Download Structure and Role of DNA Genetic and DNA Genetics

Structure and Role of DNA
Genetic and DNA
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Genetics-branch of biology that studies heredity
Traits-organisms characteristics, such as cell structure and body shape
Genetic information is contained in nucleic acids (large organic molecules made up or H, O, N, P)
Nucleic acids are made up of smaller units called nucleotides
o Nucleotide(5 carbon sugar bonded to Nitrogen base, phosphate group)
2 types of nucleic acids:
o DNA- carries genetic information and contains instructions for cellular activity and
protein production.
o Nn
Eukaryotes DNA is in nucleus in coiled structures(chromosomes)
Prokaryotes DNA is attached to cell membrane or floats freely in the cytoplasm
Endosymbiont theory- mitochondria and chloroplasts originated as separate organisms
Primitive Organisms and the Endosymbiont Theory
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1st organisms were unicellular
Oxygen was fatal to most early life forms, to survive they adapted to use oxygen for respiration
Prokaryotes lack membrane bound organelles, endosymbiant theory says that early prokaryotes
evolved internal cell membranes that lead to primitive eukaryotic cells.
Other prokaryotic organisms, entered the primitive eukaryotic cell. Eukaryotic cell formed a
mutualistic relationship with prokaryotes. Then evolved into organelles of the eukaryotic cell.
The structure of DNA
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4 bases in DNA: adenine, thymine, guanine, and cytosine
DNA molecule shaped like a twisted ladder=Double Helix(Waston/Crick)
Bases always pair
A-T
C-G
Base pairing rule
 RNA copies information from the DNA molecule. RNA carries information to ribosomes.
DNA Replication
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Replication- process when DNA makes a copy of itself
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DNA molecule replicates before a cell divides, each new cell receives a copy of genetic material
contained in parent cell.
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Stages of replication:
o 2 enzymes unzip in the DNA molecule
o Nucleotides separate and break original molecule into 2 complimentary halves
o Once speaparated into 2 strands, complimentary sequences of bases are exposed
 EX: ACTTG
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After DNA molecule unzips, enzymes in cytoplasm link nucleotides to make
duplicate strands.
o Results in 2 new DNA molecules, contains ½ or each parent cell
o DNA polymerase checks the arrangement of bases in the new DNA strands and fix
errors
Chromosomes and Genes
 Chromosomes(contain genetic information) wraps around proteins and become tightly
coiled
 Every species has a characteristic number of chromosomes in its cells
 Traits are dertermined by small parts of chromosomes
 Gene-section of a chromosome that codes for a trait
o EX: eye color-determined by two or more genes
Gene Expression and Regulation
 Main function of genes: Control the production of proteins
 Gene expression: process by which the information carried in genes is transferred into proteins
 Begin life as a single cell. 2 parents. Gene expression begins as soon as the fertilized egg begins
to divide to form cells.
 Gene expression is determined by position of a cell within the growing mass of cells
 Different genes are expressed differently as organism grows.
o EX: skin cell, nerve cell, blood cell
 Some genes expressed @ different times
o EX: estrogen in puberty
 Particular cells express only the genes that code for proteins it needs for its functions.