Basics of Genetic Inheritance

Question 1

What are the types of disorders?

Answer 1

Monogenic disorders - associated with a single gene

Polygenic disorder - associated with multiple genes

Question 2

What are genes?

Answer 2

They are discrete units of inheritance located on chromosomes, composed of DNA wound around histones

Question 3

What does the human karyotype consist of?

Answer 3

46 chromosomes (22 autosomes and 1 pair of sex chromosome)

Question 4

What are chromosomes characterised by?

Answer 4

Size, G-bonds and location of centromere

Question 5

What are the 3 types of chromosomes?

Answer 5

Metacentric (3) (smallest short arms), Submetacentric (17) (short small arms) and acrocentric (21) (longest short arms)

Question 6

What is a locus?

Answer 6

The position of a gene

Question 7

What is an allele?

Answer 7

A variant of a gene

Question 8

What is the purpose of mitosis?

Answer 8

Used for development, growth and replacing lost cells

Question 9

What are the 5 phases of Mitosis?

Answer 9

Prophase, Metaphase, Anaphase, Telophase and Cytokinesis

Question 10

What is Mitosis?

Answer 10

One round of DNA replication and one round of chromosomal segregation

Question 11

What is Meiosis?

Answer 11

The transmission of genetic information to offspring, halves genetic content
its one round of DNA replication and recombination with two rounds of chromosomal segregation

Question 12

How is variation produced in Meiosis?

Answer 12

By recombination between homologous chromosomes

Question 13

What are the phases of Meiosis?

Answer 13

Prophase, Metaphase 1, Anaphase 1 and then Metaphase 2

Question 14

What are some regions of a chromosome?

Answer 14

PAR - pseudoautosomal region - At both Y chromosome ends
MSY - Male specific region - includes…
SRY - A gene that determies testes and is the only region needed for development (all thats needed to confer maleness)

Question 15

Examples of Aneuploidy?

Answer 15

It is an irregular number of chromosomes
Down syndrome (21) (47xx or 47xy)
Patan syndrome (13) (47xx or 47xy)
Edward syndrome (18) (47xx or 47xy)

Question 16

The 3 abnormal compliment of sex chromosomes?

Answer 16

47, xxy, klinefelter syndrome
45, x, Turners syndrome
47 xyy, asymptomatic

Question 17

What causes Aneuploidy?

Answer 17

Non-disjunction of chromosomes

Question 18

How do you determine foetal karyotype?

Answer 18

Amniocentesis

Question 19

Why is being an older mother more risky?

Answer 19

As the Ova are as old as the mother whereas sperm are constantly reproduced

Question 20

What are the 4 modes of inheritance of monogenic disorders?

Answer 20

Autosomal recessive
Autosomal dominant
X-linked recessive
X-linked dominant

Question 21

Autosomal recessive example and ratios?

Answer 21

Cystic fibrosis
C dominant (normal) and c recessive so ratio is 3:1
CC is normal homozygous
Cc is normal heterozygous
cc is disease

Question 22

Autosomal dominant example and ratios?

Answer 22

Huntington’s disease

2:2 ratio

Question 23

X-linked recessive example and ratios?

Answer 23

Haemophilia A
cannot be passed from father to son
All daughters of affected fathers are carriers
XHXh, XHY or XhY are all possibilities