LEWIN'S GENES XII, 1ST
EDITION (KREBS, 2018),
CHAPTER 1-30 EXAM 2025
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Homologous gene (Homolog)
, Related genes in the same species, such as alleles on homologous chromosomes or multiple
genes in the same genome sharing common ancestry.
Interrupted Gene
A gene in which the coding sequence is not continuous due to the presence of introns.
Leghemoglobin
A hemoprotein that acts as an oxygen carrier in the nitrogenfixing root nodules of leguminous
plants. Facilitates the diffusion of oxygen in order to promote nitrogen fixation.
Mature Transcript
A modified RNA transcript. Modification may include the removal of intron sequences and
alterations to the 5′ and 3′ ends.
Myoglobin
A mutation or a mutated gene that increases the basal level of mutation. Such genes often
code for proteins that are involved in repairing damaged DNA.
Orthologous gene (Ortholog)
Related genes in different species.
Overlapping Gene
A gene in which part of the sequence is found within part of the sequence of another gene.
Paralogous Gene
Genes that share a common ancestry due to gene duplication.
Paralogs
Genes that share a common ancestry due to gene duplication.
Positional Information
The localization of certain cell structures in specific places.
Pre-mRNA
The nuclear transcript that is processed by modification and splicing to give an mRNA.
Primary (RNA) Transcript
The initial product of transcription that consists of an RNA extending from the promoter to
the terminator and possesses the original 3′ and 5′ ends.
Purine-Loading (AG) Pressure
The tendency of a species' AG (purine) content at the first, second, and third positions of the
codons of its genes to conform to an optimal value.
, RNA Splicing
The process of excising introns from RNA and connecting the exons into a continuous
mRNA.
Second Parity Rule
Rule discovered by Edwin Chargaff that, to a close approximation, there are equal amounts of
adenine (A) and thymine (T) and equal amounts of cytosine (C) and guanine (G) in each
single strand of the DNA duplex
Superfamily
A set of genes all related by presumed descent from a common ancestor but now showing
considerable variation.
cpDNA
The DNA found in the chloroplast.
ctDNA
The DNA found in the chloroplast.
D-loop
(1) A region within mitochondrial DNA in which a short stretch of RNA is paired with one
strand of DNA, displacing the original partner DNA strand in this region. (2) The
displacement of a region of one strand of duplex DNA by a complementary singlestranded
invader.
DNA Forensic
Technique used to identify individuals by characteristics of their DNA for the purposes of
paternity testing or criminal investigations. Although approximately 99.9% of human DNA
sequences are the same in every person, there are enough differences in a person's DNA that
it is possible to distinguish one individual from another (unless they are monozygotic twins).
Identification is based on the small set of DNA variations that is likely to differ between
unrelated individuals.
Alternative Splicing
The production of different RNA products from a single product by changes in the usage of
splicing junctions.
Cluster Rule
Rule discovered by Erwin Chargaff that purines tend to cluster on one DNA strand and
pyrimidines tend to cluster on the other. As applied to exons, the purines, A and G, tend to be