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Terms in this set (55)
Cell division that produces reproductive cells in sexually reproducing organisms
Germ Line Cells
During zygote development, cells that are set aside from the somatic cells and that will eventually undergo meiosis to produce gametes
A mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.
An organism or cell having only one complete set of chromosomes that forms a Zygote, Contains half the genetic material of a normal cell, has one copy of each type of chromosome
Containing two complete sets of chromosomes, one from each parent. Contains maternal and paternal genetic material (2 sets of genetic information)
Pairing of homologous chromosomes at the start of Meiosis during Prophase 1
Any cells in the body other than reproductive cells
The genetic process by which one chromosome breaks off and attaches to another chromosome during reproductive cell division
Involves the random alignment of the homologous chromosome pairs during Metaphase I as well as independent segregation of genes during the formation of gametes
Fusing of a male sex cell with a female sex cell.
The developing human organism from about 2 weeks after fertilisation through the second month
Stage of early development in mammals that consists of a hollow ball of cells
An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm.
Outermost germ layer; produces sense organs, nerves, and outer layer of skin
The middle layer of an embryo in early development, between the endoderm and ectoderm.
The inner germ layer that develops into the lining of the digestive and respiratory systems
When fertilisation happens outside the bodies of the parents.
External Fertilisation Example
Salmon where the female and male both release their gametes into the water, where they diffuse together and fertilise
When fertilisation happens inside the body of a parent.
Internal Fertilisation Example
Humans use Internal Fertilisation to fertilised the females sex cell (Egg) through the action of intercourse
Advantages of External Fertilisation
-no partner required --> helps if the organism is slow moving or immobile e.g. sea urchins undertake synchronised spawning
-number of offspring that can be produced
-can occur frequently
Advantages of Internal Fertilisation
-protection of the fertilised egg (chances of survival)
-success rate of fertilisation is increased
-decreases the need to produce large amounts of eggs
Unspecialized cells that are able to renew themselves for long periods of time by cell division
Types of Stem Cells
Totipotent,Pluripotent, Multipotent, Unipotent
Stem cells with the potential to differentiate into any type of cell.
Cells that are capable of developing into most, but not all, of the body's cell types
Cells with limited potential to develop into many types of differentiated cells
Describes the condition of being committed to a single specialised cell type
Embryonic Stem Cells
Embryonic cells, which can develop into any type of body cell
Adult Stem Cells
Undifferentiated cells found among differentiated cells in a tissue or organ
Errors that can occur in Meiosis
Non disjunction, Polyploidy, Aneuploidy
Error in meiosis in which homologous chromosomes fail to separate.
A chromosomal alteration in which the organism possesses more than two complete chromosome sets.
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number.
Sexual Reproduction Cell Cycle
Interphase, Meiosis (PMAT stage 1, PMAT stage 2)
Chromosomes duplicate within the cell
The chromosomes condense, and the nuclear envelope breaks down. crossing-over occurs.
Pairs of homologous chromosomes move to the equator of the cell.
The fibres pull the homologous chromosomes toward opposite ends of the cell
Telophase 1 and Cytokinesis (meiosis)
Chromosomes gather at the poles of the cells. The Cytoplasm divides.
A new spindle forms around the chromosomes
Centromeres of chromosomes line up randomly at the equator of each cell.
Centromeres divide, Chromatids move to the opposite poles of the cell, Sister chromatids separate
Telophase 2 and Cytokinesis
A nuclear envelope forms around each set of chromosomes, The cytoplasm divides, Results in four haploid daughter cells
Products of Meiosis
4 haploid gametes genetically unique to each other and parent cells
Occurs in Prophase1 where small genetic material is broekn off the chromosome. At each chiasma, chromatids may break and re-join which results in swapping of DNA
Stages of Crossing Over
Synapsis, Crossing Over, Recombination
Homologous Chromosomes pair up, forming a bivalent
Non-sister chromatids may overlap, forming chiasmata. Can be used interchangeably with Recombination
Alleles are swapped between non-sister chromatids, forming recombinant chromosomes. Can be used interchangeably with Crossing Over
Advantages of Sexual Reproduction
-Produces genetic variation in the offspring.
-The species can adapt to new environments due to variation, which gives them a survival advantage.
-A disease is less likely to affect all the individuals in a population.
Disadvantages of Sexual Reproduction
It is way slower than asexual reproduction
During metaphase I, not II, has to do with the random alignment of maternal and paternal chromosome in the homologous pairs on either side of the equator.
When members of a homologous pair line up randomly with respect to maternal or paternal origin during metaphase I of meiosis, thus increasing the genetic diversity of offspring.
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