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

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

CHROMOSOMES

Chromosomes – tightly coiled packages of DNA; they are rod shaped and proteins hold them together.

Strands of DNA wrap around proteins called Histones.

IMPORTANT WORDS

Chromatid – each half of a chromosome; forms as DNA copies itself before cell division

Centromere – holds the chromatids together until they separate

CHROMOSOMES

Each species has a unique number of chromosomes.

How many chromosomes do humans have?

46 chromosomes or 23 pairs.

TYPES OF CHROMOSOMES

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

KARYOTYPE: PICTURE OF CHROMOSOMES. WHAT DO YOU NOTICE ABOUT THE ARRANGEMENT?

CHROMOSOMESKaryotype – 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

CHROMOSOMES

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.

COMPARE THE KARYOTYPES. RECORD YOUR OBSERVATIONS

KARYOTYPE A KARYOTYPE B

COMPARISONS

KARYOTYPE 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!

KARYOTYPE B23 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.

HUMAN KARYOTYPE: MALE

HUMAN KARYOTYPE: FEMALE

CHROMOSOMES

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)

HAPLOID CELLSReproductive 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.

DIPLOID CELLS

Somatic Cells

Cells that make up the body of organisms.

Somatic Cells are produced through Mitosis (cell division results in 2 genetically identical cells).

KARYOTYPING ACTIVITY

http://www.biology.arizona.edu/human_bio/activities/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.

HOMEWORK

Carefully read pages 246-252

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.

GOALSLearning 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

IMPORTANT WORDS

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.