Take 5: 11/9/11 What is a gene? What does meiosis produce? What are the 2 divisions of Meiosis?

Meiosis Notes Ch 10

Mendel's Principle of Genetics 1. Each organism must inherit a ________ copy of every gene from each of its parents. 2. Each organism produces its own gametes (aka sex cells) and each gamete has _____ set of genes. single one

Diploid vs. Haploid A cell with two copies of each chromosome = __________ or _______ A cell with only one copy of each chromosome = ___________ or ______ 2n diploid 1n haploid

Diploid vs. Haploid n = ___ 3 2n = 6

Number of Chromosomes in various organisms…

The two chromosomes of each pair in a diploid cell are called One chromosome from Dad One chromosome from Mom The two chromosomes of each pair in a diploid cell are called homologous chromosomes

Each pair of homologous chromosomes has genes for the SAME traits One chromosome from Dad One chromosome from Mom Each pair of homologous chromosomes has genes for the SAME traits example: Chromosome pair #1 could code for eye color

So how do you get one chromosome from each parent? Well, I think you already know that.

Fertilization, right? Yep!

So that must mean that the sperm and egg cell are haploid. Yep!

Are there any other cells in your body that are haploid? Nope!

How do you make haploid cells? Through meiosis

What’s that? The way you produce a haploid cell from a diploid cell.

Definition: Meiosis is the process in which the number of chromosomes in a cell is cut _______ due to a separation of homologous chromosomes in a diploid cell. (2n  1n cell) in half

Meiosis involves two distinct divisions __________ Meiosis I Meiosis II

Meiosis turns a single diploid cell into ________________ 4 haploid cells meiosis I meiosis II

Prior to meiosis I: each chromosome is ______________ replicated during Interphase copied copied

Prophase I Each chromosome pairs with the corresponding homologous chromosome to form a structure called a ________ There are ______ chromatids in a tetrad tetrad MOM DAD tetrad four 1 2 3 4

Prophase I In addition to pairing up and forming tetrads, they ALSO exchange portions of their chromatids in a process called _______________ The results in an ___________ of alleles to produce new ______________ of alleles crossing over exchange recombination

NOTICE: This is one difference from mitosis NOTICE: This is one difference from mitosis. In mitosis the chromosomes line up __________. In meiosis, they ______ individually pair up !!!

The pair of homologous chromosomes _________________________ Metaphase I The pair of homologous chromosomes _________________________ Anaphase I The homologous chromosomes randomly ________. Telophase I Two new cells are formed. line up (in pairs) in the middle separate

Now these two cells enter Meiosis II UNLIKE THE FIRST DIVISION, these cells DO NOT UNDERGO ___________ replication

______________________________ Prophase II: ______________________________ Metaphase II: ______________________________ Anaphase II: _____________________________ Telophase II: ________________ are produced. spindles form & attach to centromeres line up singularly in the middle the sister chromatids separate Four daughter cells http://www.youtube.com/watch?v=D1_-mQS_FZ0

Gamete Formation In MALES, haploid gametes produced are called ______. In plants it is called _______ In FEMALES, only ______ of the cells produced is involved in reproduction AKA ______ Other three = _______________and are not used in reproduction sperm pollen one egg polar bodies

Meiosis Makes HAPLOID sperm and egg cells http://www.cellsalive.com/meiosis.htm They skipped a few steps here

The Simplified Version: MITOSIS MEIOSIS

Let’s fill this in… Mitosis Meiosis

Typical Meiosis Crossing over

Non-disjunction in Meiosis I What happened here?

What does nondisjunction mean? Non-disjunction in Meiosis II What does nondisjunction mean?

Patterns of Heredity and Human Genetics Chapter 12 Patterns of Heredity and Human Genetics

Pedigree A graphic representation of genetic inheritance

Incomplete Dominance-phenotype is a mixture between those of 2 homozygous parents

Codominance- both alleles are expressed equally

Sex Linked Inheritance

Karyotype- normal male

Karyotype- Down Syndrome (Trisomy) http://www.youtube.com/watch?v=ycrPCTP2mFE

Karyotype –Turner Syndrome (monsomy) http://www.youtube.com/watch?v=ldjb-FR-PKo Karyotype –Turner Syndrome (monsomy)