DNA STRUCTURE REPLICATION DNA AND ITS STRUCTURE DNA

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DNA STRUCTURE & REPLICATION

DNA STRUCTURE & REPLICATION

DNA AND ITS STRUCTURE • DNA stands for deoxyribonucleic acid and carries the genetic

DNA AND ITS STRUCTURE • DNA stands for deoxyribonucleic acid and carries the genetic information in all types of living organisms • DNA consists of two strands of nucleotides wound together in a spiral called a double helix

DNA AND ITS STRUCTURE • Each nucleotide is composed of: 1. A phosphate group

DNA AND ITS STRUCTURE • Each nucleotide is composed of: 1. A phosphate group 2. A sugar molecule 3. One of four different nitrogenous bases: ØAdenine (A) ØThymine (T) ØGuanine (G) ØCytosine (C) • The phosphate and sugar parts of the nucleotides form the sides of the ladder in the DNA double helix

DNA AND ITS STRUCTURE • The nitrogenous bases of the nucleotides extend toward the

DNA AND ITS STRUCTURE • The nitrogenous bases of the nucleotides extend toward the center of the double helix, forming the rungs of the ladder • Each base is matched with a complementary base in the other strand • In accord with the base-pairing rules: ØAdenine (A) pairs with Thymine (T) ØGuanine (G) pairs with Cytosine (C) • The two strands are held together by hydrogen bonds formed between the paired bases

DNA AND ITS STRUCTURE

DNA AND ITS STRUCTURE

DNA & CHROMOSOMES • Chromosomes are thread-like structures located inside the nucleus of animal

DNA & CHROMOSOMES • Chromosomes are thread-like structures located inside the nucleus of animal and plant cells • Each chromosome contains a DNA molecule, which contains multiple genes • Chromosomes are not always visible; They usually sit around uncoiled and as loose strands called chromatin • When it is time for the cell to divide, they condense and wrap up very tightly • The tightly-wound DNA is the chromosome

DNA & CHROMOSOMES • Chromosomes look like an “X” and they are usually found

DNA & CHROMOSOMES • Chromosomes look like an “X” and they are usually found in pairs • Scientists count individual strands of chromosomes because not every organism has pairs • Humans have 46 chromosomes (or 23 pairs) • Peas only have 12 chromosomes, and dogs have 78 • More chromosomes does NOT equal a more complex or intelligent creature

DNA & CHROMOSOMES

DNA & CHROMOSOMES

DNA REPLICATION • Replication is the process where DNA makes a copy of itself

DNA REPLICATION • Replication is the process where DNA makes a copy of itself • It produces two new DNA molecules that are identical to the original DNA molecule • Each of the new DNA molecules carry the same genetic information as the original DNA molecule

DNA REPLICATION • Why does DNA need to copy? • It’s simple: Cells divide

DNA REPLICATION • Why does DNA need to copy? • It’s simple: Cells divide for an organism to grow or reproduce, and every new cells needs a copy of the DNA or instructions to know how to be a cell • DNA replicates right before a cell divides

DNA REPLICATION • DNA replication is semi-conservative • That means that when it makes

DNA REPLICATION • DNA replication is semi-conservative • That means that when it makes a copy, one half of the old strand is always kept in the new strand • This helps reduce the number of copy errors (a. k. a. mutations)

DNA REPLICATION • During replication, enzymes called helicases separate DNA strands by moving along

DNA REPLICATION • During replication, enzymes called helicases separate DNA strands by moving along the strand breaking the hydrogen bonds between base pairs • The Y-shaped region that results when the two strands separate is called a replication fork • Each old strand is used as a template to form a new DNA strand

DNA REPLICATION • Next, enzymes called DNA polymerase add complementary nucleotides (free floating in

DNA REPLICATION • Next, enzymes called DNA polymerase add complementary nucleotides (free floating in the nucleus) to each of the original strands • The result is two separate and identical DNA molecules that are ready to move to new cells for in cell division • In each new DNA double helix, one strand is from the original molecule, and one strand is new (hence the name, ‘semi-conservative’)

DNA REPLICATION

DNA REPLICATION

DNA REPLICATION

DNA REPLICATION

BRAINPOP VIDEO & QUIZ ACTIVITY • Brain. Pop Video

BRAINPOP VIDEO & QUIZ ACTIVITY • Brain. Pop Video