Cellular Replication and Variation Flashcards
Homologous Chromosomes
Chromosomes of the same type; usually a pair.
Diploid
Cellular condition in which there are two of each type of chromosomes present in the nucleus.
Haploid
Cellular condition in where there is one of each type of chromosomes present in the nucleus.
Mitosis
Nuclear division resulting in daughter cells having the same number of chromosomes as the parent cell.
Meiosis
Nuclear division resulting in the daughter cells having half as many chromosomes, but the same types, as the parent cell; a reduction division, from the diploid to the haploid condition.
Chromatid
A replicated chromosome, still attached to the original at the centromere.
tetrad
Homologous chromosomes, each consisting of two chromatids, lying side by side.
Chiasma (Plural Chiasmata)
Connection between non-sister chromatids of homologous chromosomes during meiosis, where interchange occurs during crossing over.
Autosome
Non-sex linked chromosome.
Sex Chromosomes
Chromosomes carrying information that determines the sex of the individual.
X Chromosome
Female sex chromosome in vertebrates and some other animals.
Y Chromosome
Male sex chromosome in vertebrates and some other animals.
Gametogenesis
Formation of gametes.
Spermatogenesis
Formation of spermatozoa in animals.
Oogenesis
Formation of ova in animals.
Spermatogonium (Plural Spermatogonia)
Germ (or stem) cell in a layer lining the tubules in the testes.
Primary Spermatocyte
Diploid cell formed from mitosis of a spermatogonium, which undergoes meiosis I to produce two haploid secondary spermatocytes.
Secondary Spermatocyte
Haploid cell that undergoes meiosis II to form spermatids.
Spermatid
Immature spermatozoon.
Sertoli Cell
Cells in the epithelium of tubules of the mammalian testes that protect and nourish the developing spermatozoa.
Spermatozoon (Plural Spermatozoa)
Small, motile male gamete.
Ovum
Haploid female gamete.
Oogonium
A small diploid cell in the ovary that forms a primary oocyte in the female foetus.
Primary oocyte
A diploid cell developed by an ovarian germ cell in mammals, which may later develop into a ovum.
Primary Follicle
A single-layered structure in the mammalian ovary containing the primary oocyte.
Secondary Oocyte
A large haploid cells produced during meiosis I of the primary oocyte.
Polar Body
Small haploid cell produced from both meiosis I and II during oogenesis as a result of uneven cell division.
Ovulation
Release of the secondary oocyte that has started meiosis II from the ovary.
Gene Linkage
Location of genes on the same chromosome.
Allele
One of two or more forms of a gene located in equivalent positions on homologous chromosomes.
Homozygous
Describes a condition in which both alleles for the egene are the same.
Heterozygous
Each allele for the characteristic exhibiting a different expression.
recessive Allele
An allele found on a chromosome that can be masked by its dominant form in the heterozygous condition; can be autosomal or sex-linked.
Dominant Allele
An allele for a gene that overrides the effects of the recessive allele in the heterozygous condition; can be autosomal or sex-linked.
Dominant Trait
The particular trait of a characteristic that is expressed in the phenotype of a heterozygous individual.
Genotype
The genetic makeup of an individual.
Phenotype
Actual expression of the genotype.
Law of Segregation
Mendelian law that states that genes for a characteristic occur in pairs in an individual, once inherited from each parent, and when the reproductive cells are formed.
Law of Independent Assortment
Mendelian law that states the each allele pair segregates independently during gamete formation; applies when egenes for two traits are located on different pairs of homologous chromosomes.
Crossing Over
Breaking and rejoining, with exchange of DNA, between non-sister adjacent chromatids of homologous chromosomes during meiosis I.
Recombinant Gametes
Gametes produced as a result of crossing over of the chromatids of homologous chromosomes during meiosis.
In Vitro Fertilisation (IVF)
A complex series of procedures used to assist with the conception of a child, where mature eggs are collected from the ovaries and fertilised by sperm in a laboratory.
Preimplantation Genetic Diagnosis (PGD)
A procedure used prior to implantation to help identify genetic defects with embryos.
Preimplantation Genetic Screening (PGS)
The set of techniques for testing whether embryos (obtained through IVF) have abnormal chromosome numbers.
Ultrasound
A type of imaging technique that uses high-frequency sound waves.
Amnoicentesis
A surgical procedure for obtaining a sample of amniotic fluid from the amniotic sac in the uterus of a pregnant woman.
Chorionic Villus Sampling (CVS)
A prenatal test in which a sample of chorionic villi is removed from the placenta for testing.
Fetoscopy
Technique for looking directly at the foetus within the uterus (using an endoscope).
Endoscope
A lighted optical instrument that is used to look inside the body.
Gene Probe
A single-stranded DNA or RNA fragment used in genetic engineering to search for a particular gene or other DNA sequence.
