Meiosis Diploid (2N) – 2 sets of chromosomes 1) In humans what is the diploid chromosome number? Haploid (N) – 1 set of chromosomes 2) In humans what.

Meiosis

Diploid (2N) – 2 sets of chromosomes

1) In humans what is the diploid chromosome number?

Haploid (N) – 1 set of chromosomes

2) In humans what is the haploid chromosome number?

Homologous – a pair of chromosomes (1 from each

parent) that 3)___________, 4)__________ and

5)______________

Meiosis and sexual reproduction significantly contribute to genetic variation among offspring

Some steps closely resemble Mitosis

Like Mitosis, Meiosis is preceded by chromosome replication

Meiosis is different because a single chromosome replication is followed by two rounds of cell division Meiosis I and Meiosis II.

Chromosome

Genes

Chromosome:A bundle of DNA

containing many genes

B

A

C

B

a

c

d

A

C

E

A

C

B

A

C

6) Which is the homologous chromosome to 1? How do you know?

1 2 3 4

B

a

cB

a

c

B

A

C

B

A

C

1 2

7) What is the relationship between 1 and 2?

3 4

8) What is the relationship between 3 and 4?

A cell which contains two copies

of each chromosome is…

9) ____________

Normal body cells are 9)_____

A cell which contains one copy

of each chromosome is…

10)________

Gametes (sex cells) are 10)________

Sperm

Ovum

Sperm cells are produced by …

11)_________

The chromosomes in the nucleus

are copied

12)______ haploid

daughter cells are produced

Each daughter cell contains only one of

the homologous chromosomes from the diploid parent

cell

Diploid parent cell

Eggs are also produced by 13)_________

Haploid

Diploid parent cell

14) So why would we want to create haploid gametes?

15) What would happen if the sperm and egg cells generated were diploid cells?

Generation 1

Generation 2

Generation 3=16Generation 4=32Generation 5=64Generation 6=128Generation 7=256

Replication of DNA must occur before cell division.

16) When does this occur?

17) In Meiosis I the _____________split and the chromosome number goes from ____ to _____

Meiosis II looks a lot like 18)_______________

Crossing Over-when homologoues chromosomes exchange pieces with each other. This occurs during Prophase I

I need 4 volunteers.

Results in genetic variation

Summary of Meiosis

2 cell divisions.

Start with 2 copies of each chromosome (homologues), each with 2 chromatids.

In meiosis 1, crossing over in prophase mixes alleles between the homologues.

In metaphase of meiosis 1, homologues pair up, and in anaphase the homologues are separated into 2 cells.

Meiosis 2 is just like mitosis. The centromeres divide in anaphase, giving rise to a total of 4 cells, each with 1 copy of each chromosome, and each chromosome with only 1 chromatid.

Mitosis Meiosis

DNA replication During _________ During _________

Divisions _____ ______

Crossing over Does not occur Can occur in prophase I

Role in animal body

Produces cells for growth and tissue repair

Produces gametes

Results in ___ Diploid Cells (2N)

___ Haploid Cells (N)

Cells are Genetically __________

Genetically __________

Occurs in ________Cells _______ Cells

Mitosis Meiosis

DNA replication During interphase

During interphase

Divisions 1 2Crossing over Does not occur Can occur in

prophase IRole in animal body

Produces cells for growth and tissue repair

Produces gametes

Results in 2 Diploid Cells (2N)

4 Haploid Cells (N)

Cells are Genetically identical

Genetically different

Occurs in Body Cells Sex Cells

19) Where are sex cells found in your body?

20)Which process is this?

Provides for growth, repair, and asexual reproduction

Produces TWO daughter cells that are genetically identical to the parent cell

Involves one division of the DNA

Diploid parent cells produce diploid daughter cells

Happens in most cells of the body…

21) Which process is this?

Yields haploid daughter cells with only ONE member of the homologous chromosome pair

Produces FOUR daughter cells that are genetically different from the parent cell

Involves TWO divisions of the DNA

Exchange of genetic material occurs between homologous chromosomes

22) What are similarities between Mitosis and Meiosis?

Similarities?

Chromosomes duplicate only once before each stage

Both make it possible for cells to inherit genetic information in the form of chromosome copies

23) What are the differences between Meiosis and Mitosis?

Meiosis Consists of 2 cycles

Results in a reduction of the chromosome #

Is a division of sex cells

Results in 4 daughter cells

Random assortment of chromosomes

24) How does meiosis contribute to genetic diversity?

Random assortment of chromosomes

Crossing Over

How does meiosis contribute to genetic diversity?

This is important because the greater the genetic diversity the greater the probability that a population will survive an epidemic.

Fertilization:

An ova and a sperm fuse to form a diploid zygote

Ova

Sperm

Zygote

The zygote contains one allele from each

parentThis process is random

The same rules apply to inheritance in plants as apply to inheritance in animals.

The male gamete or sex

cell is …

… pollen

The female gamete is…

… the egg cell