Cell Biology and Genetics Flashcards
Define aneuploidy
The condition in which the chromosome number of the cell is not an exact multiple of e haploid number
Monosomies and trisomies are examples of aneuploidy
Define allele
One of series of alternative versions of a gene or DNA sequence at a given locus
Define antisense
A piece of nucleic acid, typically created in the lab, which has a sequence exactly opposite to an mRNA molecule made by the body
Antisense can bind tightly to its mirror image mRNA, preventing a particular protein from being made
Define autosomal dominant
A trait or disease that is produced when only one copy of a polymorphism or mutation is present on an autosome
Define autosomal recessive
A trait or disease that is produced when two copies of a polymorphism or mutation are present on an autosome
Define autosome
Any chromosomes other than sex chromosomes
Define cell
The cell is the basic unit of life
If it is to survive, each cell must maintain an internal environment that supports its essential biochemical reactions, despite changes in the external environment
Therefore, a selectively permeable plasma membrane surrounding a concentrated aqueous solution of chemicals is a feature in all cells
Define a clone
A member of a group of cells that all carry the same genetic information, and which are derived from a single ancestor by repeated mitosis
Define compound heterozygote
An individual with two different mutant alleles at the same locus
Define consultand
An individual seeking, or referred for, genetic counselling
Define exon
Region of a gene containing DNA that codes for a protein
Define gamete
The reproductive cell formed by meiosis, containing half the normal chromosome number
Define genome
This is the entire genetic complement of a cell
Define genotype
This is the genetic constitution of an individual, and it is also used to refer to the alleles present at one locus
Define heritability
The degree to which a characteristic is determined by our genes
Define heterozygote
This is an individual or genotype with two different alleles at a given locus on a pair of homologous chromosomes
Define holoenzyme
The complete enzyme including all its subunits and cofactors
Define homozygote
An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes
Define hormone
A molecule produced by an endocrine cell, which is released into the blood stream and acts on specific receptors to elicit its effect
Define host
The organism used to propagate a recombinant DNA molecule
Define an insert
The fragment of foreign DNA cloned into a particular vector
Define intron
A section of a gene that does not contain any instructions for making a protein
Define karyotype
This is the chromosome complement of a cell
In a standard karyotype, the chromosomes are conventionally arranged in order depending upon size
Chromosomes are distinguished individually by their size, centromere position and banding pattern
The normal human karyotype is 46, XY (male) or 46, XX (female)
Define library
A collection of cloned DNA fragments which, taken together, represent the entire genome of a specific organism
Using traditional techniques they allow the isolation and study of individual genes
Define ligand
A molecule, such as a hormone or neurotransmitter, which binds to the receptor, and is termed the first messenger
Define locus
The position of a gene on a chromosome
Define microarray
A large set of cloned nucleic acid molecules or proteins spotted onto a solid matrix, usually a microscope slide, and used to profile gene and protein expression in cells and tissues
Define monosomy
A chromosome constitution in which one member of a chromosome pair is missing
Define multifactorial disorders
A term used to describe disorders in which both environmental and genetic factors are important
Define mutation
A permanent heritable change in a sequence of DNA
Define neurotransmitter
A molecule that is used to transmit nerve impulses across a synapse
Define an operon
A prokaryotic locus, consisting of two or more genes that are transcribed as a unit and are expressed in a coordinated manner
Define organism
An organism is a system capable of self-replication and self-repair, which may be unicellular or multicellular
Unicellular organisms consist of a solitary cell able independently to perform all the functions of life
Multicellular organisms contain several different cell types that are specialised to perform specific functions
What is a pedigree chart?
They are used to illustrate inheritance
Define penetrance
The proportion of individuals with a specific genotype that show the expected phenotype under defined environmental conditions
The term is usually used in association with dominant disorders
Define phenocopy
The alteration of the phenotype by environmental factors during development to produce a phenotype that is characteristically produced by a specific gene
Define phenotype
The observed biochemical, physiological or morphological characteristics of an individual that are determined by the genotype and the environment in which it is expressed
What is a plasmid?
Autonomously replicating, extrachromosomal circular DNA molecules
Often exploited in the laboratory as a vector for gene cloning
Define pleiotrophy
The phenomenon in which a gene is responsible for several distinct and apparently unrelated phenotypic effects, which may concern the organ system involved and the signs and symptoms that occur
Define ploidy
This refers to the number of complete sets of chromosomes in a cell.
A haploid cell contains a single set of chromosomes
A diploid cell contains two copies of each chromosome
A polyploid cell contains more than two sets of each chromosome
What is polygenic inheritance?
This is a term used to describe the inheritance of traits that are influenced by many genes at different loci
What is polymorphism?
Polymorphism is the occurrence in a population of two or more alternative genotypes, each at frequency greater than that which could be maintained by recurrent mutation alone
A locus is arbitrarily considered to be polymorphic if the rarer allele has a frequency of at least 0.01
Any allele rarer than this is a ‘rare variant’
Define proband
The first person in a pedigree to be clinically identified as having a disease in question
Define a probe
A probe is a radioactively or fluorescently labelled piece of single-stranded DNA of defined sequence
Define recombinant DNA
A molecule of DNA created ‘in vitro’ that contains elements of more than one original sequence, e.g. vector and insert
What is rolling circle replication?
A process of nucleic acid replication that can rapidly synthesise multiple copies of circular molecules of DNA such as bacterial chromosomes and plasmids
Define translocation
The transfer of one segment of a chromosome to another
Define trisomy
The state of having three representatives of a given chromosome instead of the usual pair
(E.g. As in trisomy 21 - Down syndrome)
What is variable expressivity?
This occurs when a genetic lesion produces a range of phenotypes:
- e.g. tuberous sclerosis can be asymptotic with harmless kidney cysts, but in the next generation it may be fatal, owing to the development of brain malformations
What is vector?
A DNA molecule capable of replicating within a particular host, into which foreign DNA may be inserted
Define X-linked dominant
A trait (or a disease) that is produced when only one copy of a polymorphism or mutation is present on an X chromosome
This means that both males and females can display the trait or disorder, by only having one copy of the gene
Define X-linked recessive
A trait or disease that is produced when a polymorphism or mutation in a gene on the X chromosome causes the phenotype to be expressed
