Mitosis vs Meiosis Reflection 314 Describe the chromosome

Mitosis vs. Meiosis

Reflection 3/14 – Describe the chromosome disorder you have in your study. 3/16 – Contrast diploid and haploid cells.

• Defined: Tightly coiled DNA • Forms during cell division – New chromosomes created for new cells • 2 Parts: – 1) Chromatids: two identical parts of a chromosome – 2) Centromere: Joins chromatids together

KAROTYPE Map of chromosome used to study disorders. You had a normal and abnormal set. How many chromosomes are normal?

Down Syndrome: What’s Wrong? • Writing notation: – 1 st: total chromosome # – 2 nd: Sex chromosomes – 3 rd: extra or missing • Down Syndrome: 47, XY, +21

Turner’s Syndrome: What’s Wrong? • Write the notation for Turner’s Syndrome. 45, X, -23 or 45, XO, -23

Patau’s Syndrome: What’s Wrong? • Write the notation for Patau’s Syndrome. 47, XY, +13

Klinefelter’s Syndrome: What’s Wrong? • Write the notation for Klinefelter’s Syndrome. 47, XXY, +23

Autosomes (The Autosomes code for most of the offspring’s traits) In Humans the “Autosomes” are sets 1 - 22

Sex Chromosomes “Sex Chromosomes” ……. the This person 23 hasrd 2 set “X” chromosomes… and is a female. 23

Sex Chromosomes The Sex Chromosomes code for the sex of the offspring. ** If the offspring has two “X” chromosomes it will be a female. ** If the offspring has one “X” chromosome and one “Y” chromosome it will be a male. In Humans the “Sex Chromosomes” are the 23 rd set XX chromosome - female XY chromosome - male

• Diploid Cells = Cells with the full set of chromosomes – Paired chromosomes • Half of our chromosomes come from each parent (23 from each parent) • Somatic (non-sex) cells are diploid • Created by mitosis • Ex: Skin, Muscle, Nerve, Blood Cells

DIPLOID & HAPLOID Most cells have 2 copies of each chromosome DIPLOID 2 n = _______ (one from mom; one from dad) HOMOLOGOUS CHROMOSOMES = SOMATIC All BODY (______) cells are diploid

Homologous Chromosomes (because a homologous pair consists of 4 chromatids it is called a “Tetrad”) eye color locus hair color locus Paternal Maternal

Humans have 23 Sets of Homologous Chromosomes Each Homologous set is made up of 2 Homologues. Homologue

What is the human diploid chromosome number? Remember…Diploid = total number of chromosomes Answer = 46

• Haploid Cells = Cells with ½ the total number of chromosomes • Gametes (sex cells) are the only haploid cells – Ex: Sperm, Egg, Pollen • Chromosome number is reduced by meiosis • How do humans get 46 chromosomes? Haploid sperm cell (23) + Haploid egg cell (23) = Diploid zygote (46)

DIPLOID & HAPLOID Some cells have only one copy of each HAPLOID 1 n chromosome = _______ All sperm and egg cells are haploid

Gametes • The Male Gamete is the Sperm and is produced in the male gonad the Testes. • The Female Gamete is the Ovum (ova = pl. ) and is produced in the female gonad the Ovaries.

• Defined: Picture of an individuals chromosomes – Identify sex & chromosome defects • Size of final pair identifies sex – Same size: XX = female – Different size: XY = male • Normal human will have 46 chromosomes

Fertilization • The fusion of a sperm and egg to form a zygote • A zygote is a fertilized egg n=23 egg sperm n=23 2 n=46 zygote

• What is the diploid chromosome number? 42

• What is the haploid chromosome number? 21

• How many chromosomes would be in somatic cells? 42

• How many chromosomes would be in brain cells? 42

• How many chromosomes would be in gamete cells? 21

• How many chromosomes would be in egg cells? 21

• How many chromosomes would be in muscle cells? 42

• How many chromosomes would be in sperm cells? 21

• Is this a male or female rat? male

Quick Review • Chromsomes are tightly coiled strands of DNA • Diploid (somatic) cells contain the entire set of chromosomes • Haploid (gametes) cells contain only ½ the total number of

MEIOSIS 11 -4 http: //waynesword. palomar. edu/lmexer 2 a. htm Making gametes…

Interest Grabber 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis? 46 chromosomes 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo? 46 + 46 = 92; a developing embryo would not survive if it contained 92 chromosomes. 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have? Sperm and egg should each have 23 chromosomes.

