Lecture 4 Flashcards
Genotype
genetic makeup of an organism
- aa, Aa, AA
phenotype
a feature of an organism that is observed
size, fur, eye colour
shows how an organism varies physically
Genome
the entirety of an organisms DNA that includes exons and introns
Darwins Mechanisms of Natural Selection
- Variation
- Heredity
- Differential fitness (some forms are more successful then other)
What are the sources of genetic variation (increases genetic diversity)
- Mutations
- independent assortment within meiosis
- recombination
Detailed explanation of mutations and how it is a source of genetic variation
-stable change in DNA
-very rare
-some = neutral, bad, good
- something we cannot control
- environments can affect mutation rate
(high radioactivity, metals), temperature
Types of Mutations
-Point mutation
- Insertion/deletions (changes length of the sequence)
-Repeating
-inversions (rearrangement)
Examples of mutations
G6PD Deficiency in humans
- untreated = severe anemia
- also protects against malaria
How does independent assortment of chromosomes create diversity
- meiosis
- parents make diploid –> haploid gametes
- a lot of different combinations in offspring
How does recombination = genetic diversity
- 2 chromosomes that are homologous (code for the same alleles)
- line up during synapsis at the chiasmata = recombinant
Before Mendel people did not understand how offspring resembled their parents, what were the 2 theories that tried to explain hereditary?
- Preformationism = believed that only one parent contributed to the inheritance
- theory of blending inheritance
- believed that parents genes mix together and blend
Why doesn’t the theory of blending inheritance work
blending genes = not reversible and it will not ever be selected out
- no more variation
- if a mutation arises and it = bad - offspring will have to keep blending
- NS cannot select against this mutation
Mendel’s pea plant
when the parent pea plants were cross
-F1 generation were all the same genotype (heterozygous)
- F2 generation had variation
- offspring inherit one allele per gene at random from each parent
Discrete vs Continuous Traits
DISCRETE: simple mendelian genetics
- dominant, recessive (can tell by the phenotype)
CONT: complex, quantitative, different variation, not fixed
(human height)
T/F
Quantitative traits are often affected by many factors
TRUE
they are affected by complex polygenic inheritance
- environmental interactions
