Molecular Basis of Inheritance Test 1

• In some eukaryotes, genes consist of coding nucleotide sequences, which are separated from each other by blocks of non-coding sequences. The coding sequences here are called exons and non-coding sequences are introns.
• The primary transcript from a typical eukaryotic gene contains introns as well as exons. The introns are removed from this primary transcript by a process called RNA splicing. 

Transcription is when RNA is made from DNA.
During transcription, RNA polymerase makes a copy of a gene from the DNA to mRNA as needed. During transcription, the DNA site at which RNA polymerase binds is called the promoter.

Transcription in progress: RNA polymerase slides along the DNA and makes an RNA copy (Genes are the only parts of DNA that get copied into RNA):

The genetic code by which DNA stores the genetic information consists of "codons" of three nucleotides. 
A codon is defined by the initial nucleotide from which translation starts.

The genetic code is degenerate: Some amino acids are encoded by more than one codon, in as much as there are 64 possible base triplets and only 20 amino acids. In fact, 61 of the 64 possible triplets specify particular amino acids and 3 triplets (called stop codons) designate the termination of translation. Thus, for most amino acids, there is more than one codeword.

GGG code is present only 1 time and the amino acid produced by GGG is glycine.

Transcription is the first step of gene expression. In this process, a particular segment of DNA is copied into mRNA. Thus. it controls gene expression.

One end of the tRNA matches the genetic code in a three-nucleotide sequence called the anticodon. On the other end of the tRNA is a covalent attachment to the amino acid that corresponds to the anticodon sequence.

This covalent attachment to the tRNA 3' end is catalyzed by enzymes called aminoacyl tRNA synthetases.

Cistron is a nucleotide sequence responsible for the synthesis of a polypeptide sequence of a functional protein.

The word cistron is used to emphasize that genes exhibit a specific behavior in a cis-trans test, distinct positions (or loci) within a genome are cistronic.

A transposable element (TE or transposon) is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size.

Three base triplets form a codon that codes for an amino acid. Thus AUG codes for methionine and GUG codes for Valine. AUG and GUG are both initiating codons for translation.