Biology Chapter 6 - DNA and Gene Expression

DNA

A nucleic acid that stores hereditary information and the instructions for the proper functions for a cell.

Make up of nucleotides

Deoxyribose (5 carbon sugar), a phosphate group attached to the sugar, Nitrogenous bases

Nitrogenous Bases in DNA

Adenine, Guanine, Thymine, Cytosine.

Nitrogenous Bases

The 4 bases that make up the genetic code for all living organisms.

Thymine

Adenine and ______ bind together.

Guanine

______ and Cytosine bind together.

Linear

The physical structure of eukaryotic DNA

Double Helix

The twisted, spiraled staircase or ladder form for DNA.

DNA Structure

Twisted ladder shape made up of two strands of DNA where the sugar and phosphate groups form the backbone, and the bases form the rungs of the ladder and the bases extend out from the backbone into the middle and pairs via hydrogen bonds.

Genome

The full set of DNA found in an organism.

Plasmids

Where all genetic information is contained prokaryotes.

Linear strands

In eukaryotic organisms, genetic information is laid out in _______ _______

Chromosomes

The divided genetic strands of DNA. Humans’ DNA is divided into 23 pairs (46 total) and get one set from our mom and one set from our dad.

Genes

Specific sequences of DNA located at a specific locus on a chromosome and code for specific traits an organism has.

Locus

The position of a gene along a specific chromosome.

Traits

Hair color, height, eye color

Alleles

Alternative versions of genes that code for the same trait and is what codes for the trait that is seen on the surface.

Trait

Any single physical characteristic or feature of an organism.

Coding DNA

The DNA sequences that actually code for a protein product. It’s what codes for each individuals’ traits.

Junk DNA/Non-Coding DNA

DNA that doesn’t code for an actual trait and seems to serve no purpose and is found on the chromosome within the spaces between genes as well as within the genes themselves.

Prokaryotes

Don’t have a lot of non-coding DNA, 90% or more of their DNA codes for a product.

Eukaryotes

Have a lot of non-coding DNA interspersed with the coding DNA.

Exons

The coding regions of the gene.

Introns

The non-coding regions of the gene.

Non-coding regions

regions of DNA that consist of areas within the gene that repeat themselves thousands of times.

Components of non-coding DNA

Gene fragments, duplicate versions of genes, and pseudogenes.

Pseudogenes

Sequences that evolved from actual genes but accumulated mutations that made them lose their protein coding ability.

non-coding DNA

Some of the _________ DNA does encode extremely short RNA molecules (~20 nucleotides long) that function in gene regulation.

Genotype

The actual genes that an organism has that codes for a trait.

Phenotype

The physical manifestation of the genes an individual has.

Traits

The result of various proteins being produced in the cells.

Transcription and Translation

The two processes involved from going from the genes in your DNA to the proteins that are produced.

Transcription

Copying the gene information from the DNA into mRNA.

Translation

Translating the message in mRNA into an actual protein product.

Promoter Site

The area on the gene that tells the enzyme where to start the process of copying.

Step 1 of Transcription

The enzyme RNA polymerase recognizes the promoter site and binds to the DNA. This begins the process of unwinding the helix so it can be copied.

Step 2 of Transcription

The RNA polymerase moves down one side of the DNA strand copying the message. RNA polymerase builds an mRNA strand by binding RNA nucleotides together that match with the bases on DNA.

Nitrogenous Bases in RNA

Adenine, Uracil, Guanine, Cytosine

Step 3 of Transcription

Gene sequences are not infinite, when the end of the gene sequence is reached, the process terminates. The RNA polymerase stops copying and releases from the DNA strand.

Step 4 of Transcription

Editing the mRNA sequence by cutting out the introns and getting it ready for transport out of the nucleus.

Transfer RNA (tRNA)

The molecules that translate the mRNA code by linking specific bases on the mRNA with specific amino acids that will be used to build a protein.

Codon

A 3 base sequence on mRNA that matches with tRNA that carriers one particular amino acid.

Attachment Site

A 3 base sequence that matches up with a 3 base sequence on the mRNA.

The Codon Table

Describes which tRNA and which amino acid is specified by each codon in the mRNA with 64 total codons possible where 61 specify amino acids and 3 are stop sequences.

Stop Sequences

Codons that indicate the end of translation.

Step 1 of Translation

Recognize and initiate protein building by recognizing the start sequence AUG and then having ribosomal subunits attach to the mRNA which signals the tRNA to start bringing in the matching amino acids. This is where protein synthesis begins.

Step 2 of Translation

Elongation. The ribosome attached to mRNA moves down the strand reading it one codon at a time and at each codon, a tRNA brings in a new amino acid which are all linked together by peptide bonds, causing the protein to grow at one amino acid at a time.

Protein Synthesis

The production of a protein

Step 3 of Translation

Termination. The ribosome keeps moving down the mRNA sequence until it reaches one of the 3 stop codons and then detaches from the mRNA and releases the completed protein. Then the mRNA can be used repeatedly for several days until it’s broken by enzymes in the cytoplasm.

The 3 stop codons

UAA, UAG, and UGA