Chapter 10: Gene Action: From DNA to RNA to Protein

protein building block consisting of an amino group, an acid group, a hydrogen, and an R group.

amino acid

gene and protein connection

Genes are the instructions that tell cells which types of amino acids to attach in a specific sequence to form a particular protein.

how protein shape forms

shape arises as amino acids attract or repel one another

functions of proteins in human body

• forms blood clots

• forms antibodies n cytokines

• forms muscle

• are enzymes

• forms hair and skin

Template strand

The DNA strand carrying the information to be transcribed.

An enzyme that adds nucleotides to a growing RNA chain.

RNA Polymerase

The strand of the DNA double helix for a gene from which RNA is not transcribed.

Coding strand

RNA that, with proteins, comprises ribosomes.

Ribosmal RNA

Transfer RNA

A type of RNA that connects mRNA to an amino acid during protein synthesis.

anticodon

triplet of bases complementary to a codon

transcription factor

Proteins that form a structure that binds DNA at certain sequences, initiating transcription at specific sites on chromosomes

Promoter

A control DNA sequence that signals the start of a gene.

Intron

Part of a gene that is transcribed but is excised from the mRNA before translation into protein

Exon

parts of mRNA that remains and is translated into protein

An alternate version of a protein that arises from a certain combination of translated exons.

Isoform

The mechanism of combining exons of a gene in different ways

alternative splicing

genetic code

The correspondence between specific mRNA triplets and amino acids.

reading frame

The point in a DNA sequence from which contiguous triplets encode amino acids of a protein. A DNA sequence has three reading frames.

frameshift mutation

A mutation that alters the reading frame of the sequence used to produce a protein

RNA vs DNA

• RNA is single-stranded

• RNA has uracil instead of thymine

• uses ribose sugar

how mRNA transmits protein-building instructions

Each contiguous three bases of an mRNA encode an amino acid.

steps of transcription

1. Transcription factors bind to the promoter sequence DNA, which attracts RNA polymerase

2. the polymerase unwinds the DNA and attaches complementary RNA bases to the template strand

3. termination sequence in DNA stops the process

alternative splicing

combines the exons of a gene in different ways, forming instructions for slightly different variants of a protein

genetic code characteristics

1. triplet

2. nonoverlapping

3. universal

4. degenerate

how is translation efficient

• RNA, ribosomes, enzymes, and key proteins are recycled.

• Transcription produces many copies of an mRNA.

• Each mRNA can bind several ribosomes.

steps of translation

1. In translation initiation, the mRNA leader sequence binds to rRNA in the small ribosomal subunit and the first codon attracts a tRNA.

2. Then the large ribosomal subunit attaches and tRNAs bring in amino acids, with the tRNA anticodons binding their codons in the mRNA.

3. Peptide bonds form between the amino acids attached to the aligned tRNAs, building a polypeptide.

4. Protein synthesis halts at a stop codon.