Chapter 8: Gene Expression Flashcards
What is a genome?
All genetic material contained in an organism or a cell, including DNA existing as chromosomes within the nucleus, and DNA in mitochondria and chloroplasts (if present)
What is a gene?
Particular sections or organisms that carry instructions in the form of a code
What is polypeptide?
A polymer of many amino acids linked by peptide bonds; forms a protein or part of a protein (refer to figure 8.2.6 pg 156 for the process of polypeptide formation)
What is a codon?
A series of three adjacent nucleotide bases in DNA and mRNA; each codon specifies a particular amino acid to be added when a polypeptide is assembled; start and stop codons also occur
What is a ribosome?
Organelle where polypeptide synthesis occurs in all cells; locks onto mRNA molecule and moves along it to translate its code and link amino acids; formed in the nucleolus
What is messenger RNA (mRNA)?
A ribonucleic acid molecule formed in the nucleus during gene transcription; has a nitrogen base sequence complementary to DNA template segment; travels to the cytoplasm where ribosomes attach
What is a template strand?
The DNA strand that serves as a pattern for making complementary polynucleotide
What is transcription?
The formation of an mRNA molecule against the template strand of DNA molecule in the nucleus by complementary nucleotide base pairing (figure 8.2.2 pg 153 for more detail)
What is a non-template strand?
The DNA strand complementary to the template strand; does not form the pattern for the synthesis of a complementary polynucleotide
What is pre-mRNA?
An unmodified ‘immature’ mRNA molecule that contains introns
What are introns?
A section of DNA or pre-mRNA that does not code for a polypeptide; is removes (spliced) from pre-mRNA to form a mature mRNA molecule
What is an exon?
A section of DNA, pre-mRNA, or mRNA that codes for a polypeptide
What is mature mRNA?
A modified pre-mRNA molecule with introns removed; ready to move out of the nucleus to the cytoplasm
What is a start codon?
The first codon of an mRNA transcript translated by a ribosome; signals the ribosome to start translating mRNA
What is translation?
The joining of amino acids in a specific order, according to information in mRNA ‘read’ by the ribosome, to form polypeptide
What is transfer RNA (tRNA)?
An RNA molecule that picks up a particular amino acid from the cytoplasm and then pairs with a specific mRNA codon to deliver the amino acid to the growing polypeptide chain
What is the anticodon?
A sequence of three nucleotide bases on a tRNA molecule that pairs with complementary bases on an mRNA strand during translation at a ribosome
What is the amino acid binding site?
The site of attachment of an amino acid to a tRNA molecule
What is a peptide bond?
The bond that forms between adjacent amino acid monomers
What is a stop codon?
The codon that discontinues the synthesis of the polypeptide chain
What is coding DNA?
The small part of DNA used as a template for mRNA synthesis and thus for polypeptide synthesis; also known as a gene
What is non-coding DNA?
All DNA sequences within the genome that are not found within mRNA-coding exons i.e. do not code for polypeptides. Many functions of non-coding DNA are yet to be determined
What is ribosomal RNA (rRNA)?
A folded molecule of RNA that combines with proteins to form ribosomes; formed in the nucleolus of eukaryotic cells
What is a telomere?
Hundreds of thousands of repeated short DNA sequences at the ends of chromosomes to help maintain them; short lengths lost within each replication of DNA
What is gene expression?
The process in which information encoded in gene directs the production of RNA molecules (mRNA, tRNA, and rRNA) for polypeptide and thus protein synthesis
What is gene regulation?
Various processes that enable a gene to be expressed (or not) in specific times and allow the proteins to be produced at required rates
What are housekeeping genes?
A gene that encodes a polypeptide as part of a protein (often an enzyme) required to maintain basic cellular processes
What are the two categories of gene regulations?
Short-term and long-term regulations
What is short-term gene regulation?
Ensures that all of the different varieties of specialized cells can carry out their regular everyday functions
What is long-term gene regulation?
determines the development of the organism through all the different life stages, including the differentiation of specialized cells
What is a nucleosome?
The basic structural unit of chromatin comprising a DNA strand wrapped around a group of 8 histone molecules
How are genes switched on and off?
Refer to figure 8.5.1 pg 162 for info
What are regulatory proteins?
A protein that binds to DNA to switch a gene on or off
What are transcription factors?
A regulatory protein whose function of to activate or inhibit transcription of coding DNA by binding to specific non-coding segments near the gene to be expressed or repressed
What are some examples of environmental influences on gene expression?
- Twins that have the same genes but have different characteristics
- The Himalayan rabbit, the fur changes depending on the weather (darker for cooler days, white for hot days)
What are some examples of influences on phenotypic expression that can be passed to offspring?
- Arsenic
- Heavy metals
- Some organic pollutants
- Lifestyle
- Stress levels
- Food consumed
Can all affect how genes are expressed, which ten can be passed on to offspring
What does epigenetics mean?
The study of chemical modifications to gene function that are not due to a change in the DNA sequences
How does translation affect gene expression?
The mRNA is prevented from being translated into a polypeptide, so expression is switched off in that way
What are microRNA (miRNA)
A small non-coding segment of RNA that plays a role in regulating gene expression at the post-transcription level
What is morphology?
The shape and form of an organism or its part
What are homeobox genes?
A gene of a group that cod for proteins that regulate body formation and patterning in the developing embryo (refer to figure 8.6.3 pg 167 for more detail)
What is the most influential gene in the process of sex determination?
The SRY gene (sex-determining region of the Y chromosome), located on the right branch of the Y chromosomes, launches the genetic program for testes development