Tuesday, November 1Tuesday, November 1stst! ! • HSAP is next semesterHSAP is next semester! Let’s practice with ! Let’s practice with

some biology—write your answers in your some biology—write your answers in your journal—remember, notebook check coming journal—remember, notebook check coming up VERY soon.up VERY soon.

• You have You have 5 minutes 5 minutes after the tardy bell RINGS after the tardy bell RINGS to complete this. That’s it. We’ll go over it to complete this. That’s it. We’ll go over it tomorrow. tomorrow. GET BUSY and STAY BUSY today.GET BUSY and STAY BUSY today.

• Page 172 in your bookPage 172 in your book• ““Interpret a Bar Graph” Section, Interpret a Bar Graph” Section,

Questions 1-3Questions 1-3

6.1 KEY CONCEPT6.1 KEY CONCEPT Gametes have Gametes have halfhalf the number the number of chromosomes that body cells of chromosomes that body cells have.have.

YOUYOU have 2 major cell types! have 2 major cell types!

Body cellsBody cellsMost of body tissues, organsMost of body tissues, organsNOTNOT passed on to kids passed on to kids

body cells sex cells (sperm) sex cells (egg)

Develop from germ cells (In Develop from germ cells (In ovaries and testes)ovaries and testes)

Gametes = sex cells (egg and Gametes = sex cells (egg and sperm)!sperm)!

DNA DNA ISIS passed to kids passed to kids

• Your body cells have 23 pairs of chromosomes!– Homologous pairs

= same structure. – One chromosome

comes from each parent.

• Autosomes = chromosome pairs 1-22

• Sex chromosomes = X and Y, determine gender

Your cells have autosomes and Your cells have autosomes and sex chromosomes!sex chromosomes!

are are chroms #1 – 22, chroms #1 – 22, NON-sex chroms NON-sex chroms (have lots of (have lots of other genes)other genes)

A Homologous A Homologous pair = 1 from pair = 1 from each parent!! each parent!! (same genes, but (same genes, but may “code” for may “code” for diff traits)diff traits)Pair #23 = Sex Pair #23 = Sex chroms = X & Y, chroms = X & Y, genes determine genes determine gender!!gender!!

What’s the difference What’s the difference here??? here???

•Gametes! Gametes! (sperm, egg)(sperm, egg)•1 copy of 1 copy of every every chromosome:chromosome:

• 22 22 autosomesautosomes

• 1 sex 1 sex chromosomchromosomee

•Body cells!Body cells!•2 copies of 2 copies of every every chromosomechromosome•Half the Half the chromosomes chromosomes comes from comes from each parent!each parent!

Body Cells

Sex Cells!!!

How are these processes alike?

Different??

Body CellsBody Cells (Somatic)Body Cells (Somatic)

Sex Cells (Gametes)

Review!!!Review!!!• Where are germ cells located in the human body?Where are germ cells located in the human body?• What’s an autosome?What’s an autosome?• What’s a sex chromosome & how’s it different from What’s a sex chromosome & how’s it different from

an autosome?an autosome?• In a human DIPLOID cell, how many chromosomes In a human DIPLOID cell, how many chromosomes

are there?are there?• In a human HAPLOID cell, how many chromosomes?In a human HAPLOID cell, how many chromosomes?• After fertilization takes place (sperm meets egg), the After fertilization takes place (sperm meets egg), the

resulting cell (zygote) is .... Diploid or haploid? resulting cell (zygote) is .... Diploid or haploid? • Do you think the Y chromosome contains genes that Do you think the Y chromosome contains genes that

are crucial to the organism’s survival?are crucial to the organism’s survival?• Does mitosis or meiosis occur more frequently in Does mitosis or meiosis occur more frequently in

your body?your body?

6.2 KEY 6.2 KEY CONCEPT CONCEPT During During meiosis, meiosis, diploid cells diploid cells go thru go thru 2 cell 2 cell divisionsdivisions to to make haploid make haploid cells!!cells!!

Meiosis = Meiosis = 22 rounds of cell rounds of cell division!!division!!

• Meiosis reduces Meiosis reduces chromosome number and chromosome number and creates genetic diversity! creates genetic diversity!

Meiosis I and meiosis II each have four Meiosis I and meiosis II each have four phases, similar to those in mitosis!!phases, similar to those in mitosis!!

•Similar, not Similar, not identical – 1 from identical – 1 from each parent (same each parent (same genes)genes)•PairsPairs separate in separate in Meiosis IMeiosis I

•Copies of the same Copies of the same chromosome! (each chromosome! (each = ½ of duplicated = ½ of duplicated chrom, attached @ chrom, attached @ centromere)centromere)•Separate in M. 2Separate in M. 2

Meiosis I Meiosis I • occurs after DNA has been replicatedoccurs after DNA has been replicated• divides homologous chromosomes into divides homologous chromosomes into

4 phases.4 phases.

Turn to p. 174 – 175! Turn to p. 174 – 175! Describe the steps of Meiosis!! Describe the steps of Meiosis!!

• Meiosis II divides sister chromatids in four phases.• DNA is not replicated between meiosis I andmeiosis II.

How are they different????How are they different????– Meiosis = two cell divisions, mitosis = one– In mitosis, homologous chromosomes never pair

up.– Meiosis results in haploid cells; mitosis results in

diploid cells.

Haploid cells develop into mature Haploid cells develop into mature gametes. gametes.

• Gametogenesis = production of gametes.

• Gametogenesis differs between females and males! – Sperm become streamlined and motile.

– Sperm mostly just contribute their DNA to the embryo.

– Eggs contribute DNA, cytoplasm, and organelles to an embryo. Go GIRL!

– During meiosis, the egg gets most of the contents; the other cells form “polar bodies”.

More Review for you!!!More Review for you!!!• What is mitosis??What is mitosis??• What is meiosis?What is meiosis?• What is a somatic cell??What is a somatic cell??• What are gametes???What are gametes???• Examples of gametes???Examples of gametes???• Examples of somatic cells??Examples of somatic cells??• What are autosomes??What are autosomes??• Why are the X and Y chromosome Why are the X and Y chromosome

special???special???

And MORE Review for And MORE Review for you!!!you!!!

• What is the difference between What is the difference between haploid and diploid cells??haploid and diploid cells??

• What is a homologous What is a homologous chromosome??chromosome??

• A sister chromatid??A sister chromatid??• What is gametogenesis??What is gametogenesis??

Practice Sheet with Gametogenesis!• Smart Board Activity

Circle Activity for Meiosis Practice!