genome structure and chromosome abnormalities Flashcards
how many hydrogen bonds between AT and GC
A-T 2
C-G - 3
DNA-RNA
transcription
RNA-protein
Translation
what are introns
non-coding regions
intergenic regions
region of genome that do not contain protein-coding sequences - involved in switching on or off
Mitochondrial dna encodes for what
mitocondrial function
what happens in 3 parent embryos
mother has problem with mitocondria - nucleus removed form maternal egg and placed in donor in an empty egg containing healthy mitochondria
what makes up chromatin
DNA
RNA
protein - histones
what protein does DNA wound around to from nucleosomes( organise solenoids)
histones
what do solenoids do
loop up into structure of chromatin
what are the two types of chromatin
Euchromatin
Heterochromatin
open chromatin and prevalent in parts of genome that is regularly used - what type
euchromatin
condensed form of chromatin made up of tight loops - abundant - what type
heterochromatin
how many chromosomes in gamete - haploid
23
1 copy of autosomes and I sex chromosome
what is a somatic cell
diploid - 46
2 copies of autosome and 2 sex chromosomes
do changes in germ cells cause heritable defects
yes
MMR
mismatched repair enzyme
when does crossing over occur and what is it
homologous chromosomes exchange at chiasma
Prophase 1
genetic variation
when does independent assortment occur and what is it
during anaphase 1 - centrosomes do not duplicate and divide
only one member of each part migrates
paternal and maternal chromosomes randomly sorted due to this
Nullisomic gametes results in what
monosomic zygote - only one copy of chromosome
disomic gamete results in what
triatomic zygote - 3 copies of it
trisomy 21
downs syndrome
FISH - fluroesnece in situ hybridisation is a way of checking what
patients chromosomes for inblacne
aneuploidy
loss or gain of one or more chromosomes
gain of one of 2 homologous chromosomes called
trisomy
monosomy
loss of a single chromosome
Signs of downs syndrome
Newborn period
Hypotonia, sleepy, excess nuchal skin
Craniofacial
Brachycephaly, epicanthic folds, protruding tongue, small ears, upward sloping palpebral fissures
Limbs
Single palmar crease, small middle phalanx of fifth finger, wide gap between first and second toes
Cardiac
Atrial and ventricular septal defects, common atrioventricular canal, patent ductus arteriosus
Other
Anal atresia, duodenal atresia, Hirschsprung disease, short stature, strabismu
trisomy 13
Patau syndrome
descresed muscle tone
small hands and ears and head and mouth
slower physical development
trisomy 18
Edwards syndrome
heart defects
small head and jaw
overlapping fingers
two phenotypic consequences of chromosome deletions - syndromes
Deletions of the terminal portions of chromosome 4 cause the Wolf-Hirschhorn syndrome
Deletions of the terminal portions of chromosome 5 cause cri-du-chat syndrome (5pā)
serve learning difficulties
Degeorge syndrome
Characterized by heart malformations (particularly those involving the cardiac outflow tract)
Thymic and parathyroid hypoplasia
Cleft palate and typical facial features
The molecular defect is a 3-Mb microdeletion on chromosome 22 (22q11.2)
~ have short stature
~25% have schizophrenia-like episodes in adult life
