The Evolution of Human Genome

When did Homo sapiens appear?

Around 400,000 years ago in Africa.

What does “Mitochondrial Eve” refer to?

The most recent woman from whom all living humans descend on their maternal line, traced via mitochondrial DNA.

Name some traits that define humans.

Bipedal locomotion, large brains, stereoscopic vision, opposable thumbs, language, social behavior, parental care.

genome

An organism’s complete set of DNA, including coding and non-coding regions.

structural genes

DNA segments that code for RNAs or proteins (e.g., mRNA, tRNA, snRNA).

What are functional sequences?

Regulatory DNA elements like promoters and operator sites.

What are non-functional sequences?

Introns and repetitive DNA; essential for replication and regulation.

How many genes are in the human genome?

~24,000 genes across 3.2 billion base pairs.

What is surprising about the number of human genes?

It’s fewer than expected (~100,000 originally estimated).

Which chromosome has the most genes?

Chromosome 1 (~3168 genes).

Which chromosome has the fewest genes?

Chromosome Y (~344 genes).

What’s unusual about Chromosome 2?

It's the result of a fusion between two ancestral chromosomes.

What is “junk DNA”?

Non-coding DNA, once thought useless, now known to regulate gene activity and support evolution.

How much of our genome is non-coding?

About 50%.

Why study other species’ genomes?

To understand gene function, evolution, and develop medical applications.

What was the first organism sequenced?

Haemophilus influenzae (1995, 1M bp).

What is the Earth BioGenome Project?

A 10-year effort (launched 2018) to sequence all known eukaryotic species (~1.5 million).

HapMap Project?

A global project to identify genetic variants (SNPs) across populations.

How does genomics benefit medicine?

Enables disease diagnosis, risk prediction, drug targeting, and personalized treatment.

What is precision medicine?

Using individual genetic information to guide healthcare decisions.

How is HER2-positive breast cancer treated?

With drugs that specifically target HER2-expressing cells.

What other benefits come from genomics?

Early detection of diseases, cancer diagnostics, ancestry testing, and forensic science.

Does genome size correlate with complexity?

No, genome size and complexity do not correlate—this is known as the C-value paradox.

Give an example of genome size variation.

Humans (~3 billion bp) vs. axolotl (~32 billion bp) vs. Polychaos dubium (~670 billion bp).

What causes genome evolution?

• Gene duplication/loss

• Mutations

• Horizontal gene transfer

• Polyploidy

• Chromosome fusion/fission

What are selfish DNA elements?

DNA sequences that replicate themselves without benefiting the host organism.

How do humans differ from chimpanzees in chromosome number?

Humans have 23 pairs; chimpanzees have 24 due to a chromosome fusion in humans.

What is the challenge in genomics regarding traits?

Determining how genomic differences cause specific phenotypic changes.

Are we still evolving?

• Microevolution: Yes (e.g., lactose tolerance, high-altitude adaptation).

• Macroevolution: No new species forming currently.

What factors influence ongoing human evolution?

Diet, disease exposure, environment, and population dynamics.