18. Behaviour of chromosomes and alleles Flashcards
What does a gene do?
Codes for a polypeptide as well as the various forms of RNA (tRNA, rRNA, miRNA, snRNA)
What is the difference between diploid and haploid?
In diploid there are two of each type of chromosome while haploid has one copy of each chromosome
What is a karyotype?
Sorted chromosomes
What is a karyogram?
A drawing of chromosomes with banding shown
What is an autosome?
A chromosome not involved in determining the sex of the organism
What is a sex chromosome>
A chromosome involved in determining the sex of the organism
What are the 2 things by which chromosomes can be sorted in a karyotype?
Size and centromere position
What are the two arms of a chromosome known as?
p for the upper arm and q for the lower arm
What is a metacentric chromosome?
P and q arms equal length
What is a submetacentric chromosome?
Q arm very long, P arm short
What is an acrocentric chromosome?
P arm very short, normal Q arm
What is a telocentric chromsome?
No p arm, normal Q
What is aneuploidy?
Adding or subtracting one or two chromosomes
What is euploidy?
Increases or decreases by a whole set
What are the only 3 examples of trisomy where the foetus survives to full term?
Trisomy 21, extra 21
Trisomy 18, extra 18 for XX
Trisomy 13, extra 13 for XX
What is klinefelter syndrome?
Where the individual has XXY
What phenotype is associated with klinefelter?
Small testes, reduced testosterone, delayed or incomplete puberty, breast enlargement, reduced facial and body hair, infertility
What does the rate of aneuploidy increase with age?
Older eggs are significantly more likely to have abnormally functioning spindles which causes an increased rate of chromosomal problem with the mature eggs
How is translocation seen for trisomy 21?
Chromosome 21 become attached to another acrometric chromosome but the satellite regions are lost
What are some tests for chromosomal disorders in pregnancy?
- Preimplantation diagnosis with IVF
- Ultrasound
- Triple test of maternal blood
- Cf DNA in maternal blood
- Chorionic villus sampling
- Amniocentesis
What three substances are tested for in the triple test of maternal blood?
AFP and hCG and Oestriol
What does AFP do?
Alpha fetoprotein is a protein that is produced by the foetus
What does hCG do?
Human chorionic gonadotropin is a hormone produced within the placenta
What does oestriol do?
An oestrogen produced by both the foetus and the placenta
How can the triple test of maternal blood diagnose trisomy 21?
Depending on the stage of pregnancy the levels of AFP. hCG, and Oestriol can be higher or lower
What is the allelic notation for wild type vs mutant?
w+ for world type and w for mutant
How do the case of letters in allelic notation tell us dominant or recessive?
If the mutation is recessive use lower case letter. If the mutation is dominant use upper case letters