Remember from Chapter 1: CHARACTERISTICS OF LIVING THINGS REPRODUCE ALL LIVING THINGS _____ Planaria animation: http: //www. t 3. rim. or. jp/~hylas/planaria/title. htm Family http: //babyhearing. org/Parenet 2 Parent/index. asp

Mitosis Meiosis

ASEXUAL REPRODUCTION Bacteria reproduce using http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Bio. Bookmito. html BINARY FISSION _________________ http: //fig. cox. miami. edu/~cmallery/150/mitosis/c 7. 13. 2. hydra. jpg Budding & regeneration are used by plants and animals to reproduce asexually (mitosis) Planaria animation: http: //www. t 3. rim. or. jp/~hylas/planaria/title. htm

BINARY FISSION & MITOSIS identical Produces cells that are _____ copies of parent cell

ADVANTAGES OF ASEXUAL REPRODUCTION Can make offspring faster Don’t need a partner http: //www. mrgrow. com/images/cutting. jpg

DISVANTAGES OF ASEXUAL REPRODUCTION ALL ALIKE Species CAN’T change and adapt One disease can wipe out whole population http: //www. mrgrow. com/images/cutting. jpg

SEXUAL REPRODUCTION Family image from: http: //babyhearing. org/Parenet 2 Parent/index. asp Combines genetic material from 2 parents (sperm & egg) so offspring are DIFFERENT genetically _____ from parents

ADVANTAGES OF SEXUAL REPRODUCTION Allows for variation in population Individuals can be different Provides foundation for EVOLUTION Allow species adapt to changes in their environment http: //naturalsciences. sdsu. edu/classes/lab 8/spindex. html

Image by Riedell EGG Image by Riedell + http: //www. angelbabygifts. com/ SPERM If egg and sperm had same number of chromosomes as other body cells. . . baby would have too many chromosomes! http: //www. acmecompany. com/stock_thumbnails/13217. forty-six_chromosomes. jpg

MEIOSIS is the way… http: //waynesword. palomar. edu/lmexer 2 a. htm to make cells with ½ the number of chromosomes for sexual reproduction

Video 1 Meiosis Overview • Click the image to play the video segment 11 A.

MITOSIS • Makes ___ 2 cells genetically identical _____ to parent cell & to each other 2 n • Makes ___ cells • Makes _____ SOMATIC (body) • Used by organisms to: increase size of organism, repair injuries, replace worn out cells http: //waynesword. palomar. edu/lmexer 2 a. htm

MEIOSIS 4 cells • Makes ____ genetically different from parent cell & from each other 1 n cells • Makes __________ Germ cells OR Gametes (sperm & eggs) • Used for ______ sexual reproduction http: //waynesword. palomar. edu/lmexer 2 a. htm

WHAT MAKES MEIOSIS DIFFERENT ? 1. SYNAPSIS & CROSSING OVER (PROPHASE I) 2. SEGREGATION & INDEPENDENT ASSORTMENT (ANAPHASE I) 3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT… ONLY COPIES DNA ONCE

WHAT MAKES MEIOSIS DIFFERENT ? 1. Homologous chromosomes pair up during ________ PROPHASE I SYNAPSIS = _______ This group of FOUR (4) chromatids is called a TETRAD _________ Images modified from: http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Crossover. gif

WHAT MAKES MEIOSIS DIFFERENT? 1. Exchange of DNA between OVER homologous pairs = CROSSING _______ during PROPHASE I Allows shuffling of genetic material http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Crossover. gif

Video 5 Crossing Over SEE CROSSING OVER ANIMATION • Click the image to play the video segment. 11 E

HOMOLOGOUS CHROMOSOMES Image modified by Riedell • SAME SIZE • SAME SHAPE • CARRY GENES for the SAME TRAITS IDENTICAL • BUT NOT _______! (Don’t have to have the SAME CHOICES) http: //sps. k 12. ar. us/massengale/genetics%20 tutorial. htm

Image modified by Riedell CROSSING OVER rearranging of DNA • Allows for_________ in different combinations • After crossing over, chromatid arms NOT IDENTICAL anymore are________ http: //sps. k 12. ar. us/massengale/genetics%20 tutorial. htm

WHAT MAKES MEIOSIS DIFFERENT ? 2. Separation during ANAPHASE I SEGREGATION & INDEPENDENT ASSORTMENT Separates gene choices and allows shuffling of genetic material

Video 4 Segregation of Chromosomes • Click the image to play the video segment 11 D.

Organisms that reproduce Sexually are made up of two different types of cells. 1. Somatic Cells are “body” cells and contain the normal number of chromosomes …. called the “Diploid” number (the symbol is 2 n). Examples would be … skin cells, brain cells, etc. 2. Gametes are the “sex” cells and contain only ½ the normal number of chromosomes…. called the “Haploid” number (the symbol is n)…. . Sperm cells and ova are gametes. n = number of chromosomes in the set… so…. 2 n means 2 chromosomes in the set…. Polyploid cells have more than

During Ovulation the ovum is released from the ovary and transported to an area where fertilization, the joining of the sperm and ovum, can occur…… fertilization, in Humans, occurs in the Fallopian tube. Fertilization results in the formation of the Zygote. (fertilized egg) Sperm + Ovum (egg) fertilization Zygote

Meiosis is the process by which ”gametes” (sex cells) , with half the number of chromosomes, are produced. During Meiosis diploid cells are reduced to haploid cells Diploid (2 n) Haploid (n) If Meiosis did not occur the chromosome number in each new generation would double…. The offspring would die.

