- All cells come from other cells
2. The division of cells allows living things to:
Repair damage
Grow
Reproduce offspring
Asexual
Sexual
Chromosomes - DNA usually exists in the nucleus as chromatin “string”
Before cells divide, DNA duplicates & and condenses
Chromosomes are DNA wound around proteins (histones)
Sister chromatids joined at the centromere
The Cell Cycle - Interphase (90%): cell does normal cell activities and:
G1- increases proteins, organelles, and size
S- duplicates DNA
G2- increases supplies for cell division
2. Mitotic phase- division of cell *
Mitosis (M)- nucleus divides (PMAT)
Cytokinesis- cytoplasm divides
The Mitotic Phase
The Stages of Mitosis - Prophase- DNA condenses
Nucleus disappears
Spindle fibers appear and attach to kinetochores
2. Metaphase- DNA lines up in the middle
3. Anaphase- DNA separates - Telophase- Opposite of Prophase
Cytokinesis - Animal cells pinch in the middle (cleavage furrow)
- Plant cells from a cell plate in the middle
New cells are called daughter cells.
Reproduction in Prokaryotes
Binary fission- 1 cell divides into 2 daughter cells
Asexual reproduction
Divide every 20 minutes
Sexual Reproduction
Homologous Chromosomes
Chromosomes can be examined by amniocentesis
The display of the chromosomes is called a karyotype
2. Each chromosome has a twin referred to as a homologus chromosome
homologous pairs contain the same type of information
The genes may have different versions of the same trait
Ex: (eyes: blues/brown)
Diploid and Haloid Cells
- Diploid cells (2n) have two sets of homologous chromosomes
Human’s body cell (46)
23 homologous pairs (numbered 1-23)
One set from each parent
Pair #23 are the sex chromosomes
Female- XX
Male- XY
All the other pairs calle autosomes
Haploid cells (n) have one set of chromosomes
Human sex cells (23)
3. When two sex cells (gametes) are joined (fertilization) a zygote is formed
DNA: The Language of Life (Chapter 11 Lesson)
The Structure of DNA
History
4. DNA- Deoxyribonucleic Acid
Hereditary material of the cell
Makes up genes
Determines the traits of all living things
Located in the nucleus
Nucleotides
1. DNA (polymer) is composed of long chains of four different nucleotides (monomers)
2. Each nucleotide has:
phosphate group
sugar (deoxyribose)
nitrogenous base
adenine A
thymine T
guanine G
cytosine C
3. Adenine and Guanine are Purines (2 rings)
4. Thymine and Cytosine are Pyrimidines (1 ring)
5. DNA strands form when nucleotides join together
Repeating sugar-phosphate “Backbone”
nitrogenous bases are lined up
6. Two strands join together by hydrogen bonds
The Double Helix
1. Franklin & Wilkins and Watson & Crick determine the structure
2. DNA resembles a twisted ladder
Sugar-phosphate on the outside
Complementary nitrogenous bases pair on the inside
A - T
C - G
DNA Replication & Mutations
DNA Replication
1. Replication is the process used to make a copy of DNA
2. During DNA replication:
The two complementary strands separate to form templates
Free nucleotides line up with complementary bases
New strands are covalently bonded
Enzymes control the process
Replication is semi-conservative
Protein Production
From Gene to Protein
- For every gene (recipe) there is a protein
- Proteins determine the appearance and function of the cell/ organism
- DNA → RNA → protein
Transcription
Translation
4. The genetic code consists of 3 letter codes (codon)
Each condon stands for a particular amino acid
“All” organisms share this code
RNA - RNA (Ribonucleic Acid) differs from DNA:
Sugar (ribose)
Single Strand
2. Types of RNA
mRNA (message) copy of the recipe
rRNA (ribosome) stove
tRNA (transfer) utensils
Transcription - Transcription is the process of converting the information of DNA onto mRNA
Similar to DNA replication except:
Uses RNA nucleotides (U pairs with A)
Only 1 gene is copied
mRNA leaves the nucleus
Translation - Translation is the process of converting information of mRNA into a protein
tRNA acts as the translator b/w nucleic acids and proteins
The ribsome is the meeting place for mRNA and tRNA - Steps in reading mRNA:
AUG is the code for start
As each code word is read, amino acids are added
UAA, UAG, or UGA are the codes for stop
3. Protein is completed and released