Chapter 9 Cell Division

Why do cells need to divide? Grow Repair/heal Reproduce asexually Form gametes (ie – sperm and egg)

3 Different types of cell division 1.Bacterial cell division – binary fission 2.Eukaryotic cell division – mitosis 3.Gamete formation – meiosis

1. Bacterial cell division Bacteria have circular DNA Reproduce by BINARY FISSION – produces identical offspring.

2. Eukaryotic cell division Eukaryotes form chromosomes Chromosomes are super-coiled DNA. Remember that DNA is the genetic information in the nucleus of the cell! A segment of DNA that codes for a certain trait is called a gene

Before a cell divides, DNA is copied for form chromatids Matching chromatids are joined at the centromere to form a chromosome. During cell division, chromatids separate so each new cell has the same genetic information as the original. Each organism has a unique number of chromosomes.

In humans, somatic cells are any cells other than sperm and egg Somatic cells are a diploid, 2n. Diploid cells contain 23 pairs of chromosomes, 46 total. One set from the biological mother and the other set from the biological father. Each pair of matching chromosomes is called a homologous pair.

Time to model a chromosome! Correctly label and Identify the following: 1.Chromosome 2.Chromatid 3.Centromere 4.Homologous pair

Cell cycle

Page 3 Cell cycle

STOP Grab a book. Complete vocabulary for Sections 1 and 2 on page 260. Number and Underline each term. Do these key terms on the back of page 1 or 2 of your packets.

Haploid vs. Diploid Haploid = 1 set of chromosomes Diploid = 2 sets of chromosomes

Of the 23 pairs of chromosomes in somatic cells, 22 pairs are called autosomes Autosome – chromosomes that do not determine an individual’s gender. Sex chromosome – 1 pair of chromosomes that determine an individual’s gender. XX = female, XY = male

Human gametes (sperm and egg) are haploid, n. Each sperm and egg cell contain only 23 total chromosomes

Autosomes vs. Sex Chromosomes

Chromosome numbers in different organisms Organism# of Chromos omes Algae148 Bean22 Cabbage18 Cat38 Chicken78 Dog78 Human46 Shrimp254 Yeast32

Can organisms have the same number of chromosomes?

Does a high chromosome number mean the organism is more complex?

Karyotype An organized profile of an individual’s chromosomes. Chromosomes are arranged by size, banding patterns, and centromere positions. Karyotypes can give information on a person’s genetic makeup: –# of chromosomes –Certain genetic disorders –gender

Time to build your own Karyotype!!

Here is yours mosomes/karyotype/ mosomes/karyotype/

Down Syndrome Associated with mental retardation Characteristic facial features and stature, heart defects, repsritaory infection, leukemia, and Alszheimers disease Occurs in 1 in 700 births in US Trisomy 21

Klinefelters Syndrome XXY Typically sterile males with abnomally small testes, some female characteritics, normal intelligence Occurs in 1 in 2000 births

Double Y Syndrome XYY Affected individuals tend to be taller as a group, normal intelligence Occurs in 1 in 1000 births

Turner Syndrome XO – missing sex chromosome Sterile females with immature sex organs, normal intelligence Occurs in 1 in 5,000 births

Cru de chat Syndrome Partial Chromosome 5 Associated with smaller head, characteristic cry and facial features, death in infancy or early childhood

Fragile X Syndrome Abnormal X chromosome Common genetic cause of mental retardation

Now it’s time to construct and analyze your own abnormal karyotype!

Trisomy 13 Patau syndrome Symptoms Cleft lip or palate Clenched hands Close-set eyes -- eyes may actually fuse together into one Decreased muscle tone Extra fingers or toes (polydactyly) Mental retardation, severeMental retardation Scalp defects (missing skin)

Trisomy 18 Symptoms Clenched hands Crossed legs (preferred position) Feet with a rounded bottom (rocker-bottom feet) Low birth weight Low-set ears Mental deficiency Small head (microcephaly) Small jaw (micrognathia)