haploid cell, haploid gamete,diploid cell).5. It is the relationship between the on eachpair of homologous chromosomes that determines the hereditary traits of an organism.

N f/Rules of Heredity Quiz1. A hereditary trait is governed by of DNA called a. ( some viruses contain RNA, therefore their genes are encodedin RNA sequences)2. Genes reside on3. The gene for each trait can exist in two or more alternativeforms calleda. ALLELES help to determine the organism's:i) external appearanceii) biochemical functioningiii) patterns of behavior4. Most higher organisms have two copies of each gene in everybody cell. Body cells are called and are said to bein chromosome number.5. Chromosomes are two chromosomes that aresimilar in:a) sizeb) shapec) genetic content6. a) A zygote has two identical alleles (copies) of thegene.b) A ZYGOTE has two different alleles (copies) of the gene.

27. a) A heterozygote may have risible traits dictated by onlyone of the alleles, called theALLELE.b) The HIDDEN ALLELE is called the ALLELE8. a) The is the way an organism looks andfunctions.b) The is an organism's genetic makeup andis represented by symbols.9. a) Pairs of alleles during egg andsperm formation.b) Meiosis - results in the formation of eachhaving one copy of a gene in it.c) Such a cell is said to be orin chromosome number.10. According to the principle of ASSORTMENT,genes on different chromosomes ASSORT into gametesINDEPENDENTLY of each other.11. LINKED GENES He on the CHROMOSOME andtent to be packaged into gametes together.12. Occasionally, two genes on the same chromosome maybecome separated owing to an exchange of alleles between thatchromosome and its homologous partner. This usually occursduringin a process called

MEIOSIS KITMATH'.RTAi1.2 Homologous Chromosomal pairs represented by:a) Long Natural Colored wood splintb) Long Red Colored wood splint Jc) Short Natural Colored wood splintd) Long Red Colorid woodlspihist.-:2. Replicas for each chromosome mentioned aboveNOTE: The Long pair of chromosomes have three genes designated on them,represented y letters A C D E E or a c d e f. Each of these groups make up aLINKAGE GROUP, CTke sha--- pv-'r ko ve 3ene s XC YZ of -x U^dre:1. Using a piece of chalk draw a cell on your table- top making about 1/2 t he tablesize.Represent the nuclear area with an oval structure inside the cell boundary.2. Place 2 homologous chromosomal pairs in the nucleus. This will be ourDIPLOID NUMBER of chromosomes (2n). C 5{ ^c ks^ I f' k len^f rol.-r1, 1.3. Using your reserve sticks(chromosomes) show each homologue replicated. Eachis now called a CHROMOTTD, and there should now be twice the number ofchromosomes (sticks) present as before, or (8)^.4. Erase the nuclear membrane.5. Draw in two spindle fibers. Lines originating at the ends(poles) of your'cell-andconnecting with each other fig the shape of a football..6. Seleedt the RED LONG replicated pair (a dyad) and place them on a spindlefiber line at the center of the cell:Select the NATURAL LONG replicated pair ( a dyad) which is homologous tothe first pair and place them to the RIGHT of the first pair at the center of the cell.!r,SUCH A GROUPING IS SAID TO BE A TETRAD =, Four`THE EVENT:: SYNAPSIS C% 5 c e e x ► 5be-fweel t'vY1

7. Do the same for the short chromosomal pairs. Be sure to place the naturalcolored ones to the right of the red colored ones. can L offqei Sp r j i )Now you have TWO TETRADS at the center or EQUATOR of the cell.8. Move the dyads away from each other until they approach the ends of the cell.(ei)awe 5eivdte 1krwes)9. Enclose them within a nuclear membrane ( use the chalk).10. Pinch in the cell boundary (membrane) so that two cells are formed.This is the end of Meiosis I.NOW WE ARE DEALING WITH TWO CELLS11. Erase each cell's nuclear membrane (chalk line) once again draw in two spindlefibers in the shape of a football.2. Move each chromatid of a dyad to the opposite end. of each cell.13.Enclose the chromosomes within a nuclear membrane.14. Pinch in the cell boundary ( use the chalk) to form two cells.Since we were dealing with two cells; four cells are created.This is the end of MEIOSIS II.-DRAW -`)The color and gene combinations in each of. the four cells formed.15. Return to step #6 and set up as instructed.16. Return to step #7 now place the natural colored chromosomes the left of the redones. Then continue as before.i) The color and gene combinations in each of the four cells formed.Compare the differences formed by aligning the tetrads differently during MEIOSIS1.These differences are due to RANDOM ALIGNMENT and- INDEPENDENTASSORTMENT during synapsis. In actual cell divisions of this sod ( sex cellformation) chromosomes can align in two different ways ( when using two pairs).Since hundreds of millions of cells are engaged in these types. of divisions we willget various genetic combinations based on probability.17. How could you get the following gene combination in a gamete (sex cell)A C d e F ? ^ d e s cr ^ ^e key ; v wog- s --- o„' + b f fide s h .k f '

