Tracing Genetic Links

Question 1

During fertilisation, where do all the organelles in the resultant zygote come from?

Answer 1

• as only the chromosomes from the sperm enter the egg cell and no other organelles
• all the organelles, eg mitochondria, come from the cytoplasm of the egg cell, ie the mother

Question 2

What can mtDNA be used to establish and how?

Answer 2

• can be used to establish a direct maternal genetic line
• as mtDNA is passed on from generation to generation

Question 3

What is a marker?

Answer 3

• mtDNA mutates occasionally
• eg substitution can take place where one nucleotide is replaced by another
• resulting in a site known as a marker

Question 4

What does it mean if 2 mtDNA profiles are very similar?

Answer 4

• the organisms are closely related

Question 5

What does it mean if 2 mtDNA profiles show differences?

Answer 5

• the organisms will have diverged along different evolutionary pathways

Question 6

What is the term for tracing lineages through females?

Answer 6

• matrilineage

Question 7

What is mtDNA testing?

Answer 7

• testing for similar genetic sequences in order to identify a common female ancestor

Question 8

How can mtDNA profiles be used?

Answer 8

• to reconstruct family maternal-linked relationships
• investigate forensic cases where the chromosomal DNA is degraded
• determine if siblings have the same mother