Chapter 3

Prokaryotic chromosomes...

- are usually circular pieces of DNA - contains many genes - contain structural proteins that bind to and organize the DNA Prokaryotic chromosomes contain many genes, are usually long and circular and are located in a region of the cytoplasm called the nucleoid. Prokaryotic cells do not contain nuclei.

What occurs during prophase of meiosis I?

- chiasma formation - synaptonemal complex formation - chromosome condensation - recombination

Prophase

- nuclear membrane begins breaking apart -microtubukes form mitotic spindle -sister chromatids

Telophase and Cytokenisis

- nuclear membranes reforming - chromosomes decondensing - cleavage

Interphase

G1, S, G2

Anaphase

The sister chromatids separate into individual chromosomes and are moved apart.

Prometaphase

-nuclear membrane fragmenting into vesicles -spindle pole, mitotic spindle

Metaphase

-sister chromatids line up at center

A diploid cell has 10 chromosomes. 1. How many chromosome pairs are in the cell? 2. Following mitosis how many cells will be produced? 3. How many chromosomes will each cell have after mitosis?

1. 5 2. 2 3. 10 During S phase, each chromosome is duplicated, and these chromosomes are segregated at mitosis, so that each daughter cell has a copy of all the chromosomes. If a cell is diploid, that means it has two copies of each chromosome, so a diploid cell with 10 chromosomes would have 5 pairs of chromosomes, and after mitosis each daughter cell will have the same number of chromosomes as the original cell

T/F: 1. Chromosomes that are heterozygous for an allele are not homologous. 2. Haploid organisms can have homologous chromosomes 3. Homologous chromosomes are 99% identical 4. Homologous chromosomes carry the same types of genes 5. Homologous chromosomes may contain different alleles of a gene 6. The physical location of a gene on the chromosome is called its allele

1. False 2. False 3. True 4. True 5. True 6. False Homologous chromosomes are found in diploid organisms, and are 99% identical. Homologous chromosomes carry the same types of genes, but they may contain different alleles of a gene. The physical location of a gene on the chromosome is called its locus.

Different stages of mitosis:

1. Interphase 2. Prophase 3. Prometaphase 4. Metaphase 5. Anaphase 6. Telophase and Cytokinesis

T/F: 1. Binary fission is a form of asexual division. 2. After binary fission is completed, two identical cells result 3. Each cell has two copies of the chromosome following division 4. Most eukaryotes divide by binary fission 5. The daughter cells are separated by formation of a septum. 6. A ring of the protein FtsZ forms at the future site of the septum.

1. True 2. True 3. False 4. False 5. True 6. True Bacteria divide through binary fission, an asexual form of cell division in which each daughter cell receives a copy of the bacterial chromosome. Daughter cells are separated through a ring of FtsZ, which forms at the future site of the septum. The septum then separates the two daughter cells

Different stages of Meiosis I Prophase:

1. Leptotene: replicated chromosomes condense 2. Zytogene: Bivalent forming and synapsis begins 3. Pachytene: A bivalent has formed and crossing over has occurred 4. Diplotene: Synaptonemal complex dissociates 5. Diakinesis: Nuclear membrane breaking apart and end of Prophase I

Remember...

Chromosomes are counted by the number of centromeres. Following DNA replication a set of sister chromatids has one centromere but there are two chromatids and each one has telomeres

Cell life cycle:

G1 - a cell synthesisze proteins etc. necessary to progress through the rest og the cell cycle. (cell is committed to cell division S - Chromosomes are replicated G2 - the cell accumulates materials necessary for cell division