DNA DNA is a nucleic acid made of two strands of nucleotides wound together in a spiral called a double helix

DNA ●Each nucleotide is composed of: ○a sugar molecule known as deoxyribose ○a phosphate group ○and one or four different nitrogenous bases: ■Adenine (A) ■Thymine (T) ■Guanine (G) ■Cytosine (C)

DNA The phosphate and sugar parts of the nucleotides form the backbone of each strand in the DNA double helix

DNA The bases extend toward the center of the double helix.

DNA Each base in one strand is matched with a complementary base in the other strand in accord with the base-pairing rules: A pairs with T G pairs with C

DNA These structural characteristics of DNA are the same in all organisms. The DNA of different organisms differs in the sequence of nucleotides, and these differences in nucleotide sequence are responsible for the inherited differences among organisms.

DNA DNA -

DNA In eukaryotic cells, each chromosome consists of DNA wrapped around special proteins. The chromosomes are contained in the nucleus inside a nuclear membrane.

DNA

C HROMOSOMES Chromosomes – tightly coiled packages of DNA; they are rod shaped and proteins hold them together. Strands of DNA wrap around proteins called Histones.

I MPORTANT W ORDS Chromatid – each half of a chromosome; forms as DNA copies itself before cell division Centromere – holds the chromatids together until they separate

C HROMOSOMES Each species has a unique number of chromosomes. How many chromosomes do humans have? 46 chromosomes or 23 pairs.

T YPES OF C HROMOSOMES 2 Types of Chromosomes: 1. Sex Chromosomes – are the chromosomes that determine the sex of an organism. Female: XX Male: XY 2. Autosomes – all other chromosomes ● Humans: 44 autosomal chromosomes

K ARYOTYPE : P ICTURE OF C HROMOSOMES. W HAT DO YOU NOTICE ABOUT THE ARRANGEMENT ?

C HROMOSOMES Karyotype – is a picture of the chromosomes in a somatic (body) cell. 22 homologous pairs of autosomes. 2 sex chromosomes Is this person male or female? Male: XY Normal or abnormal Normal: 23 pairs

C HROMOSOMES Notice that the chromosomes are organized in pairs. These pairs are homologous chromosomes Homologous chromosomes – two copies of each autosome (maternal and paternal) Homologous chromosomes are the same size, shape, and carry genes for the same trait. Final pair is not numbered: Sex Chromosomes.

C OMPARE THE KARYOTYPES. R ECORD YOUR OBSERVATIONS K ARYOTYPE AK ARYOTYPE B

C OMPARISONS K ARYOTYPE A 19 pairs: Not Human Sex: Male (XY) Sister chromatids are still attached at their centromeres (these are double copies of each chromosome). This is a picture BEFORE the cell divided! K ARYOTYPE B 23 pairs: Human Sex: Female (XX) Single Copy of each chromosome. This picture was taken AFTER the cell divided! Be prepared to analyze a karyotype regardless of when the picture of the chromosomes was taken.

H UMAN K ARYOTYPE : M ALE

H UMAN K ARYOTYPE : F EMALE

C HROMOSOMES Diploid – cells have two sets (maternal and paternal) of chromosomes. ● Have all 46 chromosomes. ● Represented by 2n (means a full set of DNA) ● Somatic Cells (cells making up the body) Haploid – cells have one set of chromosomes. ● Have 23 chromosomes. ● Represented by n (means a half set of DNA) ● Gametes (reproductive cells : egg and sperm)

H APLOID C ELLS Reproductive Cells Gametes - sperm and egg cells; they have 23 chromosomes Fertilization →23 in sperm + 23 in egg = 46 in zygote Gametes are produced through Meiosis (cell division results in 4 genetically different cells) More on this later.

D IPLOID C ELLS Somatic Cells Cells that make up the body of organisms. Somatic Cells are produced through Mitosis (cell division results in 2 genetically identical cells).

K ARYOTYPING A CTIVITY ivities/karyotyping/karyotyping.html (online karyotyping lab) Complete for homework due Friday: Handwritten ON PAPER: Answer the two questions for each patient Answer 1 for the internet search question.

H OMEWORK Carefully read pages Summarize the reading in a sentence outline. Write complete sentences in outline form to summarize the important points of the reading.

10/22/14 POD: Compare and contrast chromatids and chromosomes.

G OALS Learning Objective: Describe the structure, location, and functional role of chromosomes in eukaryotic cells. Complete Karyotypes and Lab Questions = HW Quiz on DNA structure, Chromosome, and Cell Cycle on Friday Online Karyotyping Lab - Test Bonus Questions From here

I MPORTANT W ORDS chromosome - chromatid - chromatin - tightly coiled packages of DNA each half of a chromosome; forms as DNA copies itself before cell division string-like fiber of DNA and protein called chromatin

Chromosome vs. Chromatin During interphase, DNA is combined with proteins and organized into a precise, compact structure, a dense string-like fiber called chromatin, which condenses even further into chromosomes during cell division.