Molecular and Human Evolution

Question 1

Molecular Evolution

Answer 1

*Problems with gaps in the fossil record
* Especially soft bodied organisms and micro-
organisms
*Use DNA and protein sequences to study
evolution
* Changes in DNA sequence
* Changes in protein sequence
* Evolution of gene families

Question 2

How do genomes evolve?

Answer 2

*Changes occur in the DNA sequence
* Mutations
* Recombination
* These changes must become FIXED in the population to be involved in evolution

Question 3

How do genomes evolve?

Answer 3

Changes occur in the DNA sequence
* Especially soft bodied organisms and micro-
organisms
*Some DNA changes affect the protein
sequence
* Changes in the protein sequence can change the
function of the protein
* More complex evolutionary consequences

Question 4

Mutations

Answer 4

*Simple base changes
*Insertions
*Deletions
*Chromosome rearrangments

Question 5

How do we construct a phylogenetic
tree?

Answer 5

Choose appropriate DNA sequences
Need to be homologous genes
(Identical function)
e.g. Genes for
haemoglobin
α 1 and α2 are slightly different
Align the DNA sequences
The sequences need to be aligned for
comparison
Compare similarities between the DNA
sequences
Build a similarity
matrix
Build the phylogenetic tree

Question 6

Choosing useful DNA sequences for
phylogenetic analysis
1. Mitochondrial DNA

Answer 6

Mitochondrial DNA
- Does not undergo recombination
- Passed down the maternal line
- Simplifies evolutionary interpretations
- Good for identifying human evolutio

Question 7

Choosing useful DNA sequences for
phylogenetic analysis
2. Ribosomal RNA genes

Answer 7

Ribosomal RNA
- Key component of ribosomes
- Ribosomes make proteins
- Present in all life
- Highly conserved in evolutionary terms.
- Good for evolutionary studies across the whole
of life

Question 8

Evolution of gene families

Answer 8

Families of related genes that produce
proteins that have related but different
functions
e.g. Genes for
haemoglobin
α 1 and α2 are slightly different

Question 9

Haemoglobin genes

Answer 9

Adult - Alpha,
beta, delta

Foetal- Alpha,
gamma

Embryonic= Zeta,
epsilon

Question 10

Human evolution

Answer 10

Characteristics of humans
* Bipedal
* Tooth conformation
* Increased brain size
* Cultural behaviour
* Language

Question 11

6 - 7 million years ago (mya)

Answer 11

• Nine fossil skulls found in Chad, Africa, discovered in 2001
• Sahelanthropus tchadensis
  Probably bipedal –
  spine position

Question 12

4 - 3 million years ago (mya)

Answer 12

• Fossil “Lucy” found in 1974
• Australopithecus afarensis
  Clearly bipedal
  No enlarged brain
  Female

Large
number of
unlinked
fossils
discovered

Question 13

2.5 million years ago (mya)

Answer 13

• Fossils found alongside tools
• Homo habilis
  Clearly bipedal
  Enlarged brain
  Used tools

Question 14

1.8 million years ago (mya)

Answer 14

• Fossils found outside Africa (from 700,000ya)
• Homo erectus
  “Upright man”
  Enlarged brain
  “Out of Africa”
  concep

Question 15

400,000 – 40,000ya

Answer 15

Fossils found mainly in Europe
* Homo neanderthalensis
Cultural behaviour
Buried their dead and
evidence of abstract
thought
Co-existed with Homo
sapiens

Question 16

300,000ya – present

Answer 16

Only extant hominin species
* Homo sapiens

Question 17

Evolution of recent hominins
Where have we come from?

Answer 17

Two possible models of origins based on
classical fossil studies:
*Multiregional model
*Monogenesis model

Question 18

Evolution of recent hominins
Use of DNA sequence information

Answer 18

• Mitochondrial DNA
• Whole human genome sequence 2001 (Homo sapiens)
• Fossil Neanderthal genome sequencing 2013 (Homo
  neanderthalensis)
• DNA extracted from a female Neanderthal, living between
  50,000 to 100,000 years ago, from a fossilised bone fragment
  found in Siberia

Question 19

Mitochondrial DNA

Answer 19

Measurement of DNA
sequence diversity
between different races
Low sequence diversity
between extant races –
supports the monogenesis
model

Question 20

Pseudogene

Answer 20

Gene that has lost function

Question 21

Family

Answer 21

Hominidae
(orangutans, gorillas,
chimpanzees and humans)

Question 22

Subfamily

Answer 22

Homininae
(gorillas, chimpanzees and
humans)

Question 23

Tribe

Answer 23

Hominini (humans and
our close extinct relatives; the
group that was called
Hominidae in previous
classifications

Question 24

Evolution of recent hominins
Mitochondrial DNA
“Mitochondrial Eve Hypothesis’’

Answer 24

Based on early DNA results suggested that all humans evolved from a single female
INCORRECT – the data was based on incorrect
statistics…but there is still reference to it in older books

Question 25

Use of differences in mtDNA to model
migration of humans

Answer 25

“Recent” migration supports the monogenesis model

Question 26

Evolution of recent hominins
Genome and fossil genome DNA

Answer 26

Whole genome sequence comparisons between
extant human races support the mitochondrial DNA
data
- Supports the Monogenesis model

Question 27

Comparison of the genomes of H. sapiens and
H. neanderthalensis

Answer 27

-High degree of sequence similarity
-Supports the Monogenesis model
- Interbreeding between the two species
- Modern humans have 1-2% of neanderthal DNA
present in their genomes

Question 28

Evolution of recent hominins
Where have we come from?

Answer 28

More complex than is apparent from
the fossil records

Question 29

Are there genes that define us as human?

Answer 29

Genes involved in:
Enlarged brain
Language/speech - FOXP2 gene
Neural networks enabling abstract thought
processes