TG help understand how chromosomes move duringcell division, compare mitosis and meiosis. Focuson the processes of replication, alignment, andseparation as you draw chromosomes in the,,m,tv cells. First do mitosis (cells 1-13); afterstudying meiosis, come back and fill in cells Homologous21-31Mitosis:1 How many chromosomes are in cell 1?.... .2 is cell 1 " haploid or, diploid? . .. .3 How many chromatids does each chromosomehave in cell4 Is cell 2 haploid or diplaii5 in which phase 4A osi s is 1137 -6 How similar geneticallySis 611 4:10 cell 5? "chromosomestC ov# similar eneticalfy is cefl,l3 to cell i?'Meiosiscell 22hatilaidordip#ed?at is ie PYI if ere n chramasomenment betwe cell23:a cell 3?3 Comparese [o mologouscsames a_F sist , chamati sari t3 and'cell-234 Is cell 24haproiaordi laid?5 How marry^clrina3ids d eahave in cell IM6 Compare th :rep ic^iairs ep be wt enEceand 71t' thiit he entell 25 € nd 2j9 Is cell 32 haploid or`diploidr^'10 Crossing ve noo n rs figurer if it^dwere iii ivhiclt c vtou d ocr^x "kt^1f0SIS ME 10515

nLLI. Law of Dominance - when one allele (an alternate form of a gene) completely masksthe effects of the other allele.2. Law of Segregation - occurs during cell division, in this case, the "law" mostspecifically applies to meiosis. Each sex cell ends up containing only I allele of each gene(genes always exist as a pair of alleles) because the 2 alleles segregate (or separate). Eachallele ends up in a different cell.3. Independant Assortment - is the "random assortment of parental chromosomes intogametes" . It occurs only during meiosis. Maternal and Paternal chromosomes(homologous, and genetically similar in the types of genes but not necessarily identical inalleles) randomly line up on either side of the cell (during metaphase I) which is about todi=i e. There is no specific designation as to which side of the cell that the maternalchromosomes go or which side the paternal ones go.... they line up and "assort" totallyrandomly or "independently" of each other, The end result is that there are many differentcombinations of maternal and paternal chromosomes.... each different combinationrepresenting a different kind of gamete.The number of different kinds of gametes that are possible depends on the number of ofdifferent kinds of chromosomes that a cell contains.The formula 2n can be used to calculate the number of different kinds of gametes that aparent cell can produce. (n = the # of chromosomes in the gamete...i.e. the haploid #)ex. A-cell with a diploid number of 6 chromosomes has a haploid number of 3so, 23 = 8 different kinds of gametes are possible.Question 1: How many kinds of gametes can a normal human (male or female) produce?Question 2: How many different kinds of human beings are possible, given the differentkinds of gametes that both a male and a female can produce? (i.e how many differentzygotes can be produced)?Question 3: "Independant Assortment explains both the DIVERSITY and the UNITY of N.life"....explain this statement. (check out your text p. 174 - 175 1 I)(or f - Ib1 - lb 2 w' B Ive e c

Mitosis and MeiosisSummary of Mitosis• Occurs in somatic/body cells• Produces new somatic/body cells• One parent cell divides to produce 2 identical daughter cells - the chromosome #of both daughter cells is the same as the chromosome # of the parent cell.• The chromosome # of both the resulting daughter cells and the parent cell isDIPLOID - that is - each cell contains TWO sets of each different kind/length ofchromosome• There are 6 phases1. InterphaseThe longest phase in the process. The cell is living/growing for most of this phase. Atthe very end of this phase, the chromosomes double in number2. ProphaseThe chromatin threads in the nucleus shorten and thicken into chromosomestructures.... the characteristic "X" shaped bodies. Structures called spindles form(spindles will later help to align the chromosomes properly).3. MetaphaseThe chromosomes (with the help of kinetochores and spindles) will line up, singlefile, down the MIDDLE of the cell.4. AnaphaseThe chromosomes split at the centromere (button) into 2 chromatids, and the 2chromatids migrate to opposite poles of the cell.5. TelophaseThe split up chromatids arrive at the poles. The cell now contains 2 separate nuclei.6. CytokinesisThe cytoplasm of the cell divides, to complete the division of one cell into 2 cells.Summaof Meiosis• Occurs only in sex organs (ex. Ovaries and Testes)• Produces sex cells/gametes (eggs and sperm)• One parent cell divides twice to produce 4 non-identical daughter cells - thechromosome # of all 4 daughter cells is HALF of the chromosome # of the parentcell. Because the chromosome 4 is reduced, meiosis is called reduction division

• The chromosome # of the 4 resulting daughter cells is HAPLOID, whereas thechromosome # of the parent cell is DIPLOID. Haploid (also calledMONOPLOID) means that each sex cell has only ONE copy of each type/lengthof chromosome.• There are 12 phases; the same 6 from mitosis, repeated twice. Most phases havethe same thing occurring as in mitosis, with 3 exceptions:1. Interphase I - same as mitosis2. Prophase I - same3. Metaphase I - chromosomes line up in tetrads/homologous pairs (not single file)4. Anaphase I - same5. Telophase I - same6. Cytokinesis I - same7. Interphase II - chromosomes DO NOT double8. Prophase II - same9. Metaphase II - chromosomes line up in single file (same as in mitosis)10. Anaphase II - same11. Telophase II - same12. Cytokinesis II - sameMitosis and Meiosis:Differences Mitosis Meiosis# of phasesInterphaseChromosomes double at theend of InterphaseMetaphaseChromosomes line up in singlefile# of cells reproducedChromosome # ofreproduced cellsDiploidAre the cells reproducedidentical to one another?No