Meiosis Chapter 9

1. ________Male reaches under his mantle with tentacle, removes packet of sperm, and insert it into female’s egg chamber

A. Reproduction

2. _______

Larva can become adult of either sex

–Depends on conditions

3. __________• Females in summer (from unfertilized eggs)• Males in autumn

_______Reproduction

• Single _________ produces offspring• All offspring are _________________ to

one another and to parent

________ Reproduction

•Two parents contribute to offspring•All offspring are ________________

____________ Chromosomes Carry Different ___________

• Cell has two of each___________________

• One from mother, other from father

• Paternal and maternal chromosomes carry

different ________

Terminology

• Offspring inherit new combinations of alleles

•This variation in traits is the basis for __________________change

Gamete Formation• Gametes are ___ cells (_______,______)

• Arise from _____cells

testes

ovaries

anther ovary

Chromosome Number• Germ cells are ______ (2n)

• Gametes are ________(n)

• Meiosis _________ chromosome number

DNA replication

PROPHASE I

METAPHASE I

ANAPHASE I

TELOPHASE I

__________PROPHASE II

METAPHASE II

ANAPHASE II

TELOPHASE II

__________

No DNA _________

4 ______ nuclei

Meiosis: ____ nuclear divisions, ____ DNA replication

Each homologue in the cell pairs with its partner,

then the partners separate

Meiosis I and II very similar to mitosis

1. DNA exchange occurs in ________

- Homologues swap _________

PROPHASE I METAPHASE I ANAPHASE I TELOPHASE I

2. No ________________ prior to Meiosis II

Crossing Over

•_______________ chromosomes exchange segments

•Creates new allele

______________ in

offspring

These exchange points are called ___________

Meiosis II - Stages

Prophase II Metaphase II Anaphase II Telophase II

Comparison of mitosis and meiosis

End result ____ _____

Daughter cells __________________

Chiasmata?

Meiosis Mitosis

__________

_______ are the physical manifestation of crossing over, a form of genetic rearrangement.

# of divisions ____ ___

Purpose _______________

Fig. 9.10a p. 148

PROPHASE METAPHASE ANAPHASE TELOPHASE

MITOSIS

PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II

MEIOSIS II

Possible Chromosome

Combinations or

or

or

1 2 3

•number of possible combinations of chromosomes in a gamete is:

•____ (n is number of chromosome types)

Factors Contributing to Variation Among Offspring

1. Crossing over during __________

2. Random _________ of

chromosomes at metaphase I

3. Random combination of ______at

fertilization

Plant Life Cycle

multicelled sporophyte

multicelled gametophytes

zygote

gametes spores

meiosisfertilization

mitosis

mitosis

Diploid

Haploid

Animal Life Cycle

multicelled body

gametes

zygote

meiosisfertilization

mitosis

Diploid

Haploid

Spermatogenesis

GrowthMitosis I,

Cytoplasmic divisionMeiosis II,

Cytoplasmic division

spermatids (haploid)

secondary spermatocytes

(haploid)

primary spermatocyte

(diploid)

spermato-gonium

(diploid male reproductive

cell)

Oogenesis

Growth Mitosis I,Cytoplasmic division

Meiosis II,Cytoplasmic division

ovum (haploid)

primary oocyte (diploid)

oogonium (diploid

reproductive cell) secondary

oocyte haploid)

first polar body

haploid)

three polar bodies

haploid)

Fertilization

• Male and female ______ unite and

nuclei _____

• Fusion of two haploid nuclei produces

_______ nucleus in the zygote

• Which two gametes unite is _______

– Adds to variation among offspring