18. Behaviour of chromosomes and alleles

Question 1

What does a gene do?

Answer 1

Codes for a polypeptide as well as the various forms of RNA (tRNA, rRNA, miRNA, snRNA)

Question 2

What is the difference between diploid and haploid?

Answer 2

In diploid there are two of each type of chromosome while haploid has one copy of each chromosome

Question 3

What is a karyotype?

Answer 3

Sorted chromosomes

Question 4

What is a karyogram?

Answer 4

A drawing of chromosomes with banding shown

Question 5

What is an autosome?

Answer 5

A chromosome not involved in determining the sex of the organism

Question 6

What is a sex chromosome>

Answer 6

A chromosome involved in determining the sex of the organism

Question 7

What are the 2 things by which chromosomes can be sorted in a karyotype?

Answer 7

Size and centromere position

Question 8

What are the two arms of a chromosome known as?

Answer 8

p for the upper arm and q for the lower arm

Question 9

What is a metacentric chromosome?

Answer 9

P and q arms equal length

Question 10

What is a submetacentric chromosome?

Answer 10

Q arm very long, P arm short

Question 11

What is an acrocentric chromosome?

Answer 11

P arm very short, normal Q arm

Question 12

What is a telocentric chromsome?

Answer 12

No p arm, normal Q

Question 13

What is aneuploidy?

Answer 13

Adding or subtracting one or two chromosomes

Question 14

What is euploidy?

Answer 14

Increases or decreases by a whole set

Question 15

What are the only 3 examples of trisomy where the foetus survives to full term?

Answer 15

Trisomy 21, extra 21
Trisomy 18, extra 18 for XX
Trisomy 13, extra 13 for XX

Question 16

What is klinefelter syndrome?

Answer 16

Where the individual has XXY

Question 17

What phenotype is associated with klinefelter?

Answer 17

Small testes, reduced testosterone, delayed or incomplete puberty, breast enlargement, reduced facial and body hair, infertility

Question 18

What does the rate of aneuploidy increase with age?

Answer 18

Older eggs are significantly more likely to have abnormally functioning spindles which causes an increased rate of chromosomal problem with the mature eggs

Question 19

How is translocation seen for trisomy 21?

Answer 19

Chromosome 21 become attached to another acrometric chromosome but the satellite regions are lost

Question 20

What are some tests for chromosomal disorders in pregnancy?

Answer 20

• Preimplantation diagnosis with IVF
• Ultrasound
• Triple test of maternal blood
• Cf DNA in maternal blood
• Chorionic villus sampling
• Amniocentesis

Question 21

What three substances are tested for in the triple test of maternal blood?

Answer 21

AFP and hCG and Oestriol

Question 22

What does AFP do?

Answer 22

Alpha fetoprotein is a protein that is produced by the foetus

Question 23

What does hCG do?

Answer 23

Human chorionic gonadotropin is a hormone produced within the placenta

Question 24

What does oestriol do?

Answer 24

An oestrogen produced by both the foetus and the placenta

Question 25

How can the triple test of maternal blood diagnose trisomy 21?

Answer 25

Depending on the stage of pregnancy the levels of AFP. hCG, and Oestriol can be higher or lower

Question 26

What is the allelic notation for wild type vs mutant?

Answer 26

w+ for world type and w for mutant

Question 27

How do the case of letters in allelic notation tell us dominant or recessive?

Answer 27

If the mutation is recessive use lower case letter. If the mutation is dominant use upper case letters