Ch.11: DNA Biology

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Terms in this set (...)

Which answer would base pair with DNA sequence: AGT TCT CAT
TCA AGA GTA
Genome
Collection of all DNA in an organism
Proteome
Collection of proteins made by an organism
Chromsome
Collection of genes on the same strand of DNA
Genes
Sequence of DNA nucleotides that provide instructions for making a protein
Allele
Different forms of the same gene
What does our DNA do?
Amount of DNA has no complexity of the organism

Only 2% of human DNA makes up genes

About 90% of DNA in bacteria makes up genes
How do genes work?
Provide instructions for building proteins

All cells in an organism (except gametes) have exactly the same genes

Expression of a gene means its protein is actively being made

Cells only express the genes they are supposed to; the rest are turned off
Gene Expression
Genotype: Genes an organism contains

Phenotype: Physical manifestation of those genes as they are expressed
Protein Synthesis
Expression of a gene
Language and Location of DNA
DNA is the language of nucleotides and proteins are the language of amino acids

DNA resides in the nucleus while proteins are made in the cytoplasm.
DNA and RNA Similarities
Nucleic Acids

Composed of nucleotides

Sugar-phosphate backbone

Four different bases
DNA and RNA Differences
DNA:
Found in nucleus
Genetic material
Deoxyribose sugar
Bases A,T,C,G
Double stranded
Transcribed to m RNA, t RNA, and r RNA

RNA:
Found in nucleus and cytoplasm
Helper to DNA
Ribose sugar
Bases A,U,C,G
Single stranded
m RNA is translated to give to proteins
Types of RNA
Messenger RNA (m RNA)

Transfer RNA (t RNA)

Ribosomal RNA (r RNA)
m RNA
Nucleus, migrates to ribosome in cytoplasm

Carries DNA sequence information to ribosomes
t RNA
Cytoplasm

Provides linkage between RNA and amino acids; transfers amino acids to ribosomes
r RNA
Cytoplasm

Structural component of ribosomes
Transcription
Function:
Convert to DNA into a m RNA transcript

Location: Nucleus

Items needed: DNA template, RNA polymerase
Steps in Transcription
Recognize and Bind: Once RNA polymerase recognizes a promoter site, it binds to one strand of the DNA and begins reading the gene's message

Transcribe: As the DNA strand is processed through RNA polymerase builds a single strand copy of the gene, called m RNA transcript.

Terminate: When the RNA polymerase encounters a code signaling the end of the gene, it stops transcription and releases the m RNA transcript.

Capping and Editing: Before the m RNA transcript can be translated into a protein, a cap and tail are often added for protection and to promote recognition, and non-coding sections are removed.
Translation
Function: Convert m RNA to a protein

Location: Cytoplasm

Items needed:
Ribosomes, amino acids, t RNAs
t RNA
Carries an amino acid on one end

Anticodon RNA sequence on other end

Translate the m RNA code, linking specific bases on the m RNA with specific amino acids that will be used to build a protein
Steps in reading the m RNA
Recognize and Initial Protein Building: The start sequence of the m RNA- transcript signified by the bases- is recognized by a corresponding t RNA molecule and the two ribosomal subunits. The attachment site of the t RNA molecule binds to the m RNA as the ribosomal subunits assemble around them.

Elongate: As the ribosome moves along the strand of m RNA, each new amino acid carrying t RNA molecule binds to the next three bases on the m RNA.
Codon
A set of three nucleotides on the m RNA

Each codon corresponds to a different amino acid
Mutations
A change to the DNA, which alters the m RNA, and which may alter the protein produced from a gene and the phenotype of the organism.

Mutations are only passed to offspring if they occur in the gamete's DNA

Occur spontaneously at a rate of about 1 per 1 million nucleotides in normal DNA

DNA polymerase can proof read the DNA and take out the wrong nucleotides
Mutagens
Known triggers for mutations and increase the mutation rate

Common mutagens: benzene, x-rays, gamma rays, alpha particles, ultraviolet radiation
Types of mutations
Point (substitution)
Frameshift (insertion or deletion)
Chromosomal aberrations