Bellringer 10.15

1. Put the following phases of cell division in the correct order:

anaphase telophasemetaphase G2G1 cytokinesisS prophase

2. Describe what occurs in each of the phases above.

Bellringer 4/29

1. Describe the phases of meiosis.

2. How does meiosis differ from mitosis?

G1 S G2 P M A T Cytokinesis

Sexual Reproduction

Sexual reproduction•Uses genetic information from

more than one source

•Offspring are different from parents (lots of variation because of genetic recombination)

•May use gametes (sex cells)

Advantages•When an environment is changing an

organism group (species) may be able to adapt because so much variation

Disadvantages•When an environment is stable, variation

is not as necessary•Reproduction cannot occur as quickly as

asexual

How are gametes made? ... MEIOSIS•Cell division that reduces the number of

chromosomes in half•Makes haploid cells from diploid cells•Produces gametes (sperm and egg)

Interphase

•Period of cell growth and chromosome replication

•Precedes meiosis

Steps of MeiosisMeiosis I•4 phases: P I, M I, A I, T IProphase I:•Nucleolus and nuclear membrane fade,

chromatin condenses and becomes chromosomes

•Homologous chromosomes pair up (called

synapsis). ▫Homologous chromosomes = chromosomes

that have the same type of genes (one from each parent)

During synapsis, CROSSING OVER occurs

•Homologous chromosomes cross over each other▫Exchange of genetic

information▫Produces genetic

recombination, which increases variations in offspring

Metaphase I:•Homologous chromosomes line up in

center of the cell

Anaphase I:•Homologous chromosomes separate

Telophase I:•Nuclear membrane reforms

RESULT: TWO haploid cells

Meiosis II:• Separates the copied chromosomes• 4 phases: P II, M II, A II, T II

•RESULT: FOUR haploid cells

PROPHASE II:• Nuclear membrane and nucleolus disappear,

chromatin condenses into chromosomes, centrioles appear

METAPHASE II:• Chromosomes line up at center of cellANAPHASE II:• Centromeres break at center of chromosomes,

chromosomes are divided into two chromatids; chromatids are pulled to opposite poles of cell

TELOPHASE II:• Nuclear membrane and nucleolus reappear,

chromosomes uncoil into chromatin

Trait Mitosis Meiosis

Chromosome Number

Same (diploid)

Half (haploid)

Genetic Similarities

Same Diverse

Type of Cell Somatic cells (any cell other than sperm/egg)

Sex cells (egg & sperm)

Number of Divisions

1(one) I and II (two)

Type of Reproduction

Asexual Sexual

Role/Function

Produce cells for growth & repair

Produce sex cells

April 28, 2015•Bellringer:

1. List the phases of mitosis in the correct order and describe what occurs in each phase.

•Read section 10.2 (pg 263) in the blue Biology book.

•Answer section questions 1-4 (pg 273)•Define the review and new vocabulary (pg

263)

TO TURN IN!

Mendel’s Pea Plant Experiment Questions1. If the round seed shape is dominant to the

wrinkled seed shape, what would the genotype be of the parent plants in the P generation of the cross between pure round seeds vs pure wrinkled seeds? What are the possibilities of genotypes in the F1 generation? F2 generation?

2. Repeat #1 the green/yellow cross, purple/white cross, and the tall/short cross.

3. What is the ratio of:1. Round : wrinkled2. green : yellow3. Purple : white4. Tall : short