lecture 2: patterns of inheritance

Question 1

how can we examine human chromosomes?

Answer 1

by taking a sample of blood cells and stimulate them to divide.

Question 2

what is a central constriction of a chromosome called?

Answer 2

centromere

Question 3

what is an autosome?

Answer 3

22 pairs of chromosomes are equally matched

Question 4

what is gender determined by

Answer 4

sex chromosomes

females = XX
males= XY

Question 5

what is marfan’s syndrome

Answer 5

elongated hands and feet and long narrow skull

abnormal placement of lens

Question 6

what kind of trait is Marfan’s syndrome

Answer 6

autosomal dominant

Question 7

what are the genes required for blood group A

Answer 7

Ia Ia OR Ia Io

allele Ia is dominant to Io

Question 8

what are the genes required for blood group B

Answer 8

Ib Ib OR Ib Io

allele Ib is dominant to Io

Question 9

what are the genes required for blood group AB

Answer 9

Ia Ib

both are dominant as each other

Question 10

what are the genes required for blood group O

Answer 10

Io Io

Question 11

how can you test a blood sample

Answer 11

with anti-serra

Question 12

what is albinism and its symptoms

Answer 12

an autosomal recessive trait

inability to make melanin

iris is pink and light coloured

photophobia

Question 13

state all the autosomal dominant ocular diseases

Answer 13

aniridia
optic atrophy
congenital nystagmus
marfan's syndrome
retinitis pigementosa

Question 14

state all the recessive autosomal ocular diseases

Answer 14

total colour blindness
albinism
behr's syndrome
stargardt's disease
retinitis pigmentosa

Question 15

what is aniridia

Answer 15

complete or partial absence of iris

Question 16

optic atrophy

Answer 16

degeneration of optic disc

Question 17

congenital nystagmus

Answer 17

abnormal rhythmical movement of the eye

Question 18

what is retinitis pigmentosa

Answer 18

degenerative disease of retina characterised by degeneration of peripheral regions of retina gradually spreading inwards

Question 19

total colour blindness

Answer 19

seeing world in shades of grey

Question 20

Behr’s syndrome

Answer 20

degeneration of optic disc

Question 21

stargardt’s disease

Answer 21

degeneration of central parts of retina

Question 22

why is retinitis pigmentosa both autosomal and recessive

Answer 22

because it can be caused by different genes

Question 23

describe the chromosomes in Down’s syndrome

Answer 23

cells possess abnormal numbers of chromosomes- have 47 so have extra copy of chromosome 21

Question 24

state symptoms of downs syndrome

Answer 24

• short stature
• changes in head, shape, face and eyelids
• mental retardation
• heart malformation

Question 25

describe why males have a more chance of being born than females

Answer 25

Because the sperm containing Y chromosome is more capable of fertilising more eggs than the sperm containing X chromosomes.

Question 26

how can males differ from females in two ways genetically?

Answer 26

1 X chromosome rather than 2

and they Have a Y.

Question 27

Turner syndrome

Answer 27

• single X chromosome (XO)
• short stature
• broad chest
• webbing of skin joining neck to shoulders
• female genitals
• sterile with no viable eggs

Question 28

Klinfelter’s syndrome

Answer 28

• possess XX and Y (XXY)
• have the appearance of males
• male genitals but small and sterile testis
• female breasts
• long legs

Question 29

who are affected by X-linked recessive genes?

Answer 29

sons as X-linked recessive genes are passed on from the x chromosomes of mother

Question 30

what are the 2 x-linked ocular disorders?

Answer 30

ocular albinism

retinoschisis- cyst forming on retina, degenerative splitting of retina

Question 31

X-linked recessive disorders (name 4)

Answer 31

• red/green colour blindness
• retinitis pigmentosa
• Leber’s optic atrophy- degeneration of optic disc
• congenital nystagmus- abnormal rhythmical movement of eye