PHYSIO - DNA CHAPTER

Nucleic Acids

The two forms of nucleic acids are DNA and RNA.

Nucleotide Structure

A nucleotide includes a sugar with 5 carbons, a base attached to the #1 carbon, and a phosphate group attached to the #5 carbon.

Linking Nucleotides

Nucleotides form nucleic acids by linking the phosphate group of one nucleotide to the #3 carbon of the sugar of the next nucleotide.

5' end of Nucleic Acid

The 5’ end of the nucleic acid chain has a free phosphate group.

3' end of Nucleic Acid

The 3’ end of the nucleic acid chain has a free #3 carbon of sugar.

DNA

DNA stands for deoxyribonucleic acid and is organized as 46 chromosomes.

Unique DNA in Cells

Each cell in our body contains a unique set of DNA molecules.

Autosomal Chromosomes

There are 22 pairs of autosomal chromosomes.

Sex Chromosomes

The X and Y chromosomes are called the sex chromosomes.

Female Chromosomes

Females have two X chromosomes.

Male Chromosomes

Males have one X and one Y chromosome.

Inheritance of Y Chromosome

Y chromosomes are only inherited from fathers to sons.

Mitochondrial DNA

Additional DNA is present in the mitochondria and is inherited from mothers to offspring.

Sugar in DNA

The sugar in DNA is called deoxyribose.

Bases in DNA

The possible bases in DNA are guanine, adenine, cytosine, and thymine.

Hydrogen Bonding in DNA

DNA exists as a double strand by forming hydrogen bonds between the bases.

Base Pairing in DNA

Guanine pairs with Cytosine by 3 hydrogen bonds; Thymine pairs with Adenine by 2 hydrogen bonds.

DNA Strand Orientation

If one DNA strand is oriented in a 5’ to 3’ direction then the other strand will have a 3 to 5 orientation.

Genes

Genes are regions of DNA that code for a protein.

Human Genes Count

Human DNA contains approximately 20,000 genes, accounting for only 2% of all DNA.

Genome

All of DNA (genes and non-genes) are collectively called the genome.

Non-Gene DNA Functions

The non-gene portion of our DNA may be remnants of ancestral genes or used to control gene expression.

RNA

RNA stands for ribonucleic acid and is copied from DNA.

Sugar in RNA

The sugar of RNA is ribose.

Bases in RNA

The possible bases of RNA are guanine, adenine, cytosine, and uracil.

Types of RNA

mRNA contains codes to make proteins; tRNA transports amino acids; rRNA helps in peptide bond formation.

RNA Codons

RNA codons are combinations of 3 RNA nucleotides that code for amino acids.

Initiator Codon

The initiator codon is AUG, coding for methionine.

Stop Codons

The three stop codons are UAA, UGA, and UAG.

Transcription

Transcription is the process of copying DNA into RNA.

Location of Transcription

Transcription occurs in the nucleus of the cell.

Promoter

A promoter is a region of DNA that is upstream of the gene.

Splicing

During splicing, enzymes remove introns from the RNA, joining exons together to create mRNA.

Translation

Translation is the process of synthesizing proteins based on the codons contained in RNA.

Steps of Translation

The three stages of translation are initiation, elongation, and termination.

Leading and Lagging Strand

The leading strand is synthesized in the direction of the replication fork; the lagging strand is made in Okazaki fragments.

Semi-Conservative Replication

Semi-conservative replication means each DNA molecule will contain one old strand and one new strand.

DNA Polymerase Error Rate

The error rate of DNA polymerase is 1 error in 1 billion.