Human genome Flashcards
How many chromosomes in a human?
23 homologous pairs = 46
from whom do you inherit your mitochondrial DNA
Your mother
What are the two arms of a chromosome called?
P (short) and Q
What is a telomere?
protective cap on the end of a chromosome
What characteristic does telomere DNA have?
repetitive
what are the names of the two sorts of bands on a chromosome and what are their characteristics?
G-light:
gene rich, Guanine and Cytosine rich, early replicating,
G-dark:
gene poor, Adenine and Thymine rich, late replicating
what does the centromere do?
keeps sister chromatids together,
attaches sc’s to microtubules
what is it called when all the chromosomes are displayed in size order?
karyotype
what sort of chromosomes are the 22 paris of not sex-chromosomes
autosomes
What is an abnormal number of chromosomes called?
Aneuploidy
From which end is DNA read?
5 prime
What is found at the 5 prime end?
free phosphate group
Name a translation start codon
aug
What do you find at the 3 prime end?
free OH group
Name some non-coding elements of DNA
Introns, promoters, enhancers (regulate transcription)
Name the mechanisms of 5 abnormal chromosome structures
Deletion, inversion, duplication, translocation, Robertsonian translocation
What is a feature of Gliobastoma Multiforme
Many de novo translocations
name 3 autosomal aneuploidy conditions and specify their chromosomes
trisomy 21 Down Syndrome
Trisomy 18 Edwards Syndrome
trisomy 13 Patau Syndrome
What is Turner syndrome?
X chromosome missing or partially missing
What is Klinefelter syndrome
XXY male
Name 3 features of Down Sydrome
Muscle hypotonia
Upwards slanting eyes
Single palmar crease
Why does Down Syndrome increase chance of early onset dementia?
APP is on gene 21
What is mosaic Down syndrome?
Only some cells have the trisomy. Effects can be less than full trisomy
Name some features of Edwards syndrome
multiple malformations
clenched hands with overlapping fingers
very poor prognosis
How rare is Patau syndrome?
1/5000 live births
Name 2 features of Klinefelter syndrome
tall
poorly developed secondary sexual characteristics
infertile
Name 2 features of Turner syndrome
short, primary amenorrhoea, congenital heart disease (20%), webbed neck
What is the likelihood of a girl with Turner syndrome being carried to term?
1%
When is amniocentesis carried out?
15-18 weeks
what is chorionic villus sampling?
transabdo or transcervical sampling of placental tissue
what is the neck fluid test looking for?
Nuchal translucency
What is X-ist
long non-coding RNA in the X-chromosome. Inactivates one of the X chromosomes
Where is Xist found
X Inactivation Centre on the X chromosome
What does Xist do to the X chromosome and how
deactivates its transcription by causing the chromatin to wind very tight.
Describe the Y chromosome
few genes, many repeat sequences
what is the SRY?
Sex determining region of teh Y chromosome
