The Organism and the Cell Chapter 2

Cells Eukaryotes are organisms with DNA in the nucleus Prokaryotes lack a nucleus to enclose DNA

Basic Body Plan We are similar to animals we share a common ancestry with Cells- fundamental units of life Cells are organized into tissues, which form organs, which function together in organ systems, which make up an organism

Cells Each cell in a body has a full set of genetic information that directs growth, development, and metabolism Cells are held within a membrane. In eukaryotes a nucleus separates the genetic material from the cytoplasm, which houses organelles, which have various functions. Page 19 has a full list of all organelles and their functions

Classes of Cells Somatic cells: thousands of types of cells making up our body structure Gametes: sex cells (egg or sperm) Important!!

Cell Development All of the cells in an individual are derived from the fertilized egg, the zygote half of the information in the zygote comes from the mother and half from the father Right after fertilization the zygote divides into 2 cells, which then begin the process of differentiation, meaning they grow in different ways These then develop into organs, musculoskeleton system, nervous system

Cell Development The process of cell division with somatic cells is called mitosis The process of cell division with gametes is meiosis (Chapter 4)

Chromosomes Most genetic material is found in the cell’s nucleus Nuclear DNA is packaged into chromosomes Chromosomes have arms, centromeres and sister chromatids, seen on page 21 The number of chromosomes is species specific The normal number for a human is 46

Chromosomes in Humans The number 46 refers only to somatic cells This number is the diploid number (full number) In gametes, the number of chromosomes is 23…why? This is the haploid number (half number)

Chromosomes in Humans The number 46 refers only to somatic cells This number is the diploid number (full number) In gametes, the number of chromosomes is 23…why? This is the haploid number (half number) You can only pass down half of your genetic information to a child. Half also comes from the other parent

Chromosomes in Humans The 23 pairs of chromosomes are lined up according to their size, called a karyotype. They also have different banding patterns Each chromosome is in a pair, which is called homologous. This means that the genes are found at the same location on each pair The 23rd pair are the sex chromosomes, X or Y Look at page 22. label the chromosomes 1-23

What makes a pair of chromosomes homologous is where each gene is found on the chromosome

Homologous Chromosomes A gene is a segment of DNA that codes for a specific function or trait in the body The position a gene occupies on a chromosome is called the locus Two chromosomes are homologous when the genes at a given locus code for the same trait on both chromosomes. Remember, different versions of genes are called alleles

Homologous Chromosomes

Chromosomes can be identified by size position of the centromere banding pattern LONG MEDIUM SHORT VERY SHORT CENTER AWAY FROM CENTER AT OR NEAR THE END

Chromosome Groups Group A: Very long, centromere in center (1-3) Group B: Long, centromere away from center (4-5) Group C: Medium, centromere away from center (6-12) Group D: Medium, centromere at or near the end (13-15) Group E : Short, centromere away from center (16-18) Group F: Short, centromere in center (19-20) Group G: very short, centromere at or near the end (21-22)

Chromosomal Abnormalities Error in cell division: usually in meiosis Structural Modifications Cat Cry Syndrome deletion of part of Chromosome 5 infants cry like a cat 14/21Translocation Carrier, Chromosomes are connected has Down Syndrome-like characteristics Fragile X: long arm of the X chromosome is loose or has broken off Shorter than average Large heads with long, narrow faces and large ears

Irregular number Trisomy 21 XO Turner XXY Klinefelter Down’s Syndrome XO Turner Short, Webbed necks, sterile females Most fetuses die before birth XXY Klinefelter High-pitched voice, reduced fertility, some mental impairment XXX Superfemale (metafemale) Taller, normal development, fertile XYY Supermale (metamale) Tall, high testosterone levels, Fertile predisposed to antisocial behavior?

Assignment Each group will complete two labs/Dived the group in two Group 1: complete the lab starting on page 25 Group 2: Grab a Mystery Packet Self-Test 2.1 Additional Self-Test, pg. 33-34 are good study questions (but not turned in)