sex determination and sex linked -lecture 13

Question 1

Monoecious (=one house

Answer 1

individual has both male and female reproductive structures (aka hermaphrodite)

Question 2

Dioecious

Answer 2

individual has either male or female reproductive structures

Question 3

Who and when were the X and Y chromosomes discovered?

Answer 3

1905/06 , Nettie Stevens

Question 4

Heterogametic sex

Answer 4

produces gametes with different types o fsex chromosomes ( human men)

Question 5

homogametic sex

Answer 5

produces games that all contain the same type of sex chromosome ( female humans)

Question 6

XX-XO systems

Answer 6

XX - female
XO - male
e.g. grasshoppers

Question 7

X1X2-X1X20

Answer 7

spiders
X1X2X1X2 female
X1X20 male

Question 8

X1X2X3X4X5 YX1X2X3X4X5 X1X2X3X4X5- 1Y2Y3Y4Y5 system:

Answer 8

duck billed platypus

Question 9

What is haplo - diploidy in ants, wasps and bees?

Answer 9

Unfertilized haploid eggs develop into males*

Fertilized diploid zygotes develop into females

Question 10

parthenogenesis

Answer 10

development of eggs without fertilization

Question 11

XO, 1/3000 female

Answer 11

Turner syndrome

Question 12

XXY, XXXY, XXXXY,XXYY, 1/1000-1/500 male

Answer 12

Klinefelter syndrome

Question 13

XYY males

Answer 13

Jacobs syndrome

Question 14

Androgen - insensitivity syndrome

Answer 14

• Have female external structures, but no uterus, oviduct or ovaries - instead a pair of testes
• These women are actually XY , due to mutations in the androgen receptor

Question 15

external sex determination

Answer 15

e.g - In turtles the temperature decides the sex determination

Question 16

Genic sex determination

Answer 16

sex determine gene, no chromosome for it

Question 17

Sex limited

Answer 17

Gene present in both sexes but only expressed in one

Question 18

Sex biased

Answer 18

genes present in both but expressed in one sex more than another

Question 19

sex - linked

Answer 19

genes on sex chromosomes

Question 20

x - linked traits

Answer 20

colour blindness

Question 21

Z - linked traits

Answer 21

males are zz whereas females ar ZW . In birds

Question 22

x - inactivation : Lyon hypothesis

Answer 22

Barr bodies are inactivated X chromosomes

Question 23

Which X chromosome becomes inactivated?

Answer 23

one of the two randomly becomes inactivated, get mosaicism in females . The reason you get different coloured cats

Question 24

Anhidrotic ectodermal dysplasia

Answer 24

X - linked recessive disorder - small teeth , no sweat glands, spare Body hair

Question 25

Are human X and Y chromosomes homologous at all?

Answer 25

Yes , pseudoautosomal regions , which are where the X and Y join up to in meiosis

Question 26

How many genes does the Y chromosome have?

Answer 26

78

Question 27

How many genes are on the X chromosome?

Answer 27

800