Meiosis is Two cell divisions (called meiosis I and meiosis II) II with only one duplication of chromosomes.

Meiosis in males is called spermatogenesis and produces sperm. Meiosis in females is called oogenesis and produces ova.

Spermatogenesis Secondary Spermatocyte human sex cell 2 n=46 sperm n=23 Primary Spermatocyte n=23 Secondary Spermatocyte diploid (2 n) 4 sperm cells are produced from each primary meiosis I spermatocyte. haploid (n) n=23 meiosis II

Oogenesis *** The polar bodies die… only one ovum (egg) is produced from each

Interphase I • Similar to mitosis interphase. • Chromosomes replicate (S phase). • Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres • Centriole pairs also replicate.

Interphase I • Nucleus and nucleolus visible. chromatin nuclear membrane cell membrane nucleolus

Meiosis I (four phases) • Cell division that reduces the chromosome number by one-half. • four phases: phases a. prophase I b. metaphase I c. anaphase I d. telophase I

Prophase I • Longest and most complex phase. • 90% of the meiotic process is spent in Prophase I • Chromosomes condense. • Synapsis occurs: homologous chromosomes come together to form a tetrad • Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).

Prophase I - Synapsis Homologous chromosomes sister chromatids Tetrad sister chromatids

During Prophase I “Crossing Over” occurs. Crossing Over is one of the Two major occurrences of Meiosis (The other is Non-disjunction) • During Crossing over segments of nonsister chromatids break and reattach to the other chromatid The Chiasmata (chiasma) are the sites of crossing over

Prophase I • This is a crucial phase for mitosis. • During this phase each pair of chromatids don’t move to the equator alone, they match up with their homologous pair and fasten together (synapsis) in a group of four called a tetrad. • Extremely IMPORTANT!!! It is during this phase that crossing over can occur. • Crossing Over is the exchange of segments during synapsis.

Prophase I spindle fiber aster fibers centrioles

Crossing Over creates variation (diversity) in the offspring’s traits. Tetrad nonsister chromatids chiasmata: site of crossing over variation

Metaphase I • Shortest phase • Tetrads align on the metaphase plate • INDEPENDENT ASSORTMENT OCCURS: 1. Orientation of homologous pair to poles is random. 2. Variation 3. Formula: 2 n Example: 2 n = 4 then n = 2 thus 22 = 4 combinations

Metaphase I • The chromosomes line up at the equator attached by their centromeres to spindle fibers from centrioles. – Still in homologous pairs

Metaphase I OR metaphase plate

Anaphase I • Homologous chromosomes separate and move towards the poles. • Sister chromatids remain attached at their centromeres

Anaphase I • The spindle guides the movement of the chromosomes toward the poles – Sister chromatids remain attached – Move as a unit towards the same pole • The homologous chromosome moves toward the opposite pole – Contrasts mitosis – chromosomes appear as individuals instead of pairs (meiosis)

Anaphase I

Telophase I • Each pole now has haploid set of chromosomes • Cytokinesis occurs and two haploid daughter cells are formed.

Telophase I • This is the end of the first meiotic cell division. • The cytoplasm divides, forming two new daughter cells. • Each of the newly formed cells half the number of the parent cell’s chromosomes, but each chromosome is already replicated ready for the second meiotic cell division

Telophase I

Cytokinesis • Occurs simultaneously with telophase I – Forms 2 daughter cells • • • Plant cells – cell plate Animal cells – cleavage furrows NO FURTHER REPLICATION OF GENETIC MATERIAL PRIOR TO THE SECOND DIVISION OF MEIOSIS

Meiosis II • No interphase II (or very short - no more DNA replication) replication • Remember: Meiosis II is similar to mitosis

Meiosis II : Separates sister chromatids • Proceeds similar to mitosis • THERE IS NO INTERPHASE II !

