introduction to genetics and biological variation · introduction to genetics and biological...
TRANSCRIPT
![Page 1: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/1.jpg)
Introduction to genetics and biological variation
Introduction to Evolution and Scientific InquiryDr. Spielman, Spring 2020
![Page 2: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/2.jpg)
A systems view of biological organization
Carbon, nitrogen, oxygen, hydrogen, etcDNA (chromosomes*)
Nucleus*
Individuals
Group of individuals of same species
Interacting populations of DIFF speciesBiotic and abiotic interactions
EARTH
Applies only to certain multicellular organisms
![Page 3: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/3.jpg)
What is evolution?
Biological evolution is heritable change in populations over time (generations)
● Heritable: evolving trait requires a genetic* basis● Populations: individuals do not evolve● Time: evolution occurs over multiple generations, not within a generation
AKA: Biological evolution is change in allele frequencies in populations over generations
![Page 4: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/4.jpg)
The genetic basis of variation: A brief overview
![Page 5: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/5.jpg)
Humans have 23 pairs of chromosomes
One copy from mom, one copy from dad = 23*2 = 46 total
We are diploid (most animals are)
There are roughly 3 billion nucleotides in the human genome
Across the chromosomes, there are roughly 20,000 genes
![Page 6: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/6.jpg)
Chromosomes are VERY variable ("karyotype")
https://molecularcytogenetics.biomedcentral.com/articles/10.1186/1755-8166-4-22
Indian muntjac
smallest # in mammals
Viscacha rat
largest # in mammals
Siberian Roe deer
has weird transient "B" chromosomes
Transcaucasian mole vole female ("X" is not universal!)
Images during metaphase (DNA replication)
![Page 7: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/7.jpg)
Some fun facts about chromosomes
Most human chromosomes are submetacentric
![Page 8: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/8.jpg)
One more view...
![Page 9: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/9.jpg)
What is a gene?
● A gene is a stretch of nucleotides in the genome that CODES for something○ A "blueprint" to make other types of molecules○ Can code for a protein end-product, or an RNA end-product (which also has a function!)
Proteins are small "machines" in cells that carry out the functions of life
They are not a food group!
![Page 10: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/10.jpg)
There is a lot of variation across the tree of life
Don't memorize these values - understand the CONCEPT
![Page 11: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/11.jpg)
Genes are not magic formulas
THERE IS NO SUCH THING AS "the X gene"
What headlines have you seen for "scientists find the GENE that does THING?"
Instead, an individual's genetics ("genotype") interact with the environment to produce an individual's phenotype.
![Page 12: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/12.jpg)
The location of a gene on a chromosome is called the locus
BUT THERE IS NO REAL SUCH THING AS GENE FOR "FLOWER COLOR"
Genotype → Phenotype is HARD!!!
1. Mendelian traits: One allele for one phenotype. Extremely rare - exceptions!
2. Quantitative traits**: Dozens, hundreds, thousands of genes interact to produce a phenotype
3. Most variation in traits is affected by environment nonetheless
mom origindad origin
allele = "gene version"
![Page 13: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/13.jpg)
Genetic terminology
Homozyote: An individual with the same version (allele) of the gene on both chromosomes
Heterozygote: An individual with a different allele on each chromosome
![Page 14: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/14.jpg)
Genetic terminology
Phenotype = physical appearance
Genotype = underlying genetics
Trait itself: The flower has color
Trait variation: What color is it?
![Page 15: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/15.jpg)
Types of phenotypic variation
Discrete variation is usually caused by a single gene (Mendelian)
Continuous variation is usually a complex result of hundreds or thousands of interacting genes. The exact genotype is often unknown.
"Big A, little a" combinations.AA: blackAa: black (with "A" dominant)aa: white
![Page 16: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/16.jpg)
How many alleles does each gene has? Is it always "big A, little a"?
Some genes have one allele in a species
Some genes have dozens or hundreds of alleles in a species
Brainstorm: Why are there different numbers of alleles across genes? Are more alleles "good", "bad", "neutral"?
![Page 17: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/17.jpg)
What does it really mean to be a different allele?
● We can think of genes as their DNA sequence:
...AGGATCGATAGGACACTCGCGGTA... "wild type" (most in species have this sequence)
...AGGATTGATAGGACACTCGCGGTA... a single nucleotide difference
...AGGATAGATAGGACACTCGCGGTG... 2 nucleotide differences
...AGGATAGATAGGACACTCGCGGTA... some nucleotides are "deleted"
...AGGATAGATAGGACACTCGCGGTGATAACA... some nucleotides are "inserted"
![Page 18: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/18.jpg)
So what are mutations?
● When DNA copies itself (cells divide to make more cells), errors sometimes occur. These errors are MUTATIONS!○ Imagine copying a 3 billion page book by hand. You're going to mess up. Add letters, remove
letters
● Sometimes environmental factors (i.e. radiation) cause DNA to change. These changes are MUTATIONS!
● Mutations are random mistakes.
● Mutation is the raw source of ALL variation (aka source of all new alleles)○ Without mutation, there is NO EVOLUTION (keep coming to class for more information!)
![Page 19: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/19.jpg)
How many brand new mutations do YOU have?
DNM = de novo mutation= not in Mom or Dad. Yours!
New mutations originating in SPERM
New mutations originating in EGGS
![Page 20: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/20.jpg)
Somatic vs germline mutations
Mutation occurs in SPERM OR EGG
Mutation occurs in ANY OTHER CELL
These "somatic mutations" can result in cancer/tumors
![Page 21: Introduction to genetics and biological variation · Introduction to genetics and biological variation Introduction to Evolution and Scientific Inquiry Dr. Spielman, Spring 2020](https://reader034.vdocument.in/reader034/viewer/2022043000/5f77ab15624b9b70af381add/html5/thumbnails/21.jpg)
What are the potential consequences of a mutation?
● This is a very active area of research!● There are two competing views of "mutational effects", but it is generally
agreed that most random changes are BAD
Most mutations are deleterious (bad for organism)
A small proportion are advantageous (helpful for organism)
~Half mutations are deleterious (bad for organism)
~Half mutations are neutral (different, but basically "fine")
Very small proportion are advantageous (helpful for organism)