Human genetics & Intro to evolution

Genetics 

the study of inherited variation in humans 

Difficulties in studying human genetics

few offspring

long generations

unethical

Ways to study human genetics

population studies of extended families

natural experiments 

DNA sequencing from many generations

Pedigree 

a family tree that shows inheritance over several generations 

Autosomal recessive

genetic condition that requires 2 copies of an altered gene (homozygous recessive)

Sickle cell disease

the most common inherited condition among people of African descent

2 outcomes of sickle cell disease

1. cell gets destroyed

2. sickle cells clump together

Autosomal dominant

genetic condition that only requires one copy of an altered gene

Disomy

has two copies of each chromosome (1 homologous pair)

Aneuploidy

genetic disorder which causes a presence of an atypical number of chromosomes

Trisomy

has 3 copies of a chromosome 

2n + 1 

Monosomy

lacks 1 chromosome from a pair

2n -1

Changes in chromosome structure

due to errors during meiosis, radiation, and chemical mutations

4 main chromosomal structural changes 

1. deletion

2. duplication

3. inversion

4. translocation 

Deletion

removes a chromosome segment

Duplication

repeats a chromosome segment

Inversion 

reverses a segment within a chromosome 

Translocation

moves a segment from one chromosome to a different chromosome

Fetal testing

genetic tests done before birth

Newborn screening

genetic tests done at birth

Carolus linnaeus findings

created the hierarchical classification system and the binomial nomenclature

James huttons findings 

gradualism 

Gradualism

observable processes that change and accumulate over time 

Charles lyells findings

redefined ideas of gradualism into to theory of uniformitarianism 

Uniformitarianism  

geological processes are uniform over time 

Jean-Baptiste Lamaracks findings

proposed that evolution was a natural mechanism → concluded that biological evolution is a natural process

2 natural mechanisms for evolution

1. use and disuse

2. inheritance of acquired traits

Use and disuse mechanism 

body parts that are used become larger and stronger

body parts that are not used deteriorate 

Inheritance of acquired traits mechanism

traits that are acquired via use will be passed to offspring 

Charles darwin’s findings 

proposed natural selection as a mechanism for evolution 

Darwins 4 observations

1. overproduction

2. unequal survival and reproduction

3. heritable variation

4. non-random survival and reproduction

Overproduction

more offspring are born compared to the amount than can survive

Unequal survival and reproduction 

some organisms survive longer and have more offspring → competition

Heritable variation

when individuals have variation their offspring will resemble their parents

Non-random survival and reproduction 

survival and reproduction are based on phenotype

better adapted individuals → more offspring 

Natural selection

beneficial traits suited to a species environment will be passed down to offspring

Descent with modifications

populations change over time as beneficial traits increase in frequency and detrimental traits decrease in frequency

Fitness

genetic contribution to the next generation relative to other members of the population

Evolutionary fitness 

an organism's ability to survive and reproduce

Illustrations of evolution

1. artificial selection

2. direct observations

3. homology

4. fossil records

Artificial selection

humans pick which individuals reproduce based on desired traits

Homology

structures/features inherited from a common ancestor

Fossil record

remains or traces of previously existing organisms in sedimentary rock