chromosomes and cell division, meiosis, chromosome abnormalities Flashcards
What does DNA ligase do?
ligates the fragments together
Why do telomeres shorten?
due to ageing or stressors. When telomeres start shortening too much, can lead to problems in our body.
What are the different stages in mitosis?
prophase
metaphase
anaphase
telophase
cytokinesis
What happens in prophase?
Chromosomes condense
Nuclear membrane disappears
Spindle fibres form from the centriole
What happens in metaphase?
Chromosomes aligned at the equator of the cell
Attached by fibre to each centriole
Maximum condensation of chromosome
What happens in anaphase?
Sister chromatids separate at centromere
Separate longitudinally
Move to opposite ends of cell
What happens in telophase?
New nuclear membranes form
Each cell contains 46 chromosomes (diploid)
What happens in cytokinesis?
Cytoplasm separates
Two new daughter cells
Give characteristics of centromeres?
Constricted region joining sister chromatids
Repetitive DNA sequences
Satellite DNA
Site of kinetochore
Protein complex that binds to microtubules
Required for chromosome separation during cell division
Difference between heterochromatin and euchromatin?
heterochromatin so tightly stuck together that it won’t allow any of the machinery to actually get attached and do anything.
Genes are silenced.
What are satellite, minisatellite, SINEs and LINES (long and short interspersed nuclear elements) for? {extragenic sequences in introns}
-Satellite DNA- extreme structural importance for our DNA and for chromosomes and lots of AT repeats
-Minisatellite DNA-
SINE and LINEs- serve a structural purpose and make up 45% of genome
Describe the levels of how we go from DNA down into chromosome?
level 1 - nucleosome (one of beads on string)
level 2 - chromatin fibre (condensation by factor 40- beads on string forming solenoids - these bumped together)
level 3 - fibre-scaffold complex
level 4- chromosome
What is the purpose of packaging DNA?
- DNA takes up less space
-helps with managing and regulating how our genes are going to be activated
-Inactive DNA can be folded into inaccessible locations until required
-Inactive chromatin characterised by specific histone convalent modification (e.g. methylation)
Which is the P and which is the Q arm?
p= petite and top arm
q= bottom arm
Meaning of metacentric, sub-metacentric, acrocentric?
metacentric- centromere in middle
sub-metacentric- shorter p arm and standard q arm
acrocentric- really short p arm where so short its inactive
What do we use to see centromeres?
fluorescent in situ hybridisation
Where does mitosis happen?
only happens to our somatic cells
What is process of meiosis?
used to make more sex cells
What is the difference between meiosis and mitosis?
instead of two identical cells like mitosis, get four cells that have half of genetic info (haploid)
Why do we get the genetic diversity?
crossing over
between prophase and metaphase 1 they cross over and exchange a part of their genetic material
What happens in gametogenesis?
where meiosis happens, we make new gametes
What is spermatogenesis?
create through meiosis 1 and 2 create 4 sperm cells
Describe oogenesis?
start with first egg and then it matures into primary oocyte. Divides into a secondary oocyte and a polar body. Polar body has no role so gets flushed out. Secondary oocytes divide and creates one egg and three polar bodies.
What determines if embryo is male or female?
whether sperm contains and x or y chromosome
