Ch.17: Genes and Proteins Flashcards
Our DNA accounts for specific traits by
dictating the synthesis of proteins
are the links between genotype and phenotype
protein
The process by which DNA directs protein synthesis is called
Gene Expression
Gene expressionincludes two stages:
Transcription and translation
the genetic code is written into a strand of mRNA. It is the synthesis of RNA under the direction of DNA. produces mRNA
transcription
the mRNA code is converted into an amino acid sequence. It is the synthesis of a polypeptide, which occurs under the direction of mRNA
translation
what is the intermediate between genes (DNA) and the proteins for which they code. SINGLE STRANDED
RNA
Translation heavily relies on
Transfer RNA (tRNA)
There are 20 amino acids, but there are only
four nucleotide bases in DNA
The flow of information from gene to protein is based on a
triplet code
a series of three-nucleotides called
codon
These triplets can code for
all amino acids
The three stages of transcription are:
Initiation
Elongation
Termination
Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides
introns
Not providing instructions
Coding regions are called______because they are eventually expressed, usually translated into amino acid sequences
exons
removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence
RNA Splicing
A cell translates an mRNA message into protein with the help of
Transfer RNA
Molecules of tRNA are not identical:
Each carries a specific amino acid on one end
Each has an anticodon on the other end
the anticodon base-pairs with a complementary codon on mRNA
Protein synthesis:
1.RNA polymerase transcribes RNA from DNA
2.introns are excised from the RNA transcript, and the
remaining exons are spliced together, producing mRNA.
3.ribosomal subunits bind to the mRNA
4. tRNA molecules become attached to specific amino acids
5.tRNAs bring their amino acids in at the A site on the ribosome.
6. Peptide bonds form between amino acids
7The polypeptide chain grows until the protein is completed
True or False: Genes can be transcribed and translated after being transplanted from one species to another
True, because genes are universal
are changes in the genetic material of a cell, the raw material for evolution, not directly beneficial
mutations
are chemical changes in just one base pair of a gene, sickle cell
point mutation
Point mutations within a gene can be divided into two general categories
Base-pair substitutions
(Nucleotides are inserted or substituted for others)
Base-pair insertions or deletions
(Add or take away a nucleotide)
replaces one nucleotide with another
base pair substitution
have no effect on the amino acid because of redundancy in the genetic code
silent mutation
code for a different amino acid
missense mutation
change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein
nonsense mutation
Insertion or deletion of nucleotides may alter the reading frame, producing a
frameshift mutation
We have considered a gene as:
A discrete unit of inheritance
A region of specific nucleotide sequence in a chromosome
A DNA sequence that codes for a specific polypeptide chain
