Mitosis/Meiosis Flashcards
Meiosis vs mitosis
In mitosis we stay diploid and in meiosis we go from diploid to haploid. There is a different way that the chromosomes rearrange
Locus (plural: loci)
Each gene occupies a specific place, or locus, on the chromosome
Condensation can be condensed during mitosis
True
Centromere
Where two sister chromatids hook together (middle of X)
Top half: p arm
Bottom: q arm
Telomere
The two ends of a chromosome consist of repeated nucleotide sequences called telomeres, which are essential for chromosome stability
22/23 pairs of chromosomes are called _______
Autosomes
Autosomes have similar appearance and similar DNA sequences, and are paired in diploid cells of both sexes
Sex chromosomes
The 23rd pair of chromosomes and is different in the male and female
A typical human cell has how many pairs of chromosomes?
23
The male X and Y chromosomes behave as a pair during meiotic cell division
True
X=chromosome, made up of 2 chromatids
True
Further from centromere you get bigger numbers
True
Homologous chromosomes are usually not identical
True
Changes are called mutations
Enduring mutations that are inherited are called alleles (different eye color, hair, bird songs etc)
Our gametes are only cells that are ______
haploid
Interphase
Time for acquisition of nutrients, growth, chromosome duplication
During cell division, one copy of every chromosome and half of the cytoplasm and organelles are divided out into the 2 daughter cells
Mitotic cell division
Consists of the division of one parental cell into two daughter cells; it consists of two processes: mitosis and cytokinesis
Mitosis
Division of the nucleus
During mitosis (nuclear division), the nucleus of the cell and the chromosome divide
Each daughter nucleus receives one copy of each of the replicated chromosomes of the parent cell
Cytokinesis
Cytoplasmic division
Cytoplasm is divided roughly equally between the two daughter cells, and one daughter nucleus enters each of the daughter cells
Mitotic cell division
Takes place in all eukaryotic organisms
Mechanism of asexual reproduction
Followed by differentiation of the daughter cells allows a fertilized egg to grow into an adult with perhaps trillions of specialized cells
Allows organisms to maintain, repair, and even regenerate body parts
Mechanism whereby stem cells reproduce
Prophase
Chromosomes condense, spindle microtubules form, nuclear envelope breaks down, and chromosomes are captured by spindle microtubules
Centrioles
Region from which the spindle microtubules originate contains a pair of microtubule-containing structures called centrioles
Kinetochore
Protein-containing structure located at the centromere
Wraps around centromere
Microtubules
The spindle microtubules radiate from the poles, both toward the nucleus, forming a basket around it and outward toward the plasma membrane
Cell cycle has checkpoints
True
Slows it down to make sure enzymes can go double check that everything is correct
Cohesin complex
Begin to wrap around DNA
Keeps chromatids attached
Facilitates spindle attachment
Facilitates recombination
Gametogenesis
From 46 to 23 chromosomes
Meiosis only occurs for making sperm and eggs
Meiotic cell division
The key to sexual reproduction in eukaryotic cells
A diploid cell with paired chromosomes produces haploid daughter cells with unpaired chromosomes
Prophase 1
Homologous chromosomes pair up and exchange DNA
One round of DNA replication produces how many chromatids in each duplicated chromosome?
2
Prophase I
Can last days or weeks
For women it can be occurring during the month
Metaphase 1
Paired homologous chromosomes line up at the equator of the cell
X chromosome is always the default
True
We get 4 equal sperm and only 1 ovum in females, the other 3 are called polar bodies
True
Genomic Imprinting
Imprinted genes=methylation=down regulated
Chance for mitotic errors
If meiosis doesn’t occur until after or during ovulation, then you get improper segregation after fertilization and so you’ll get too many chromosomes in egg
Nondisjunction
Most common way we get developmental errors in meiosis
When we get an abnormal chromosome number
- Trisomy 21/Down syndrom: most common single cause of mental retardation
- 90% of trisomy 21 individuals, the additional chromosome is maternal in origin
- 70% occur during M1 and 30% in M2
Prader Willi syndrome and Angelman syndrome
Two different conditions occur with the exact same deletion on chromosome 15. If the paternal chromosome is deleted, the child develops Prader Willi syndrome. If the maternal chromosome is deleted, the child develops Angelman syndrome
Prader Willi syndrome
When paternal chromosome is deleted on chromosome 15
Angelman syndrome
When maternal chromosome is deleted on chromosome 15
More chromosomal errors
Errors on chromosomes 13, 18, 21 cause major developmental defects. Events can occur during non-disjunction
You can either have entire copies of chromosomes go to one cell so that when you have division you have an additional chromosome and 2 gametes and a loss of chromosomes and other gametes, or you can have that happen in meiosis 2 and you get two viable eggs and then that same problem
Homologous recombination problems
During homologous recombination there is a good chance for errors because you are having a double strand break and so pieces might get not put back correctly. So if mom doesn’t express that gene and dad has a deletion, then we have problems.
Trisomy 21, 18, 13
Non-disjunction during meiosis. , so you get an extra 21 chromosome
Down syndrom=Drinking age=trisomy 21
Edward syndrome = Election age = trisomy 18
Patau syndrome = Puberty age = trisomy 13
Lyonization
used to create Barr bodies. Females don’t use both X chromosomes in every cell. Creates mosaic pattern. Different regions of body can be using the copy you got from mom and copy from dad
Nondisjunction
Homologs fail to separate properly
-Nondisjunction errors are very common during egg development and increase with advancing maternal age
Trisomy 21/Down syndrome is an example of what type of error?
Aneuploid: cells with abnormal chromosome number
– Trisomy 21/Down syndrome: most common single cause of mental
retardation.
– 90% of trisomy 21 individuals, the additional chromosome is maternal in
origin
• 70% occur during MI and 30% in MII
