What is DNA and how does it code for different traits?

DNA Structure DNA: deoxyribose nucleic acid One of the 4 macromolecules (nucleic acid) Polymer of nucleotides

DNA Structure

Nucleotide: subunits of nucleic acids

Nucleotides are made up of 3 major parts: Phosphate group Nitrogenous base 5 carbon sugar

12.1 DNA: The Genetic Material Chapter 12 Molecular Genetics 12.1 DNA: The Genetic Material DNA Structure Nucleotides Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base

DNA is made up of 4 different nitrogenous bases: Adenine (A) Cytosine (C) Guanine (G) Thymine (T)

Purine bases: A and G Pyrimidine bases: C and T

Chargaff’s Rule: A always bonds with T and G always bonds with C

Weak hydrogen bonds hold bases together

Chargaff’s rule: C = G and T = A Chapter 12 Molecular Genetics 12.1 DNA: The Genetic Material Chargaff Chargaff’s rule: C = G and T = A

What do you notice about different species’ nucleotides?

12.1 DNA: The Genetic Material Chapter 12 Molecular Genetics 12.1 DNA: The Genetic Material When the nucleotides bond together, DNA forms a double helix

DNA Structure DNA looks like a twisted ladder Sides of the ladder —alternating deoxyribose (sugar) and phosphate groups Steps of the ladder —complimentary nitrogenous bases (cytosine–guanine or thymine–adenine)

Two scientists, Watson and Crick, are credited with building the double helix model

two outside strands consist of alternating deoxyribose and phosphate Chapter 12 Molecular Genetics 12.1 DNA: The Genetic Material Watson and Crick Built a model of the double helix that conformed to the others’ research two outside strands consist of alternating deoxyribose and phosphate cytosine and guanine bases pair to each other by three hydrogen bonds thymine and adenine bases pair to each other by two hydrogen bonds

12.1 DNA: The Genetic Material Chapter 12 Molecular Genetics 12.1 DNA: The Genetic Material Chromosome Structure DNA coils around histones (proteins) to form nucleosomes Nucleosomes package and fold the DNA into chromatin fibers The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis

Semiconservative Replication Chapter 12 Molecular Genetics 12.2 Replication of DNA Semiconservative Replication Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA.

Chapter 12 Molecular Genetics 12.2 Replication of DNA Unwinding An enzyme, DNA helicase, is responsible for unwinding and unzipping the double helix.

Bases are exposed “Free” nucleotides found in the nucleus bond to their complimentary bases of both strands (A to T and C to G) Two new identical molecules of DNA are formed

Each new cell gets a copy of the DNA

This occurs during interphase!!

DNA polymerase (an enzyme) attaches nucleotides to the leading strand Chapter 12 Molecular Genetics 12.2 Replication of DNA One strand is called the leading strand and is elongated as the DNA unwinds. DNA polymerase (an enzyme) attaches nucleotides to the leading strand The other strand of DNA, called the lagging strand, elongates away from the replication fork.