Classical Genetics 7

Question 1

What is extra-nuclear DNA?

Answer 1

Transmission of genes that occur outside the nucleus
Organelle DNA replicates independently during cell division in mitochondria and chloroplasts

Question 2

Describe mitochondrial DNA inheritance;

Answer 2

mtDNA is only passed down from mother’s lineage
Only egg supplies mitochondria to fertilised zygote
Mitochondrial genome extremely small compared to the nuclear genome
Despite small size, mitochondrial DNA mutations important cause for inherited disease

Question 3

What does a square, diamond and circle mean in pedigree diagrams?

Answer 3

Square = male
Circle = female
Diamond = unknown sex

Question 4

What is the difference between mtDNA and Y-DNA?

Answer 4

mtDNA passed down through maternal lineage
Y-DNA passed down through paternal lineage

Question 5

Define autosomal dominant and its key traits;

Answer 5

One copy of the dominant allele from either parent is enough to express the trait.
Can’t be any carriers
All non-affected individuals in the family tree have to be homozygous recessive

Question 6

Define autosomal recessive;

Answer 6

Two copies of the recessive allele (one from each parent) are necessary to express the trait.

Question 7

Define X-linked dominant

Answer 7

The gene causing the trait is located on the X chromosome, and the dominant allele results in the expression of the trait

Question 8

Define X-linked recessive

Answer 8

The gene causing the trait is located on the X chromosome, and the recessive allele results in the expression of the trait
More common in males

Question 9

What are key traits of autosomal recessive?

Answer 9

There can be carriers
Each affected child does not have at least one
affected parent, skips generations, both F & M are affected
All affected individuals in this family tree have to be homozygous, as the disease allele is recessive

Question 10

What inheritance pattern does ____ show;
Li-Fraumeni syndrome
Cystic fibrosis
Duchenne Muscular Dystrophy
MERRF

Answer 10

Li-Fraumeni syndrome - autosomal dominant
Cystic fibrosis - autosomal recessive
Duchenne Muscular Dystrophy - X-linked recessive
MERRF - mitochondrial