In prokaryotic cells, what is the shape of the DNA molecule and is it associated with proteins?
Short circular DNA not associated with histone proteins.
Prokaryotes lack histones and typically have a single circular chromosome in the cytoplasm.
In the nuclei of eukaryotic cells, DNA molecules are long and linear. Which proteins are they associated with to form chromosomes?
Histones
DNA wraps around histone proteins to form chromatin, which condenses into chromosomes.
What structure is formed when a DNA molecule combines with its associated proteins in eukaryotic cells?
Chromosome
A chromosome consists of one long DNA molecule packaged with proteins.
Besides the nucleus, which two organelles in eukaryotic cells also contain their own DNA?
Mitochondria and chloroplasts
These organelles have circular DNA similar to that found in prokaryotes.
True or False:
DNA in mitochondria and chloroplasts is linear and associated with histone proteins.
False
Their DNA is short, circular and not associated with histone proteins, similar to prokaryotic DNA.
What do we call a sequence of DNA bases that codes for a polypeptide or a functional RNA molecule?
Gene
Genes can code for polypeptides or functional RNA such as rRNA and tRNA.
What term describes the fixed position that a gene occupies on a DNA molecule?
Locus
Each gene is located at a specific locus on a chromosome.
What is the name given to a sequence of three DNA bases that codes for a specific amino acid?
Triplet or codon
Each triplet of DNA bases corresponds to one amino acid in a polypeptide.
True or False:
The genetic code is overlapping, meaning a base can belong to multiple triplets.
False
The genetic code is non-overlapping, so each base is part of only one triplet/codon.
What property of the genetic code means that several different base triplets can code for the same amino acid?
Degenerate
For example, multiple codons can specify the same amino acid.
Fill in the blank:
Within a gene, the sequences that actually code for amino acid sequences are called ______.
Exons
Exons remain in the mature mRNA after RNA processing.
Fill in the blank:
Non-coding sequences found within genes that separate coding regions are called ______.
Introns
Introns are removed during RNA splicing before translation occurs.
True or False:
Much of the DNA in eukaryotic nuclei does not code for polypeptides.
True
Eukaryotic genomes contain large amounts of non-coding DNA including repeats and introns.
What is the term for the complete set of genes present in a cell or organism?
Genome
Includes all coding and non-coding DNA sequences within a cell.
What term describes the entire range of proteins that a cell is capable of producing?
Proteome
Varies between cell types because different genes are expressed.
Which type of RNA carries a copy of genetic information from DNA to a ribosome?
mRNA
Messenger RNA is complementary to the DNA template strand.
Which RNA molecule carries specific amino acids to the ribosome during protein synthesis?
tRNA
Each tRNA has an anticodon that pairs with a codon on mRNA.
Which enzyme catalyses the joining of RNA nucleotides during the formation of an RNA strand from DNA?
RNA polymerase
The enzyme moves along the DNA template strand during transcription.
What is the process called in which a strand of RNA is produced using a DNA template?
Transcription
Produces RNA that is complementary to the DNA template strand.
What is the name of the RNA molecule initially produced in eukaryotic transcription before processing occurs?
pre-mRNA
This molecule still contains introns that must be removed.
What process removes introns and joins exons to produce a functional RNA transcript in eukaryotic cells?
Splicing
Occurs in the nucleus before the mRNA leaves for translation.
What process produces a polypeptide using the sequence of codons on an mRNA molecule?
Translation
Occurs at ribosomes in the cytoplasm or on rough ER.
What three-base sequence on an mRNA molecule specifies a particular amino acid during protein synthesis?
Codon
The genetic code is read in triplets during translation.
Fill in the blank:
During protein synthesis, energy used to attach amino acids to tRNA molecules is supplied by ______.
ATP
ATP provides energy for amino acid activation before translation.
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2: Biological Molecules119
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2: Cells52
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