Prophase II • Each of the daughter cells forms a spindle, and the double stranded chromosomes move toward the equator

Prophase II • same as prophase in mitosis

Metaphase II • The chromosomes are positioned on the metaphase plate in a mitosis-like fashion

Metaphase II • same as metaphase in mitosis metaphase plate

Anaphase II • same as anaphase in mitosis • sister chromatids separate

Anaphase II • The centromeres of sister chromatids finally separate • The sister chromatids of each pair move toward opposite poles – Now individual chromosomes

Telophase II • Same as telophase in mitosis • Nuclei form. • Cytokinesis occurs. • Remember: four haploid daughter cells produced. gametes = sperm or egg

Telophase II

Telophase II and Cytokinesis • Nuclei form at opposite poles of the cell and cytokinesis occurs • After completion of cytokinesis there are four daughter cells – All are haploid (n)

Non-disjunction is one of the Two major occurrences of Meiosis (The other is Crossing Over) • Non-disjunction is the failure of homologous chromosomes, or sister chromatids, to separate during meiosis. • Non-disjunction results with the production of zygotes with abnormal chromosome numbers…… remember…. An abnormal chromosome number (abnormal amount of DNA) is damaging to the offspring.

Non-disjunctions usually occur in one of two fashions. • The first is called Monosomy, the second is called Trisomy. If an organism has Trisomy 18 it has three chromosomes in the 18 th set, Trisomy 21…. Three chromosomes in the 21 st set. If an organism has Monosomy 23 it has only one chromosome in the 23 rd set.

Common Non-disjunction Disorders • • Down’s Syndrome – Trisomy 21 Turner’s Syndrome – Monosomy 23 (X) Kleinfelter’s Syndrome – Trisomy 23 (XXY) Edward’s Syndrome – Trisomy 18

Amniocentesis • An Amniocentesis is a prrocedure a pregnant woman can have in order to detect some genetics disorders…. . such as nondisjunction.

Amniocentesis Amniotic fluid withdrawn

WHAT MAKES MEIOSIS DIFFERENT? What causes Variation! 1. CROSSING OVER (PROPHASE I) 2. INDEPENDENT ASSORTMENT (ANAPHASE I)

INDEPENDENT ASSORTMENT http: //fig. cox. miami. edu/~cmallery/150/mitosis/c 13 x 9 independent-assortment. jpg

Figure 13. 7 The stages of meiotic cell division: Meiosis I

Figure 13. 7 The stages of meiotic cell division: Meiosis II

One Way Meiosis Makes Lots of Different Sex Cells (Gametes) – Independent Assortment Independent assortment produces 2 n distinct gametes, where n = the number of unique chromosomes. In humans, n = 23 and 223 = 6, 0000. That’s a lot of diversity by this mechanism alone.

Another Way Meiosis Makes Lots of Different Sex Cells – Crossing-Over Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.

The Key Difference Between Mitosis and Meiosis is the Way Chromosomes Uniquely Pair and Align in Meiosis Mitosis The first (and distinguishing) division of meiosis

Boy or Girl? The Y Chromosome “Decides” Y chromosome X chromosome

Boy or Girl? The Y Chromosome “Decides”

Meiosis – division error Chromosome pair

Meiosis error fertilization Should the gamete with the chromosome pair be fertilized then the offspring will not be ‘normal’. In humans this often occurs with the 21 st pair – producing a child with Downs Syndrome

21 trisomy – Downs Syndrome Can you see the extra 21 st chromosome? Is this person male or female?

SEGREGATION (Anaphase I)

SEGREGATION & CROSSING OVER together make even more combinations See an animation http: //waynesword. palomar. edu/lmexer 2 a. htm

INDEPENDENT ASSORTMENT http: //fig. cox. miami. edu/~cmallery/150/mitosis/c 13 x 9 independent-assortment. jpg

INDEPENDENT ASSORTMENT at ANAPHASE I Lots of different combinations are possible! This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

http: //www. tokyo-med. ac. jp/genet/anm/mimov. gi

WHAT MAKES MEIOSIS DIFFERENT ? Crossing over Segregation Independent assortment are ALL ways MEIOSIS results in =_______________ GENETIC RECOMBINATION different So daughter cells are _______ from parents and from each other

WHAT MAKES MEIOSIS DIFFERENT ? 3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE MITOSIS: G 1 S G 2 P MEIOSIS: G 1 S M G 2 P M P M A T C (I) C ( II ) A T

Video 2 Animal Cell Meiosis, Part 1 & Part 2 • Click the image to play the video segment 11 B. & C Video 2

Figure 11 -15 Meiosis Section 11 -4 Meiosis I

Figure 11 -17 Meiosis II Section 11 -4 Meiosis II Prophase II Metaphase II Anaphase II Meiosis I results in two The chromosomes line up in a The sister chromatids haploid (N) daughter cells, similar way to the metaphase separate and move toward each with half the number of stage of mitosis. opposite ends of the cell. chromosomes as the original. Telophase II Meiosis II results in four haploid (N) daughter cells.

Ways Meiosis is different? • Homologous pairs match up & trade DNA (SYNAPSIS & CROSSING OVER) in PROPHASE I • SEGREGATION & INDEPENDENT ASSORTMENT in Anaphase I create genetic recombination • Skipping INTERPHASE II(Dividing TWICE but copying DNA once) produces 1 n cells