Intro to cell division Flashcards
The developmental process from a single cell to a baby (in 9 months)
is called :
Embryology
It provides a logical framework for understanding adult anatomy
Provides a bridge between basic sciences and clinical sciences.
The first ___ weeks of human development is called the embryogenesis and the product is called ___.
8 weeks
Embryo
The process of the progressing from a single cell up to the period of establishing organ primordia is called ______.
Embryogenesis
Define teratology
The study of embryological origins and causes for birth defects
What is the definition of gametogenesis :
Preparation of male and female germ cells for fertilization.
Fertilization refers to the fusion between male and female _____.
Pronucleus.
The cell that results from the union of an oocyte and sperm during fertilization is called ______.
Zygote
Puberty refers to the period during which __________ develop. Usually occurs around ____ years in girls and ____ in boys.
Secondary sexual characteristics
12-15 in females
13-16 in boys
Briefly describe the chormosome theory of inheritance.
The idea that genes are located on chromosomes.
It states simply that chromosomes, which are seen in all dividing cells and pass from one generation to the next, are the basis for all genetic inheritance.
Genes that site close to each other on the same chromosome tend to be inherited together : this is the principle of linked genes.
In somatic cells chromosomes appear as 23 homologous pairs to form diploid number of 46.
There are 22 pairs of matching chromosomes (autosomes) and one pair of sex chromosomes.
Each gamete contains an haploid number of 23 chromosomes and the union of gametes at fertilization restores the diploid number.
The cell cycle completes in two phases : name them and explain them.
- Interphase : period in the cell cycle between the end of a previous division and the start of the new division
- M phase : when the cell can reach a certain size or receives a certain signal, it will start the process of dividing (mitosis or meiosis)
Mitosis occurs in both somatic and germ cells. It maintains constant chromosome number and genetic stability in all somatic cells. It increases the cell number so that the zygote transforms into a multicellular adult. It also provides new cells for repair, regeneration and wound healing.
Meiosis occurs only in the sperms and the oocytes. It is responsible for the formation of germ cells (gametes). It reduces the number of chromosomes from 46 to 23 in each germ cell in order for each gamete to have an haploid number of chromosomes.
During meiosis, crossing over occurs which produces a group of new traits in the genetic material of new cells.
Name the phases of interphase :
G1 phase
S phase
G2 phase
** G0 is when the cell cycle arrests
Describe G1 phase of interphase
G1 phase : growth in all cellular contents and growth in size of cell but no change in the chromosome (only the cytoplasm changes)
Describe S phase of interphase
S phase : Synthesis of new DNA (active synthesis of a new set of all the 46 chromosomes - thus each chromosome will duplicate but stay attach to eachother)
Describe G2 phase of interphase
G2 phase : preparation for cell division (marked growth of cellular components in prep for dividing into 2 new cells).
Cells in G2 phase are characterized by :
Intact nuclear envelops
The nucleus contains a nucleoli
Two centrosomes are formed, each with 2 centrioles
In the G2 phase, can chromosome be seen individually? why or why not.
No, because they have not condensed.
During mitosis, _____ phase is the longest and _____ phase is the shortest.
Metaphase
Anaphase
Regarding cytokinesis, the plasma membrane becomes indented to form the _____.Then contraction of the cytoskeleton will lead to formation of two new cells.
Cleavage furrow
Meiosis 1 is called _____ division, while meosis 2 is called _____ division.
Reduction
Equatorial
What is a chiasmata ?
a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands.
Pairing homologous chromosomes is referred to as _____. Does it occur in meiosis 1 or 2 ?
Synpasis
1
In meoisis 1, ______ homologues duplicated chromosomes align at the metaphase plate. In meiosis 2, only ____ homologous duplicated chromosomes align.
46
23
In meiosis 1, do centromeres split ?
What about in meosis 2 ?
No, they do not split in meiosis 1
Yes, they do split in meiosis 2
The end product of meiosis 1
2 secondary gametocytes
(Haploid)
The end product of meiosis 2 is :
4 gametes are formed having half chromosome number
Chromosomal abdormalities could be _____ or _______.
Numerical or structural
What is aneuploidy as opposed to euploidy
An abnormal number of chromosomes
Euploidy is the normal number of chromosomes (i.e. 46)
True or false. Abnormalities in chromosomes number may originate during meiosis (1& 2 ) or mitosis due to non disjunction.
When someone has an extra pair chromosome its is called ____. When someone has a pair missing it is referred to as_____.
Trisomy
Monsomy
Occasionally, nondisjunctions occurs during mitosis in an embryonic cell during the earliest cell divisions. Such conditions lead to _______. With some cells having an abdnormal number of chromosomes and others being normal. Mosaic Down, Klinefelter, Turner and neurofibromatosis are all examples.
Mosaicism.
Give 3 examples of trisomy of autosomes.
trisomy 21 (Down syndrome)
trisomy 18 (Edwards syndrome)
trisomy 13 (Patau syndrome)
Give 2 examples of trisomy of sex chromosomes
Klinefelter syndrome 47 (XXY)
Triple X syndrome 47 (XXX) : pts with Triple X syndrome are infantile, with scanty menses and some degree of mental retardation. They have two sex chromatin (Barr) bodies in their cells.
Give 1 example of monosomy
Turner syndrome 45 (XO)
Structural chromosome abnormalities usually result from chromosome breakage. Breaks are caused by environmental factors such as viruses, radiation and drugs. Two types of structural chromosome abnormalities exist and they are ___ and ___.
Deletions
Translocations
Give one example of a syndrome caused by chromosome deletion.
Cri-du-chat
Caused by a partial deletion of the short arm of chromosome 5.
Affected children have a cat-like cry, microencephaly, mental retardation and congenital heart disease.
Translocations is when a portion of a chromosome is transferred to another chromosome. 2-3 % of ________ cases are due to translocations between chromosome 14 & 21.
Down syndrome
Sometimes, only a few contiguous genes are deleted which is referred to as microdeletions.
microdeletions on the maternal chromosome 15 causes ______.
Angelman syndrome.
Children are mentally retarded, cannot speak, exhibit poor motor development, and are prone to unprovoked and prolonged periods of laugher.
Which syndrome does this refer to : microdeletion on the paternal chromosome 15 that causes affected individuals to have hypotonia, obesity, mental retardation, hypogonadism and cryptorchidism (undescended testies)
Prader-Willi syndrome
Normally, FMR1 gene makes a protein needed for the brain to grow properly. A defect in this gene makes the body produces too little of the protein or none at all. People affected by this syndrome are mentally retarded, have prominent jaw, large ears and pale blue irises. Boys and girls can both be affected, but since boys only have 1 X chromosome, a single fragile X is likely to affect them more severely.
Fragile X syndrome
