Meiosis Diploid 2 N 2 sets of chromosomes

Meiosis Diploid (2 N) – 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.

Genes A Chromosome: B A bundle of DNA containing many genes C Chromosome

6) Which is the homologous chromosome to 1? How do you know? 1 A 2 A B C C E 3 A 4 a d B C c

7) What is the relationship between 1 and 2? 3 1 4 A A B B C C 2 a a B B c c 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)_____ Diploid parent cell 12)______ haploid daughter cells are produced The chromosomes in the nucleus are copied 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

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=16 Generation 4=32 Generation 5=64 Generation 6=128 Generation 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 Results in genetic variation I need 4 volunteers.

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 Divisions During _________ Crossing over Does not occur DNA replication Role in animal body Can occur in prophase I Produces cells for Produces gametes growth and tissue repair Results in ___ Diploid Cells (2 N) ___ Haploid Cells (N) Cells are Genetically __________ Occurs in ____Cells _______ Cells

Mitosis Meiosis DNA replication During interphase Divisions 1 Crossing over Does not occur Role in animal body 2 Can occur in prophase I Produces cells for Produces gametes growth and tissue repair Results in 2 Diploid Cells (2 N) 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?

How does meiosis contribute to genetic diversity? Random assortment of chromosomes Crossing Over 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 Zygote Sperm The zygote contains one allele from each parent This 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