Traits/inheritance

Question 0

Chromosomes are viewed by karyotyping -

Draw __ml of blood. Add _______ to stimulate mitosis. Incubate at ___*C for __to__ days. Add _____, culture for _______ hours to stop mitosis in metaphase. Transfer cells to tube. Transfer to a tube containing a _________. Centrifuge to concentrate cells. Add low-______ solution to eliminate _______ and swell _______. Put cells onto microscope slide and stain with _______ to produce _______. Examine with microscope. Digitalised chromosome images produced to make karyotype.

Answer 0

Chromosomes are viewed by karyotyping -

Draw 10-20ml of blood. Add phytohemagglutinin to stimulate mitosis. Incubate at 37*C for 2 to 3 days. Add colcemid to culture for 1 - 2 hours to stop mitosis in metaphase. Transfer cells to tube. Transfer to a tube containing a fixative. Centrifuge to concentrate cells. Add low-salt solution to eliminate red blood cells and swell lymphocytes. Put cells onto microscope slide and stain with giesma to produce g banding. Examine with microscope. Digitalised chromosome images produced to make karyotype.

Question 1

How many somatic cells do humans have? How many are autosomal?

Answer 1

46 chromosomes
44 autosomes (22 pairs)
2 sex chromosomes (1 pair)

Question 2

What are the 3 main recognisable chromosome features?

Answer 2

Size
Centromere position
Banding patterns

Question 3

What are the 3 centromere positions?

Answer 3

Metacentric
Submetacenteic
Acrocentric

Question 4

What regions to the sex chromosomes pair at during meiosis?

Answer 4

Pseudoautosmal regions at tips of the arms

Question 5

Little or no crossover at meiosis means that Y chromosomes are passed on intact from ______ to son. This is called _______ inheritance.

Answer 5

Father

Holandric

Question 6

In x linked recessive inheritance…
Carrier females will have ___% sons affected and ____% daughters carriers
All daughters of affected males are ____, all sons are _____

Answer 6

50% 50%

Daughters - carriers, sons - unaffected

Question 7

Why are females genetic mosaics?

Answer 7

They have 2 X chromosomes and randomly deactivate one copy of each chromosome in each cell in the early embryo (visible as a Barr body)

Question 8

Why might a pedigree follow non Mendelian inheritance?

Answer 8

Maternal/mitochondrial inheritance
Phenocopies
Incomplete penetrance - genetic environment or imprinting

Question 9

What is a phenocopy?

Answer 9

A trait that is not the true phenotype eg. Dyed hair

Question 10

What is lyonisation?

Answer 10

Dosage compensation

Question 11

What causes chimeras

Answer 11

Started with twins
Early stage fusing of fertilised eggs
Half and half of genetic information