DEFINITIONS Flashcards
Gamete
a mature haploid or female germ cell which is able to fuse and form a zygote.
Zygote
a diploid cell resulting from the fusion of two haploid gametes.
Haploid
a cell having a single set of unpaired chromosomes
Diploid
a cell containing two complete sets of chromosomes, one from each parent.
Homologous chromosomes
a pair of chromosomes joined by a centromere with the same genes in the same order with variation between them.
Karyotype
the number of visual appearance of the chromosomes in the cell of an organism
Bivalent
a pair of homologous chromosomes
Chiasma
a point at which paired chromosomes remain in contact during the first metaphase of meiosis. The point at which crossing over occurs.
Crossing over
an exchange of genetic material between two chromosomes.
Cytokinesis
the cytoplasmic division of a cell at the end of mitosis or meosis.
Reduction division
the first cell division in meiosis, the process by which germ cells are formed.
Locus
the physical site of a specific gene on a chromosome
Allele
one of two or more DNA sequences occurring at a particular gene locus.
Independent assortment
how different genes independently separate from one another when reproductive cells develop.
Random fertilisation
a source of genetic variation in offspring’s. The idea that a random gamete will fuse with another random gamete.
Genotypes
the genetic makeup of an organism
Phenotypes
the visual characteristics expressed by an organisms genetic makeup
Homozygous
two identical alleles at a gene locus
Heterozygous
Two different alleles at a gene locus
Dominant
always expressed and masks the recessive allele.
Recessive
only expressed when there are two recessive alleles.
Multiple alleles
three or more alleles for one particular gene.
Codominant
a type of inheritance in which two versions of alleles of the same gene are expressed separately to yield different traits in an individual
Monohybrid inheritance
the inheritance of characteristics controlled by a single gene
DIHYBRID inheritance
the inheritance of two genes that determine two different characteristics or influence the same characteristics.
Punnett square
a graphical representation of the possible genotypes of an offspring arising from a particular cross.
Test cross
an experimental cross of an individual organism of dominant phenotype but unknown genotype and an organism with a homozygous recessive genotype and phenotype.
Sex linkage
characteristics or traits that are influence by genes carried on the sex chromosomes.
Carrier
an individual who carriers one recessive allele for an autosomal disorder.
EPISTASIS
a circumstance where the expression of one gene is modified by the expression of one or more other genes.
Autosomal linkage
two or more genes on the same chromosome do not a sort independently during meiosis. These genes are linked and stay together in the original parental combination.
Recombinants
DNA, proteins, cells or organisms that are made by combining genetic material from two different sources.
Chi-squared test
a statistical tests commonly used to determine if there is a significant association between two variables.
TYR gene
a gene which provides instructions for making an enzyme called tyrosinase. Tyrosinase’s absence leads to albinism.
HBB gene
provides instructions for making a protein called beta-globin. Its absence leads to sickle cell traits.
HTT gene
provides instructions for making a protein called Huntingtin. Its absence lead to Huntingtons disease
F8 gene
provides instructions for making a protein called coagulation factor VIII which helps blood clot. Its absence leads to haemophilia.
Le gene
codes for giberellin which elongates plant cells for growth. Its absence leads to short plants with little growth.
B-galactosidase
an enzyme which catalyses hydrolysis of lactose into galactose and glucose
Transacetylase
any enzyme that catalyses the transfer of an acetyl group from one molecule to another.
Lactose permease
a transmembrane protein that facilitates the passage of lactose across the phospholipid bi-layer of the cell membrane
Structural gene
codes for a protein - structural / enzyme
Regulatory gene
codes for a protein that regulates expression of another gene.
OPERON
a length of DNA making up a unit of DNA expression in a bacterium - includes both structural and regulatory genes.
Inducible enzyme
an enzyme that is expressed only under conditions in which it is clearly of adaptive value.
Repressible enzyme
an enzyme which is supposed or production is inhibited by a particular metabolite produced in a pathway.
Transcription factor
proteins involved in the process of converting or transcribing DNA into RNA
Promoter region
Where RNA polymerase binds
Operator region
Where repressor protein binds
Repressor protein
Inhibits the expression of one or more genes by binding to the operator
