Mitosis and Meiosis Flashcards
What is a telomere?
repeated sequence, shorten with replication, causes senescence
What are sister chromatids?
X shaped chromosomes, 2 identical dna molecules, same alleles
What is a homologous pair?
Not X shaped, same DNA sequence, genes may be different variants (alleles)
What is diploid vs haploid?
Diploid = full 46 chromosomes, haploid = 23 chromosomes
List the stages of mitosis
Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis
List the stages of meiosis
Prophase I, metaphase I, anaphase I, telophase I, Interkinesis – Prophase II, metaphase II, anaphase II, telophase II, cytokinesis
Describe interphase
Everything in the cell cycle apart from mitosis: G1, S, G2, mitosis, G0
What is chiasma?
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.
What is independent assortment vs crossing over?
crossing over is the process of exchange of DNA between homologous chromosomes whereas the independent assortment is the process in which the chromosome pairs align themselves at the middle of the cell
List the function of G1, S and G2
Cell enters G1 - cytoplasmic components are made, S phase - copy of each chromosome is made, G2- more growth so cell is ready to divide, checking for DNA errors, repair if needed
How does a sperm cell develop?
Spermatogenesis = Stem cell –> primary spermatocyte –> meiosis I –> 2 secondary spermatocyte –> meiosis II –> 4 spermatids –> maturation –> mature sperm
Describe the development of an oogonia
Oogenesis = Oogonia –> mitosis –> born –> primary oocyte –> meiosis –> stops at prophase I –> monthly 1 primary oocyte finishes meiosis I –> becomes secondary oocyte, ovum, released from ovary –> fertilisation –> meiosis II
What are the consequences of faulty meiosis?
Third of all identified miscarriages, Infertility, Leading cause of mental retardation
How are chromosomes grouped?
Grouped according to size, groups A-G, X = C, Y = G
What is karyotype?
the number and visual appearance of the chromosomes in the cell nuclei of an organism or species, Chromosome number, sex complement, structural changes –> 47,XY,+21 = male with trisomy 21
What is trisomy?
extra copy of a chromosome is present
What is monosomy?
presence of only one chromosome from a pair, cell line usually lost unless involves X
Describe nondisjunction
failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
What does aneuploidy mean?
presence of an abnormal number of chromosomes in a cell, result of mitotic nondisjunction
What is mosaicism?
presence of 2 or more cell lines in an individual degree depends on when: first post-zygotic division, later mitotic divisions
What is a post-zygotic mutation?
change in an organism’s genome that is acquired during its lifespan, instead of being inherited from its parent(s) through fusion of two haploid gametes.
What stage does crossing- over occur?
meiosis prophase I
What stage does random assortment occur?
meiosis metaphase I
What happens during prophase?
chromosomes condense, spindle fibres form, nuclear envelope starts to break down
What happens during prometaphase?
kinetochore microtubules penetrate nuclear region
Explain what happens during metaphase
chromosomes line up in the middle, metaphase plate
Describe anaphase
microtubule spindles pull chromatids to separate ends
Explain telophase
chromosomes reach opposite ends, spindles disappear, nuclear membrane forms, cleavage furrows appear
What happens during cytokinesis?
cleavage furrow at the equator of cell, constricting tightens by contraction of filaments, cell eventually divides into 2 daughter cells
what happens at a cell cycle checkpoint to allow the cycle to continue?
the proteins controlling the checkpoints are phosphorylated
what is the structure of a chromosome?
short (p) arm, long (q) arm - held together by centromere
what are the 4 chromosome structures due to centromere placement?
metacentric, submetacentric, acrocentric, telocentric
what links sister chromatids?
centromere (consists of repetitive sequences)
