Summary
Volledige samenvatting van Principles of Human Genetics
- Course
- Institution
Volledige samenvatting van colleges, literatuur en lesmateriaal!
[Show more]
Seller
Followveradewit1
Content preview
Lecture 1 – Introduction & Genetics Revolution (H1)Transmission of genetic information at three levels:
• Transmission genetics from parents to offspring within families
o Individual / family
o Parent offspring
• Molecular-developmental genetics from DNA to gene action within and between
cells
o Cell
o DNA gene action
• Population-evolutionary genetics over generations within populations of organisms
o Population
o Across populations / generations
In 1865, Mendel presented his laws of inheritance about the transmission from parents to
offspring. LET OP! Mendel demonstrated that genes behave like particles and not fluids.
Around 1900, Mendel was rediscovered with new ideas and questions: Where in the cell are
Mendel’s genes? How do genes function in the cell? A flood of new thinking and ideas was
unleashed.bb
Mendel proposed that each individual pea plant has two copies of the gene controlling
flower color in each of the cells of the plant body (=somatic cells). However, when the plant
forms sex cells, or gametes, only one copy of the gene enters into these reproductive cells.
He concluded 2 things:
1) Genes behaved like particles that do not blend together
2) One allele is dominant to the other, enabled him to explain the lack of blending in the
first-generation hybrides
One gene, one enzyme hypothesis = proposed that genes encode enzymes that carry out
biochemical enzymes that carry out biochemical functions within cells Tatum and Beadle
proposed this model based on the study of the synthesis of arginine in the bread mold
Neurospora crassa
DUS: The rediscovery of Mendel’s laws launched a new era in which geneticists resolved
many fundamental questions about the nature of the gene and the flow of genetic
information within cells. During this era, geneticists learned that genes reside on
1
,chromosomes and are made of DNA. Genes encode proteins that conduct the basic
enzymatic work within cells.
DNA is in the form of a double helix. The sides of the ladder are made of sugar and
phosphate groups. The rungs are made of four bases: adenine (A), thymine (T), guanine (G),
cytosine (C).
Characteristics of DNA (double helix) that make it suitable as carrier of genetic information:
• Enormous capacity for data storage and diversity
• Replication
• Translation into form / function
• Stability
• Mutability (heritable mutations in genes: alleles genetic variation, evolution)
LET OP! Only 1% of the human genome is DNA. 80% consists of regulatory functional
elements.
The structure of a protein-coding gene
showing a regulatory DNA element to which
a regulatory protein binds, the promoter
region where the RNA polymerase complex
binds to initiate transcription, and a protein-
coding region.
Many diseases are complex:
Polygenic
Affected by environment
Genetic mutations outside protein-encoding region
Genetic mutations within the gene may depend on interactions between genes
(=epistasis)
Most genetic studies are performed on one of a limited number of model organisms that
have features that make them especially suited for genetic analysis model organism = a
species used in experimental biology with the presumption that what is learned from the
analysis of that species will hold true for other species, especially other closely related
species.
DNA polymerase: can make copy of a single DNA strand by synthesizing a matching
strand with the complementary sequence of A, C, G or T
Nuclease: cuts DNA molecules in specific locations or degrade an entire DNA
molecule into single nucleotides
Ligases: can join 2 DNA molecules together end-to-end
DNA sequencing: the process used to decipher the exact sequence of A, C, G and T’s
in a DNA molecule
2
,Progress in genetics has both produced and been catalysed by the development of molecular
and mathematical tools for the analysis of single genes and whole genomes.
Classical transmission genetics provides the foundation for modern medical genetics. The
integration of classical genetics and genomic technologies can allow the causes of inherited
diseases to be readily identified.
LET OP! Variation in genomes show specific points that can be associated with a specific
trait.
Genetic variation = any difference between two copies of the same gene or DNA molecule
simplest form is called single nucleotide polymorphisms (SNPs) most common type
of variation
LET OP! Genome sequences of parents and their children clarify the factors that contribute
to new point mutations. Fathers contribute four times as many new mutations to their
offspring as do mothers more miotic divisions into the sperm. The number of mutations
passed on from father to his children rises with the age of the father. For women, the
process of making eggs already took place before a women is born. Not for men, their sperm
will have a history that involves over 25 times as many rounds of DNA replication as for eggs
in a woman of the same age.
Signatures of selections in the population
Evolutionary genetics provide the tools to document how gene variants that provide
beneficial effect can rise in frequency in a population and makes individuals better adapted
to the environment in which they live.
Some human populations have lactase gene variants expressed in adults provides
instructions for making the enzyme lactase; helps to digest lactose
Lactose intolerant? Can not digest the lactose from milk.
LET OP! People in Europe are adapted to drink milk as adults; evolve in response to
the conditions in which they live.
Lecture 2 – Single gene inheritance and Mendel (H2 + H3)
The most common form of any property of an organism is called the wild type, which is
found “in the wild”. The heritable variants observed in an organism that differs from the wild
type are mutants. Most natural populations also show polymorphisms = coexistence of two
or more reasonably common phenotypes of a biological property (such as occurrence of
both red- and orange fruited plants)
3
, Genetic analysis begins with mutants:
1) Amass mutants affecting the biological property of interest
2) Cross the mutants to wild type to see if their descendants show rations of wild to
mutant that are characteristic of single-gene inheritance
3) Deduce the functions of the gene at the molecular level
4) Deduce how the gene interacts with other genes to produce the property in question
The use of mutants is called genetic dissection the biological property in question is
picked apart to reveal its underlying genetic program. Each mutant potentially identifies a
separate gene affecting that property.
So the genetic approach to understanding a biological property is to discover the genes that
control it. One approach to gene discovery is to isolate mutants and check each one for
single-gene inheritance patterns (specific rations of normal and mutant expression of the
property in descendants).
Mendel’s pioneering experiments
Mendel did some systematic experiments, studied with seven phenotypic pea pairs. All of
the lines were pure (parental) lines meaning that, for the phenotype in question, all
offspring produced by matings within the members of that line were identical. Bv. within the
yellow-seeded line, all the progeny of any mating were yellow seeded.
To make a cross (cross-pollination), pollen is simply transferred from the anthers of one
plant to the stigmata of another. Special type of mating is self (self-pollination), which is
carried out by allowing pollen from a flower to fall on its own stigma.
The progeny peas from the cross between different pure lines were found to be all yellow
first filial generation (F1). Mendel grew F1 peas into plants, and he selfed these plants to
obtain the second filial generation (F2).
Yellow F1 x yellow F1 F2 comprised of 6022 yellow (75%) and 2001 (25%) green
So, in this situation you have a 3:1 ratio (=Mendel’s first law / law of equal segregation).
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller veradewit1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $5.39. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
67096 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now