(9)(9)

Types of Asexual Reproduction Types of Asexual Reproduction (hand out) 5.8 (160)(hand out) 5.8 (160)

Meiosis 7.2 (206)Meiosis 7.2 (206)Atypical Meiosis 7.9 (222)Atypical Meiosis 7.9 (222)

Binary FissionBinary Fission

Organism splits Organism splits directly into 2 equal-directly into 2 equal-sized offspring.sized offspring.

Each with a single Each with a single copy of the parents copy of the parents genetics genetics information.information.

Ex. Bacteria Ex. Bacteria

Binary FissionBinary Fission

BuddingBudding

Offspring begins as a small outgrowth Offspring begins as a small outgrowth from the parent.from the parent.

Bud eventually breaks off and Bud eventually breaks off and becomes an organism of its own.becomes an organism of its own.

Ex. YeastEx. Yeast

In the photograph, you will see a brown hydra with twoOther budding hydras already completely formed but still attached

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjun98/janhydra.html

FragmentationFragmentation

A new organism is A new organism is formed from a part formed from a part that breaks off the that breaks off the parentparent

Ex. StarfishEx. Starfish

Spore FormationSpore Formation

Organism undergoes Organism undergoes frequent cell frequent cell division to produce division to produce many smaller many smaller identical cells identical cells called called SPORESSPORES..

Ex. MushroomEx. Mushroom

Penicillin (mold)Penicillin (mold)

spores

Vegetative ReproductionVegetative Reproduction

Produce “runners” that can develop Produce “runners” that can develop into another plant with identical into another plant with identical genetic information.genetic information.

Ex. StrawberriesEx. Strawberries

QuestionsQuestions

1.1. How is asexual reproduction different from How is asexual reproduction different from sexual reproduction?sexual reproduction?

2.2. How is the zygote, produced by sexual How is the zygote, produced by sexual reproduction, different from daughter cells, reproduction, different from daughter cells, produced by asexual reproduction?produced by asexual reproduction?

Zygote is a fertilized egg.Zygote is a fertilized egg.

MeiosisMeiosisThe function of meiosis is to The function of meiosis is to produce eggs and produce eggs and

sperm for sexual reproduction.sperm for sexual reproduction. (sex cells) (sex cells)

1. Egg and sperm cells 1. Egg and sperm cells must have half the must have half the number of chromosomesnumber of chromosomes as the parent cell as the parent cell so that when put together they will have so that when put together they will have the same number of chromosomes as the the same number of chromosomes as the parent cells. (23 vs. 46 in our body cells.)parent cells. (23 vs. 46 in our body cells.)

2. Egg and sperm cells are NOT genetically 2. Egg and sperm cells are NOT genetically identical to the parent cell like you see in identical to the parent cell like you see in mitosis.mitosis.

3. Although you may 3. Although you may look more like one look more like one parent than the other, parent than the other, you receive the same you receive the same amount of genetic amount of genetic information from each.information from each.

4. Chromosomes similar 4. Chromosomes similar in shape, length and in shape, length and gene arrangement are gene arrangement are called called homologous homologous chromosomeschromosomes..

Summary of MeiosisSummary of MeiosisFirst, First, the genetic material must be the genetic material must be

replicatedreplicated so that each daughter cell so that each daughter cell can be given the appropriate amount of can be given the appropriate amount of genetic information. This occurs in genetic information. This occurs in Interphase.Interphase.

Second, Second, the genetic material must be the genetic material must be divided twicedivided twice so that each of the so that each of the four four daughter cellsdaughter cells gets a set of information. gets a set of information.

Interphase Interphase PMAT PMAT PMAT PMAT Interphase Interphase

Atypical Meiosis (7.9) FYIAtypical Meiosis (7.9) FYI

Errors occurring during cell divisions Errors occurring during cell divisions may not harm an organism… but if may not harm an organism… but if something goes wrong during something goes wrong during meiosis of reproductive cells, the meiosis of reproductive cells, the resulting embryo is in serious trouble resulting embryo is in serious trouble since all of its cells will be affected.since all of its cells will be affected.

Nondisjunctive DisordersNondisjunctive Disorders(failure to separate)(failure to separate)

Is an error that occurs when two Is an error that occurs when two homologous chromosomes move to the homologous chromosomes move to the same pole during meiosis.same pole during meiosis.

… … the resulting sex cell may have 22 or 24 the resulting sex cell may have 22 or 24 chromosomes.chromosomes.

… … Therefore, the resulting zygote may have Therefore, the resulting zygote may have 45 or 47 chromosomes rather than 46.45 or 47 chromosomes rather than 46.

In general, people with In general, people with Down SyndromeDown Syndrome have an extra chromosome in pair 21 have an extra chromosome in pair 21 (trisonomy 21). Children may have mental (trisonomy 21). Children may have mental disabilities and some muscular weakness.disabilities and some muscular weakness.

Most common with elderly mothers.Most common with elderly mothers.

This is a cause of several medical conditions in This is a cause of several medical conditions in humans, including:humans, including:

Down SyndromeDown Syndrome - trisomy of chromosome 21 - trisomy of chromosome 21 Patau Syndrome - trisomy of chromosome 13 Patau Syndrome - trisomy of chromosome 13 Edward Syndrome - trisomy of chromosome 18 Edward Syndrome - trisomy of chromosome 18 Klinefelter Syndrome - an extra X chromosome in Klinefelter Syndrome - an extra X chromosome in

males males Turner Syndrome - only one X chromosome present in Turner Syndrome - only one X chromosome present in

females females XYY Syndrome - an extra Y chromosome in males XYY Syndrome - an extra Y chromosome in males Triple X SyndromeTriple X Syndrome - an extra X chromosome in females - an extra X chromosome in females

Klinefelter Syndrome:Klinefelter Syndrome:

The child is a male, but at The child is a male, but at puberty he begins puberty he begins producing high levels of producing high levels of female sex hormone and female sex hormone and can not father children. can not father children. (1 in every 1000 births.)(1 in every 1000 births.)

Turner Syndrome:Turner Syndrome: Females with T.S. do not Females with T.S. do not mature sexually and are mature sexually and are shorter in height. (1 in shorter in height. (1 in every 10000 births)every 10000 births)

Both caused by Both caused by nondisjunction.nondisjunction.

Turner SyndromeTurner Syndrome also can occur also can occur

when nondisjunction happens during when nondisjunction happens during meiosis forming the human females meiosis forming the human females gametes.gametes.