Genome structure and chromosome abnormalities Flashcards
Adenine and Thymine make how many hydrogen bonds?
2
“A Tea for 2”
Guanine and Cytosine make how many hydrogen bonds?
3
Degenerate meaning
More than 1 codon per aa
Mitochondria DNA comes from which parent?
Mother
How do you avoid transmitting mitochondrial disease?
Want maternal egg but not cytoplasm
Nucleus removed from maternal egg and placed in donor empty egg with healthy mitochondria
What is a chromatin?
Substance within chromosomes consisting of DNA and protein
What are 2 different types of Chromatin
Euchromatin
Heterochromatin
What is Euchromatin (chromatin)?
Prevalent in part of genome that is regularly used- where genes on
Less condensed
Can be transcribed
What is heterochromatin (chromatin)?
Condensed form of chromatin made of tight loops- most abundant of genome where genes switched off
More condensed
Cannot be transcribed usually
What is the P arm on chromosome?
Short arm of structure (of the X)
What is the Q arm on chromosome?
Long arm of structure (of the X)
Pathogenic variant
Affect on genome so no longer perform its function
Genetic variant
Not going to have any impact on function of genome
How can changes in DNA cause no effect?
Synonymous aa change (codes for same aa)
In non functional regions of genome
How many chromosomes in gametes?
23 chromosomes
How many chromosomes in somatic cells?
46 chromosomes
When does variation occur in meiosis?
During crossing over
Independent assortment
“Errors” in replication- mutations- good for evolution or bad
What do miss match repair enzymes do?
Look for missmatches and remove incorrect base and put in correct base
When does crossing over occur in meiosis?
Prophase 1
Where does crossing over occur?
At chiasma
When does independent assortment occur?
During anaphase 1
Nullisomy
caused by error at meiosis, causing 2 of gametes to have no chromosomes and other 2 to have double
Monosomic zygote
Only one copy of chromosome after fertilisation
Disomic gametes
Gametes having double amount of chromosomes
What is trisomic zygote?
What causes it?
3 copies of a chromosome
If have disomic gametes
Down syndrome is trisomy what?
21
What is turner syndrome?
One copy of X chromosome
Aneupolidy
Loss or gain of one or more chromosome
Monosomy
Loss of a single chromosome
Trisomy/tetrasomy
Gain of one or two homologous chromosomes
Polyploidy
Have more than 2 sets of chromosomes
Hydatidoform mole
growth of an abnormal fertilized egg or an overgrowth of tissue from the placenta.
What is trisomy 21?
Downs syndrome
What is trisomy 13
Patau syndrome
What is Trisomy 18
Edwards syndrome
Trisomy 13 (patau syndrome) symptoms
Cleft lip + palette Too many fingers Brain malformation Small eyes Reduced distance between eyes Clenched hands with outer fingers over lapping inner Reduced muscle tone
Trisomy 18
William syndrome
DiGeorge Syndrome symptoms
Heart problems
Speech + hearing problems
Learning + behaviour problems
Hormone problems
DiGeorge syndrome cause
Deletion of chromosome 22
Aneuploidy risk
Maternal serum proteins, maternal age, fetal nuchal fold translucency
