Lecture 13

Question 1

Describe gametes

Answer 1

Gametes that gain a chromosome have offspring with trisomy and the one that’s lacking have gametes with monosomy

Question 2

How does having an extra chromosome affect phenotype

Answer 2

• Gene balance – genes have evolved to function in a diploid background and that affects function
• Aneuploids are more abnormal than polyploids (have extra chromosomes for their set so gene balance is maintained)
• Haplo or triplo abnormal genes
• Monosomics are more severe than trisomics – any lethal mutations will be expressed in monosomics

Question 3

deletions in chromosome structure

Answer 3

– can be small or large to be visualised on a karyotype

Smaller deletions can be visualised using fluroscent probes – detect whether DNA sequences are there

Question 4

Duplications in chromosome structure

Answer 4

less of an effect not moving genes but play an important role in evolution of genome

Question 5

Inversions in chromosome structure

Answer 5

don’t involve the gain or loss of genetic material, meiosis this can lead to duplications or deletions

Question 6

Translocations in chromosome structure

Answer 6

exchange material

Question 7

Y chromosome

Answer 7

repeated sequence, few genes, SRY maleness-determining gene

Question 8

X chromosome

Answer 8

many genes , males are hemizygous for X linked genes

Question 9

Why is there no phenotypic difference between males or females

Answer 9

• In females one X chromosome is epigentically inactivated – highly condensed – random

Question 10

ZW system

Answer 10

males are ZZ, females are ZW

Question 11

• X linked recessive trait clues:

Answer 11

o More males express than females
o Skips a generation
o All male offspring with express it If the female expresses the characteristic