W1 L1 Flashcards
(24 cards)
where is most of the DNA found in the cell ?
95% in the nucleus the rest is in the mitochondria (mitochopndirial dna from mother)
How many hydrogen bond do each of the DNA complementary base pairs create ?
A=t. 2
G=-C. 3
Describe the structure of dna unravelled to condemned
DNA - double helix
The double helix is wrapped around a group of histones= nucleosome
These nucleosomes coil again into a supercoil
Supercoil again into chromosomes
How many chromosomes does the genome have ? Pairs ?
46 chromosomes
22 pairs
Describe the structure of a chromosome
Kp- short arm (p= petite )
Kq- long arm
Centrosome connecting the two
End of chromosomes telomeres - shorten with age
How can chromosomes been prepared for analysis ?
They can be stained
Giemsa: G banding, Quinacrine: Q banding)
G banding gives ~ 400-500 bands/haploid human chromosome set
Each band ~6-8 Mbp
What are the phase stein the cell cycle ?
interphase
(G0
G1
S
G2)
Mitosis -
Prophase
Pro-metaphase
Metaphase
Anaphase
Telophase
In s-phase of interphase what’s happens to the cell
DNA replication
Centrosome replication
In prophase of mitosis what happens in the cell
Chromatin condensed into chromosomes
Centrosomes nucleate microtubles
+ move to opposite poles of the nucleus
What are the steps of mitosis in prometaphase
Nuclear membrane breaks down
Microtubules invade nuclear space
Chromatids attach to microtubules
What are the steps of mitosis - metaphase
Chromosomes line up along equatorial plane
what are the steps of mitosis - anaphase
Sister chromatids separate…
…and are pushed to opposite poles of the cell
what are the steps of mitosis - telophase
Nuclear membranes reform
Chromosomes unfold into chromatin
Cytokinesis begins
what are the steps of mitosis - telophase
Nuclear membranes reform
Chromosomes unfold into chromatin
Cytokinesis begins
which drug that interrupts mitosis causes a halo like ring of genetic information in a histological image ?
what phase does this interrupt ?
colchicine- like drugs
interrupts anaphase
where does meiosis take place ?
Only in gametes
how many cell divisions in mitosis / meiosis ?
mitosis- 1
meiosis -2
describe how meiosis causes genetic variety
crossing over in prophase 1
describe sperm production
-cell origin
-when it happens
-no. of divisions
-types of cells produces
Primordial germ cells → lots of mitoses →Spermatogonia
Meiotic divisions commence at puberty
The cytoplasm divides evenly
After meiosis II four equal gametes
describe egg production
-origin
-time span
-types of cells produced
-stages of meiosis that it takes place at (under what conditions )
-Primordial germ cell → 30 mitoses → oogonia/ova
-1Oogonia/ova enter prophase of meiosis I by 8th month of intrauterine life
-2Process suspended
-3Cells enter ovulation 10-50 years later
-Cytoplasm divides unequally – 1 egg and 3 polar bodies (that apoptose)
-Meiosis I is completed at ovulation
-Meiosis II only completed if fertilisation occurs
what is Non-disjunction
Failure of chromosome pairs to separate in Meiosis I or sister chromatids to separate properly in meiosis II
what is Non-disjunction
Failure of chromosome pairs to separate in Meiosis I or sister chromatids to separate properly in meiosis II
describe down syndrome + karyotype
Most cases result from regular trisomy 21
47,XX/XY,+21
what is Gonadal mosaicism?
what factors increase the chance of this ?
how are the parents effected?
examples
what inheritance patters are common with this
when precursor germline cells are a mixture of two or more genetically different cell lines One cell line is normal, the other mutated
increases with age
parents are not effected but fetus may have genetic disease
conditions, including osteogenesis imperfecta and Duchenne muscular dystrophy
most commonly autosomal dominant and X-linked
